Engineering Report PDF
Engineering Report PDF
Engineering Report PDF
Draft
September 2012
HITCON Engineering
Tel: +251 (0)11 618 3227/28, Fax: +251 (0)11 663 9310, P.O. Box 3097/1250
Addis Ababa, Ethiopia
ENGINEERING DESIGN REPORT (Draft)
Consultancy Services for the Detailed Engineering Design, Tender Documents Preparation and
Construction Supervision of Addis Ababa Goha Tsion Road Overlay Project
TABLE OF CONTENTS
1 INTRODUCTION
1.1 General
The Ethiopian Roads Authority has entered into contract agreement with HITCON
Engineering to perform the Consultancy Services for the Detailed Engineering Design,
Tender Document Preparation and Construction Supervision of Addis Ababa Goha
Tsion Road Overlay Project. The Consultancy service agreement was signed on
December 09, 2011 and later on the date of notification to commence the services
was given on December 28, 2011.
The road, with a total length of approximately 177.2km is located within the bounds of
the Oromia Regional State.
The following Engineering Design Report shall focus on the detailed engineering design
activities carried out for the project.
As specified in the Contract the consultancy assignment shall be carried out in two
distinct phases. These are:
and Time for Completion allowed under the Contract or any agreed
amendments thereto.
The Addis Ababa - Goha Tsion Road is located in the Federal Government and
Oromiya regional State, in the Northern part of Ethiopia stretching for about 177 km.
The project road starts from the capital and the rural section starts at about km 9 and
passes through towns; Sululta, Chanco, Muketuri, Fiche, Gebre Guracha and ends at
Goha Tsion. The project road is part of the road segment from Addis Ababa
Metema, particularly being part of the Addis Ababa Debere Markos trunk road which
has high traffic volume and load as it is the main corridor of Port Sudan, and additional
traffic load arising from traffic generated as a result of industrial developments along
the road corridor.
Gebre Guracha
Chancho
Start of Project
Addis Ababa
2 GEOMETRIC DESIGN
Basically road design standards are selected based on function and traffic. The
function of the road is determined by the character and anticipated level of service
that the road would render. Typically this relates into categorization or classification of
the road as Trunk, Link, Main Access, Collector and Feeder for which a generic
definition is given indicating its primary function and purpose. The project road is one of
the trunk roads of the country.
Road standards are also selected based on the roads intended capacity to
accommodate traffic. Normally, for high traffic volumes a higher set of design standard
(i.e., wider carriageways, gentle curves, flatter vertical gradient, full overtaking
distances etc.) are associated while the vice versa is true for low traffic.
For the purpose of the determination of the design standard of the project traffic
forecast was carried out dividing the road into two road segments, i.e. Addis Ababa
Chancho (Section I) and Chancho Goha Tsion (Section II). The following tables show
this forecast.
Medium Bus 25 -
Wagon/ Pick ups
Land Rover/ Sta.
Medium Truck
Heavy Truck
Minibus (12
Small Cars
Remark
45 seat
seats)
seats
Total
Year
seat
2012 212 395 452 458 44 108 586 242 271 323 3091 0 Years for
2013 225 427 484 490 47 116 642 265 297 354 3346 1 Construction
2014 240 463 519 526 51 124 705 291 326 388 3633 2
Opening
2015 255 501 556 563 54 133 771 319 357 425 3934 1
Year
2016 270 539 592 600 58 141 839 347 388 463 4237 2
2017 286 579 630 638 61 150 911 376 421 502 4555 3
2018 302 620 668 677 65 160 987 408 457 544 4889 4
2019 318 664 709 718 69 169 1,068 441 494 588 5238 5
2020 335 709 750 760 73 179 1,152 476 533 635 5601 6
2021 352 755 793 803 77 189 1,240 512 573 683 5979 7
2022 370 803 836 848 81 200 1,332 550 616 734 6371 8
2023 387 853 881 893 86 211 1,428 590 660 787 6776 9
2024 405 904 927 939 90 221 1,527 631 706 842 7193 10
2025 424 957 973 986 95 232 1,630 673 754 899 7622 11
2026 443 1,012 1,022 1,035 99 244 1,741 719 805 959 8080 12
2027 462 1,070 1,072 1,086 104 256 1,856 766 858 1,023 8553 13
2028 482 1,129 1,123 1,138 109 268 1,975 816 913 1,089 9042 14
2029 502 1,190 1,175 1,191 114 281 2,099 867 971 1,157 9546 15
2030 523 1,252 1,228 1,245 120 293 2,227 920 1,030 1,227 10065 16
2031 544 1,316 1,282 1,299 125 306 2,359 974 1,091 1,300 10596 17
Medium Bus 25 -
Wagon/ Pick ups
Land Rover/ Sta.
Medium Truck
Heavy Truck
Minibus (12
Small Cars
Remark
45 seat
seats)
seats
Total
Year
seat
2032 564 1,381 1,337 1,355 130 319 2,495 1,030 1,154 1,375 11141 18
2033 586 1,448 1,393 1,411 136 333 2,634 1,088 1,218 1,452 11697 19
2034 607 1,515 1,449 1,468 141 346 2,777 1,147 1,284 1,531 12263 20
Medium Truck
Heavy Truck
Minibus (12
Small Cars
Remark
45 seat
seats)
Seats
Total
Year
Seat
From the forecasted traffic, the project design traffic volume at opening year (2015), at
5th year (2019), at 10th year (2024), at 15th year (2029) and at 20th year (2034) of the
road would be 3934, 5238, 7193, 9546 and 12263 AADT respectively for Addis Ababa
Chancho section and 1862, 2476, 3396, 4501 and 5775 AADT respectively for Chancho
Goha Tsion section. The design standards required according to the forecasted traffic
of different year are as shown below:
It can be seen from the above table for the majority of the design period the design
standard of the road for Section I falls in DS2 and Section II falls in DS3. It is known that
the existing standard of the road is DS4 standard. Moreover at some locations, such as
the winding steep road that traverses Entoto Mountain, deviate even from DS4
standard. When standard of an existing road is upgraded to a higher standard there
will be significant changes with respect to geometry (horizontal and vertical alignment
and cross-section) which is basically caused by the increase in the design speed. The
change in geometry in turn calls for significant investment due to the required
reconstruction activity, i.e. earthwork, pavement work as well as drainage facilities. This
would significantly deviate from the scope of overlay design. Based on this prevalent
situation appropriate design adjustments and recommendations are made.
The geometric design elements of a road depend primarily on the terrain through
which the road passes. According to ERA Design Manual, terrain properties are
generally categorized into four classes as follows:
Rolling Rolling, hilly or foothill country where the slopes generally rise
and fall moderately and where occasional steep slopes are
encountered, resulting in some restrictions in alignment
(transverse terrain slope from 5 percent to 25 percent).
Mountainous Rugged, hilly and mountainous country and river gorges. This
class of terrain imposes definite restrictions on the standard
of alignment obtainable and often involves long steep
grades and limited sight distance (transverse terrain slope
from 25 percent to 50 percent).
Based on the above criteria and using information gathered field investigation as well
as DTM generated from surveying terrain classification is performed for the road
project. However within this classification change in terrain properties at pockets
locations have been observed. At these locations key design parameters (such as
design speed) might differed according to their respective terrain properties.
Station
Terrain Type
From To
Station
Terrain Type
From To
Station
Terrain Type
From To
It is stated in ERAs geometric design manual that the present fleet in Ethiopia includes
a high number of four-wheel drive utility vehicles and overloaded trucks. Until more
detailed information becomes available regarding the makeup of the vehicle fleet in
Ethiopia, the four design vehicles indicated in the table below should be used in the
control of geometric design.
It is also indicated that for roads included within DS1 to DS5 design standard the most
restrictive of all that is DV4 (semi-trailer combination) should be used for design.
Therefore since the road is being designed for DS2 and DS3 road standard this
condition has been met.
Design speed is defined as the speed which is used to determine the various geometric
design features of the roadway, such as horizontal curve radius, maximum gradient,
super elevation, curtailed sight distance and so on. During selection of design speed
factors such as functional classification, topography, adjacent land use and
anticipated operating speed are considered.
The design speed recommended for the different terrain classifications based on ERAs
Geometric Design Standard is as follows:
Table 2.4: Design Speed Vs Terrain Category as per ERA Design Manual
Terrain Urban/Peri-
Flat Rolling Mountainous Escarpment urban
Design speed
(km/h) for 100 85 70 60 50
DS3
In general during the design process it is best to achieve the upper design speeds
whenever it was economically justifiable. However, in this case in order not to abandon
the overlay principle, i.e. avoid earthwork, departure from specified design speeds was
inevitable. In these cases, traffic safety is maintained by advising motorists for speed
changes with advisory or mandatory traffic signs and guiding road furniture as
appropriate.
Since this section of the road is being designed in most cases, except the first 28km,
with overlay design principle, it was as much as possible was tried to match the design
centerline with that of the existing road.
Limiting design standard values of ERAs Geometric Design Manual are presented in
the table below.
Curve Urban/Peri-
Flat Rolling Mountainous Escarpment
Elements urban
Design Speed 120 100 85 70 50
Min. radius
630 395 270 175 85
(m)
Max super-
8 8 8 8 4
elevation in %
Curve Urban/Peri-
Flat Rolling Mountainous Escarpment
Elements urban
Design Speed 100 85 70 60 50
Min. radius
395 270 175 125 85
(m)
Max super-
8 8 8 8 4
elevation in %
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
0+026.546 1004017.851 469414.661 200 Escarpment DS-2 70 175 200 Ok
Sub-
0+087.881 1004042.079 469358.272 60 Escarpment DS-2 70 175 60
standard
Sub-
0+233.116 1004184.891 469316.121 60 Escarpment DS-2 70 175 60
standard
Sub-
0+343.946 1004236.809 469215.004 50 Escarpment DS-2 70 175 50
standard
Sub-
0+439.746 1004331.736 469329.007 95 Escarpment DS-2 70 175 95
standard
Sub-
0+668.574 1004564.375 469345.725 150 Escarpment DS-2 70 175 150
standard
0+828.598 1004684.766 469228.365 600 Escarpment DS-2 70 175 600 Ok
Sub-
0+949.625 1004756.06 469130.264 80 Escarpment DS-2 70 175 80
standard
Sub-
1+075.364 1004740.349 469002.497 68 Escarpment DS-2 70 175 68
standard
Sub-
1+174.675 1004892.451 469026.573 100 Escarpment DS-2 70 175 100
standard
Sub-
1+565.983 1005120.968 468692.166 300 Rolling DS-2 100 395 300
standard
1+965.061 1005466.757 468488.2 1200 Rolling DS-2 100 395 1200 Ok
Sub-
2+893.304 1006200.729 467919.605 150 Rolling DS-2 100 395 150
standard
3+134.092 1006414.593 468103.67 5000 Flat DS-2 120 630 5000 Ok
3+243.931 1006499 468173.959 5000 Flat DS-2 120 630 5000 Ok
Sub-
3+436.375 1006645.901 468298.276 200 Flat DS-2 120 630 200
standard
3+802.687 1006802.5 468631.199 5000 Flat DS-2 120 630 5000 Ok
3+888.751 1006840.061 468708.635 5000 Flat DS-2 120 630 5000 Ok
4+249.035 1006993.046 469034.826 10000 Flat DS-2 120 630 10000 Ok
4+456.947 1007082.424 469222.548 10000 Flat DS-2 120 630 10000 Ok
4+633.871 1007157.682 469382.667 500 Rolling DS-2 100 395 500 Ok
Sub-
5+114.224 1007434.169 469775.795 120 Rolling DS-2 100 395 120
standard
Sub-
5+250.322 1007439.447 469914.465 120 Rolling DS-2 100 395 120
standard
Sub-
5+373.691 1007512.222 470016.586 300 Rolling DS-2 100 395 300
standard
5+516.404 1007563.586 470150.302 200 Urban DS-2 50 85 200 Ok
5+943.090 1007857.224 470461.26 300 Urban DS-2 50 85 300 Ok
6+266.423 1007997.417 470753.493 500 Urban DS-2 50 85 500 Ok
6+683.509 1008258.183 471079.639 120 Urban DS-2 50 85 120 Ok
6+931.464 1008494.26 471161.666 500 Urban DS-2 50 85 500 Ok
7+287.290 1008809.94 471326.138 1500 Urban DS-2 50 85 1500 Ok
7+600.781 1009074.776 471494.025 200 Urban DS-2 50 85 200 Ok
7+815.827 1009193.246 471675.202 300 Urban DS-2 50 85 300 Ok
8+001.022 1009242.062 471854.695 300 Urban DS-2 50 85 300 Ok
8+249.765 1009224.517 472103.822 200 Urban DS-2 50 85 200 Ok
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
8+385.551 1009290.974 472225.938 150 Urban DS-2 50 85 150 Ok
8+593.007 1009245.265 472433.385 200 Urban DS-2 50 85 200 Ok
8+740.546 1009253.372 472581.039 150 Urban DS-2 50 85 150 Ok
8+908.213 1009422.935 472658.456 160 Urban DS-2 50 85 160 Ok
9+222.971 1009662.495 472863.212 500 Urban DS-2 50 85 500 Ok
9+412.121 1009829.74 472952.506 500 Urban DS-2 50 85 500 Ok
9+616.862 1010025.409 473013.736 220 Urban DS-2 50 85 220 Ok
9+740.346 1010149.602 473002.351 450 Urban DS-2 50 85 450 Ok
9+907.251 1010309.576 472953.593 400 Urban DS-2 50 85 400 Ok
10+166.871 1010547.123 472848.672 180 Urban DS-2 50 85 180 Ok
10+320.691 1010702.291 472869.256 400 Urban DS-2 50 85 400 Ok
10+542.025 1010923.43 472854.954 1000 Urban DS-2 50 85 1000 Ok
12+972.504 1013351.527 472965.002 500 Urban DS-2 50 85 500 Ok
14+645.983 1014950.616 473460.821 300 Urban DS-2 50 85 300 Ok
15+159.451 1015464.851 473449.862 200 Urban DS-2 50 85 200 Ok
15+492.449 1015757.698 473287.006 140 Urban DS-2 50 85 140 Ok
15+747.875 1015998.867 473401.32 1500 Rolling DS-2 100 395 1500 Ok
Sub-
16+040.513 1016249.825 473552.075 120 Mountainous DS-2 85 270 120
standard
16+351.636 1016562.984 473533.913 2000 Mountainous DS-2 85 270 2000 Ok
16+457.997 1016669.002 473525.349 1000 Mountainous DS-2 85 270 1000 Ok
Sub-
16+602.470 1016813.396 473520.325 180 Mountainous DS-2 85 270 180
standard
17+231.741 1017364.538 473212.547 10000 Flat DS-2 120 630 10000 Ok
Sub-
17+638.417 1017720.592 473016.049 200 Flat DS-2 120 630 200
standard
17+955.622 1018039.095 472997.86 10000 Flat DS-2 120 630 10000 Ok
18+143.721 1018226.833 472986.205 5000 Flat DS-2 120 630 5000 Ok
Sub-
18+298.653 1018381.682 472980.853 600 Flat DS-2 120 630 600
standard
18+992.104 1019073.878 472939.138 30000 Flat DS-2 120 630 30000 Ok
19+394.673 1019475.888 472917.908 1000 Rolling DS-2 100 395 1000 Ok
Sub-
20+180.229 1020260.227 472874.217 160 Mountainous DS-2 85 270 160
standard
20+854.521 1020785.47 473307.352 380 Mountainous DS-2 85 270 380 Ok
21+572.631 1021462.562 473550.78 600 Rolling DS-2 100 395 600 Ok
21+728.566 1021616.417 473577.687 5000 Rolling DS-2 100 395 5000 Ok
22+238.947 1022117.825 473672.975 40000 Flat DS-2 120 630 40000 Ok
22+663.418 1022535.548 473748.381 50000 Flat DS-2 120 630 50000 Ok
23+023.680 1022889.684 473814.543 10000 Flat DS-2 120 630 10000 Ok
23+239.600 1023102.447 473851.341 15000 Flat DS-2 120 630 15000 Ok
23+595.561 1023452.463 473916.132 2000 Rolling DS-2 100 395 2000 Ok
Sub-
23+771.087 1023625.496 473945.614 300 Rolling DS-2 100 395 300
standard
Sub-
24+054.264 1023907.559 473913.508 320 Rolling DS-2 100 395 320
standard
Sub-
24+318.347 1024155.531 474014.544 150 Rolling DS-2 100 395 150
standard
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
24+813.481 1024507.221 473626.888 1600 Rolling DS-2 100 395 1600 Ok
25+027.317 1024635.747 473455.854 500 Mountainous DS-2 85 270 500 Ok
25+321.056 1024874.087 473282.148 280 Mountainous DS-2 85 270 280 Ok
Sub-
25+589.581 1025148.173 473275.117 160 Mountainous DS-2 85 270 160
standard
25+894.235 1025392.537 473086.49 800 Mountainous DS-2 85 270 800 Ok
26+052.417 1025525.762 473001.119 280 Mountainous DS-2 85 270 280 Ok
Sub-
26+264.069 1025743.459 473016.928 120 Mountainous DS-2 85 270 120
standard
26+411.777 1025876.67 472947.962 450 Mountainous DS-2 85 270 450 Ok
26+621.640 1026082.125 472901.881 850 Mountainous DS-2 85 270 850 Ok
27+053.239 1026512.86 472870.998 5000 Rolling DS-2 100 395 5000 Ok
27+428.143 1026887.165 472849.783 1000 Mountainous DS-3 70 175 1000 Ok
27+584.859 1027042.881 472831.962 200 Mountainous DS-3 70 175 200 Ok
27+853.397 1027292.577 472937.234 120 Urban DS-3 50 85 120 Ok
28+269.430 1027641.282 472688.225 500 Urban DS-3 50 85 500 Ok
28+383.491 1027745.613 472641.335 150 Urban DS-3 50 85 150 Ok
28+460.833 1027824.037 472642.816 500 Urban DS-3 50 85 500 Ok
28+699.228 1028060.956 472669.613 5000 Urban DS-3 50 85 5000 Ok
28+917.450 1028278.489 472687.112 800 Urban DS-3 50 85 800 Ok
29+342.896 1028693.9 472779.8 260 Urban DS-3 50 85 260 Ok
29+473.420 1028802.525 472854.355 150 Urban DS-3 50 85 150 Ok
29+618.683 1028852.043 472994.364 300 Urban DS-3 50 85 300 Ok
Sub-
30+047.445 1028892.685 473421.568 150 Mountainous DS-3 70 175 150
standard
Sub-
30+209.805 1028997.882 473548.818 155 Mountainous DS-3 70 175 155
standard
30+372.484 1029170.55 473546.535 200 Mountainous DS-3 70 175 200 Ok
30+589.568 1029351.33 473674.339 400 Rolling DS-3 85 270 400 Ok
Sub-
30+916.859 1029658.713 473788.623 200 Rolling DS-3 85 270 200
standard
31+167.468 1029904.808 473720.896 400 Rolling DS-3 85 270 400 Ok
31+278.412 1030015.348 473709.578 400 Rolling DS-3 85 270 400 Ok
31+502.118 1030226.641 473634.724 500 Rolling DS-3 85 270 500 Ok
31+709.980 1030436.44 473637.747 440 Rolling DS-3 85 270 440 Ok
Sub-
31+954.923 1030668.914 473555.359 140 Rolling DS-3 85 270 140
standard
32+124.400 1030802.937 473689.78 600 Rolling DS-3 85 270 600 Ok
Sub-
32+279.531 1030897.535 473812.882 150 Rolling DS-3 85 270 150
standard
32+421.321 1031028.401 473871.381 320 Mountainous DS-3 70 175 320 Ok
Sub-
32+693.755 1031302.636 473826.359 120 Mountainous DS-3 70 175 120
standard
Sub-
32+896.199 1031396.28 473636.297 140 Mountainous DS-3 70 175 140
standard
33+038.189 1031557.686 473639.456 600 Mountainous DS-3 70 175 600 Ok
33+164.772 1031681.825 473665.93 600 Mountainous DS-3 70 175 600 Ok
Sub-
33+449.772 1031966.477 473683.099 125 Mountainous DS-3 70 175 125
standard
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
Sub-
33+717.486 1031970.58 473995.907 120 Mountainous DS-3 70 175 120
standard
33+843.142 1032128.192 474021.279 500 Mountainous DS-3 70 175 500 Ok
33+922.144 1032203.647 474045.125 500 Mountainous DS-3 70 175 500 Ok
Sub-
34+116.427 1032393.322 474087.343 200 Rolling DS-3 85 270 200
standard
Sub-
34+261.403 1032520.227 474158.646 100 Flat DS-3 100 395 100
standard
Sub-
34+462.596 1032609.912 474341.651 150 Flat DS-3 100 395 150
standard
34+795.048 1032864.502 474557.321 20000 Flat DS-3 100 395 20000 Ok
35+222.816 1033188.496 474836.631 5000 Rolling DS-3 85 270 5000 Ok
Sub-
35+303.930 1033250.769 474888.61 200 Rolling DS-3 85 270 200
standard
Sub-
35+400.876 1033335.847 474935.34 160 Mountainous DS-3 70 175 160
standard
Sub-
35+589.650 1033526.028 474901.934 120 Mountainous DS-3 70 175 120
standard
35+923.043 1033769.105 475144.001 600 Mountainous DS-3 70 175 600 Ok
36+230.578 1034057.22 475260.471 500 Rolling DS-3 85 270 500 Ok
36+376.921 1034186.41 475329.354 500 Rolling DS-3 85 270 500 Ok
Sub-
36+528.247 1034327.207 475385.024 240 Rolling DS-3 85 270 240
standard
Sub-
36+830.555 1034466.451 475662.551 115 Rolling DS-3 85 270 115
standard
Sub-
37+133.403 1034787.216 475535.199 180 Rolling DS-3 85 270 180
standard
Sub-
37+308.181 1034955.988 475605.022 135 Rolling DS-3 85 270 135
standard
Sub-
37+464.365 1035015.947 475756.56 120 Flat DS-3 100 395 120
standard
Sub-
37+907.717 1035466.49 475826.622 130 Rolling DS-3 85 270 130
standard
Sub-
38+156.027 1035682.21 475694.47 60 Rolling DS-3 85 270 60
standard
38+601.929 1035763.659 476201.827 2000 Rolling DS-3 85 270 2000 Ok
38+984.105 1035851.076 476573.935 600 Rolling DS-3 85 270 600 Ok
39+520.052 1036177.256 477003.933 350 Rolling DS-3 85 270 350 Ok
39+709.815 1036234.97 477186.062 1000 Rolling DS-3 85 270 1000 Ok
39+868.479 1036261.458 477342.733 600 Rolling DS-3 85 270 600 Ok
40+036.452 1036301.533 477505.875 220 Mountainous DS-3 70 175 220 Ok
Sub-
40+223.298 1036452.742 477624.902 120 Mountainous DS-3 70 175 120
standard
40+338.522 1036438.896 477750.965 300 Mountainous DS-3 70 175 300 Ok
40+472.949 1036456.103 477884.626 1000 Mountainous DS-3 70 175 1000 Ok
Sub-
40+603.692 1036459.841 478015.398 125 Mountainous DS-3 70 175 125
standard
40+863.449 1036672.137 478178.405 1000 Mountainous DS-3 70 175 1000 Ok
41+020.790 1036786.004 478287.143 2000 Rolling DS-3 85 270 2000 Ok
Sub-
41+242.700 1036950.777 478435.789 160 Rolling DS-3 85 270 160
standard
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
Sub-
41+502.908 1037047.718 478679.041 135 Rolling DS-3 85 270 135
standard
Sub-
41+705.410 1037253.172 478735.637 150 Rolling DS-3 85 270 150
standard
Sub-
41+887.794 1037433.719 478702.604 180 Rolling DS-3 85 270 180
standard
42+062.169 1037596.854 478773.925 1000 Rolling DS-3 85 270 1000 Ok
Sub-
42+193.746 1037721.555 478816.077 115 Rolling DS-3 85 270 115
standard
Sub-
42+483.296 1037749.701 479121.271 110 Rolling DS-3 85 270 110
standard
42+734.612 1038007.34 479202.315 450 Rolling DS-3 85 270 450 Ok
43+148.875 1038326.002 479470.816 750 Rolling DS-3 85 270 750 Ok
43+678.434 1038544.776 479959.465 280 Rolling DS-3 85 270 280 Ok
Sub-
43+897.409 1038730.753 480083.436 110 Rolling DS-3 85 270 110
standard
44+157.548 1038684.041 480357.289 350 Rolling DS-3 85 270 350 Ok
Sub-
44+532.857 1038788.105 480720.816 120 Rolling DS-3 85 270 120
standard
44+739.249 1038624.315 480872.183 360 Rolling DS-3 85 270 360 Ok
Sub-
45+403.417 1038277.026 481439.057 200 Rolling DS-3 85 270 200
standard
Sub-
45+729.242 1038317.274 481768.159 100 Rolling DS-3 85 270 100
standard
Sub-
46+024.753 1038031.498 481901.092 120 Rolling DS-3 85 270 120
standard
46+198.780 1038023.212 482089.702 2000 Rolling DS-3 85 270 2000 Ok
46+260.346 1038021.562 482151.247 2000 Rolling DS-3 85 270 2000 Ok
46+380.743 1038015.632 482271.499 2000 Rolling DS-3 85 270 2000 Ok
Sub-
46+494.402 1038014.351 482385.16 150 Rolling DS-3 85 270 150
standard
Sub-
46+648.070 1038087.189 482522.722 120 Rolling DS-3 85 270 120
standard
Sub-
46+879.779 1038333.06 482524.221 150 Rolling DS-3 85 270 150
standard
47+072.557 1038455.358 482686.744 1000 Mountainous DS-3 70 175 1000 Ok
47+190.662 1038531.29 482777.222 250 Mountainous DS-3 70 175 250 Ok
Sub-
47+333.990 1038580.686 482912.72 120 Mountainous DS-3 70 175 120
standard
Sub-
47+525.236 1038787.555 482931.824 150 Mountainous DS-3 70 175 150
standard
47+792.737 1039018.488 482790.087 200 Mountainous DS-3 70 175 200 Ok
47+928.586 1039158.54 482841.261 250 Mountainous DS-3 70 175 250 Ok
Sub-
48+119.603 1039303.779 482966.875 160 Mountainous DS-3 70 175 160
standard
Sub-
48+256.488 1039430.459 483019.86 350 Flat DS-3 100 395 350
standard
Sub-
48+374.299 1039522.113 483095.026 120 Flat DS-3 100 395 120
standard
Sub-
48+481.664 1039632.792 483095.648 160 Flat DS-3 100 395 160
standard
48+671.299 1039801.192 483004.79 1000 Flat DS-3 100 395 1000 Ok
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
49+080.903 1040182.38 482854.48 400 Flat DS-3 100 395 400 Ok
49+462.154 1040563.53 482825.69 1200 Rolling DS-3 85 270 1200 Ok
Sub-
49+592.832 1040694.266 482829.594 200 Rolling DS-3 85 270 200
standard
49+740.828 1040834.272 482879.686 2000 Rolling DS-3 85 270 2000 Ok
Sub-
49+976.587 1041053.228 482967.118 150 Rolling DS-3 85 270 150
standard
Sub-
50+075.521 1041126.869 483034.051 120 Rolling DS-3 85 270 120
standard
50+171.356 1041152.95 483128.181 500 Rolling DS-3 85 270 500 Ok
50+304.581 1041196.571 483254.073 400 Rolling DS-3 85 270 400 Ok
Sub-
50+478.737 1041201.679 483429.179 120 Rolling DS-3 85 270 120
standard
Sub-
50+671.296 1041372.527 483538.331 180 Rolling DS-3 85 270 180
standard
51+067.886 1041574.6 483881.429 2000 Mountainous DS-3 70 175 2000 Ok
Sub-
51+243.003 1041665.355 484031.194 130 Mountainous DS-3 70 175 130
standard
51+343.181 1041661.62 484133.507 1000 Mountainous DS-3 70 175 1000 Ok
Sub-
51+607.381 1041627.911 484395.611 52 Rolling DS-3 85 270 52
standard
Sub-
51+604.951 1041785.035 484179.203 80 Rolling DS-3 85 270 80
standard
51+701.880 1041883.804 484162.292 320 Rolling DS-3 85 270 320 Ok
Sub-
52+008.727 1042190.395 484182.962 65 Mountainous DS-3 70 175 65
standard
52+206.162 1042149.825 484412.542 1000 Mountainous DS-3 70 175 1000 Ok
Sub-
52+433.317 1042097.757 484633.663 64 Mountainous DS-3 70 175 64
standard
Sub-
52+603.470 1042357.133 484523.402 120 Mountainous DS-3 70 175 120
standard
52+860.835 1042589.061 484652.86 320 Rolling DS-3 85 270 320 Ok
53+096.868 1042710.999 484859.939 1200 Rolling DS-3 85 270 1200 Ok
53+208.946 1042776.396 484951.05 500 Rolling DS-3 85 270 500 Ok
Sub-
53+367.507 1042894.357 485057.616 250 Rolling DS-3 85 270 250
standard
Sub-
53+588.722 1043102.023 485137.358 250 Rolling DS-3 85 270 250
standard
53+867.343 1043381.662 485109.667 250 Mountainous DS-3 70 175 250 Ok
54+134.033 1043629.379 485215.572 500 Mountainous DS-3 70 175 500 Ok
54+227.682 1043707.763 485267.253 300 Mountainous DS-3 70 175 300 Ok
54+362.362 1043821.972 485338.633 600 Rolling DS-3 85 270 600 Ok
Sub-
54+485.835 1043914.638 485420.576 200 Rolling DS-3 85 270 200
standard
Sub-
54+830.301 1044255.889 485484.351 125 Rolling DS-3 85 270 125
standard
Sub-
54+989.217 1044340.808 485626.713 220 Rolling DS-3 85 270 220
standard
Sub-
55+234.399 1044557.167 485748.244 120 Rolling DS-3 85 270 120
standard
Sub-
55+425.472 1044571.114 485950.751 120 Rolling DS-3 85 270 120
standard
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
Sub-
55+679.709 1044757.408 486130.952 250 Rolling DS-3 85 270 250
standard
Sub-
56+230.183 1045278.338 486314.047 120 Mountainous DS-3 70 175 120
standard
Sub-
56+427.848 1045312.764 486522.698 120 Mountainous DS-3 70 175 120
standard
Sub-
56+599.405 1045476.29 486601.035 130 Mountainous DS-3 70 175 130
standard
Sub-
56+727.236 1045605.069 486581.998 100 Mountainous DS-3 70 175 100
standard
Sub-
56+944.915 1045692.536 486808.378 75 Rolling DS-3 85 270 75
standard
Sub-
57+344.201 1046100.988 486688.165 200 Rolling DS-3 85 270 200
standard
57+521.361 1046277.62 486716.974 200 Mountainous DS-3 70 175 200 Ok
57+657.798 1046381.959 486809.617 200 Mountainous DS-3 70 175 200 Ok
57+847.826 1046558.91 486880.751 200 Mountainous DS-3 70 175 200 Ok
57+957.321 1046669.389 486880.158 400 Rolling DS-3 85 270 400 Ok
Sub-
58+097.702 1046808.645 486898.814 180 Rolling DS-3 85 270 180
standard
58+380.578 1047078.11 486808.022 1000 Rolling DS-3 85 270 1000 Ok
58+521.887 1047207.14 486750.217 500 Rolling DS-3 85 270 500 Ok
Sub-
58+737.387 1047410.737 486679.504 110 Rolling DS-3 85 270 110
standard
Sub-
58+980.726 1047483.916 486437.382 100 Rolling DS-3 85 270 100
standard
Sub-
59+261.528 1047734.392 486299.554 250 Rolling DS-3 85 270 250
standard
Sub-
59+533.025 1048002.457 486397.864 160 Flat DS-3 100 395 160
standard
59+940.946 1048397.243 486279.555 3000 Flat DS-3 100 395 3000 Ok
60+089.232 1048539.836 486238.863 600 Flat DS-3 100 395 600 Ok
60+579.154 1049027.439 486188.257 4000 Flat DS-3 100 395 4000 Ok
60+851.960 1049299.518 486168.245 5000 Flat DS-3 100 395 5000 Ok
61+047.320 1049494.003 486149.726 5000 Flat DS-3 100 395 5000 Ok
61+668.281 1050111.685 486085.992 600 Flat DS-3 100 395 600 Ok
62+413.762 1050854.206 486156.991 20000 Flat DS-3 100 395 20000 Ok
Sub-
62+770.728 1051209.436 486192.153 320 Flat DS-3 100 395 320
standard
63+998.827 1052416.846 485963.586 700 Flat DS-3 100 395 700 Ok
64+446.204 1052864.545 485959.049 10000 Flat DS-3 100 395 10000 Ok
66+252.267 1054670.403 485931.864 1200 Urban DS-3 50 85 1200 Ok
66+450.102 1054867.653 485948.301 900 Urban DS-3 50 85 900 Ok
67+000.779 1055417.739 485918.785 280 Urban DS-3 50 85 280 Ok
67+381.339 1055767.627 485765.891 5000 Urban DS-3 50 85 5000 Ok
68+099.148 1056442.453 485520.91 2000 Rolling DS-3 85 270 2000 Ok
68+291.355 1056622.081 485452.519 800 Rolling DS-3 85 270 800 Ok
68+919.301 1057235.518 485317.278 2000 Rolling DS-3 85 270 2000 Ok
69+718.666 1057995.599 485069.255 10000 Flat DS-3 100 395 10000 Ok
70+962.296 1059190.443 484724.224 12000 Flat DS-3 100 395 12000 Ok
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
71+084.322 1059308.051 484691.681 2000 Flat DS-3 100 395 2000 Ok
71+347.118 1059563.863 484631.456 20000 Flat DS-3 100 395 20000 Ok
Sub-
71+676.586 1059885.146 484558.468 200 Flat DS-3 100 395 200
standard
72+388.628 1060374.702 484035.804 500 Flat DS-3 100 395 500 Ok
72+682.492 1060621.848 483875.603 1000 Flat DS-3 100 395 1000 Ok
72+837.987 1060760.514 483805.023 30000 Flat DS-3 100 395 30000 Ok
73+262.473 1061139.439 483613.7 600 Flat DS-3 100 395 600 Ok
73+800.678 1061563.955 483282.198 1000 Flat DS-3 100 395 1000 Ok
74+237.722 1061936.8 483053.929 2400 Flat DS-3 100 395 2400 Ok
74+822.733 1062415.388 482717.402 600 Flat DS-3 100 395 600 Ok
75+487.257 1063009.59 482419.462 3000 Flat DS-3 100 395 3000 Ok
75+754.316 1063239.585 482283.569 50000 Flat DS-3 100 395 50000 Ok
76+456.314 1063845.109 481928.405 50000 Flat DS-3 100 395 50000 Ok
76+780.622 1064125.72 481765.821 5000 Flat DS-3 100 395 5000 Ok
77+192.842 1064481.496 481557.618 800 Flat DS-3 100 395 800 Ok
77+394.850 1064633.03 481423.243 3000 Rolling DS-3 85 270 3000 Ok
77+643.307 1064822.997 481263.103 4000 Rolling DS-3 85 270 4000 Ok
Sub-
78+227.652 1065285.5 480905.917 180 Rolling DS-3 85 270 180
standard
Sub-
78+497.088 1065399.796 480659.706 250 Rolling DS-3 85 270 250
standard
Sub-
78+801.652 1065619.475 480447.243 220 Rolling DS-3 85 270 220
standard
79+145.910 1065950.126 480343.915 1000 Rolling DS-3 85 270 1000 Ok
79+867.768 1066605.099 480039.991 30000 Rolling DS-3 85 270 30000 Ok
Sub-
80+084.385 1066802.321 479950.399 110 Rolling DS-3 85 270 110
standard
80+530.567 1067211.226 480147.428 600 Rolling DS-3 85 270 600 Ok
80+752.893 1067428.19 480198.402 2000 Rolling DS-3 85 270 2000 Ok
80+984.052 1067652.752 480253.233 2000 Rolling DS-3 85 270 2000 Ok
81+084.216 1067749.528 480279.067 500 Rolling DS-3 85 270 500 Ok
Sub-
81+514.701 1068115.892 480507.18 150 Rolling DS-3 85 270 150
standard
Sub-
81+723.152 1068326.022 480459.58 250 Rolling DS-3 85 270 250
standard
82+331.194 1068925.784 480568.745 800 Flat DS-3 100 395 800 Ok
Sub-
82+546.177 1069140.615 480580.121 180 Flat DS-3 100 395 180
standard
82+837.947 1069387.433 480740.5 1500 Rolling DS-3 85 270 1500 Ok
Sub-
83+348.586 1069841.467 480974.455 240 Rolling DS-3 85 270 240
standard
84+507.531 1070994.296 480812.651 460 Rolling DS-3 85 270 460 Ok
85+010.835 1071440.419 480575.987 3000 Flat DS-3 100 395 3000 Ok
85+572.773 1071938.214 480315.268 550 Flat DS-3 100 395 550 Ok
86+135.201 1072501.192 480263.926 580 Flat DS-3 100 395 580 Ok
86+468.192 1072820.781 480369.057 20000 Flat DS-3 100 395 20000 Ok
Sub-
86+957.428 1073284.524 480524.925 250 Rolling DS-3 85 270 250
standard
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
87+361.108 1073659.009 480348.41 290 Rolling DS-3 85 270 290 Ok
Sub-
87+588.138 1073731.536 480117.509 75 Mountainous DS-3 70 175 75
standard
Sub-
87+762.791 1073925.079 480138.539 140 Mountainous DS-3 70 175 140
standard
Sub-
87+877.249 1074001.51 480231.309 140 Mountainous DS-3 70 175 140
standard
87+985.444 1074098.874 480280.404 300 Mountainous DS-3 70 175 300 Ok
Sub-
88+777.096 1074622.465 480876.07 74.8 Mountainous DS-3 70 175 75
standard
88+597.531 1074343.4 480280.672 330 Mountainous DS-3 70 175 330 Ok
88+738.380 1074247.791 480176.197 200 Mountainous DS-3 70 175 200 Ok
Sub-
89+025.700 1074117.106 479919.949 57 Mountainous DS-3 70 175 57
standard
89+084.798 1074367.05 480057.639 5000 Mountainous DS-3 70 175 5000 Ok
89+162.841 1074434.694 480096.568 2000 Mountainous DS-3 70 175 2000 Ok
89+388.304 1074632.733 480204.339 300 Rolling DS-3 85 270 300 Ok
89+602.151 1074844.498 480240.109 120 Urban DS-3 50 85 120 Ok
89+801.644 1074928.383 480025.022 100 Urban DS-3 50 85 100 Ok
90+004.629 1074863.473 479829.628 85 Urban DS-3 50 85 85 Ok
90+117.958 1075018.379 479794.327 140 Urban DS-3 50 85 140 Ok
90+222.864 1075121.644 479818.273 600 Urban DS-3 50 85 600 Ok
90+570.839 1075444.176 479949.415 95 Urban DS-3 50 85 95 Ok
90+975.546 1075246.841 479376.893 360 Rolling DS-3 85 270 360 Ok
Sub-
91+282.250 1075246.975 479069.075 110 Mountainous DS-3 70 175 110
standard
Sub-
91+408.620 1075090.452 479043.798 60 Mountainous DS-3 70 175 60
standard
Sub-
91+508.179 1075008.295 478986.762 80 Mountainous DS-3 70 175 80
standard
91+804.599 1075040.718 478682.835 200 Mountainous DS-3 70 175 200 Ok
Sub-
91+965.660 1074980.261 478531.437 50 Mountainous DS-3 70 175 50
standard
92+062.206 1075106.411 478505.699 800 Mountainous DS-3 70 175 800 Ok
Sub-
92+243.584 1075280.253 478453.793 78 Mountainous DS-3 70 175 78
standard
Sub-
92+396.635 1075241.982 478694.386 120 Mountainous DS-3 70 175 120
standard
Sub-
92+665.940 1075452.364 478880.082 67 Mountainous DS-3 70 175 67
standard
92+737.947 1075389.968 478579.525 200 Mountainous DS-3 70 175 200 Ok
92+999.014 1075454.396 478324.907 500 Rolling DS-3 85 270 500 Ok
93+210.515 1075458.858 478112.928 10000 Rolling DS-3 85 270 10000 Ok
93+483.308 1075465.786 477840.223 10000 Rolling DS-3 85 270 10000 Ok
Sub-
93+670.748 1075472.76 477652.912 160 Rolling DS-3 85 270 160
standard
Sub-
94+087.192 1075814.3 477397.159 150 Rolling DS-3 85 270 150
standard
Sub-
94+239.650 1075867.411 477251.056 150 Rolling DS-3 85 270 150
standard
94+423.877 1076012.334 477134.007 3000 Rolling DS-3 85 270 3000 Ok
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
94+584.769 1076138.383 477034.018 3000 Flat DS-3 100 395 3000 Ok
95+923.351 1077181.118 476194.671 20000 Flat DS-3 100 395 20000 Ok
96+048.304 1077278.942 476116.928 5000 Flat DS-3 100 395 5000 Ok
96+326.723 1077495.698 475942.189 400 Flat DS-3 100 395 400 Ok
96+802.712 1077782.235 475561.473 5000 Flat DS-3 100 395 5000 Ok
97+004.727 1077901.615 475398.505 1000 Rolling DS-3 85 270 1000 Ok
97+207.968 1078005.036 475223.452 1000 Rolling DS-3 85 270 1000 Ok
97+810.512 1078363.281 474738.859 1200 Rolling DS-3 85 270 1200 Ok
98+118.137 1078507.835 474466.945 500 Rolling DS-3 85 270 500 Ok
98+381.831 1078570.998 474210.275 10000 Rolling DS-3 85 270 10000 Ok
98+566.253 1078612.137 474030.496 600 Rolling DS-3 85 270 600 Ok
99+001.660 1078766.944 473623.382 500 Rolling DS-3 85 270 500 Ok
99+335.663 1078981.842 473365.62 2000 Rolling DS-3 85 270 2000 Ok
99+451.075 1079058.286 473279.148 400 Rolling DS-3 85 270 400 Ok
99+614.144 1079118.548 473126.082 4000 Rolling DS-3 85 270 4000 Ok
99+980.513 1079241.259 472780.861 300 Rolling DS-3 85 270 300 Ok
100+174.676 1079254.53 472586.637 10000 Rolling DS-3 85 270 10000 Ok
100+689.127 1079292.811 472073.612 220 Urban DS-3 50 85 220 Ok
100+807.345 1079369.143 471978.04 5000 Urban DS-3 50 85 5000 Ok
101+652.313 1079901.827 471322.128 5000 Urban DS-3 50 85 5000 Ok
101+693.732 1079927.617 471289.717 1000 Urban DS-3 50 85 1000 Ok
101+881.091 1080047.734 471145.927 5000 Urban DS-3 50 85 5000 Ok
101+973.686 1080106.364 471074.259 20000 Urban DS-3 50 85 20000 Ok
102+690.377 1080618.109 470446.394 650 Urban DS-3 50 85 650 Ok
103+198.146 1080806.243 469973.055 10000 Urban DS-3 50 85 10000 Ok
103+376.128 1080868.973 469806.489 7000 Urban DS-3 50 85 7000 Ok
103+968.607 1081088.352 469256.117 10000 Mountainous DS-3 70 175 10000 Ok
104+104.160 1081137.338 469129.724 10000 Mountainous DS-3 70 175 10000 Ok
104+786.748 1081389.781 468495.532 1000 Mountainous DS-3 70 175 1000 Ok
106+595.809 1081762.352 466724.816 10000 Mountainous DS-3 70 175 10000 Ok
106+834.020 1081806.765 466490.775 10000 Mountainous DS-3 70 175 10000 Ok
107+374.396 1081901.561 465958.778 800 Mountainous DS-3 70 175 800 Ok
107+465.992 1081925.929 465870.427 600 Mountainous DS-3 70 175 600 Ok
107+594.162 1081941.9 465743.104 400 Mountainous DS-3 70 175 400 Ok
107+698.794 1081975.16 465643.626 300 Mountainous DS-3 70 175 300 Ok
Sub-
107+823.450 1081976.507 465518.211 150 Mountainous DS-3 70 175 150
standard
107+957.396 1082071.182 465416.115 400 Mountainous DS-3 70 175 400 Ok
108+103.842 1082130.662 465280.929 300 Mountainous DS-3 70 175 300 Ok
Sub-
108+258.791 1082223.499 465156.505 150 Mountainous DS-3 70 175 150
standard
108+349.231 1082311.485 465125.874 600 Mountainous DS-3 70 175 600 Ok
Sub-
108+458.188 1082411.197 465081.887 160 Mountainous DS-3 70 175 160
standard
Sub-
108+692.905 1082646.042 465113.899 125 Mountainous DS-3 70 175 125
standard
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
108+962.211 1082649.57 464773.187 320 Mountainous DS-3 70 175 320 Ok
Sub-
109+650.141 1082928.731 464142.455 160 Mountainous DS-3 70 175 160
standard
110+215.327 1083516.17 464131.054 300 Rolling DS-3 85 270 300 Ok
111+314.313 1083785.917 462994.256 1500 Rolling DS-3 85 270 1500 Ok
113+115.133 1084345.769 461282.597 10000 Rolling DS-3 85 270 10000 Ok
113+385.191 1084433.156 461027.066 1000 Rolling DS-3 85 270 1000 Ok
113+517.305 1084459.055 460897.315 400 Rolling DS-3 85 270 400 Ok
113+783.025 1084435.706 460631.844 10000 Urban DS-3 50 85 10000 Ok
116+289.010 1084231.05 458134.23 30000 Mountainous DS-3 70 175 30000 Ok
116+628.037 1084206.331 457796.103 15000 Mountainous DS-3 70 175 15000 Ok
117+484.065 1084135.766 456942.988 15000 Mountainous DS-3 70 175 15000 Ok
117+712.524 1084114.985 456715.475 200 Mountainous DS-3 70 175 200 Ok
Sub-
119+696.219 1085167.537 455027.943 160 Mountainous DS-3 70 175 160
standard
120+051.570 1085508.578 454911.455 180 Mountainous DS-3 70 175 180 Ok
120+510.636 1085773.506 454531.141 210 Mountainous DS-3 70 175 210 Ok
121+077.451 1085722.876 453959.894 400 Mountainous DS-3 70 175 400 Ok
122+098.927 1085345.055 453009.898 400 Mountainous DS-3 70 175 400 Ok
Sub-
124+058.309 1084146.09 451459.153 160 Mountainous DS-3 70 175 160
standard
124+610.034 1084942.29 451395.253 240 Mountainous DS-3 70 175 240 Ok
124+865.158 1084502.996 450886.014 400 Mountainous DS-3 70 175 400 Ok
124+992.248 1084449.221 450770.07 400 Mountainous DS-3 70 175 400 Ok
125+200.032 1084388.977 450571.115 650 Mountainous DS-3 70 175 650 Ok
Sub-
125+445.763 1084271.955 450354.532 120 Mountainous DS-3 70 175 120
standard
125+623.468 1084070.519 450474.003 2000 Mountainous DS-3 70 175 2000 Ok
125+843.458 1083888.156 450597.105 200 Mountainous DS-3 70 175 200 Ok
125+986.969 1083741.358 450599.604 200 Mountainous DS-3 70 175 200 Ok
126+151.544 1083585.893 450543.15 300 Mountainous DS-3 70 175 300 Ok
Sub-
126+339.296 1083421.632 450452.008 140 Mountainous DS-3 70 175 140
standard
126+460.307 1083376.34 450335.391 240 Mountainous DS-3 70 175 240 Ok
Sub-
126+576.137 1083301.884 450245.775 140 Mountainous DS-3 70 175 140
standard
Sub-
126+722.199 1083292.126 450097.028 90 Mountainous DS-3 70 175 90
standard
Sub-
126+869.909 1083130.625 450058.394 150 Mountainous DS-3 70 175 150
standard
127+079.532 1083032.797 449862.914 200 Mountainous DS-3 70 175 200 Ok
127+220.153 1082891.475 449815.343 260 Mountainous DS-3 70 175 260 Ok
127+355.570 1082790.964 449722.119 1000 Mountainous DS-3 70 175 1000 Ok
127+525.411 1082678.747 449594.514 350 Mountainous DS-3 70 175 350 Ok
127+629.191 1082588.766 449541.014 180 Mountainous DS-3 70 175 180 Ok
Sub-
127+716.330 1082540.969 449466.315 145 Mountainous DS-3 70 175 145
standard
127+889.380 1082383.503 449389.714 500 Mountainous DS-3 70 175 500 Ok
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
128+101.774 1082249.278 449220.193 600 Mountainous DS-3 70 175 600 Ok
128+263.646 1082162.927 449083.204 180 Mountainous DS-3 70 175 180 Ok
128+537.030 1082250.865 448812.804 290 Mountainous DS-3 70 175 290 Ok
Sub-
128+731.263 1082198.458 448620.692 160 Mountainous DS-3 70 175 160
standard
128+891.974 1082052.025 448538.683 360 Mountainous DS-3 70 175 360 Ok
129+169.290 1081857.252 448340.308 260 Mountainous DS-3 70 175 260 Ok
129+327.637 1081804.241 448189.116 200 Mountainous DS-3 70 175 200 Ok
Sub-
129+464.348 1081795.52 448052.339 120 Mountainous DS-3 70 175 120
standard
Sub-
129+703.298 1081557.586 447958.878 120 Mountainous DS-3 70 175 120
standard
129+930.860 1081418.078 448178.189 325 Mountainous DS-3 70 175 325 Ok
Sub-
130+287.833 1081059.87 448268.586 140 Mountainous DS-3 70 175 140
standard
Sub-
130+433.481 1080926.088 448200.233 130 Rolling DS-3 85 270 130
standard
130+817.186 1080832.432 447820.56 640 Urban DS-3 50 85 640 Ok
131+874.641 1080420.516 446846.402 240 Mountainous DS-3 70 175 240 Ok
132+292.838 1080437.697 446426.735 800 Mountainous DS-3 70 175 800 Ok
132+479.568 1080479.928 446244.386 850 Mountainous DS-3 70 175 850 Ok
132+840.623 1080501.668 445883.646 280 Mountainous DS-3 70 175 280 Ok
133+142.802 1080390.67 445600.505 400 Mountainous DS-3 70 175 400 Ok
133+298.237 1080309.842 445467.492 400 Mountainous DS-3 70 175 400 Ok
133+375.752 1080278.007 445396.72 600 Mountainous DS-3 70 175 600 Ok
133+456.177 1080240.982 445325.316 500 Mountainous DS-3 70 175 500 Ok
133+556.008 1080206.398 445231.58 2000 Mountainous DS-3 70 175 2000 Ok
133+857.364 1080091.295 444953.061 1000 Mountainous DS-3 70 175 1000 Ok
134+231.654 1079912.705 444624.014 300 Mountainous DS-3 70 175 300 Ok
134+373.525 1079816.369 444519.352 300 Mountainous DS-3 70 175 300 Ok
Sub-
134+744.192 1079506.802 444314.829 162 Mountainous DS-3 70 175 162
standard
134+913.817 1079920.832 444155.354 300 Rolling DS-3 85 270 300 Ok
Sub-
135+026.394 1080032.782 444140.391 100 Rolling DS-3 85 270 100
standard
Sub-
135+293.782 1080220.375 443946.189 140 Rolling DS-3 85 270 140
standard
135+552.493 1080213.242 443680.561 300 Mountainous DS-3 70 175 300 Ok
135+695.437 1080260.524 443544.399 250 Mountainous DS-3 70 175 250 Ok
136+116.899 1080243.014 443122.18 600 Mountainous DS-3 70 175 600 Ok
Sub-
136+706.666 1080341.424 442540.217 120 Rolling DS-3 85 270 120
standard
137+342.063 1079982.878 442008.995 400 Rolling DS-3 85 270 400 Ok
137+497.550 1079932.525 441861.189 4000 Rolling DS-3 85 270 4000 Ok
137+842.284 1079834.13 441530.775 270 Rolling DS-3 85 270 270 Ok
Sub-
139+270.975 1080675.448 440352.729 160 Rolling DS-3 85 270 160
standard
Sub-
139+520.484 1080695.068 440101.37 260 Rolling DS-3 85 270 260
standard
PI Min. Design
Terrain Design Design Hor. Hor.
RAD. Status
Classification Sta. Speed Curve Curve
STATION EASTING NORTHING Radius Radius
Sub-
140+033.417 1080917.275 439637.66 220 Rolling DS-3 85 270 220
standard
140+656.201 1081441.074 439294.495 490 Flat DS-3 100 395 490 Ok
Sub-
142+221.309 1082133.889 437883.756 265 Rolling DS-3 85 270 265
standard
143+230.735 1083147.853 437702.765 360 Urban DS-3 50 85 360 Ok
145+150.908 1083940.486 435919.523 310 Urban DS-3 50 85 310 Ok
147+598.861 1085610.392 434128.115 10000 Urban DS-3 50 85 10000 Ok
147+808.794 1085756.601 433977.457 10000 Urban DS-3 50 85 10000 Ok
149+467.324 1086886.215 432763.076 50000 Rolling DS-3 85 270 50000 Ok
150+637.550 1087676.032 431899.582 550 Rolling DS-3 85 270 550 Ok
153+011.653 1090065.347 431728.551 800 Flat DS-3 100 395 800 Ok
157+195.616 1093625.512 429515.795 5000 Flat DS-3 100 395 5000 Ok
157+777.912 1094119.393 429207.332 600 Flat DS-3 100 395 600 Ok
162+058.998 1097106.601 426139.652 600 Urban DS-3 50 85 600 Ok
162+905.147 1097799.075 425652.774 15000 Urban DS-3 50 85 15000 Ok
163+765.734 1098504.913 425160.43 2000 Urban DS-3 50 85 2000 Ok
166+804.153 1100875.32 423259.519 3000 Urban DS-3 50 85 3000 Ok
167+719.341 1101553.945 422645.405 2500 Urban DS-3 50 85 2500 Ok
172+656.100 1105004.479 419114.698 400 Urban DS-3 50 85 400 Ok
173+006.443 1105083.229 418767.424 500 Urban DS-3 50 85 500 Ok
173+782.048 1105080.556 417991.338 360 Urban DS-3 50 85 360 Ok
175+443.231 1106509.837 417079.776 180 Urban DS-3 50 85 180 Ok
176+485.002 1107506.959 417419.857 110 Urban DS-3 50 85 110 Ok
176+757.856 1107741.055 417265.451 300 Urban DS-3 50 85 300 Ok
176+934.166 1107904.918 417199.821 140 Urban DS-3 50 85 140 Ok
177+041.277 1108010.283 417236.856 160 Urban DS-3 50 85 160 Ok
Sub-
177+131.754 1108101.3 417236.46 35 Urban DS-3 50 85 35
standard
Based on these about 32% of the curves have substandard radius based on DS-2
standard upto km 28 and DS-3 standard for the rest. Some have greatly deviated while
some have deviated with limited amount. Some adjustments have been made at
locations with frequent accident even though the scope of the project is limited.
Furthermore road safety furniture such as signs and guide structures are included in the
design. It is recommended that adjustment should be done on those locations with
deviation during future upgrading.
Two major aspects of vertical alignment are vertical curvature, which is governed by
sight distance and comfort criteria, and gradients, which are related to vehicle
performance and level of service. There are two types of vertical curves summit (or
crest) and sag (or valley) curves which are introduced at vertical grade changes. The
lengths of vertical curves are controlled by sight distance requirements. However
longer curve lengths are always recommended for better aesthetics and riding
comforts.
The selection of the most appropriate vertical alignment design was done with the
following priorities in mind:
Wherever practicable compliance with the ERAs geometric design standards.
To avoid earthworks since the scope of the project in most cases is overlay.
To avoid extension drainage structures and construction of retaining walls for the
same reason mentioned above.
2.6.1 Gradient
ERAs Geometric Design Standard recommends values for maximum grade for DS2 and
DS3 road standard based on terrain and design speed as follows:
Table 2.7: ERAs Maximum Gradient Recommendations for DS2 and DS3 Road Standards
Max. Gradient
Terrain Speed
Desirable Absolute
Flat 100 3 5
Rolling 85 4 6
Mountainous 70 6 8
Escarpment 60 6 8
Escarpment 50 6 8
ERAs geometric design manual gives minimum lengths based on type of terrains
described with respect to K values are:
Urban/
Flat Rolling Mountainous Escarpment Peri-
Urban
Speed in KPH 100 85 70 60 50
Crest Vertical Curve 105 60 31 18 10
Sag Vertical Curve 51 36 25 18 12
Urban/
Flat Rolling Mountainous Escarpment Peri-
Urban
Speed in KPH 100 85 70 60 50
Crest Vertical Curve 105 60 31 18 10
Sag Vertical Curve 51 36 25 18 12
Based on these about 18% of the grades are substandard based on desirable grade standard and 7% based on absolute
maximum gradient. About 27% of the vertical grades are substandard based on their K-values. Increment of length of vertical
curve has been made at some locations to improve K-values even though the scope of the project is limited. It is recommended
that adjustment should be done on those locations with deviation during future upgrading.
Terrain ERA
Classification c/w* sh*
Flat/Plain 7.3 3
Rolling 7.3 3
Hilly/Mountainous 7.3 0.5 2.5
Escarpment 7.3 0.5 2.5
Terrain ERA
Classification c/w* sh*
Flat/Plain 7 1.5 3++
Rolling 7 1.5 3++
Hilly/Mountainous 7 0.5 1.5
Escarpment 7 0.5 1.5
c/w* Carriage way width in meters
Sh* Single side soft shoulder width in meters
++ The actual shoulder width provided shall be
determined from an assessment of the total traffic
flow and level of non-motorized traffic for each road
section
Since the project road has 7m of carriage way and 1.5m shoulder width on each side,
the same was adopted in order to avoid major reconstruction resulting from widening
and to fulfill the overlay design principle.
Table 2.11: List of Towns with Proposed Provision of Parking Lane and Walkway
Station
Town Name
Beg. End
Curve widening is applied to horizontal curves with small radii so that the operating
conditions are compatible with those on large radii curves or straights. In accordance
with ERAs geometric design standard and design practice, widening is applied on
both sides of the curve for the full length of the fully super-elevated section and
tapered back to standard road width along the super-elevation runoff length.
Within this section since all radius of the curves are greater than 250m widening to
curvature is not required.
Normally, fill widening is applied at high fill areas for psychological comfort of drivers. It
is applied to either or both sides where required and will be added to curve widening
values, if any. The height of fills is measured vertically from edge of shoulder to toe of
foreslope.
Surface
Camber (%)
Category
2.10.2 Super-elevation
Super-elevation rate is provided as per ERAs manual. The super elevation runoff is
placed on spiral curves. The following table shows the super-elevation rates and length
of run-off used for design.
The selection of side slopes is dependent upon stability, height of fill or cut and type of
material. Cut and fill slopes that are used for design are summarized in the table below.
Height of Slope
Material Slope in Fill (H:V) Slope in Cut (H:V)
(m)
0.0 1.0 3:1 3:1
Earth or Soil 1.0 2.0 2:1 2:1
> 2.0 1.5:1 1.5:1
0.0 2.0 6:1
Black Cotton Soil -
> 2.0 4:1
0.0 2.0 0.5:1
Rock -
Over 2.0 0.25:1
Moreover for those sections with rock cut higher than 10m as well as for all sections with
cross sectional slope greater than 25% benching for 3m width is applied.
Though the safety of the road is as much as possible met by considering the
appropriate standard design of the vertical and horizontal alignment, the provision of
reflective traffic signs and guide structures helps drivers to anticipate the property of
the road ahead thereby helping maintain utmost safety of the road users. Inventory of
existing road safety furniture has been done so that to determine the extent and
location of additional furniture would be required.
Guideposts as well as guard rails will be provided, if there is no existing guide structure
or is completely damaged, according to the criteria mentioned in ERA design manual
as well as by applying recognized design practices. With this in mind guide posts
and/or guard rails are provided in high fill areas, sharp curves, approaches to
structures, etc.
Using the surveying data collected from ground survey by total station, the digital
ground model is developed after importing the raw data in the design software.
Afterwards the horizontal and vertical alignments are designed. Following these,
templates are generated every 20 meters from which earthwork and pavement
quantities are computed using end area method with the help of the software.
3.1 Introduction
This part of report deals with the problems observed during field visit to the project,
analyses result and proposed drainage solution for the Road project. The study is
initiated to identify the structural and drainage problems observed on the project and
gives possible solution. The problems observed are of different kinds like, siltation,
erosion effect, overtopping & scouring etc... Each problem needs special treatment
according to the cause which created the damage in a way which is effective and
relatively economical treatment.
The causes for each problem observed is as much as possible described to equip the
contractor with a good understanding which enables to take the remedial measures.
The purpose of this study is to carry out hydrological & hydraulic survey of bridges,
Culverts, and side ditches & other water courses to study their capacity (water mark
during field visit), scouring effects and siltation problems of these structures & propose
drainage solution for the identified problems
Almost all the structures has been inspected by the Hydrologist and the Bridge Engineer
to ascertain the following information
Information about the stream channel, i.e. boulder, flashy, well defined,
presence of pools, weeds growth and bushes in the channels has been
collected.
The terrain classification is made based on the specification, which is commonly used
by most manuals in the country, i.e. 0 - 10% for flat to rolling terrain, 10% - 20% for hilly
terrain and > 21% for mountainous terrain.
Based on the above terrain classification criteria, the project road is classified into flat,
rolling, hilly & mountainous terrains as shown in Appendix 2.
The soil type & vegetation cover of the catchments are also incorporated in Appendix
2
Climate
The project area is located on the highlands of the Ethiopian plateau, i.e. having
altitude over 2000. Therefore the project area is considered Dega. The effective
temperature is lower than 250c, which is good and most of the time comfortable.
The project area gets mean annual rainfall in the range of 918 - 1567mm, and the rainy
period is between June through September, although occasional shower is expected
in the months of March, April, May, October and November.
The mean monthly rainfall is maximum during the months of July and August i.e. 250mm
and 280mm and it is minimum during the months of November and December i.e.
8mm and 9mm respectively.
Month Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Rainfall 17.6 39.7 68.5 91.3 77.3 119.2 253.6 279.6 172.9 39.2 8.1 9.2
(mm)
For the project area, the monthly temperature is maximum during the months of March
through May, about 27.50c, and it is minimum in the months of November through
January, 4.70c.
Table 4.2: Monthly Maximum and Minimum Temperature (0C) for the Area
Month Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Max. 25.1 26.0 27.0 27.2 2709 24.4 22.3 21.3 23.1 24.4 24.7 24.4
Min. 4.7 5.5 8.7 9.4 9.7 8.9 9.1 9.3 8.7 6.5 4.7 4.7
A terrain model covering the catchment areas of interest for the road project was
established using SRTM 30 m digital elevation data, downloaded from the Consortium
for Spatial Information, CGIAR-CSI. The DEM has been used for delimitation of all
catchment areas and the drainage network.
All geo-referenced information used by the hydrologists has been assembled using
Google Earth, primarily:
In order to apply the available rainfall data for the computation of discharges, the
readily available and collected rainfall data were analyzed and processed as
discussed in the following sections.
The rainfall depth computation for the return periods of 100, 50, 25, 10, 5 years of the
respective rain gauge stations is carried out using the following relationship:
hT X avg KT *
1 in
And X Xi
n i 1
1
1
22
Xi X
n 1
Rainfall-Duration relationship
For rainfall intensity duration curve computation, rainfall data of A.A. and Fiche
Metrological Stations are used, whichever is closer to the project areas.
Using Gumbel probabilistic methods of analysis the value h and I for different return
periods, which are rainfall in mm and rainfall intensity (mm/hr), are given for different
duration as shown in tables below.
Table 4.3: Rainfall Depth for Different Duration and Different Return Period
Table 4.4: Rainfall Intensity for Different Duration and Different Return Period
Taking into account the values for the project area, the following relationships between
rainfall h (in mm) and duration T (in minutes) were determined for different return
periods:
h50 = 6.891*T0.4827
h25 = 6.3581*T0.4829
h10 = 5.6354*T0.4834
h5 = 5.0591*T0.4839
The following relationships between rainfall intensity I (in mm/hour) and duration T (in
minutes) correspond to those above indicated:
1
P( X X T )
T
Where:
P = Frequency Exceedance
T = Occurrence of design flood exceeded or equalled once (Return
period), in years
The ERA DDM is recommended different design frequency based on the road
standards. The subjected road under study is DS2 for the part upto Chancho and DS3
for the rest. Hence, the recurrence interval values which are given the table below are
used for hydraulic design of drainage structures as per recommendation of the
manual.
Rational Methods
The rational methods of estimating design flood on small watershed is based, in
concept, on the criterion that storms of uniform intensity distributed evenly over the
basin, maximum rate of runoff equal to a certain percentage of rainfall intensity occurs
when the entire basin area is contributing at the outlet. This condition met after the
elapsed time Tc, time of concentration. The equation of rational formula is function of
Catchment area, runoff coefficient and time of concentration. The equation is
expressed as:
Qd = 0.278 C Cf I A
Where:
Qd = Design Discharge m3/sec
Cf = Frequency factor
C =Runoff Coefficient
A =Drainage area (km2)
I=Rainfall Intensity for duration equal to time of concentration
This method is adopted for catchments area up to 0.5km2. The parameters which are
used in the computation of design flood using rational formula are discussed as follows.
Return Period Cf
5 1.00
10 1.00
25 1.10
Runoff
Factor Description
Coefficient
<3.5% flat 0.05
Average 3.5%-10% Flat to moderate 0.10
Cs Slope of 10%-25% 0.15
Catchment 25%-35% hilly 0.20
>35% Mountainous 0.25
Well drained soil e.g. Sand & Gravel 0.05
Fair drainage soil e.g. Sand & 0.10
Gravel with fines Poor drainage soil 0.15
Permeability e.g. Silt 0.25
Cp
of Soil Impervious soil e.g. Clay, organic 0.50
silts & clay 0.40
Water-logged black cotton soil
Rock
Dense forest / thick bush 0.05
Sparse forest /dense grass 0.10
Grass land / scrub 0.15
Cv Vegetation
Cultivation 0.20
Sparse grass land 0.25
Barren 0.30
C = 0.60 (Cs + Cp + Cv) for contoured cultivated land and
for lake, swamps and dams C=Cs + Cp + Cv
The time of concentration is the sum of sheet flow travel time, shallow
concentrated flow travel time and open channel flow travel time. Sheet flow
occurs in the upper reaches of the watershed. Such flow occurs over short
distance and at shallow depths prior to the point where topographic and
surface characteristics cause the flow to concentrate in rills and swales.
Concentrated flow is the runoff that occurs in rills and swales with depth on the
order of 0.04m to 0.10m where as depth of sheet flow is 0.02 and 0.03m or less.
Velocity in the open channels is usually determined assuming bank-full depth.
0.091 nL
0.8
Tt
P2 0.5 s 0.4
Where
Tt = travel time, hr
n =Mannings roughness coefficient (given the table below)
L = flow length, m
P2 =2-years, 24 hours rainfall, mm
S =Land slope, m/m
Surface Description n1
Smooth surfaces (concrete, asphalt, 0.011
gravel, or bare soil)
Fallow (no residue) 0.05
Cultivated soils:
Residue cover < 20% 0.06
Residue cover > 20% 0.17
Grasses:
Short grass 0.15
Dense Grasses 0.24
Range (natural) 0.13
Woods:2
Light underbrush 0.4
Dense underbrush 0.8
The n values are a composite of information compiled by Engman (1986).
When selecting n, consider cover to a height of about 0.03 m. This is the only
part of the plant cover that will obstruct sheet flow.
Source: ERA Design Drainage Manual
Travel time for shallow concentrated flow is determined from average velocity
computed in from the following expression
The above equations is based on the solution Mannings equation with the
following assumption
n =0.050 and r =0.12 for unpaved area and
n =0,025 and r =0.06 for paved area
L
Tt
V
Where
Tt =travel time of the sheet flow, second
L = flow length, meter
V = average velocity in m/s computed by the above
equation
When cross sectional information of the open channel (stream cross section
parameter for the entire reach) is acquired, the average velocity of the open
channel flow can be calculated using Mannings equation.
1 2 / 3 1/ 2
V r s
n
Where
V = Average velocity, m/s
r =Hydraulic radius, m (equal to A/Pw)
A =Cross section area of the flow, m2
Pw =Wetted perimeter, m
S =Slope of the hydraulic grade line, m/m
n =Mannings roughness coefficient
The travel time can be computed for each stream segment from average
velocity of flow computed using the above expression and reach length.
As it is known, the cross section of the stream varies along reach for large
catchments area. Acquiring the cross sectional information of the stream along
entire length is difficult (it varies). But Kirpichs equation for time of concentration
computation in the open channel depends only on the stream length and
stream slope. These parameters can be easily determined on the topographic
map. Hence, Kirpichs equation was used for time of computation in open
channel with caution for large catchments (long stream length) in order not to
under estimate the time of concentration. Depending on the slope of the river,
the time of concentration is computed on reach bases
i n 0.77
0.00032 Li
Tc 0.385
i 1 Si
Where:
Tc =Time of concentration, in hr
Li =Length of stream segment, in m
Si = Slope equal to H/L, where H is the difference in
elevation between in the segment (reach), in m
For small catchments areas, where the maximum elevation difference of the
watershed could not be determined on the available map scale. The velocity
method is adopted. It is based on the concept of travel time (Tv) for a flow
segment is a function of length of flow (L) and the velocity. The following
equations were used:
L
TC
60 * V
Where:
TC = Time of concentration [minutes]
L = Distance from remote point to the point of crossing [m]
V = Average velocity [m/sec] (Table below)
Table 4.10: Average velocity for ground type and terrain condition
The result of hydrological design /peak flood computation using rational formula is
presented in Appendix 2.
The US Soil Conservation Service has developed this method, which is applicable for
major catchments. The inputs for peak discharge estimation includes variables reflect
the size of the contributing areas, the amount of rainfall, the potential watershed
storage, and the time-area distribution of the watershed.
The SCS runoff equation is a method of estimating direct runoff from 24-hour or 1-day
storm rainfall. The equation is:
PC
P 0.2 S 2
P 0.8 S
Where:
PC=direct runoff (mm)
P=design rainfall (mm)
S =potential infiltration or potential maximum soil water retention
The potential maximum soil water retention, S, is related to hydrologic soil properties,
land cover and management conditions as well as, the soil moisture status of the
catchments prior to rainfall event and expressed by a dimensionless response index
termed the catchments curve number (CN).
25400
S 254
CN
The CN number is selected according to the soil, moisture and the land cover of the
watershed area.
The runoff conditions related to soil and cover have been determined for each
individual catchment area.
The soils in the project area generally belong to Hydrologic Soil Group B, soils having
a moderately low runoff potential due to moderate infiltration rates. These soils
primarily consist of moderately deep to deep, moderately well to well drained soils
with moderately fine to moderately coarse textures.
Vegetation and land use characteristics have been analyzed in accordance with the
classification indicated in the Land Use Map of Ethiopia. Delimitation of the land use
units has been performed by use of satellite imagery. For a given catchment, the area
has generally been fractioned into homogeneous sub areas based on the following
combinations of soil group and land use:
The curve numbers/ runoff coefficient depends on the soil type as well as land use of
the watershed as shown in table below
Table 4.11: SCS Curve Number (CN) for relevant combinations of soil type and
land use
Peak Discharge
The SCS Unit Hydrograph method peak rate of flow is computed using the following
equation:
0.2083 A PC 0.2083 A PC
Q
0.5 TC 0.6 TC
0.5
tp
Where
tp = time to peak (hrs) = 0.5 TC0.5 + 0.6 TC
Qp = peak discharge (m3/sec)
A = catchments area (km2)
PC = storm flow depth or direct runoff (mm)
TC = concentration time (hrs)
The discharge computation of the crossing structures using SCS method is given in
Appendix 3.
3.8 Hydraulics
3.8.1 General
The amount of runoff expected from the drainage area that crosses the route is
determined in the previous section. The next step is to design appropriate drainage
facilities that adequate, economical and sustainable drainage system that suite the
site peculiar conditions. This section presents hydraulic design and selection of
appropriate drainage structure type.
The section of the project road feature generally rolling & mountainous topography
which in turn cause a concentrated flow as stream or river in most of its sections as
described in Appendix 2.
The discharges for a few crossings must have been underestimated in the design of
these structures as the downstream and upstream sides of the structures scoured
significantly. Thus, a few existing culvert sizes are replaced as shown in Appendix 7.
Generally for the condition surveys of the existing structures has been incorporated
in the report & the detailed structures schedules are presented in Appendix 7.
Measure Identified Existing Drainage problems during the study for the project road
Few of the major identified drainage problems during our study for the section road
are the following
a. Siltation
b. Over flooding
c. Scouring & Erosion
Siltation
Deposition tends to occur as the velocity of sediment transporting streams
decreases. Excessive quantities of sediment cause structure under capacity &
finally over toping
In this study section, the general soil type is clay & silt type & the land use is farming
with flat topography & consequently siltation of the structures is one of the major
drainage problems
The identified siltation problems for the section during field visit with the assumed silt
percentage is indicated in Appendix 7 of the report.
The general proposed siltation remedial measure is cleaning before every rainy
season begins and supervising at least twice during the duration of the rainy
seasons
Over Flooding
From observed water marks during site visit, analyses result & local consultation
Overtopping during rainy season at a few crossings were occurring as shown in
Appendix 7.
Big Catchment of these crossings observed on the 1:50,000 scale topo map, but
most of the outlets of these crossings are highly scoured due to constriction of flow.
From the observed over flooding; Rise of Embankment height & Provision of
adequate size opening structures could be the drainage solution
Detail hydrological & hydraulic analyses has been done as shown in Appendix 2
though Appendix 7 of this report & appropriate crossing structures proposed
following the procedures stipulated in ERA Drainage Design Manual (2002)
Special protection is required in the d/s of a few crossings as deep erosion formed
because mainly erodible nature of the soil & absence of the protection outlet
system as shown in Appendix 7. The proposed protection will either be fill of big size
boulders at spacing to accumulate silt and protect further erosion or spoil material
to the formed gully, or a combination of both depending on the extent and
severity of the erosion. Areas of specific interest of crossings at the outlets where
extensive erosion has taken place and proposed mitigation measure are given in
Appendix 7.
Generally Identified Drainage problems of the study section & proposed drainage
solutions for maintenance purpose are presented in Appendix 7
The headwater is not allowed to be higher than the low point in the road grade
The minimum size of pipe culvert dimension would be 36 (910mm) taking
considering siltation rate and easiness for maintenance and clearing.
The slope of the culverts is maintained to be the same as the natural ground
surface
Culverts
A complete theoretical analysis of the hydraulics of a particular culvert is time-
consuming and complex. However, under most conditions, a simplified procedure
can be used to determine the type of flow control and corresponding headwater
elevation that exist at a culvert for the chosen design flow for the analysis and
design. The designs of culverts are carried out based on the procedures stipulated
on the ERADDM. Opening area culverts were designed hydraulically to pass the
predetermined discharge safely taking in to account the above design
consideration.
Culverts are operating under inlet and outlet control. For culvert with inlet control,
the headwater (HW) design charts (monograph 7.1, 7.2 and 7.6 from ERADDM)
were used. For culvert with outlet control, the following expression were used
19.6n2 L v 2
H = Hv+He+Hf = 1 ke
R1.33 2 g
Where
v2
Hv = Velocity head (exist loss) =
2g
19.6n 2 L v 2
Hf = friction loss =
R1.33 2 g
v2
He = Entrance loss = K e
2g
Ke = entrance loss coefficient
n = Mannings friction coefficient
L = Length of the barrel (m)
R = Hydraulic radius (m)
V = Mean velocity of flow in the culvert barrel, m/s
The results of the computations of culverts are given in Appendix 4 & culver
schedules are presented table as Appendix 7.
Bridges
The span and height of the streams/Rivers is determined based on the stream/River
parameters. Constriction of flow width is avoided for crossings having erodible bed
material
A discharge rating curve was developed based on the river geometry, roughness
coefficient and slope of riverbed for defined cross sections. After developing a
Then the backwater for different opening area (bridge span) was determined using
expression below. The span with backwater less than the maximum allowed (0.5m)
were taken at least minimum bridge span from hydraulic point of view. And normal
depth obtained from rating curve is considered as high water mark. The following
expression is used for backwater computation if there is constriction width of the
channel
Vn 2
2 A 2 A 2 V 2
h1 * K * 1 n 2 n 2 n 2
2g A4 A1 2 g
Where
h1* = total backwater, m
K* = total backwater coefficient
Scour
The foundation of all rivers at the crossings is rock, in which it shows scouring is not
serious problem. To avoid localized scouring in the joint of the rock constriction of
channel is avoided.
Ditches
Ditches are provided to intercept and dispose runoff safely as fast as possible
without damaging/eroding the road section. In this project trapezoidal type in rural
areas & paved rectangular type in urban sections are proposed on the cut
sections of the road to intercept the longitudinal flow of the road based on the
amount of flow.
The Manning formula was used for ditch cross section area design
2 1
1
QT A R 3 S 2 A V
n
Where:
QT=Capacity of ditch for 10 years return period flood [m3/sec]
A =Cross sectional area of the ditch [m2]
V = Velocity of flow [m/sec]
R = Hydraulic radius A/P where P is the wetted perimeter in m and
A is the area in m2
S=Average longitudinal slope [m/m]
Based on the slope and flow velocity, ditch lining may be required in some
sections. However, the maximum length of the ditch shall be checked for design
discharge in order not flow velocity should not exceed the maximum permissible
velocity. If the velocity exceeds, relief structures shall be provided. Limiting values
for the velocity of flow in the ditch to prevent scour, together with the
corresponding roughness coefficients for the different types of ditch materials,
which are normally encountered are given in the Table below:
The detail ditch schedules are incorporated in Appendix 6 & Appendix 7 of this report.
4 STRUCTURAL DESIGN
4.1 General
This section of Hydrological, Hydraulics and Structures Report describes the activities
performed in the structural design process of major and minor drainage structures as
well as retaining walls and miscellaneous items. Findings of the Consultant during the
condition survey of existing drainage structures and site selection of new bridges are
also summarized in the report. The design standards used, decisions made based on
the findings of detail field investigations of both major and minor drainage structures;
geometrical parameters of the existing structures as well as structural computations
made through the detail design process are also incorporated in the report. Design
calculation sheets of structural components are attached as Appendix.
Based on the design stage of the project, several site visits were made to collect
relevant data to be used in the design of drainage structures either for replacement
due to inadequacy, widening around town section and identification of major defects
on all drainage structure for rehabilitation works along the route under consideration.
For data submission for the construction crews of Era Road Construction Corporation,
the project was separated into three lots during design stage services. Lot-1 is from
Addis Chancho (0+000-28+700), Lot-2 from Chancho-Fitchie (i.e 28+700-102+000) and
Lot-3 from Fitchie-Gewatsion (i.e. 102+000-177+149.67).
During the inception stage of the design, a sort of detailed structural reconnaissance
survey was conducted, to gather information regarding general condition, major
observed defects of existing structures, total number and types of existing drainage
structures so as to appreciate the workload concerning design of drainage structures
along existing and new alignment of the subject road on this overlay project.
Other site visits were also conducted to collect data regarding the detail condition of
drainage structures and to select new crossing sites for those bridges and culverts,
which were found to be replaced due to inadequacy, sever damage and other
reasons. The detail condition survey of bridges and other drainage structures was
important in that it was possible to critically evaluate existing structures so as to decide
whether these structures shall be incorporated in the design of the new overlay road or
shall be replaced by new ones due to various reasons.
The findings of the Consultant during the detail condition survey and site selection
stages of design are described in the following sections of the report.
Accordingly, the condition of minor and major drainage structures was investigated to
decide on the type and extent of maintenance measures that shall be taken or the
way they are to be replaced by new ones, if replacing these structures is justifiable
based on objective realities like hydraulic insufficiency, observed sever damages and
realignment of the road due to geometric refinement of the existing road.
During the condition survey, the Consultant observed the condition of inlet and outlet
channels, paved waterways, end walls, barrels and ancillary components of minor
drainage structures. The condition of banks and beds of rivers, substructures like
Superstructure, abutments, wing walls, piers, bearings, joints, railings and other
components of major drainage structure were also observed and their conditions are
recorded so as to make use of these records in the decision making process during the
design adjustment of these drainage structures.
It is not only the condition of existing drainage structures but their dimensions are also
important factors that shall be considered to check their suitability to be incorporated
in the new design of the road. Therefore, the Consultant had measured every
dimension like, their span length, height or diameter, total width, all dimensions of end
structures etc.
The detail conditions of major and minor drainage structures available along the
subject road are as shown in the next section.
Therefore, with respect to drainage the alignment requires minor and medium
size drainage structures if exiting structures need to be replaced or enlarged by
either realignment of its approach geometry or by inadequacy confirmed by
hydrology/hydraulics findings or found during detailed site reconnaissance
period.
During the site visit period, all existing drainage structures were assessed
physically. The conditions are surveyed and general recommendations are
given though the recommendation will be verified based on detailed
hydrological study and hydraulic analysis.
As discussed above the route Addis Ababa Goha Tsion covers about length of
177.150Km. There are about 374 cross drainage structures were identified on this
route. Fourteen bridge, Two hundred Forty Nine RC slab culverts, Ninety Five
reinforced concrete box culvert, Three corrugated steel pipe, Six masonry Arch
culvert and four reinforced concrete pipes.
After fifteen days detail structural and hydraulic investigation along the project
route, the site visit team identified the following general problem on the existing
374 cross drainage structures along the subject road segments.
The condition of the existing structures are summarized and presented in the
table below at this stage based the initial field visit for the inception report
preparation and based on the hydrological study and hydraulic analysis.
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
proposed opening
Left side Paved trapezoidal
16 468031 1006048 L to R BC 2 0.5 0.5
ditch in the section required
Left side Paved trapezoidal
17 467949 1006243 L to R CSP 2 0.61 ditch required up to this
location
Channel about 60% silt
18 468971 1006973 L to R BC 2 0.5 0.5
clearing required
Channel about 10% silt
19 469702 1007389 L to R BC 2 0.5 0.5
clearing required
Inlet should be with type B
end wall to properly direct
20 470013 1007520 L to R BC 1 0.5 0.5
the longitudinal flow to the
opening
Channel about 10% silt
21 470464 1007866 L to R BC 2 0.6 0.6
clearing required
22 470956 1008169 L to R BC 2 0.6 0.6 Good Condition
Inlet should be with type B
23 471947 1009244 L to R BC 1 0.6 0.6 end wall & culvert about
50%silted,clearing required
Inlet should be with type B
24 472471 1009255 L to R BC 2 0.6 0.6 end wall & culvert
100%silted,clearing required
Outlet scour protection with
25 472630 1009372 L to R SC 1 1.5 1.5 boulders required (about
50m3 packed fill of boulder)
Channel about 70% silt
26 472824 1009626 L to R AC 1 2 1.2
clearing required
27 472969 1009907 L to R AC 1 1.2 1.2 Good Condition
Channel about 10% silt
28 473001 1010019 L to R BC 1 0.6 0.6
clearing required
Channel about 10% silt
29 472945 1010311 L to R BC 1 0.6 0.6
clearing required
Channel about 10% silt
30 472898 1010421 L to R BC 1 0.6 0.6
clearing required
Left side 10m length & 24"
31 472855 1010519 L to R BC 1 0.6 0.6 dia. crossing pipe required
for the existing junction road
Channel about 10% silt
32 472888 1011773 L to R SC 2 1.5 1
clearing required
33 472912 1012342 L to R AC 3 1.1 1.8 Good Condition
Outlet channel blocked by
masonry fence, opening the
34 472921 1012471 L to R AC 1 2.1 1
fence with the channel size
required
Outlet channel blocked by
35 472922 1012499 L to R BC 2 0.6 0.6 fence, opening the fence
with the channel size
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
required
outlet about 20m length
36 472927 1012567 L to R SC 1 1 0.8
channelization required
Channel about 10% silt
37 472971 1013371 L to R AC 1 1.5 1
clearing required
outlet about 50m length
38 473065 1013685 L to R BC 1 0.6 0.6
channel excavation required
39 473179 1013994 R to L Bridge 1 6 3 Main Channel
U/s about 50m length and
6m width paved channel
40 473187 1014022 R to L Bridge 1 10 3 training work to this crossing
required from the main
channel
Channel about 10% silt
41 473256 1014239 R to L SC 2 3 1.6
clearing required
Both side Longitudinal drain
42 473466 1015291 R to L Bridge 1 9 3 inside Sululta required up to
this location
Outlet scour protection with
concrete paved waterway
43 473342 1015838 R to L BC 1 0.6 0.6
of minimum 4m length
required
44 473565 1016266 R to L BC 1 0.6 0.6 Good Condition
45 473548 1016579 R to L AC 1 3 3 Good Condition
Overtopping observed from
46 473533 1016816 R to L SC 1 5 3 local consultation and
Analyses result
47 473393 1017074 R to L BC 2 0.6 0.6 Good Condition
Channel about 10% silt
48 473355 1017139 R to L SC 1 1 1.1
clearing required
Channel about 10% silt
49 473287 1017258 R to L SC 1 1.9 1.5
clearing required
50 473181 1017449 R to L BC 2 0.6 0.6 Good Condition
Channel about 6m length for
51 473073 1017642 R to L SC 1 1.5 1.1 the scoured section properly
paving required
BC & Inlet side 3m length concrete
52 473000 1018340 R to L (2x1)SC+2(0.6x0.6)BC
SC paved waterway required
Inlet side 3m length concrete
53 472997 1018371 R to L BC 3 0.6 0.6
paved waterway required
Channel about 10% silt
54 472992 1018505 R to L SC 1 3 1
clearing required
55 472978 1018675 R to L SC 1 2.1 1.5 Good Condition
Inlet side existing catch pit
height should be lowered by
56 472907 1019880 R to L SC 1 2 1 atleast 0.5m as it is blocking
the natural flow & outlet
channel excavation for
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
constriction observed
Outlet about 30m length
120 482773 1038511 R to L BC 1 0.6 0.6
channelization required
121 482903 1038575 R to L SC 1 1.5 2.5 Good Condition
122 482898 1038860 R to L BC 1 0.6 0.6 Good Condition
Outlet scour protection with
123 482877 1039186 R to L BC 1 0.6 0.6 rock riprap required (about
12m2 packed fill of boulder)
124 482942 1039262 R to L SC 1 1 1 Good Condition
Outlet about 20m length
125 483081 1039640 L to R BC 1 0.6 0.6
channelization required
126 482904 1040095 R to L SC 1 1 1.2 Good Condition
127 482844 1040464 R to L SC 1 0.8 1.2 Good Condition
128 482893 1040841 R to L SC 1 1 1.2 Good Condition
129 483399 1041190 R to L SC 1 3 3.5 Good Condition
130 483804 1041509 R to L SC 1 4 7 Good Condition
Outlet scour protection with
131 484235 1041757 R to L SC 1 0.8 1.2
rock riprap required
Outlet about 30m length
132 484199 1042143 R to L BC 1 0.6 0.6
channelization required
Outlet about 30m length
133 484220 1042165 R to L BC 1 0.6 0.6
channelization required
Inlet side existing catch pit
134 484491 1042126 R to L SC 1 3 2 height should be lowered by
at least 0.5m
Inlet side channel shaping
135 484593 1042142 R to L Bridge 1 7 7
required
Inlet side existing catch pit
136 484562 1042407 R to L SC 1 1.2 1 height should be lowered by
at least 0.5m
Outlet about 50m length
137 484785 1042658 R to L SC 1 0.8 0.8
channelization required
138 485039 1042859 R to L SC 1 1 1.5 Good Condition
139 485122 1043027 R to L SC 1 0.9 0.8 Good Condition
Inlet side existing catch pit
140 485180 1043516 R to L SC 1 4 1.5 height should be lowered by
at least 0.5m
Inlet side existing catch pit
141 485252 1043668 R to L BC 1 0.6 0.6 height should be lowered by
at least 0.5m
Inlet side existing catch pit
height should be lowered by
142 485640 1044382 L to R SC 1 1 0.8 at least 0.5m & outlet
channel excavation of about
30m length required
143 486160 1044845 L to R SC 1 1.2 1 Good Condition
144 486243 1044969 R to L Bridge 2 7 5 Good Condition
145 486555 1045374 L to R SC 1 1.5 1 Channel about 10% silt
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
clearing required
146 486555 1045643 L to R SC 1 1 0.8 Good Condition
Duber River Crossing
Structure replaced due to
147 486762 1046481 R to L Bridge 2 18 8
structural failure, refer new
size
148 486583 1047462 R to L CSP 1 1.06 Excellent existing drop height
149 486393 1047950 R to L CSP 1 1.06 Good Condition
Outlet about 20m length
150 486389 1048075 R to L BC 1 0.6 0.6
channelization required
151 486259 1048438 L to R SC 1 2 1 Good Condition
152 486179 1049328 R to L BC 2 0.6 0.6 Good Condition
153 486147 1049645 R to L SC 1 2 1 Good Condition
154 486093 1051692 L to R SC 1 2 1 Good Condition
Outlet about 10m length
155 485949 1053100 L to R BC 1 0.6 0.6
channelization required
Culvert about 20% silted,
clearing required. Out let
156 485960 1053307 L to R BC 1 0.6 0.6
about 10m length channel
excavation required
157 485942 1053559 L to R BC 1 0.6 0.6 Good Condition
158 485933 1054341 L to R BC 1 0.6 0.6 Good Condition
Both side proper paved
159 485928 1055131 R to L BC 1 0.6 0.6 Longitudinal drain inside
Muke Turi town required
160 485805 1055706 R to L SC 1 0.8 0.8 Good Condition
161 485752 1055842 R to L SC 1 0.8 0.8 Good Condition
Both side proper paved
Longitudinal drain inside
162 485538 1056438 R to L SC 1 2 1.5
Muke Turi town required up
to this crossing
Culvert about 20% silted,
clearing required. Out let
163 485427 1056798 R to L SC 1 2 1
about 10m length channel
excavation required
Culvert about 20% silted,
clearing required. Out let
164 485388 1056892 R to L SC 1 2 1
about 10m length channel
excavation required
165 485377 1057041 R to L SC 4 2 1.5 Good Condition
Culvert about 20% silted,
clearing required. Out let
166 485360 1057079 R to L SC 1 2 1
about 10m length channel
excavation required
Culvert about 20% silted,
clearing required. Out let
167 484951 1058447 R to L SC 1 2 1
about 10m length channel
excavation required
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
excavation required
Culvert about 20% silted,
clearing required. Out let
184 480375 1071842 R to L SC 1 1.5 1
about 50m length channel
excavation required
Culvert about 20% silted,
clearing required. Out let
185 480448 1073478 R to L SC 1 1.4 1
about 20m length channel
excavation required
Culvert about 10% silted,
clearing required. Out let
186 480409 1073560 R to L SC 1 1 0.8
about 20m length channel
excavation required
187 480267 1074049 R to L BC 1 0.6 0.6 Outlet Bush clearing required
188 480190 1074246 L to R SC 1 1.5 1
Inlet side existing catch pit
height should be lowered by
at least 0.5m & channel
189 480098 1074428 R to L SC 1 1.5 1 shaping with a length of
about 10m paved ditch
required. Inlet side type B
wall required
Culvert about 10% silted,
clearing required. Out let
190 480185 1074581 R to L SC 1 2 1
about 15m length channel
excavation required
191 479815 1074958 R to L BC 1 0.6 0.6 Inlet side type B wall required
Out let about 10m length
192 479666 1075339 L to R BC 1 0.6 0.6
channel excavation required
Inlet, Goha Tsion side about
10m length type B wall
193 479409 1075250 L to R SC 1 2 1
required to guide the
distributed flow
Demolish inlet catch pit &
replace with Type B wall. Inlet
194 479151 1075240 L to R SC 1 2 1 side channel shaping with
about 5m length paved
ditch required
195 478988 1075071 L to R Bridge 3(8x5)+2(5x5) Good Condition
Demolish inlet catch pit &
replace with Type B wall. Inlet
196 478723 1075041 R to L SC 1 2 1 side channel shaping with
about 5m length paved
ditch required
197 478479 1075208 L to R SC 1 2 1 Good Condition
Out let about 10m length
198 478639 1075259 L to R SC 1 2 1
channel excavation required
199 477879 1075472 R to L SC 1 1 0.8 Culvert about 10% silted,
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
section
Both side Right approach
ditch should be paved in the
298 440580 1080525 R to L BC 1 0.6 0.6 section &outlet about 50m
length channelization
required
Both side Right approach
299 440526 1080566 R to L SC 1 1.5 1 ditch should be paved in the
section
Culvert about 10% silted,
300 439424 1081256 R to L SC 1 2 1
clearing required.
Inlet & Outlet Bush clearing
301 439202 1081492 R to L SC 1 2 1
required
302 438838 1081675 R to L SC 1 2 1 Good Condition
Inlet & Outlet Bush clearing
303 438317 1081927 L to R SC 1 2 1
required
Inlet & Outlet Bush clearing
304 438179 1081978 L to R SC 1 1.2 1
required
305 438027 1082049 L to R SC 1 2 1 Good Condition
Culvert 10% silted, clearing
required. Out let about 20m
306 437839 1082327 L to R SC 1 1 0.8
length channel excavation
required
Culvert 10% silted, clearing
required. Out let about 20m
307 437812 1082497 L to R SC 1 2 1
length channel excavation
required
Both side proper paved
Longitudinal drain inside
308 437514 1083220 L to R BC 1 0.6 0.6
Gebreguracha town
required from this location
Culvert 10% silted, clearing
309 437166 1083373 L to R SC 1 2 1
required.
310 436963 1083464 L to R BC 1 0.6 0.6 structure is inadequate
Proper town section both
311 436652 1083604 L to R SC 1 1.5 1
side ditch required
Proper town section both
312 436442 1083700 L to R SC 1 1.5 1
side ditch required
Proper town section both
313 436314 1083756 L to R BC 1 0.6 0.6
side ditch required
Proper town section both
314 436210 1083799 L to R BC 1 0.6 0.6
side ditch required
Proper town section both
315 435952 1083914 L to R SC 1 2 1
side ditch required
316 435412 1084429 R to L Bridge 1 8 3 Good Condition
Culvert 10% silted, clearing
317 435004 1084803 R to L SC 1 1 1
required.
318 434557 1085223 R to L SC 1 2 1 Culvert 10% silted, clearing
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Northing
Flow Dir.
Easting
Height, m
Width, m
Other Recommendations
No Cell
Type
based on Field Inspection
Damage Description
After conducting detailed components of this bridge, the site visit crew
identified that major cracks on the center of both RC deck girder including on
the central RC railings. Concrete peel off and reinforcement bar exposure is
observed on most concrete pavement surface of this bridges. Major crack were
also observed on reinforced concrete railings located at the center of both
spans. Further damage is also observed on RC railing due to traffic accident.
More over very loud noise of girder were heard while traffic bypass on top of this
Bridges if anybody stands either on pavement surface or around the channel of
this bridge.
Moreover the bridge superstructure on both span is tilted towards the channel
due to excessive deflection of superstructure. This deflection might be
happened either camber was not be made on top of girder soffit form work for
dead load deflection while it is constructed by ERA or designed cross-sectional
dimension were not respected during construction period.
Consultant Recommendation
From visual observation the site visit crew recommends to replace this bridge by
new RC bridge at upstream side of the existing bridge. The new bridge is
recommended to be constructed on realigned section in order not to create
any traffic hindrance during construction time of the new bridge.
Fig-1 Side View of Dubber river bridge Fig-2 Plan Viw of Dubber Bridge
Fig-3 Observed Cracks on the center of both span RC deck girder railings
After detailed hydrological investigation the following hydraulic findings were made.
Around fifteen minor drainage structures are recommended to be replaced by wider
openings and nine structures is proposed to be enlarged by provision of additional
openings either Addis or Gewatsion side approach road. Dubber bridge is
recommended to be replaced considering observed sever damages observed due to
execeve deflection of most of its structural components. Some of the existing structure
is replaced due to minor realignment of the road in order to satisfy the current ERA
geometric design requirements for the subject road.
4.5 New Crossing Site Selection and Description (For New Bridges)
There is only one new bridge, one bridge widened by additional RC box opening and
more than Twenty Eight Culvert designed along the Addis Ababa Goha Tsion road.
These bridges are found at km 57+734.20 and at km 29+900. New Reinforced Concrete
Box Girder bridge at km 57.7342 is designed on realigned section due to sever structural
damages observed on most of its superstructure components. Additional openings of
4*3 were recommended on existing RC slab bridge at km29.90 due to inadequacy
reported by the local people and confirmation obtained from hydraulic findings during
conducting detailed hydraulically investigation.
The span width of the new bridges is determined at river hydraulics computations stage
by the hydrologist. After the hydrologist determined the design high water mark level
the structural engineer had also checked the sufficiency of the recommended span.
Accordingly some adjustments are made on the span of the bridge, considering other
factors like geometrical requirements.
This is done during the preliminary layout and general plan and elevation preparation
process. It was checked that no flow obstruction is introduced which affects the natural
flow of rivers and causes turbulence as well as suction effect at downstream channels.
Accordingly the span width of the bridge was decided as shown on the general plan
and elevation drawings. For bridge at km57.734, 30.00m reinforced concrete deck
girder is designed while 4.00m by 3.00 RC Box culvert is designed for the second one as
per the hydrologist recommendation.
2002 ERAs bridge design manual is adopted along with AASHTO LRFD bridge design
specification, 1998, for the structural design of bridges found along the subject route.
There is a need of using larger spans bridge for which no standard superstructure
is available.
The yield strength of reinforcement steel used in designing of these standard
superstructures is 500Mpa, which is not available in the country. Therefore, the
Consultant has redesigned the superstructures of all the bridges using the design
properties of the available construction materials.
The 2011 revised ERAs Standard drawings of minor drainage structures including box
and slab culverts are used with some modifications.
Dubber bridge is designed with single span 30.00m Reinforced Concrete Box Girder
superstructures supported on class B masonry abutments and wing walls. The followings
are some of the factors considered during the detail design of substructure and
superstructure of these bridges.
Types of Superstructure
One 30.00m clear span Reinforced Concrete Deck Girder superstructures is
designed. The RC Box Girder superstructures of the bridges are composed of
three reinforced concrete box openings spaced at 2.80m center to center of
girders web having 0.25m web thickness, 0.22m and 0.20m thickness of top and
bottom slabs respectively.
Loading
HL-93 live load is used combined with the dead load of bridge components as
per the recommended load combination of ERA bridge design manual. HL-93
loading is a combination of truck and lane load or tandem axle and lane load
and the design is performed taking the maximum effect of these loads
combined with that of the dead load multiplied by the corresponding load
factors. (Please refer to the structural computation sheets attached as Appendix
in this report).
HL-93 live load is a combination of Design Truck load or Design Tandem load
and Design Lane load.
Design track load is applied as per article 3.8.3 of ERA Bridge Design Manual.
Accordingly three axles of the design truck the first of which is 35KN and the 2nd
and the rear axles of 145KN are applied at the specified axle spacing. A total of
32.5 Ton load is used as design truckload on superstructures of bridges.
In addition to the truck load a design lane load of 9.3KN/m uniformly distributed
in the longitudinal direction is applied on each traffic lane of bridges. It is the
combined effect of Truck and Lane load or Tandem axle and lane load
whichever is greater that is taken for design of bridge components.
Tandem axle loads consists of a pair of 110KN axles spaced at 1.2m intervals. The
total load of tandem axle loads is far more less than that of design truckload.
However the axle spacing of tandem axle loads is very small that it results in
higher internal stresses on some bridge components.
Material Properties
A) Reinforcement steel
The steel industries available in the country produce grade 60-reinforcement
steel for diameter of bar equal to and greater than 20mm, and grade 40 steel
for those less than 20mm diameter. The minimum yield strength of grade 60
reinforcement steel is 413Mpa, while that of grade 40 is 276Mpa. These and other
strength parameters are used in the design of the superstructures of the bridges.
B) Concrete
Design parameters of C-30 concrete are used in the structural computations of
superstructure of the bridges. These strength parameters are specified on design
drawings and technical specifications attached in the final design documents of
the project.
Software Used
A software called STAAD 2004 (Structural analysis and design) is used to
compute maximum bending moment and shear forces of structurally
indeterminate members. The software is also used in the computation of
maximum deflection of girders.
Design Philosophy
LRFD (Load and resistance factor design) method is strictly followed in the design
of the superstructure of the bridges. The appropriate load and resistance factors
are used for each and every load combination case as per article 3.3 and 9.6.3
of ERA bridge design manual.
Types of Substructures
No geotechnical investigation or DCP were conducted on Dubber bridge
foundation. Only for the draft bridge design, we use around 3.50kg/cm2
Allowable Bearing capacity of at both abutment locations for physical
observation.
The height of abutments of the bridge is within applicable limit for masonry
structures. Masonry structures are considered to be economical and feasible for
heights up to 9 to 11m. Therefore the substructures of the bridge are designed to
be composed of masonry abutments and wing walls and Class B masonry
piers. It is optional to use plain concrete leveling course under all substructures,
which shall be decided after excavation of foundation materials. However
reinforced concrete footings are designed for substructures of bridges as
required.
I would like to inform ERA that the substructure type and foundation size are
designed on Dubber river bridge is made only for completeness of the draft
hydrology/hydraulics report and it is subjected to change in the final report after
getting exact allowable bearing capacity of both abutment foundation from
the results of geotechnical investigation findings.
Loading
Substructure components are designed for maximum reactions of dead and live
loads of superstructures, surcharge load, their own dead loads and earth
pressure loads. The masonry abutments and wing walls are designed as gravity
retaining structures under the action of the above indicated load cases.
Design Philosophy
The substructures are designed as gravity retaining walls to resist overturning,
sliding and bearing failures due to their own weight and loads imposed on them.
Since the ultimate bearing capacity of foundation materials is practically
unknown, allowable bearing capacity of foundation material is checked for the
above load effects based on working stress design philosophy.
Material properties
A) Reinforcement steel
The steel industries available in the country produce grade 60-reinforcement
steel for diameter of bar equal to and greater than 20mm, and grade 40 steel
for those less than 20mm diameter. The minimum yield strength of grade 60
reinforcement steel is 413Mpa, while that of grade 40 is 276Mpa. These and other
strength parameters are used in the design of the substructures of the bridges.
B) Concrete
Design parameters of C-25 & C-30 concrete are used in the structural
computations of substructure of the bridge as required. These strength
parameters are specified on design drawings and technical specifications to be
attained during construction stage.
C) Stone Masonry
The unit weight of stone masonry used in the design of substructure components
is taken from table 3-4 of ERA bridge design manual.
As per ERA's Standard Specification cement mortared stone masonry walls shall
be constructed with mortar of 6:1 cement sand ratio. However the past
experience of masonry construction for bridges in the country was using sand
cement ratio of 2:1. In the opinion of the consultant it is not reasonable to make
such a big change of material quality without improving the workmanship of
construction activity in the country. Therefore sand cement ratio of 3:1 and 4:1
are recommended to be used for major and minor drainage structures,
4.9.1 General
I would like to inform ERA that the substructure type and foundation size are
designed on Dubber River Bridge is made only for completeness of the draft
hydrology/hydraulics report and it is subjected to change in the final report after
getting exact allowable bearing capacity of both abutment foundation from
the results of geotechnical investigation findings.
5.1 Introduction
The Addis Ababa - GohaTsion Road is located in the Federal Government and
Oromiya regional State, in the Northern part of Ethiopia stretching for about 180
km. The project road starts from the capital and the rural section starts at about
km 9 and passes through towns; Sululta, Chanco, Muketuri, Fiche,
GebreGuracha and ends at GohaTsion. The project road is part of the road
segment from Addis Ababa Metema, particularly being part of the Addis
Ababa DebereMarkos trunk road which has high traffic volume and load as it
is the main corridor of Port Sudan, and additional traffic load arising from traffic
generated as a result of industrial developments along the road corridor. A
number large scale industries and factories are under construction along the
stretch. Hence, maintenance of the project/upgrading of the road is very of
paramount importance for transporting both agricultural and industrial products
as well as import and export goods.
5.1.2 Geology
The Ashangi volcanic covering more than 80% of the road length
Sediments which are confined to the Blue Nile gorge and which
occasionally out crop
Geologically, basalt rock and its conglomerate layers are observed. Most of the
soils in this region can be classified as class A-1 and A-2 in accordance with the
AASHTO M-145 classification of Soils and Soil-Aggregate Mixtures for Highway
construction. From Northeast to Southwest runs the great trough, placing the
project area in an earthquake zone.
In view of these, geologic investigation for the entire length of the project, Addis
Ababa to Goha Tsion via Chancho town, has been carried out in the first and
second weeks of January, 2012. During the field investigation, it has been
observed that the area along the route corridor of the Addis Ababa Goha Tsion
road is covered by various types of volcanic rocks.
The major lithologic units encountered along the project route traverses are:
From Entoto check point and including the Sululta area, fine to
medium grained pyroclastic deposits (tuffs, ignimbrites and
pumices), ryholites, aphanitic basalts, aphanitic to porphyritic
trachyte rocks are observed. Except the aphanitic basalt, most of
these rocks are highly weathered; those changes the colors of the
minerals, partially decomposed, become significant for rock
formations around the Entoto ridge.
In the route corridors ahead of the town of sululta to Chancho
extended to Dubar towns, are covered by dark color and fine
grained olivine basalt.
Along the towns of Muketuri, Debre Tsige, Fiche, Hambisso, Tulu Milky
and Goha Tsion, the geologic formation/lithologic units are
dominated by aphanitic basalt. However, before Degem (Hambisso)
area, vesicular basalt is also encountered. Weathering effect is more
pronounced on the vesicular basalts than the aphanitic ones.
However, thick quaternary sediments are also found at localized
section dominantly in Gerbe Guracha to Goha Tsion areas on top of
the volcanic units.
In general, the texture and structure of volcanic rocks are largely determined by
the arrangement of the constituent minerals, compositions and grain sizes. Due
to internal stresses during igneous formations, set of fractures (joints) are also
common on these rocks. The vesicular basalts are not recommended for works
of engineering structures since the water absorptions and specific gravities are
by far lower than the other basalts. The aphanitic basalts, on the other hand, are
suitable for asphalt concretes, cement concretes, etc. these rocks are known for
its weathering resistant and higher compressive strength values. In some
sections, like the Durer towns towards sululta, the overburden materials are very
thin and the underlain igneous rocks are classified as hard excavation. While in
parts where quaternary soils are found such as in GerbeGuracha area, the
overburden black soils are very thick underlain by the aphaniticbasaslts. In such
sections, the excavation will be soft and unsuitable. Apart from these, in the
route traverse of the road project, no major geologic structure (tectonics) is
observed but it should be borne in mind that the City of Addis Ababa is located
in margin of the main Ethiopian rift system. Hence, for engineering structures
such as bridges etc, appropriate ground acceleration should be considered.
Topographic Features
The project area is located in Oromia Regional State north showa zone. The
topography of the route corridor is marked by Gojjam highlands and Shewa
plateau with high elevation ranging between 2,500 m ~ 3, 300 m a.m.s.l. The
route also descends to the Abay Gorge which lies 1,500 m below the general
elevation of the plateau.
Climatic Features
The region is generally characterized by two distinct climatic features. The
highland plateau is temperate, moderately warm, while the lowland areas are
warm. The mean temperature of the region during the coldest month of
December is around 14.50C and the highest temperature during the month of
April is about 17.70C. Annual average rainfall ranges from 1,000 mm 1,500 mm,
where rainy season extends from June to September.
During the field investigation, different activities have been conducted to assess the soil
extension, the engineering properties of the alignment soils and roadbed making
materials. The activities conducted include: soil extension survey, test pit logging and
sampling of sub grade soil, DCP testing, construction materials investigation and
sampling. Detailed discussion about the field works undertaken is presented hereunder.
A test pits were dug for subgrade investigation and sampled for CBR tests and
classification tests were collected. The collected samples were subjected to
laboratory tests to assess the engineering and index properties of the materials
and determine their suitability for road making.
Accordingly, the subgrade samples collected every 1.5 km were tested for:
Classification tests [Sieve analysis and Atterberg limits]
Gradation tests
Modified Proctor - 3 point CBR and swell tests
Natural Moisture Content test and
The subgrade samples collected every 1km and 500m were tested for:
Classification tests [Sieve analysis and Atterberg limits] and
Natural Moisture Content test
For rural sections of the road, field density and sample spacing is defined to be
at 1.5 km intervals while for town sections, field density and the sample spacing
is at 2 km interval pertaining to the homogeneity of the terrains in the route
corridors. More over DCP tests has been carried out for comparison with the
laboratory CBR values.
DCP Testing
Dynamic Cone Penetro meter testing was conducted to determine the
structural properties/strength of the foundation for crossings and the underlying
sub grade material. The test was conducted at both the right and left side
shoulder beginning from the subgrade layer of the existing pavement at an
interval of 2km on the alignment. The DCP test was extended up to a depth of
1m below the subgrade level.
The penetration data collected from the test has been analyzed by the UK DCP
version 2.2 software developed by TRL. The DCP values are then used to
compute the in situ CBR value using correlations developed by TRL as:
September 2012
HITCON Engineering
0
5
10
15
20
25
30
35
40
45
50
178+635.623
173+222.762
168+670.393
ENGINEERING DESIGN REPORT (Draft)
164+114.028
159+058.608
154+577.697
148+330.881
142+672.464
5-120
130+040.030
124+813.128
Construction Supervision of Addis Ababa Goha Tsion Road Overlay Project
119+857.456
114+509.269
109+500.000
104+822.673
99+638.048
Consultancy Services for the Detailed Engineering Design, Tender Documents Preparation and
94+634.162
90+206.893
84+066.487
Station [km]
79+159.210
74+264.137
71+077.394
Similar to the subgrade investigation samples were collected from the test
pits for subbase investigation and sampled for CBR tests and classification
tests were collected. The collected samples were subjected to laboratory
tests to assess the engineering and index properties of the materials and
determine their suitability as subbase road making materials.
From the test pits, subbase samples were collected every 3km for CBR and
classification tests for both the Chancho - Gohatsion overlay and Addis
Ababa -Chancho rehabilitation projects.
The laboratory investigation results for both the subbase and subgrade
materials are reported as an Appendix to the Soils and Material report.
During the field investigation, the Consultant has located 5 rock sources for
aggregate crushing/asphalt mix, 10 borrow sources and 5 water sources. The
Consultant has assessed the type, quality and quantity of materials, the
overburden material and its use for the construction purpose, and their
accessibility. Besides the possible environmental impacts that may arise due
to the development of the quarries, i.e. displacement of houses, claim for
farmlands, etc were properly observed.
Finally, samples were collected from the sources for the respective
laboratory tests to assess their suitability for the intended works.
Samples were collected from six sources to assess their suitability for the
intended works. The collected samples were tested for:
The laboratory result of the rock sample is presented in the Appendices in the
soil and material report.
Table 5.1: Rock Source along the Project Route for Crushing and Masonry
The borrow material sources in the project area are summarized and
presented in the table below, the detail investigation results are presented in
the Appendices in the soil and material report.
Water Source
Water for compaction, mortar, and concrete works could be obtained from
surrounding Rivers was sampled. The following river and ground/spring water
sources could be considered as potential sources of water.
Sample of water taken from the sources were tested for the following
chemical and physical tests to confirm their suitability for the intended works
as indicated below.
available all
4 River 64 + 700 0486272 1045137
times
Well (ground available all
5 42+000,RHS,50m 0473944 1032182
water) times
Based on observations made during the field investigation and the laboratory test
results, the majority of the alignment soils are acceptable to good roadbed
materials. However, some sections of the project alignment are covered with
expansive soils and weak bearing strength. Thus the top 60cm of the expansive soil
shall excavate and replace with an impermeable capping layer material of
minimum CBR 7%.
The borrow materials from each of the selected sources satisfy the specification
requirements of fill materials for embankment construction and replacement of
weak soil stretches. Thus, there are adequate sources of borrow material in the
project area located at reasonable intervals.
The test results of rock samples taken from the quarry sources reveal that rock
sources can be used as crushed aggregate for base course, asphalt mix and
concrete work. However, there are limited rock sources in the project area at
relatively long intervals.
6 PAVEMENT DESIGN
From the view point of preserving a road asset, the most cost-effective way of
extending the life of a road is to make the best use of its residual strength by
applying an overlay at the appropriate time, normally before the road shows signs
of serious distress. Close follow up of the road network is necessary so that exact
timing for overlay (or preventive maintenance in general) is identified. This
identification of proper timing is vital for successful implementation of appropriate
preservation action. In many developing countries only few strategic roads are
considered for overlaying, or other strengthening, until the condition of the
pavement has deteriorated beyond the point where this is a straightforward option.
In this road project for most of the segments the timing is appropriate for the overlay
and this effort will significantly extend the life of the pavement.
This report presents the asphalt-overlay pavement structural design of the Addis
Ababa Gohatsion for the last 20 km of the road section i.e. on the first 20 km from
the Gohatsion. The asphalt overlay design of the project road described briefly in
this report is based on the prevailing conditions of the road during the study period
of the project. The project area is located in Oromia Regional State north Showa
zone. The project road is existing asphalt paved road which starts from Addis Ababa
and pass through Gohatsion about 185 km from Addis Ababa and goes to
Debremarkos the Gonder and peroceed to Sudan trough Metema.
All roads deteriorate with time as a result of traffic and environmental effects.
Depending on the causes and extent of deterioration, the deterioration may be
relatively easy to correct, but sometimes major works are required. The works
processes for keeping them in good condition are often subdivided into various
categories:
Routine and periodic maintenance- maintenance that needs to be
done more frequently
Rehabilitation structural strengthening including overlaying
HITCON Engineering 6-125 Ethiopian Roads Authority
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For the design of rehabilitation or strengthening, the condition of the existing layers
of the pavement plays a vital role. Thus the essential component of the design of
the asphalt-overlay rehabilitation for the road project is the assessment and
evaluation of the pavement condition. The detail study of pavement condition has
been carried out with visual inspection, roughness measurement and pavement
structure assessment from deflection measurements as well as pavement and
subgrade material investigation. This detail assessment believes to provide sufficient
data to identify the modes of deterioration and their causes. The traffic inputs for the
pavement rehabilitation design are considered in terms of an equivalent standard
axle load of 8.16 tons. In this way the appropriate rehabilitation treatments has been
identified and designed.
The following chapters describes the design input parameters such as the traffic
load and subgrade material investigation and the pavement distress and structural
condition investigation which is carried out through detail visual condition survey,
pavement profiler or roughness measurement and pavement deflection
measurements.
magnitude of the individual wheel loads and the number of times these loads
are applied.
The traffic count was made at two different points along and in the vicinity of
the project road, i.e. Addis Ababa Chancho and Chanch Gohatsion, for
both economic analysis and pavement rehabilitation work. The detail traffic
analysis conducted and discussed in the Traffic Survey and Safety Measures
Report was adopted for the asphalt-overly and rehabilitation design work.
As there is no recent axle load data available in the vicinity of the project
route, it was necessary to carry out the axle load survey for the proposed
road project. Accordingly, the Design Consultant has sent a crew to conduct
the axle load survey and AADT traffic counts along the project route. These
traffic counts has been compared with and verified by the traffic counts
recorded by the Ethiopian Roads Authority considering the traffic growth rate
for the last few years.
The Equivalent Standard Axle Loads for the pavement rehabilitation design is
obtained based on the assumed truck factors.
The design traffic or the cumulative Equivalent Standard Axle of 8.16 ton is
derived from the total number of heavy vehicles during the design life of the
road converted to ESA using the following equivalence factor.
4.5
Axle Load in tons
Equivalenc e S tan dard Axle Load Factor
8.16
o The individual axle loads are converted and expressed as the number
of equivalent standard axles (ESAs), in units of 8.16 Tons. The
relationship between a vehicles EF and its axle loading is normally
considered in terms of the axle mass measured in kilograms.
o After determining the equivalency factors for each of the axle loads of
the vehicle category, the factors for the axles are added to give the
equivalency factor for each of the vehicles.
o The mean equivalency factor for each class of vehicle is determined
for the number vehicles surveyed.
Based on this relationship and using the axle load data obtained from the
survey the equivalence factors are derived as summarized on table 7.1. of
the traffic survey and safety measures report. The damage caused by light
vehicles such as cars and station wagons are insignificant compared to the
other commercial and heavy vehicles and hence not included in the
cumulative equivalent standard axle load for pavement design.
The Consultant has carried out the detailed field and laboratory
investigation testing between December, 2011 and January, 2012. As per
the terms of reference (TOR), part 2 section 6 of the document for the
procurement of consultancy services for Detailed Engineering Design ,
Tender document preparation and construction supervision of Addis ~
Chancho ~ Gohatsion Road Overlay Project, soils and materials
investigation has been scheduled as follows:
o For sub grade and pavement materials investigations, samples for
the following confirmatory tests are conducted:
Atterburg limit tests, LL and PL (PI)
Soils classification, sieve analysis
Volumetric Shrinkage (Expansiveness)
Density tests, MDD/OMC (AASHTO T 180 D)
three points CBR, (AASHTO T 193)
For rural sections of the road, field density and sample spacing is defined
to be at 1.5 km intervals while for town sections, field density and the
sample spacing is at 2 km interval pertaining to the homogeneity of the
terrains in the route corridors. More over DCP tests has been carried out for
comparison with the laboratory CBR values.
CBR tests of the subgrade for the overlay design have been performed on
representative samples collected in the project section. For design
purposes subgrade soils are usually conducted at proctor density
(AASHTO T-99) and the design CBR is selected from ranges of 4-days
soaked 3-point CBR values, carried out on samples collected from fairly
homogeneous sections. This method often doesnt provide the chance to
analyse the strengths of the soils at different levels of densities or
compactions. In order to overcome this short coming and evaluate the
strength behaviour of the alignment soils, 3-point CBR tests have been
executed at 3-energy levels in accordance to AASHTO T-180. The design
CBR is normally considered as the CBR Value in a soaked condition at
95% of the maximum dry density determined in the laboratory. For roads
like that of the project this method will also provide sufficient room to
determine the design CBR.
7.1. General
There are several causes for pavement to show roughness: traffic loading,
environmental effects, construction materials, and built-in construction
irregularities are all considered to cause rough surface on pavement. All
pavements have irregularities built into the surface during construction, so
even a new pavement that has not been opened to traffic can exhibit
roughness. The roughness of a pavement normally increases with exposure
to traffic loading and the environment.
Fair 4.5 6
Poor >6
It will be understood that IRI values may not reflect the level of surface
distresses as the initial stage of crocodile cracks, which is the
characteristics of this segment, does not contribute to roughness of the
pavement. This road segment is a good example of this phenomenon as
almost the whole 20 km analyzed has exhibited fatigue cracks and yet the
road is in good riding condition.
Figures 4-1 and 4-2 show distribution of the IRI values both in percentage
and along the chainage for the first 20 km driving from Gohatsion towards
Addis. Figure 4-1 shows the percentage of good and fair proportion of the
road (no segment with poor riding quality for this section) while the line in
Figure 4-2 shows the average roughness with respect to right and left lane
roughness values measured.
Figure 7-1: IRI % of good, fair and poor section for the full 178 km length of
the Addis Gohatsion road project
Figure 7-2: IRI distribution over the full length of the project (chainage start from Gohatsion to Addis)
In this project road the section from Gohatsion to Addis Ababa, the first 60
km has developed extensive cracks that are at initial stage for alligator
cracking while at significant number of locations the cracks has already
developed in to full Alligator cracking where the pavement is
disintegrated to form small blocks as shown in the figure above. At couple
of locations the crack has further deteriorated and potholes are formed
associated with deformations.
Though the severity level is small the extent of the distress developed is
severe which means that the coverage is wide. At location where the
cracks are associated with depressions and potholes further tests of
materials and structural strength survey are carried out to see whether the
pavement is strong enough to carry the future traffic. These locations can
be seen on figure 4-3 where maximum area of crack with higher severity
level is observed.
Experiences show that the asphalt fatigue life increases with asphalt
thickness. The thickness of this road pavement is only 50 mm and the wide
extent of cracks developed over significant section of the project might
be caused as a result of the small thickness of asphalt and traffic action.
Spot problems of alligator cracking that is associated with subsidence and
potholes are related to material and construction problem coupled with
poor surface drainage.
Figure 7-4: Distribution of crack over the full length of the project
(chainage start from Gohatsion to Addis)
7.3.4. Rutting
For the purpose of getting complete view of the situation a laser profiler
from ERA has been used to record longitudinal and transverse profile of
the pavement. From the transverse profile reading the mean rut depth for
the pavement is obtained and the result shows significant portion about
50% of the road show rut depth that is in excess of 10 mm. The remaining
50% of the pavement is also affected by rutting but the depth is varying
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Figure 7-5: Distribution of rutting over the whole stretch of the project (chainage start from Gohatsion to Addis)
7.3.5. Potholes
Figure 7-6: Distribution of pothole over the full length of the project
(chainage start from Gohatsion to Addis)
the damage types are categorized in two parts based on their relevancy
to structural condition of the pavement. The first group consists of
pavement distress types such as deformations, rutting, fatigue cracks and
crazing. These damages are caused by structural deficiency of the
pavement structure and they are primarily identified and measured to
obtain solutions coupled with bearing capacity of the pavement.
From the recorded Global Damage Index, Is the full length of the first 20
km falls under the second category of the Damage Index, which shows
that this section of the road has intermediate surface condition, bad
enough to trigger maintenance work in the absence of any other
consideration.
Figure 7-8: Distribution Global Visual Index, Cracking index and deformation index (Chainage start from Gohatsion)
i. Combining results from condition survey for surface distress and deflection
measurement and based on this develop Pavement Quality Rating, see chapter
5
ii. Combine Pavement Quality Rating with Traffic level to decide the type of work
to be carried out, see chapter 6.
8.1. General
The use of nondestructive deflection testing has been an integral part of the
structural evaluation and rehabilitation process for many decades in many
countries especially the developed world. In its earliest application, the total
measured pavement deflection under a particular load arrangement was used
as a direct indicator of structural capacity. Several countries/agencies
developed failure criteria that related the maximum measured deflection to the
number of allowable load application particularly in flexible pavements.
for this purpose, the FWD being by far the most popular. It has the advantage of
being able to apply impact loads which more accurately simulate the effect on
pavements of heavy vehicles moving at normal traffic speeds than the slowly
moving load applications associated with the Deflectograph or the deflection
beam.
The deflections have been measured with an FWD. Measurements have been
made in outer wheel path of each direction where the pavement is susceptible
for moisture and weak due to less lateral confinement.
Basically the FWD measures the deflection bowl accurately but its proper and
reliable automatic interpretation requires more sophisticated analysis programs
than are currently available. Therefore good analysis relies on the skill of the
analyst who will make use of the deflection data but only as one of the various
data sets at his disposal.
The value of the central maximum deflection is still an essential for analysing
road pavements and determining appropriate rehabilitation measures. Other
characteristics of the deflection bowl can provide extremely valuable
comparative information. A performance chart of FWD deflection data may be
plotted to show the variation of pavement response along the road. The most
preferred deflection criteria are usually d0, d1500 and surface curvature index
(SCI) and sometimes base damage index (BDI); where the subscripts refer to the
distance in millimetres of the measured deflection from the point of maximum
deflection and recommended as follows in table 5-1 for an FWD with 9
geophone sensors and:
Surface curvature index (SCI) = d0 d600
Base damage index (BDI) = d300 d600
The pavement structural capacity has been measured using Falling Weight
Deflectometer (FWD) at interval of 200 m in each direction staggered with 100m
so that to obtain a deflection data at 100 m for a given road section.
Figure 8-1: FWD deflection profile for the first 28 km (from Gohatsion side)
Figure 8-2: FWD deflection profile for the entire route (chainage from Addis to
Gohatsion)
The deflection profiles are shown in figures 5-1 and 5-2 for the first 28 km (from
Gohatsion side) and full length of the project. Although the actual values of
deflection will depend on the type and condition of the pavement layers, such
plots show relative differences in their condition and give an indication of any
structural weaknesses. In addition to the deflection measurement profiles along
the route the figures demonstrates the measurement variation in both the left
and right lanes.
For the design purpose, the deflection measurement were analysed in order to
determine homogeneous sections based on the pavement structural condition.
The cumulative sum method has been used on various deflection parameters
to identify the uniform sections and compared with the distress and subgrade
strength measurements to decide the final homogenous sections for design.
Figure 8-3: FWD deflection profile cumulative sum (Chainage from Addis to
Gohatsion side)
Figure 8-4: FWD deflection profile cumulative sum right lane (0+000 at Addis) and
left lane (0+000 at Gohatsion)
Figure 5-3 and 5-4 shows the cumulative sum curve for the different deflection
measurements. Although not very distinctive to divide the road segment
confidently into homogenous sections, it is attempted to see the design
outcome with ten homogenous sections as shown in figure 5-3. Further the effect
of directional load distribution as well as construction variation has been
considered by approaching the deflection profile of the two directions
separately. As shown in Figure 5-4 the difference on the cumulative sum of the
two directions is not very significant except at the last 40 km of the road on the
Gohatsion side which show some difference. It is decided then to treat both
directional lanes the same way and design and construct with the same cross
sectional structure.
The values of d1 and d2 are fixed during the development of PMS and are
adopted for this project as there is no change in this regard so far by ERA. The
choice of thresholds for d1 and d2 depends up on many factors, such as climate,
the type and thickness of pavements, soil types, axle loads etc. It is the belief of
the consultant that this value shall be revised. This is because a lot of changes
happening with regard to the factors indicated above since the first
development of PMS in 1998.
At the time of the introduction of the PMS, the study selected the threshold
deflections as:
d1 60/100 mm
d2 80/100 mm
The following table gives the quality rating Qi as a function of the Global Visual
Index, Is and the deflection values.
Based on the Quality Rating Qi, the method provides the following options, as
illustrated in table 5-2.
Q5 : same analysis as above; allowance will be made for the position of the
deflection with respect to the limits and to the traffic; depending upon the
answer, may be reclassified as Q3, Q7, or Q8.
Combining results from condition survey for surface distress and deflection
measurement and based on this develop pavement Quality Rating. (Note: Since
this method is developed based on the deflection measurement by Benkelman
Beam, the result from the Falling Weight Deflectometer shall be converted by
appropriate adjusting factor). Paterson (1987) reports: The loading applied by
FWD is currently considered to be more similar to traffic loading in both the load
and the time domains than either the Benkelman Beam test (which applies
similar loads at creep speed) or the light-loading, high frequency devices. Under
similar applied loads, the ration of FWD to Benkelman Beam deflections ranges
Where deflections are less than 1 mm, under a 40 kN FWD impact load, adopt a
Beam: FWD ratio of about 1.1. Where deflections exceed 1 mm, the ratio is likely
to be in excess of 1.1, and related to deflection as defined by: Beam : FWD ratio
= 1.1 x (FWD deflection in mm)0.4
9 ASPHALT-OVERLAY DESIGN
9.1. General
The principle of overlay design is that if the failure of the existing pavement is not
too far advanced, it should be possible to strengthen the road so that it can
carry traffic for many more years. If the deterioration is too advanced then a
more substantial form of rehabilitation will be required.
The mean and standard deviation of the adjusted individual deflection readings
are then calculated. The representative rebound deflection RRD is taken as:
RRD = ( x + 2s) c
Where:
x is the arithmetic mean of the individual deflection measurements adjusted for
temperature
s is the standard deviation of the adjusted individual measurements
c is a critical period adjustment factor
The critical period for roads in most part of the Ethiopian highlands is considered
to be September to October which is after the main rain season (June August)
in these areas. Since the deflection measurement of the road project is carried
out in February/March a critical period factor of c = 1.1 is assumed to be
reasonable in the absence of calibrating factor from research data.
The design future traffic in terms of ESA predicted for the design period of 10
years is given in chapter 3.
To find the thickness of asphalt concrete overlay required, enter the overlay
thickness design chart, Figure 4.2 in ERA-PRAODM 2002, with the RRD obtained
and the design ESA.
Therefore, for a temperature adjustment factor of 1 and critical period factor 1.1
for the measured deflections adjusted in to equivalent Benkelman Beam (BB)
deflection with a factor of 1.1 as all deflections are less than 1 mm, the resulting
summary the fourteen homogenous sections is presented in table 6-1 below:
48+900
48+900
657 162 0.98 130
39+818
39+900
643 189 1.02 135
30+069
30+069
633 176 1.00 130
24+980
24+980*
685 215 1.11 ~350
8+859
8+859 0+000 597 192 0.98 ~325
*Note that the station 24+980 is where the Chancho - Derba road joins the Addis
Chancho road, thus a traffic load of 138 ESA for design period of 20 years is
considered in the analysis.
The structural capacity of the pavement declines with time and traffic, and by
the time an evaluation for overlay design is conducted, the structural capacity
has decreased to residual/effective structural capacity (SC eff). The effective
structural capacity for flexible pavement type is expressed in terms of structural
number (SNeff).
If a structural capacity of SCf is required for the future traffic expected during the
overlay design period, an overlay having a structural capacity of SCol (i.e. SCf
SCeff) must be added to the existing structure. This approach to overlay design is
commonly called the structural deficiency approach.
The primary objective of the structural evaluation is to determine the effective
structural capacity of the existing pavement. The problem is no single, specific
method exists for evaluating structural capacity. The evaluation of effective
structural capacity must consider the current condition of the existing pavement
materials, and also consider how those materials will behave in the future. Two
alternative evaluation methods are adopted to determine effective structural
capacity.
9.4.1. Effective structural capacity based on visual survey and material testing
The layer coefficients assigned to the materials based on the condition survey
and material testing and their effective structural strength are summarized in
table 6-2 below for the four homogenous sections of the 20 km.
Where:
SNnew = Structural number determined for new pavement structure required
based on subgrade strength
SNeff = effective structural number of the existing pavement, table 6-2
Dol = required overlay thickness, cm
aol = structural coefficient for the AC overlay
The pavement structure required for new pavement based on the subgrade for
the four homogenous sections and traffic 21.6 mESA has been determined using
ERA Pavement Design Manual Vol.1 Flexible Pavements 2002 and summarized as
follows in table 6-3:
127+200 AC 15 0.44
5 S3, T8 Base 25 0.14 1 13.1
123+000 Subbase 27.5 0.11 1
123+000 AC 15 0.44
5 S3, T8 Base 25 0.14 1 13.1
105+600 Subbase 27.5 0.11 1
105+600 AC 15 0.44
5 S3, T8 Base 25 0.14 1 13.1
103+298 Subbase 27.5 0.11 1
103+298 AC 15 0.44
95+600 13 S4, T8 Base 25 0.14 1 12
Subbase 17.5 0.11 1
95+600 AC 15 0.44
94+634 13 S4, T8 Base 25 0.14 1 12
Subbase 17.5 0.11 1
94+634 AC 15 0.44
88+400 Base 25 0.14 1
2 S1, T8 16.3
Subbase 27.5 0.11 1
Capping 35 0.09 1
88+400 AC 15 0.44
87+100 11 S4, T8 Base 25 0.14 1 12
Subbase 17.5 0.11 1
87+100 AC 15 0.44
80+844 Base 25 0.14 1
2 S1, T8 16.3
Subbase 27.5 0.11 1
35 0.09 1
80+844 AC 15 0.44
73+690 11 S4, T8 Base 25 0.14 1 12
Subbase 17.5 0.11 1
73+690 AC 15 0.44
57+393 Base 25 0.14 1
2 S1, T8 16.3
Subbase 27.5 0.11 1
35 0.09 1
57+393 AC 15 0.44
52+900 12 S4, T8 Base 25 0.14 1 12
Subbase 17.5 0.11 1
52+900 AC 15 0.44
48+900 12 S4, T8 Base 25 0.14 1 12
Subbase 17.5 0.11 1
48+900 AC 15 0.44
39+818 12 S4, T8 Base 25 0.14 1 12
Subbase 17.5 0.11 1
39+900 AC 15 0.44
30+069 Base 25 0.44 1
2 S1, T8 16.3
Subbase 27.5 0.14 1
Capping 35 0.11 1
30+069 AC 15 0.44
12 S4, T8 Base 25 0.14 1 12
24+980
The overlay thickness is then determined from the SNnew and SNeff summarized
above in table 6-3 and 6-2 respectively assuming the layer coefficient (aol) for
the overlay asphalt concrete to be 0.44.
95+600
12 6.2 13.1 131
94+634
94+634
16.3 6.6 22 220
88+400
88+400
12 6.5 12.6 126
87+100
87+100
16.3 7.1 20.8 208
80+844
80+844
12 6.6 12.6 126
73+690
73+690
16.3 7.1 20.8 208
57+393
57+393
12 5.6 14.7 147
52+900
52+900
12 5.3 15.3 153
48+900
48+900
14.1 5.6 14.7 147
39+818
39+900
20 5.8 23.8 238
30+069
30+069
14.1 5.9 13.9 139
24+980
24+980*
18.7 6.8 27 270
8+859
8+859
16.3 7.7 19.5 195
0+000
It is unlikely that the overlay thickness determined by the two methods will agree
exactly, here sound engineering judgment is required to estimate the possible to
make a choice or a compromise between the results obtained by both
methods. Table 6-5 show a comparison of the overlay thickness from the two
methods and the recommended overlay thickness adopted along the
rehabilitation or correction required on the existing pavement.
Table 9-5: Comparison of overlay thickness based on the two methods and
recommended pavement overlay/reconstruction
Visual
Deflection
Condition
method
method
178+600 115 AC => 100
144 Overlay (OV1)
177+500
AC => 120
177+500 80 Reconstruction
246 Base => 250
173+222 (RE1)
Subbase => 30
173+222 75 127 Overlay (OV1) AC =>100
160+577
160+577 80 127 Overlay (OV1) AC => 100
150+600
150+600
100 150 Overlay (OV2) AC => 120
144+784
144+784
135 166 Overlay (OV2) AC => 120
135+200
135+200 Reconstruction AC => 120
130 180
127+200 (RE2) Base => 150
127+200 Reconstruction AC => 120
130 175
123+000 (RE3) Base => 250
123+000
125 146 Overlay (OV1) AC => 100
105+600
105+600 Reconstruction AC => 120
115 186
103+298 (RE2) Base => 150
103+298
100 144 Overlay (OV2) AC => 120
95+600
95+600
70 131 Overlay (OV1) AC => 100
94+634
94+634 AC => 120
100 Reconstruction
88+400 220 Base => 250
(RE1)
Subbase => 300
88+400
75 126 Overlay (OV1) AC => 100
87+100
87+100
70 208 Overlay (OV2) AC => 120
80+844
80+844
70 126 Overlay (OV1) AC => 100
73+690
73+690
75 208 Overlay (OV2) AC => 120
57+393
57+393
120 147 Overlay (OV2) AC => 120
52+900
52+900 140 153 Overlay (OV2) AC => 120
48+900
48+900
130 147 Overlay (OV2) AC => 120
39+818
39+900 Reconstruction AC => 120
135 238
30+069 (RE2) Base => 150
30+069
130 139 Overlay (OV2) AC => 120
24+980
28+800* AC => 50
15+828 ~275 Reconstruction DBM => 150
195
(RE5) Base => 250
Subbase => 250
15+828 AC => 50
8+859 ~325 Reconstruction DBM => 200
270
(RE4) Base => 250
Subbase => 300
8+859 AC => 50
0+000 DBM => 150
~275 Reconstruction
195 Base => 250
(RE5)
Subbase => 250
Existing
Base
Existing
Base
RE1
Asphalt layer => 12 cm AC
AC 12 cm
Crushed Base => 25 cm
Subbase => 35 cm Base 25 cm
Subbase 35 cm
Improved
subgrade
RE2
Asphalt layer => 12 cm AC AC 12 cm
Crushed base => 15 cm
Base 15 cm
Base
Existing
Subbase
Base
Existing
Subbase
AC 5 cm
DBM 20 cm
RE4 Wearing surface => 5 cm AC Base 25 cm
Asphalt base => 20 cm DBM
Crushed base => 25 cm Subbase 30 cm
Granular subbase => 30 cm
Improved
subgrade
Subbase 25 cm
Existing
subbase
Figure 9-1: Illustration of typical pavement overlay and reconstruction sections
10. APPENDICES