MS-15-Ranwediyawa Tunnel Construction Rev A
MS-15-Ranwediyawa Tunnel Construction Rev A
MS-15-Ranwediyawa Tunnel Construction Rev A
Contract No.: MMD E/MWS I P/AD B/NWPC P/r C B-2l3267-3268-SRl/l C B/20 1 7/003
Received by Letter Ref.: C SC EC- I C 82-P M DSC-3 1 O -20 1 9 Dated: 21st June 2019
1. A detailed review of ventilation calculations can be carried out between our respective Site Engineers
at site.
2. Working site lay outs are required. They may be submitted separately
3. Site proformas and lnspection and Test Plan will be reviewed on site between relevant PMDSC site
staff and China State Engineers when work proceeds. Adjustments to be agreed and made on site
4. lnformation in annexes 1,2 &3 to be included
5. Confirm that shotcrete/ concrete batching mixing will not be done at the portal site or if it is proposed
to produce at site portal area advise all relevant information on storage of materials operation of plant
and facilities for maintaining dusU noise free environment
6. Please confirm how equipment will be maintained at site and who will carry it out in absence of fitter/
mechanic on tunnel team?
7. H&S and Environmental sections of Method Statement may be subject to comment from PMDSC
relevant staff.
8. For requirements of working site set up area etc. please see comments on appropriate submission
(which has been rejected)
9. For portal layouts including access and surrounding surface features please see comments on
appropriate submission (which has currently been rejected for lack of detail).
The approval of drawings and documents shall not relieve the Contractor of any of his duties, obligations or
responsibilities under the Contract.
Checked by PMDSC
ilIal !P211
Resident Engineer Date
Construction of Main Canal from Nebadagahawatta to Mahakithula Reservior Inlet Tunnel (from 5+250km to 22+300).
MS-015
Rev.A
Ref.Letter No :
Construction of Main Canal from Nebadagahawatta to Mahakithula Reservior Inlet Tunnel (from 5+250km to 22+300).
Contents
1.0 Introduction ................................................................................................................................... 4
2.0 Purpose of the method statement ................................................................................................... 4
3.0 Work Force Allocation ................................................................................................................... 5
4.0 Documents to be referenced with this method statement .............................................................. 8
5.0 Detailed method of carrying out method statement activity.......................................................... 9
6.0 Temporary Access to Tunnel ......................................................................................................... 9
7.0 Equipment and Material .............................................................................................................. 10
7.1 Equipment ................................................................................................................................ 10
7.2 Material .................................................................................................................................... 11
8.0 Construction Method ................................................................................................................... 12
8.1 Blasting Design for Ranwediyawa Tunnel .............................................................................. 12
8.2 Drilling ..................................................................................................................................... 12
8.3 Blast holes arrangement for the drilling pattern ...................................................................... 13
8.4 Conceptual drilling geometry and firing sequences................................................................. 13
8.5 Top heading part of the tunnel ................................................................................................. 13
8.6 Lower part or the bench ........................................................................................................... 13
8.7 Charging ................................................................................................................................... 14
8.8 Charging method for Perimeter holes ...................................................................................... 15
8.9 Charging method for Production holes .................................................................................... 15
8.10 Approximate Blasting Parameters ........................................................................................... 16
8.11 Sample specific charge calculation .......................................................................................... 16
8.12 Mechanical Excavation – Using excavator/Backhoe Loader or Hammer ............................... 17
8.13 Forepoling ................................................................................................................................ 18
9.0 Mucking and Disposal of Excavated Materials ........................................................................... 21
10.0 Tunnel Support ............................................................................................................................ 22
10.1 Shotcrete and Wire Mesh ......................................................................................................... 25
10.2 Installation of Rock Bolt .......................................................................................................... 26
10.3 Lattice Girders and Steel Ribs ................................................................................................. 28
10.4 Tunnel Lining ........................................................................................................................... 33
11.0 Temporary Facilities for Tunnel Excavation ............................................................................... 34
11.1 Compressed Air Supply for Construction ................................................................................ 34
11.2 Water Supply for Construction ................................................................................................ 35
11.3 Electricity for Construction...................................................................................................... 35
11.4 Lighting .................................................................................................................................... 35
11.5 Ventilation ................................................................................................................................ 36
11.6 Drain ........................................................................................................................................ 39
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11.7 Communication ........................................................................................................................ 40
12.0 Quality Control ............................................................................................................................ 41
12.1 Survey Works ........................................................................................................................... 41
12.2 Laboratory and Testing ............................................................................................................ 41
13.0 Working Programme .................................................................................................................... 42
14.0 QA/QC Measures ........................................................................................................................ 42
15.0 Inspection and Test Plan for Tunnel Construction ....................................................................... 43
16.0 Environmental Management Plan for Tunnel construction ......................................................... 43
16.1 Environmental Monitoring Plan .............................................................................................. 54
17.0 Safety Requirements for Tunnel Construction ............................................................................ 56
17.1 Safety Orientation Course and Employee Registration ........................................................... 56
17.2 Duty Oriented Safety Courses ................................................................................................. 56
17.3 General Safety Requirements .................................................................................................. 56
17.4 Safety Procedure ...................................................................................................................... 57
In this project there are two tunnels namely Ranwediyawa tunnel and Nilagama tunnel.
Renwediyawa tunnel starts at Ch. 9+060km and ends at ch.9+680km. Nilagama tunnel starts at
ch.13+420km and ends at ch.14+240km.
- To provide a document that project staff must read and understand before starting the job.
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Fallowing manpower will be deployed for the tunnel construction work.
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•co-ordinate with GSMB and any other third party
monitoring team
•Participation in tunnel construction meeting and
discussions
4 Material Engineer 1 •Conduct or supervise laboratory tests in order to ensure
material quality
•Analyses laboratory test results in order to determine
causes of problems and develop solutions.
•Design and direct the testing and/or control of processing
procedures.
•Monitor material performance and evaluate material
deterioration.
•Coordination with the Engineers on all QA/QC matters.
•Participation in construction discussions and meetings
5 QA/QC Engineer 1 •Initializing and establishing the quality management
system through project QA/QC plan
•Having responsibility to assure that all project activities
affecting quality are in compliance with the plan.
•Establishing objectives of continual improvement.
•Ensuring surveillance, evaluation and inspection of
materials.
•Administering non conformity with respect to material and
work execution.
•Determining, collecting and analyzing appropriate data to
demonstrate the suitability and effectiveness of the quality
management system.
•Coordination with the Engineers on all QA/QC matters.
•Production of material and laboratory testing record
6 Site Engineer 2 •Preparation of work procedures
•Document and drawing control.
•Coordination with QA/QC department regarding
inspection and testing
•Check and review of progress schedule.
•Control of manpower and equipment
•Coordination with design and planning department
•Assisting the Construction manager in any aspect
regarding engineering matter.
7 Surveyor 2 •Create the miniature of the construction plans that would
serve as the source of the site plans
•Keep in touch with the engineering and design personnel’s.
•Responsible/in charge for all construction layout and
survey documentation,
•Provides and maintains horizontal and vertical survey
control by use of a level, total station, etc. Including
organized documentation of survey notes.
•Assists in the preparation of final records for the project,
including as-built.
•Works with site engineer/foreman to ensure structures are
built in conformance with the design alignment and
contractual requirements.
• Responsible for tunnel deformation monitoring and
ground settlement monitoring.
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8 Safety Officer 1 •Avoid all personal injuries during the execution of the
Project by targeting to Zero LTI.
•Ensure that all personnel employed on the Project are
competent to carry out their designated tasks
Safely by supporting continuous HSE training, adequate
HSE measures, instruction and supervision.
•Create positive health, safety and environment attitudes
and perceptions at all levels of the Site organization, and to
raise health, safety and environmental awareness in general.
•Implement a training program that supports the
achievement of personnel competency in relation to Health
and Safety.
•Continually monitor and improve HSE performance
9 Environment Officer 1 •Complete the site work without any significant damage to
environment such as flora, fauna, natural water resources
and etc.,
•Complete the site work without incurring any significant
property damage to permanent or temporary facilities.
•Implement a training program that supports the
achievement of personnel competency in relation to the
Environment
•Carry out all operations related to construction and
commissioning with the health and safety of personnel and
the impact on the environment as the prime consideration.
•Continually monitor and improve Environment
performance
10 Forman 3
11 Blasting workers 6
12 Electrician 1
13 Drivers 6
14 Machine Operators 6
15 General Labor 12
a. Technical Specification
b. Construction drawings
c. Site Safety & Environmental Plan
d. Method Statement for Construction of Tunnel Portal( MS-004)
e. Method Statement for Blasting
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Tunneling work would be inspected regularly to ensure the tunnel and supporting systems remain
stable, intact and work can be carried out safely. The inspection would compare the actual
conditions with those assumed in the original or amended designs, excavation method or safety
management plan and the adequacy of control measures.
Tunnel excavation will be preceded after completion of temporary access and completion of tunnel
portal construction. Ranwediyawa Tunnel construction will be carried out from two direction inlet
and outlet portals. Temporary Access Road will be constructed at both side of the portal and it
would be a ramp and generally having a driveway width about 6m, where practicable to do so and
not less 4m. Longitudinal slope of the Access Road is not more than 15%. The typical cross section
is shown on the Figure.4.
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7.1 Equipment
No. Description Total Specification Note
units
Excavating/Blasting:
1 Drilling machine 10 YT28 For blasting hole
2 Geological drilling rig 1 M13 For fore hole
3 Excavator + Breaker 2 Pc-200
4 Loader 2 2C-30L
5 Explosive Transportation Truck 2 2.5t
Hauling:
6 Wheel Loader 2 ZW140
7 Dump Trucks 8 1 cub
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Supporting Works:
8 Welding Machine 3 400A
9 Steel Bar Bender 1 Q32
10 Steel Bar Cutter 1 GQ40
11 Shotcrete Machine 1 TK-961
12 Grout Mixer 2 HFV-50
13 Grout Pump 2 8.0A
Concrete Lining
7.2 Material
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According to the given geological profile along the tunnel alignment the same excavation method
cannot be used. The reason is that the rock condition and rock class varies along the alignment
having a range from good rock to very poor rock based on RMR classification. This section
consists of good rock, fair rock, poor rock and very poor rock. As the geology changes specific
excavation methods and supporting techniques are required for each section. Depending on the
ground condition, drill and blast will be used along with mechanical and manual excavation
techniques. Excavation can be done using an excavation machine (Excavator) and in case of hard
rock encounter which cannot be scraped using the excavation machine it can be done according to
conventional drill and blast method
8.1 Blasting Design for Ranwediyawa Tunnel
As per available geological information of Ranwediyawa tunnel rock class is mainly class IV and
V which is known as soft rock. The existing rock condition and thus the parameters for the tunnel
construction are planned based on the guidelines for excavation and supports of 10m span rock
tunnels in accordance with RMR system (after Bieniawski 1989, seen Table:4)
Blasting will be done only in rock which are hard enough to be blasted .The sections having a
RMR more than 20 (except Class V) will be excavated using the conventional drilling and blasting
method as follows
Common steps in drill and blast excavation method are
1. Drilling
2. Charging
3. Blasting and Ventilation
4. Scaling
5. Loading and carrying excavated material
6. Surveying and Geological mapping
7. Tunnel rock supporting
8.2 Drilling
Drilling will be done by using hand held rock drilling machine with an air leg to position to
required orientation. Excavation progress is mainly dependent on drilling pattern and quality of
drilling. A “V – cut” drilling method is proposed. Drilling diameter will be 40mm and the drilling
depth will vary according to the ground/rock condition and it is summarized in the table No.3.
Lookout angle will be approximately 3 degrees outwards the contour.
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8.3 Blast holes arrangement for the drilling pattern
A conceptual drilling geometry and firing sequence is given herewith. The exact drilling pattern
and firing sequence will be changed slightly form the given design based on the initial test blasting
works and exact ground condition when exposed
8.4 Conceptual drilling geometry and firing sequences
The blasting in Ranwediyawa tunnel will be done in two stages as top heading part and benching
part. There is a “V cut” at the middle of the top heading section. The prepared pattern is marked
carefully in the site face by the surveyor and then using jack legs, holes will be drilled with
required angles and length
8.5 Top heading part of the tunnel
Delay sequence is shown using numbers from 0 to 5 and the distances are in meters (Figure No.5)
“V-cut” has proposed in order to obtain a higher progression rate and alternatively a parallel cut
also can be used. Cut hole angles are shown in Degrees and can be changed to suit the advance and
drilling depth.
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Can be done using benching or horizontal drilling – but horizontal drilling is proposed to maintain
the smooth shape of the outer edge of the tunnel (Figure No.6)
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For the tunnel works non-electric detonators will be used. Non-electric detonators (Nonel) are
safer as they are not affected by stray electric current. The very common detonator of this type is
Nonel blasting detonator. In Nonel blasting detonator system tubes transferring waves replace
electrical wires. The tube in Nonel system is not sensitive to electrical current, magnetic field, high
temperature, humidity and thunder. In the portal area and close to the inlet Electric delay
detonators will be used in case of unavailability of NONEL.
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8.10 Approximate Blasting Parameters
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As the rock class belongs to class IV and V, New Austrian Tunneling Method will be adapted and
based on the soil/rock mass performance following steps will be followed (if required)
Applying thin layer of shotcrete immediately after phase advance (temporary support due
to high early strength and rigidity of shotcrete )
Rock mass deformation will be continuously monitored after each blast
If gravel clay and sand encounter, a pipe arch canopy will be used which is made of steel
pipes drilled in to the ground and grouted
8.12 Mechanical Excavation – Using excavator/Backhoe Loader or Hammer
An excavator or backhoe loader with suitable dimensions will be adopted for excavation of
completely weathered rock (CW) and this will incorporate manual rectification and trimming
works.
In most of the cases for competent rock which cannot be excavated by excavator, then hammering
can be done, specially for loose jointed and fractured rock. Hammer/Breaker is successful for
tunneling compared to drilling and blasting when the fractured rock structure makes controlled
blasting hard to achieve.
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8.13 Forepoling
Forepoling will be done based on the client’s design. In segments where completely (CW) and
highly weathered (HW) rock encounter and for sections identified as class IV support, grouted
rebar will be installed prior to start excavation to prepare a pipe arch canopy in the crown section.
After installing the rebar and grouting, excavation will be done in multiple drifts of as top heading
to suit the ground condition. Refer the picture below (Figure No.11). Excavation will not be done
until 24 hours after grouting.
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Class IV and V be 1.7m, forepolling will be done prior to start the excavation
Support Class 4 works as given support class is 4.
High Risk Excavation sequence will be top heading and benching
HW – MW
9+270 – 9+510 Drilling and Blasting. maximum advance will be 3m.
RMR 41 -80 Excavation sequence will be top heading and benching.
Class II and III – Possibility of full face excavation will be considered if the site
According to RMR condition allows.
Support Class 3
High Risk
SW
9+510 – 9+540 Mechanical excavation using Breaker and Backhoe loader – In
RMR 15 -25 case of hard boulder encounter occasional blasting will be done.
Class V – According to forepolling will be done prior to start the excavation works.
RMR Maximum advance will be 1.7m. Excavation sequence will be
Support Class 4 top heading or multiple drifts
High Risk
HW
9+540 – 9+680 Mechanical excavation using Breaker and Backhoe loader – In
RMR 0-25 case of hard boulder encounter occasional blasting will be done.
Rock Class V – According forepolling will be done prior to start the excavation works.
to RMR Maximum advance will be 1.7m. Excavation sequence will be
Support class 4 top heading or multiple drifts
High Risk
CW – HW
Table 3: Method of excavation for each segment of rock type According to the given
geological profile along the tunnel.
Combination of all above methods will be utilized to suit the site condition where necessary.
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Table 4: Guidelines for Excavation support of 10m Span Rock Tunnel in accordance with
RMR system (after Bieniawski 1989)
Loose material and hard rock fragment can be expected as a result of blasting while constructing of
Ranwediyawa tunnel. Therefore, loose material and hard rock will be separated and transported to
respective disposal/stock file. The mucking (excavated material) out will be done with loaders and
dump trucks. The mucking will be loaded to dump trucks to transport to the designated location or
the disposal yard for storage.
The selection of locations, the design and the management practices relating to the muck disposal
sites are all based on technical, environmental and safety criteria.
The measures adopted during the setup, operation and abandonment phases of the muck disposal
sites will be implemented and also an environmental monitoring plan will be implemented for site
management and use, which will include field inspections, and regular control of entries to the
sites, among other actions.
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The excavation and the installation of support elements will be executed according to the approved
working cycles for respective ground conditions. Applying the tunnel ground support in the form
of rock bolts and shotcrete as determined by the deforming ground as the excavation is carried out
is known as the New Austrian Tunneling Method (NATM).The type and amount of tunnel support
will be installed immediately after excavation is directly related to the Rock Class established by
BIENIAWSKY and the subsequent Support Class as established.
The standard primary support associated with the established rock support classification system is
shown on the Drawings. However, variations from the anticipated rock conditions may imply that
the standard support systems as shown on the Drawings for each rock support class may require
modifications and adjustment during construction will be proposed and as directed and approved
by the Engineer. The support elements will be installed or applied in such a manner and sequence
as to prevent deterioration, disintegration and loosening of the rock mass surrounding the
excavated tunnel. Temporary support within weak rock zones will depend on the geological
conditions encountered and will be installed as foreseen in the respective rock support classes
shown on the relevant rock support Drawings or as directed by the Engineer. Support Classes have
been designed for tunnel sections provided with both shotcrete lining and the watertight concrete
lining to cope with all anticipated rock conditions. Each Support Class defines the permissible
round length and the support measures required in order to achieve equilibrium of the respective
rock mass. The Support Classes are indicated on the construction Drawings.
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The steel mesh will be placed on the excavated surface where required and it will be fastened back
against expose rock surface to ensure no possibility of retaining air pockets behind shotcrete. The
steel mesh will be 6mm dia, high yield steel fyk 500N/mm2 and arranged in 150mm x 150mm
square grid. Shotcrete will be sprayed by appropriate shotcrete spray machine with skilled people.
The shotcrete grade will be C20/25 grade. Curing measure will be adopted for keep moist for 3
days after shotcreting. Each completed layer of shotcrete will be checked, to the satisfaction of the
Engineer. Repair work will be carryout all hollow, sandy, cracked or any other areas where, in the
opinion of the Engineer. Shotcreting strength will be tested by crushing 100mm diameter of cores
from casted shotcrete panels as per specification. Five cores with a diameter of 100mm and length
not less than 100mm will be drilled from each panel.
10.2 Installation of Rock Bolt
The Engineer’s approval will obtain for the rock bolt and for all the necessary auxiliary material
prior to fully grouted rock bolt construction. And also, the approval will be obtained for the
grouting slurry mix proportion from the Engineer in advance.The scaffoldings and access facilities,
such as ladders, will be arranged and the holes for rock bolt will be marked in accordance with the
approved construction drawings. The deviation of marked location from design will be controlled
within 50mm tolerance. The engineers’ inspection will be called upon after completing the setting
out of holes locations and drilling work will be started after his confirmation.
Preparation
Drilling Hole
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Pneumatic drill or Down – the – hole, (DTH) drilling machine will be used to drill the rock bolt
holes in compliance with design length plus additional 100mm and inclination. Diameter of the
bolt hole is between φ+15mm and φ+35mm. The dross in the rock bolt hole will be cleaned with
compressed air as soon as bolt hole drilling completed. Then the hole will be kept clean until
grouting and bolt installation completed.
Grout will be mixed from ordinary Portland cement and clean water. The water-to-cement ratio is
the most important factor in grout which will not be exceeded 0.45 as per engineer’s requirement.
The appropriate grout mix design will be proposed to the Engineer and mix design will be carried
out under engineer’s supervision and confirm the specified strength and a proper workability in
association with the grouting device used.
The influence of additives to the strength development which may use for improving workability
will be tested by grout mortar cub compressive strength testing. Five cubes (50mm) will be
prepared for each compressive strength test and the resultant strength will be the average evaluated
from the 3 remaining values after eliminating of the highest and lowest results.
The grout will be free from segregation and grout will be mixed on site and will be pumped under
appropriate pressure in to the holes and the bolts will be inserted to the center of the drilling holes.
It is important to ensure that the grout mortar is perfectly compacted in the hole to prevent in
accurate results.
Ten cubes (50mm Cubs) of grout mortar will be taken weekly during construction for testing
purpose.
Any remaining void at the exterior end of the drilled hole of a rock bolt assembly will be filled
with grout and the rock bolt secured at the surface with shotcrete.
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Figure14: Fully grouted rock bolt. The bolt consists of three parts; rod, face plate and a
bonding.
Rock bolts will be carried out according to the Support Class and will be installed with the lengths
and in the patterns shown on the Drawings for each relevant standard support system which is
decided by engineering geologist after tunnel mapping, unless otherwise directed by the Engineer.
Comprehensive records about details of the installation of rock bolts, such as grout consistency,
drilling depth, length and type of rock bolts, type and time of grouting, time of tightening, special
observations, etc. will be kept for each round and countersigned by the representative of the
Engineer during all rock bolt installation activities.
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(a.) Steel Girder Processing and Production
Processing Sequence
(b).Operation method
Rebar and steel section processing:
- The required rebar shall be cut out as per required dimensions according to
bending schedule.
- Adjust the shape of reinforcement bar according to the tunnel curvature as
shown in lattice girder drawing.
Welding forming:
- all parts of the welded girder shall be assembled according to the
requirements of the drawings.
- The end steel section shall be tightened with connection bolts and steel plate
holes to ensure the accuracy of connection holes of all parts of the girder.
After the parts of the girder are preliminarily welded and fixed in the mold, the
parts of the girder are uniformly and symmetrically removed from the mold to
avoid the distortion of the girder. According to the welding specification and
design requirements, the steel girder parts shall be welded into shape, and the
welding shall be evenly and symmetrically to reduce the stress and deformation
acceptance:
- after welding all components of the reinforcement grid, a trial assembly shall
be carried out to check the geometric size of the reinforcement grid, bolt
joints of each component and welding quality, etc.
- After the first truss is qualified and accept, then carry on the batch
production, and carries on the batch acceptance according to the stipulation
sampling.
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(c).Installation of steel girder
Processing Sequence
( d.)Operation method
Grid erection:
(1) on-site sampling and trial assembly: the steel girder shall be sampled and assembled
in batches. The ground shall be flat and spacious, and only after qualified assembly can
the girder be installed.
(2) After qualified on-site test, the girder shall be placed in the design position and
pre-fixed. The elevation and position of the girder shall be controlled and positioned by
laser instrument.
(3) after the girder is installed and positioned, the outer bolt of the vault shall be
tightened first, and then the inner two bolts shall be tightened. If necessary, the
reinforcement of the same type as the main reinforcement can be used for welding.
Installation of the outer mesh:
After the girder is installed, the outer mesh shall be installed according to the design
requirements. The processing width of the steel mesh shall be the same as the
construction step distance of the girder. The longitudinal and circumferential lap length of
the steel mesh shall be no less than two grid widths. Between the mesh, mesh and steel
girders, longitudinal connection of steel should be welding binding firm.
Welding of longitudinal connecting rebar
(1) after the girder is installed and positioned, longitudinal connecting rebar shall be
set as required in the drawings.
(2) Longitudinal connecting bars are distributed along the main ring of the girder,
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which are divided into two inner and outer rows. The spacing between connecting bars
and rings in each row meets the design requirements, and is firmly welded.
(3) Installation of the inner mesh: the inner mesh shall be laid along the main arcing
bars and longitudinal connecting bars on the inner side of the girder and shall be firmly
tied.
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10.4 Tunnel Lining
Steel system formwork shall be used for lining concrete works in Ranwediyawa tunnel. The
formwork model arrangement for tunnel lining is as shown below.
Concrete lining shall start after finished the soil excavation and rock blasting works. Because
as per above sketch, there is a limited space after placing the formwork system. It is unable to
travel any dumping truck or machinery within this limited space.
The length of formwork system is 12m. This total length is divided into two segment with 9m
and 3m lengths. The 3m long segment will be used to curve lining works. As well as separate
windows are available in formwork panels to pour the concrete and to other works. Mainly
three numbers of panels are available in sectional view as shown below.
(Refer Attachment 2- System Formwork Panel Arrangement)
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11.4 Lighting
Proper Tunnel Lighting Systems will be developed for the Tunneling. The lighting system
complies with the Requirements of BS 6164. This system will be designed with the construction
and tunneling environment in mind.
Apply 400W miner’s lamps near cutting face, as illustrated in longitudinal profile.
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11.5 Ventilation
A proper ventilation system will be installed for the tunnel which would sufficient capacity to
maintain an adequate supply of uncontaminated air in underground excavations throughout the
tunnel construction period.
And also, tunnel atmosphere will be monitored by a standard atmosphere monitoring system.
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Ventilation calculation
1. Calculate the wind volume according to the maximum number of people working at the same
time in the tunnel
The maximum number of working personnel on the working surface is 6, and the air volume
required by the construction personnel is calculated according to the following formula:
Q1 = Q * M * K = 3 * 10 * 1.15 = 34.5 m3 / min
Where;
Q -- Fresh air requirement per person inside the cave;(3 m3/min per person)
M -- The maximum number of people working in the hole at the same time( 10 person)
K -- Air volume reserve coefficient, take 1.0~1.15, (consider 1.15 here.)
2. Calculate the air volume according to the minimum allowable wind speed in the tunnel
Q2 = 60 * S * v
Where;
S -- Tunnel cross section area, m2,( 13.85m2 for this project);
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V -- Minimum allowable wind speed, (0.15m/min for full section excavation);
Q2=60 * 13.85 * 0.15 = 124.6 m3 / min
3. Calculate the maximum explosive amount used for blasting within the same time in the cave
Q3=5 m * B/T
Where;
Q3 -- quantity required for smoke extraction by blasting, m3/min
M -- Consumption of explosive for a single blasting, kg, take 91.4kg here;
B -- Carbon monoxide volume (L) produced by blasting of 1kg explosive, generally 40;
T -- Ventilation time, take 40min here;
Q3 = 5 * 91.4 * 40/40 = 457 m3 / min
4. Selection of ventilation equipment
4.1 fan volume calculation
Qj= (1+PL/100) Qi= (1+2%*310/100) *457= 485.3m3 /min
Qj- fan calculates air volume
Qi- the operating surface needs air volume
P- Duct wind resistance coefficient
L- Ventilation distance
4.2 fan pressure calculation
The fan pressure is the sum of the frictional resistance and local resistance of the duct
Hf=H friction +HD+H other =RfQjQi/3600+HD+H other
Rf=6.5 alpha L/D5, when D=0.6m, Rf=38.87;When D=0.8m, Rf=9.23.
Hf 457/3600 = 38.87 * 485.3 * + 50 + 60
= 2505.6
5. Fan power calculation
W = QHK / 60 eta
60 * = 485.3 * 2505.6 * 1.05 / (0.8) = 26599.3 w = 26.6 kw
Q- Working air volume of fan
H- Fan operating pressure
K- Power reserve factor
Eta -work efficiency
Ventilation equipment selection of 2x11kw axial fan, ventilation pipe used with 80cm flame
retardant hose.
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11.6 Drain
The seepage ground water from the tunnel will be controlled in systematically to make proper
working area. Proposed ground water controlling is based on to the procedures and specifications
detailed in the section 5 Clause (5.3.7) of the Technical Specification.
After tunnel excavation, if there is a concentrated seepage point on the surface of the surrounding
rock, a half drainage pipe can be arranged along the circumferential direction of the surface of the
surrounding rock, and the water on the top of the tunnel can be directed to the drainage ditch along
the half drainage pipe, rather than dropping randomly. Drainage and half pipe using phi 50 of the
PVC tube is split in two and fix with Ω plastic positioning device. (Refer Figure 17) The invert of
the tunnel is provided with a transverse slope of 2% to discharge water into the temporary drainage
ditch. The section size of the drainage ditch is 20cm*20cm, and the longitudinal slope at the
bottom of the trench is equal to the slope ratio of the tunnel body. Drain longitudinal every 30
meters set up a water pit, 40cm*40cm of the cross section, in order to use water pump drainage.
A sump pit shall be arranged at a suitable location to collect all the drain water. The collected
water will be pumped out with a 7.5kW water pump. The construction wastewater will be
discharged to the sedimentation tank which would be located in a suitable location. Once the water
is clear from the sediment it will be discharged to the ground surface or natural stream channel
after checking the water quality.
During the tunnel excavation through water-bearing area, seepage from the discontinuities is taken
place. A large amount of water which inflows into the tunnel can be affected for lowering of
groundwater table around the project area. Hence, water inflow of tunnel will be recorded as
inflow rate (ℓ/min) during tunnel construction. Reduction of seepage after applying for rock
support also will be noticed.
According to technical specification Section 5.3.4.4 Rock Probe Drilling Ahead of D&B
Excavation, in order to detect cavities, pockets filled with soft and broken material, shear zones,
gauge filled faults and groundwater, probe drilling will be carried out whenever it is required and
subject to the Engineer instruction.
Probe hole will be drilled by means of percussion drilling at the 3 or 9 o’clock position or as
indicated by the Engineer. Probe drilling in advance would always keep a distance of at least 5
meters from the excavation face. The standard probe drilling length is 20 m and hole diameter is
between 48mm and 56mm. Probe drilling would be done only in the presence of contractor’s
geologist who would be recorded all findings.
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Inflowing of groundwater may cause of the weakening of rock joints contact, thus, it may also
weaken the stability of rock mass of the tunnel. Therefore, if an unexpectedly severe influx of
water is encountered from faults or fracture zones, it will be reduced the inflow of water by
grouting as directed by the Engineer.
Sufficient water samples will be collected from water flowing out of fissures or faults and
chemically analyzed in order to determine the aggressivity of the water towards concrete in
accordance with the requirement of Section 3 [Concrete Works] of the Specification. The pH and
temperature of the water will be measured directly in the tunnel where the sample is taken.
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Construction of Main Canal from Nebadagahawatta to Mahakithula Reservior Inlet Tunnel (from 5+250km to 22+300).
Ranwediyawa Tunnel construction will be carried out from two direction inlet and outlet portals.
Basically single workman shift will be implemented at the beginning and double workman shift
will be operated whenever required during tunnel construction as day and night shift which is
subjected to the Engineer’s approval.
Day Shift will be from 7:00 Am to 7:00 Pm
Night Shift will be from 7:00 Pm to 7:00Am
Start Finish
m
Excavation & Support Work at RanwediyawaTunnel 1-Jul-19 16-Jul-20 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20 May-20 Jun-20 Jul-20
Ite
2 Tunnel Excavation and Support(~310m from Intlet portal) 1-Sep-19 15-Jan-20 1/9/2019 - 15/1/2020
3 Tunnel Lining(~310m from Intlet portal) 16-Jan-20 16-May-20 16/1/2020 - 16/5/2020
4 Outlet Portal Construction and Temporaray Facilities 1-Sep-19 30-Oct-19 1/ 9 / 19 - 3 0 / 10 / 19
5 Tunnel Excavation and Support(~310m from Outlet portal) 1-Nov-19 15-Mar-20 1/11/2019 - 15/3/2010
6 Tunnel Lining(~310m from Outlet portal) 16-Mar-20 16-Jul-20 16/3/2020 - 16/7/2020
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15.0 Inspection and Test Plan for Tunnel Construction
To improve the quality of the work, the proposed inspection and test plan is included as an
attachment (Refer Annexure- 1)
The Tunneling area consists of paddy land, Home garden, Forest reservation, abandoned land rock
area, irrigation and natural stream as well as surrounded by human settlements. Therefore, it has
been subjected to various human pressures on biological environment for many decades. There are
natural habitats within to the forest area. Also, the proposed project important as a biologically
significant.
The proposed site which is consist of different land fatten with forest area too, Therefore, the
environmental and biological importance is also significant. However, the Constructer proposed all
construction activity to mitigation measures to reduce the environmental issues.
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approval.
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drainage system will be done to separate it
out from the clean water drainage system.
As the tunnel will be open for vehicular
traffic carrying dangerous goods, the
drainage system will consist of a slotted
gutter. This will be connected to the
principal longitudinal drains by gully pits
containing a siphon system
Water collection basins will be put at each
end of the portals where drainage water will
be collected.
Implement Proper drainage management
plan with engineering designs.
To avoid siltation in the waterways
crossing the project site, temporary
drainage paths from construction sites
will not be directly sent to the Streams
without passing through a silt trap
Implementation of suitable disposal
methods of sediment construction
debris in tune with the local condition
to avoid water logging at construction
site
Proper drainage and sanitation facilities
will be provided at the construction site
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four time’s day) as the levels of dust can be
elevated during dry periods.
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Construction of Main Canal from Nebadagahawatta to Mahakithula Reservior Inlet Tunnel (from 5+250km to 22+300).
where necessary
To avoid siltation, drainage paths will not
be directed to paddy fields / marshy lands
and they will be kept separated from the
paddy fields / marshy lands when road
lying along paddy fields / marshy lands
Disposed materials will not be allowed to
wash away during floods
To avoid erosion of unloaded soil, the
disposal will be leveled once a week in dry
period or regularly during rainy season.
Water spraying will be done regularly
Air Quality Due to the Storage areas should be located Identify construction
and dust constructi downwind of the habitation area. activity to small
emissions machineries/ vehicles
on activity
(Vehicles, Mask and other PPE shall be provided to
the all construction workers.
Machineri
es) Road transportation vehicles should not
be loaded with bulk materials beyond
the safe-clearance and the materials
should be covered during transportation;
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Construction of Main Canal from Nebadagahawatta to Mahakithula Reservior Inlet Tunnel (from 5+250km to 22+300).
gases of engines.
. Leakage of Constructi Grouting poor quality fractured rock in the Frequent Monitoring
ground on tunnel face will be done. programs
water into the activities Shot creating and anchor bolting of the
tunnel tunnel face will be done.
. Ground Rock The contractor carries out crack surveys Frequent Monitoring
vibration, blasting programs
cracks, activities The complains through GRC will be
foundation attended.
failures
during
tunnel
construction,
rock blasting
Effects on All archaeological property found during Frequent Monitoring
archaeological works will be treated in accordance with programs
sites national legislation. In the event of the
unexpected discovery of archaeological
objects the Contractor will immediately
cease the activity at the site until further
order from the Supervision Engineer, and
immediately inform the Supervision
Engineer, the Employer, and the local and
archaeological authorities and follow their
directions of Archaeological department
through Engineer/PD of PIU
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sedimentary Appropriate blasting design will be adopted
considering safety, blast geometry, free
b. The blasting faces, burden, spacing, initiation pattern and
operations angled holes followed by test blasting and
will
obtaining required approvals
lead to rock
movement,
minor
fragmentations
and vibrations.
Thus directly
impacting the
geology.
Nuisance to Temporary access will be provided when
the public due permanent access is blocked for
to hindrance construction. When construction work is in
to access,
progress on one side, the other side will be
dust, noise and
traffic issues opened for traffic & properly trained
etc. flagmen will be made available with proper
sign boards for control vehicles. At the end
of each day, the debris that blocked access
path will be cleared away under the
supervision of a supervisor.
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The Contractor with the Site Engineer will
ensure to comply with the mitigatory
measures.
Surface soil
erosion,
siltation into The debris material will be disposed in
water bodies, such a manner that waterways, drainage
paddy fields & paths would not get blocked.
marshy lands, Drainage paths in LB / RB of the canal will
blockage of be improved / erected to drain rain water
water ways & properly.
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drainage paths, Earth / scupper drains on the road along
wash away the LB canal, will be developed (erected,
of disposing deepen & reshaped) to drain rain water
soil materials properly.
during floods Silt traps will be constructed to avoid
are created siltation into waterways and paddy fields
while handling where necessary
dispose soil & To avoid siltation, drainage paths will not
other be directed to paddy fields / marshy lands
construction and they will be kept separated from the
waste material paddy fields / marshy lands when road
lying along paddy fields / marshy lands
Disposed materials will not be allowed to
wash away during floods
To avoid erosion of unloaded soil, the
disposal will be leveled once a week in dry
period or regularly during rainy season.
Water spraying will be done regularly
The Contractor with the Site Engineer will
ensure to comply with the mitigatory
measures.
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Muck disposal Muck disposal will be done only in the Waste designated at the
and Impact designated areas. site
due to Soft soil from excavations may be used
construction in road embankments if necessary, after Making the workers
waste aware on the waste
proper treatment.
Recrement obtained from tunnel management
excavation can be used in production of
aggregates for road making.
Hard rock can be used in construction
of retaining walls as well as gabion
walls. Reuse of excavated material after
testing their suitability will minimize
requirement surface areas for dumping.
The debris and spoil shall be disposed
in such a manner that;
(i) waterways and drainage paths
are not blocked
(ii) the disposed material should not
be washed away by runoff an
(iii) should not be a nuisance to the
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Construction of Main Canal from Nebadagahawatta to Mahakithula Reservior Inlet Tunnel (from 5+250km to 22+300).
All the rock drilling and blasting works shall be done under the supervision of a qualified Mining
Engineer as per the Contract agreement.
Monitoring on following factors will be done by third party monitoring group accepted by Central
Environmental Authority (CEA) and Geological Survey and Mines Bureau (GSMB);
Soil erosion
Disposal waste
Loss of vegetation cover and Spreading on invasive species
Surface water
Ground water
Noise and vibration
Fauna and Flora
Blasting Parameters
Ground vibration level
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17.0 Safety Requirements for Tunnel Construction
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new charge in close contact with the undetonated one. If the shooting of undetonated
explosive is unsuccessfully, try to remove it with water under pressure.
After undetonated explosive have been taken care of, the area shall be carefully checked
again.
During the loading with electric detonators, the following points must be observed:
Do not let the leads to the detonators, at any time during the loading; come in contact with
metallic objects
Do not keep electrical lamps and. electrical pumps too close to the work place during
loading.
Increased safety during loading is achieved by use of insulator sleeves at the free end of the
leads.
Under thunder weather and risk of lightning, the procedure is to discontinue all loading
with electric detonators.
Exhaust emission from vehicle can also cause static electricity buildup and should not be
allowed too close to places. Where detonators are being hooked up.
Note: Effective lightning devices are available. They register flashes of lightning and electricity
in atmosphere.
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