Experiment 11-Consolidation

119
EXPERIMENT 11
CONSOLIDATION
TEST
Purpose:
This test is performed to determine the magnitude and rate of volume
decrease that a laterally confined soil specimen undergoes when subjected to
different vertical pressures. From the measured data, the consolidation curve
(pressure-void ratio relationship) can be plotted. This data is useful in determining
the compression index, the recompression index and the preconsolidation pressure
(or maximum past pressure) of the soi. In addition, the data obtained can also be
used to determine the coefficient of consolidation and the coefficient of secondary
compression of the soil.
Standard Reference:
ASTM D 2435 - Standard Test Method for One-Dimensional Consolidation
Properties of Soils.
Significance:
The consolidation properties determined from the consolidation test are used
to estimate the magnitude and the rate of both primary and secondary consolidation
settlement of a structure or an earthfill. Estimates of this type are of key importance
in the design of engineered structures and the evaluation of their performance.
Equipment:
Consolidation device (including ring, porous stones, water reservoir, and load plate),
Dial gauge (0.0001 inch = 1.0 on dial), Sample trimming device, glass plate, Metal
Engineering Properties of Soils Based on Laboratory

Testing Prof. Krishna Reddy, UIC
119
straight edge, Clock, Moisture can, Filter paper.

120

12
Test Procedure:
(1) Weigh the empty consolidation ring together with glass plate.
(2) Measure the height (h) of the ring and its inside diameter (d).
(3) Extrude the soil sample from the sampler, generally thin-walled Shelby tube.
Determine the initial moisture content and the specific gravity of the soil as
per Experiments 1 and 4, respectively (Use the data sheets from these
experiments to record all of the data).
(4) Cut approximately a three-inch long sample. Place the sample on the
consolidation ring and cut the sides of the sample to be approximately the
same as the outside diameter of the ring. Rotate the ring and pare off the
excess soil by means of the cutting tool so that the sample is reduced to the
same inside diameter of the ring. It is important to keep the cutting tool in
the correct horizontal position during this process.
(5) As the trimming progresses, press the sample gently into the ring and
continue until the sample protrudes a short distance through the bottom of
the ring. Be careful throughout the trimming process to insure that there is
no void space between the sample and the ring.
(6) Turn the ring over carefully and remove the portion of the soil protruding
above the ring. Using the metal straight edge, cut the soil surface flush
with the surface of the ring. Remove the final portion with extreme care.

12
(7) Place the previously weighed Saran-covered glass plate on the freshly cut
surface, turn the ring over again, and carefully cut the other end in a similar
manner.
(8) Weigh the specimen plus ring plus glass plate.
(9) Carefully remove the ring with specimen from the Saran-covered glass plate
and peel the Saran from the specimen surface. Center the porous stones that
have been soaking, on the top and bottom surfaces of the test specimen.
Place the filter papers between porous stones and soil specimen. Press very
lightly to make sure that the stones adhere to the sample. Lower the
assembly carefully into the base of the water reservoir. Fill the water
reservoir with water until the specimen is completely covered and saturated.
(10) Being careful to prevent movement of the ring and porous stones, place the
load plate centrally on the upper porous stone and adjust the loading device.
(11) Adjust the dial gauge to a zero reading.
(12) With the toggle switch in the down (closed) position, set the pressure gauge
dial (based on calibration curve) to result in an applied pressure of 0.5 tsf
(tons per square foot).
(13) Simultaneously, open the valve (by quickly lifting the toggle switch to the
up (open) position) and start the timing clock.

12
(14) Record the consolidation dial readings at the elapsed times given on the
data sheet.
(15) Repeat Steps 11 to 13 for different preselected pressures (generally

includes loading pressures of 1.0, 2.0, 4.0, 8.0, and 16.0 tsf and
unloading pressures of 8.0, 4.0, 2.0, 1.0 and 0.5 tsf)
(16) At the last elapsed time reading, record the final consolidation dial reading
and time, release the load, and quickly disassemble the consolidation
device and remove the specimen. Quickly but carefully blot the surfaces
dry with paper toweling. (The specimen will tend to absorb water after
the load is released.)
(17) Place the specimen and ring on the Saran-covered glass plate and, once
again, weigh them together.
(18) Weigh an empty large moisture can and lid.
(19) Carefully remove the specimen from the consolidation ring, being sure not
to lose too much soil, and place the specimen in the previously weighed
moisture can. Place the moisture can containing the specimen in the oven
and let it dry for 12 to 18 hours.
(20) Weigh the dry specimen in the moisture can.
Analysis:
(1) Calculate the initial water content and specific gravity of the soil.

12
(2) For each pressure increment, construct a semilog plot of the consolidation
dial readings versus the log time (in minutes). Determine D0, D50, D100, and
the coefficient of consolidation (cv) using Casagrande’s logarithm of time
fitting method. See example data. Also calculate the coefficient of
secondary compression based on these plots.
(3) Calculate the void ratio at the end of primary consolidation for each
pressure increment (see example data). Plot log pressure versus void ratio.
Based on this plot, calculate compression index, recompression index and
preconsolidation pressure (maximum past pressure).
(4) Summarize and discuss the results.

12
EXAMPLE DATA

12
Consolidation Test
Data Sheets
Date Tested: October 05, 2002
Tested By: CEMM315 Class, Group A
Project Name: CEMM315 Lab
Sample Number: GB-08-ST-13’-15’
Visual Classification: Gray silty clay
Before test
Consolidation type = Floating type

Mass of the ring + glass plate = 465.9 g
Inside diameter of the ring = 6.3 cm
Height of specimen, Hi = 2.7 cm
Area of specimen, A = 31.172 cm2
Mass of specimen + ring = 646.4 g
Initial moisture content of specimen, wi (%) = 19.5 %
Specific gravity of solids, Gs = 2.67
After test
Mass of wet sample + ring + glass plate = 636.5 g

Mass of can = 59.3 g
Mass of can + wet soil = 229.8 g
Mass of wet specimen = 170.50 g
Mass of can + dry soil = 208.5 g
Mass of dry specimen, Ms = 149.2 g
Final moisture content of specimen, wf = 14.27 %

12
Calculations
Mass of solids in specimen, Ms =149.2 g

(Mass of dry specimen after test)
Mass of water in specimen before test, Mwi = wi x Ms

= 0.195*149.2 = 29.094 g
Mass of water in specimen after test, Mwf (g) = wf x Ms

= 0.1427*149.2 = 21.29 g
Height of solids, Hs = Ms 149.2 = 1.792 cm

A  Gs  
31.172  2.67 
w
1
(same before and after test and note w = 1 g/cm3)
Height of water before test, Hwi = M wi 29.09 = 0.933 cm

 31.172 1
A  w
Height of water after test, Hwf = M wf  21.29 = 0.683 cm

A 31.172  1
w
Change in height of specimen after test, H =0.257 cm

(H for all pressures – see t vs Dial Reading plots)
Height of specimen after test, Hf = Hi - H = 2.7-0.257 = 2.443 cm
H i  Hs 2.7  1.792
Void ratio before test, eo =  = 0.506
Hs 1.792
H f  Hs 2.443 -
Void ratio after test, ef =  = 0.3617
Hs 1.792
1.792
Degree of saturation before test, Si =

12
H wi
H i  Hs 
0.933
100
2.7 
1.79
2
=102.7
%

12
Degree of saturation after test, Sf = H wf 0.683

 2.443  1.792  100
Hf H
s =105.08%
Dry density before test, d = Ms 149.2

 = 1.77 g/cm3
Hi 2.7  31.172
A =(110.6 pcf)

13
Table 1: Time - Settlement Data (1 unit on dial guage = 0.0001 inches)

loading= ¼ tsf loading=1/8 tsf loading=1/2 tsf loading=1 tsf
time dail reading time dail reading time dail reading time dail reading
0 0 0 0 0 0 0 0
0.1 0 0.1 0 0.1 13 0.1 6
0.25 0 0.25 0 0.25 18 0.25 8
0.5 0 0.5 0 0.5 25 0.5 11.5
1 1 1 34 1 15
2 2 2 40 2 20.5
4 4 4 54 4 27
8 8 8 77 10 42
15 15 15 90 15 46
30 30 30 126 31 58
60 60 60 144.5 60 79
120 120 130 160 121 81
300 162 240 85
1380 169 562 86
loading=2 tsf
time dail reading
0 255 loading=4 tsf loading=2 tsf (unloading) loading=1 tsf (unloading)
0.1 255.5 time dail reading time dail reading time dail reading
0.25 256 0 313 0 496 0 492.5
0.5 256.5 0.06 319 0.1 496 0.1 492.5
1 257 0.15 328 0.25 496 0.25 492.5
2 257.5 0.3 336 0.5 495.5 0.5 492
4 258 1 357 1 495 1 490.5
8 258.5 2 375 2 494 2 486.5
15 262.5 4 398 4 493.5 4 481.5
30 283 8 428 8 493 8 477.5
60 286 15 453 15 492.5 15 474.5
128 292.5 30 464 30 492.5 44 472.5
240 297 60 472.5 70 492.5 60 471.5
335 299 120 479.5 140 492.5 218 470.5
390 300 290 486 215 492.5
678 303 395 488
1380 303.5 1230 496
1520 304
loading=1/2 tsf loading=1 tsf (reloading) loading=2 tsf (reloading) loading=4 tsf (reloading)
(unloading) time dail reading time dail reading time dail reading
time dail reading
0 470.5 0 440.5 0 442.4 0 446.5
0.06 469.5 0.1 440.7 0.1 442.9 0.1 446.5
0.5 466 0.25 441 0.25 443.4 0.25 446.6
1 464.5 0.5 441.2 0.5 444.4 0.5 449.5
2 461.5 1 441.5 1 445.1 1 456.5
4 458.5 2 441.6 2 445.3 2 465.5
8 454 4 441.8 4 445.4 4 473.5
15 450.5 8 442 8 445.9 8 481
30 447 15 442.1 15 446.3 17 485.5
60 444.5 30 442.4 30 446.4 30 488
110 443.5 60 442.4 60 446.5 108 490.5
930 440.5
120 442.4 120 446.5 947 500

13
loading=8 tsf loading=16 loading=32 tsf

time dail reading time dail reading
0 500 tsf 0 867
0.1 510 time dail reading 0.1 877
0.25 518 0 652 0.25 893
0.5 528 0.1 672 0.5 908
1 542 0.25 687 1 928
2 561.5 0.5 702 2 953
4 580 1 727 4 983
8 604 2 754 8 1012
15 619.5 4 800.5 15 1027
30 631.8 8 816 30 1040
60 640 15 836.5 50 1047.5
127 642 30 850 76 1052.5
205 651 60 860 138 1060
228 652 115 867 240 1063

13
Consolidation Test (ASTM D

2435) Sample: GB-08-ST-13'-15'
Pressure = 1/2 tsf
0
D0 = 8
20 D 100
D  8 159  83.5
D  0
50 22
40
Dail Reading (x 0.0001
60
   in t50=10 min

80
100
120
140
D100 = 159
160
180
0.01
0.1 1 10 100 1000 10000
Time (min)
Consolidation Test (ASTM D 2435)

Sample: GB-08-ST-13'-15'
Pressure = 1 tsf
170
180
190
200
210 H = 0.008 in t50 = 11.5 min
220
230
240
250
260
0.01
0.1 1 10 100 1000 10000
Time (min)

13

Pressure = 2 tsf
240
250
260
270
t50 = 30 min
280 H = 0.0048 in
290
300
310
320
0.01
0.1 1 10 100 1000 10000
Time (min)

Pressure = 4 tsf
300
320
340
360
380 t50 = 3.3 min

H = 0.0156 in
400
420
440
460
480
500
520
0. 0 1 10 1 10 100
Time

13

Pressure = 2 tsf (Unloaded)
497
496.5
496
495.5
495
494.5
H = 0.00035 in t50 = 1.9 min
494
493.5
493
492.5
492
0.01
0.1 1 10 100 1000 10000
Time (min)

Pressure = 1 tsf (Unloaded)
495
490
485
H = 0.00203 in t50 = 3.5 min
480
475
470
465
0. 0 1 10 1 10 100
Time

13

Pressure = 1/2 tsf (Unloaded)
480
475
470
465
460
H = 0.0029 in t50 = 6.0 min
455
450
445
440
435
430
0.01
0.1 1 10 100 1000 10000
Time (min)

Pressure = 1 tsf (Reloaded)
440
440.5
441
H = 0.00018 in t50 = 1.2 min

441.5
442
442.5
443
0. 0 1 10 1 10 100
Time

13

442
443
444
t50 = 0.6 min

H = 0.00038 in
445
446
447
448
0.01
0.1 1 10 100 1000 10000
Time (min)

445
455
465 t50 = 2.4 min

H = 0.0043 in
475
485
495
505
0. 0 1 10 1 10 100
Time

13

Pressure = 8 tsf
500
520
540
560
t50 = 3.0 min
H = 0.0143 in
580
600
620
640
660
0.01
0.1 1 10 100 1000 10000
Time (min)

Pressure = 16 tsf
650
670
690
710
730
H = 0.02 in
750 t50 = 2.0 min
770
790
810
830
850
870
0.01 0.1 1 10 100 1000 10000

Time (min)

13

Pressure = 32 tsf
850
870
890
910
930
t50 = 3.0 min
950
H = 0.0192 in
970
990
1010
1030
1050
1070
1090
0.01 0.1 1 10 100 1000 10000

Time (min)

138
Table 2: Analysis of Consolidation Test Data
Time for 50% D0 D100 H Coefficient of

Pressure D50 = Hj = D50 *
consolidatio (from (from (from  H* H**
Hd** consolidatio Hv*** e***
(tsf) graph) (D0+D100)*0.5 0.0001
n t 50 (min) graph) graph) n Cv
(in2/min)***
0 1.06299
0.5 10 8 159 83.5 0.00835 0.0153 0.0153 1.04769 0.52593 5.45E-03 0.34 0.48
1 11.5 173 254 213.5 0.02135 0.008 0.0233 1.03969 0.52518 4.72E-03 0.33 0.47
2 30 254 301 277.5 0.02775 0.0048 0.0281 1.03489 0.52438 1.81E-03 0.33 0.47
4 3.3 310 362 336 0.03360 0.0156 0.0437 1.01929 0.51805 1.60E-02 0.31 0.44
2 1.9 496 492.5 494.25 0.04943 0.0004 0.04335 1.01964 0.52218 2.83E-02 0.31 0.44
1 3.5 493 472.5 482.5 0.04825 0.002 0.04132 1.02167 0.52290 1.54E-02 0.32 0.45
0.5 6 472 442 457 0.04570 0.0029 0.03842 1.02457 0.52371 9.01E-03 0.32 0.45
1 1.2 441 442.4 441.5 0.04415 0.0002 0.0386 1.02439 0.52323 4.49E-02 0.32 0.45
2 0.6 443 446.5 444.55 0.04446 0.0004 0.03898 1.02401 0.52312 8.98E-02 0.32 0.45
4 2.4 446 489 467.5 0.04675 0.0043 0.04328 1.01971 0.52154 2.23E-02 0.31 0.44
8 3 504 650 577 0.05770 0.0143 0.05758 1.00541 0.51713 1.76E-02 0.30 0.42
16 2 660 861 760.5 0.07605 0.02 0.07758 0.98541 0.51172 2.58E-02 0.28 0.40
32 3 869 1060 964.5 0.09645 0.0192 0.09678 0.96621 0.50722 1.69E-02 0.26 0.37
*
H for applied pressure = H of all previous pressures + H under applied pressure
H
j H j
** H   and H  H  H (- for Loading and + for Unloading)
dj 4 j i j1
2
2
Hd , Hv
*** C v  0.197 
t
50
Hv  i

H  Hs  H and e 
 Hs
Engineering Properties of Soils Based on Laboratory Testing

Prof. Krishna Reddy, UIC
13

Void Ratio vs Log Pressure
Pc=3.5 tsf
0.49
0.47
0.45
Cr=0.013
0.43
Void
0.41
Cc=0.11
0.39
0.37
0.35
0.1 1 10 100
Pressure (tsf)
Final Results:
Compression Index (Cc) = 0.11
Recompression Index (Cr) = 0.013
Preconsolidation pressure (Pc) or Maximum past pressure (vmax) = 3.5 tsf
Coefficient of consolidation (Cv)= 1.54x10-2 to 9.01x10-3 in2/min (depends on

the pressure)
Coefficient of secondary compression (C) = 0.001

(It is the slope of time vs settlement curve beyond the end of primary consolidation)

14
BLANK DATA SHEETS

14
Consolidation Test
Data Sheets
Date Tested:
Tested By:
Project Name:
Sample Number:
Sample Description:
Before test
Consolidation type =
Mass of the ring + glass plate =
Inside diameter of the ring =
Height of specimen, Hi =
Area of specimen, A =
Mass of specimen + ring =
Initial moisture content of specimen, wi (%) =
Specific gravity of solids, Gs =
After test
Mass of wet sample + ring + glass plate =

Mass of can =
Mass of can + wet soil =
Mass of wet specimen =
Mass of can + dry soil =
Mass of dry specimen, Ms =
Final moisture content of specimen, wf =

14
Calculations
Mass of solids in specimen, Ms =

(Mass of dry specimen after test)
Mass of water in specimen before test, Mwi = wi x Ms=
Mass of water in specimen after test, Mwf (g) = wf x Ms=
Height of solids, Hs = Ms
A  Gs   w =
(same before and after test and note w = 1 g/cm3)
Height of water before test, Hwi = M wi

=
A  w
Height of water after test, Hwf = M wf

A  w 
=
Change in height of specimen after test, H =

(H for all pressures – see t vs Dial reading plot)
Height of specimen after test, Hf = Hi - H =
Void ratio before test, eo =

Hi  Hs
Hs =
Void ratio after test, ef = H f  Hs

H =
s
H wi
Degree of saturation before test, Si = =
Hi  Hs
Degree of saturation after test, Sf = H wf

H f  H s=

14
Dry density before test, d = Ms

HiA =

14
Time - Settlement Data
Conversion: 0.0001 inch = 1.0 on dial reading (confirm this before using)
LOADING = tsf LOADING = tsf LOADING = tsf

ELAPSED DIAL ELAPSED DIAL ELAPSED DIAL
TIME, min READING TIME, min READING TIME, min READING
0 0 0
0.1 0.1 0.1
0.25 0.25 0.25
0.5 0.5 0.5
1 1 1
2 2 2
4 4 4
10 10 10
15 15 15
30 30 30
60 60 60
120 121 120
240 240 240

144
Analysis of Consolidation Test Data
Time for 50% D0 D100 H Coefficient of

Pressure D50 = Hj = D50 *
consolidatio (from (from (from  H* **
H Hd** consolidatio Hv*** e***
(tsf) graph) (D0+D100)*0.5 0.0001
n t 50 (min) graph) graph) n Cv (in2/min)
*
H for applied pressure = H of all previous pressures + H under applied pressure
H
j H j
** H   and H  H  H (- for Loading and + for Unloading)
dj 4 j i j1
2
2
Hd , Hv
*** C v  0.197 
t
50
Hv  i

H  Hs  H and e 
 Hs
Engineering Properties of Soils Based on Laboratory Testing

Prof. Krishna Reddy, UIC

Experiment 11-Consolidation

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119

Engineering Properties of Soils Based on Laboratory

Engineering Properties of Soils Based on Laboratory

Engineering Properties of Soils Based on Laboratory

Engineering Properties of Soils Based on Laboratory

(8) Weigh the specimen plus ring plus glass plate.

(11) Adjust the dial gauge to a zero reading.

Engineering Properties of Soils Based on Laboratory

(15) Repeat Steps 11 to 13 for different preselected pressures (generally

(18) Weigh an empty large moisture can and lid.

(20) Weigh the dry specimen in the moisture can.

Engineering Properties of Soils Based on Laboratory

(4) Summarize and discuss the results.

Engineering Properties of Soils Based on Laboratory

Engineering Properties of Soils Based on Laboratory

Date Tested: October 05, 2002

Tested By: CEMM315 Class, Group A

Project Name: CEMM315 Lab

Sample Number: GB-08-ST-13’-15’

Visual Classification: Gray silty clay

Consolidation type = Floating type

Mass of wet sample + ring + glass plate = 636.5 g

Engineering Properties of Soils Based on Laboratory

Mass of solids in specimen, Ms =149.2 g

Mass of water in specimen before test, Mwi = wi x Ms

Mass of water in specimen after test, Mwf (g) = wf x Ms

Height of solids, Hs = Ms 149.2 = 1.792 cm

Height of water before test, Hwi = M wi 29.09 = 0.933 cm

Height of water after test, Hwf = M wf  21.29 = 0.683 cm

Change in height of specimen after test, H =0.257 cm

Height of specimen after test, Hf = Hi - H = 2.7-0.257 = 2.443 cm

Degree of saturation before test, Si =

Engineering Properties of Soils Based on Laboratory

Degree of saturation after test, Sf = H wf 0.683

Dry density before test, d = Ms 149.2

Engineering Properties of Soils Based on Laboratory

Table 1: Time - Settlement Data (1 unit on dial guage = 0.0001 inches)

Engineering Properties of Soils Based on Laboratory

loading=8 tsf loading=16 loading=32 tsf

Engineering Properties of Soils Based on Laboratory

Consolidation Test (ASTM D

   in t50=10 min

Consolidation Test (ASTM D 2435)

210 H = 0.008 in t50 = 11.5 min

Engineering Properties of Soils Based on Laboratory

Consolidation Test (ASTM D 2435)

Consolidation Test (ASTM D 2435)

380 t50 = 3.3 min

Engineering Properties of Soils Based on Laboratory

Consolidation Test (ASTM D 2435)

Consolidation Test (ASTM D 2435)

H = 0.00203 in t50 = 3.5 min

Engineering Properties of Soils Based on Laboratory

Consolidation Test (ASTM D 2435)

Consolidation Test (ASTM D 2435)

H = 0.00018 in t50 = 1.2 min

Engineering Properties of Soils Based on Laboratory

Consolidation Test (ASTM D 2435)

t50 = 0.6 min