consolidation 7

8/11/2019 Consolidation 7

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CONSOLIDATION LAB REPORT

By:

.

CEGR 3258 -001

Dr. Anderson

Performed on:

April 19, 2005

Submitted on:

April 19, 2005

Group Members:

.

.

Integrity Statement

I have committed no violations of the UNCC Code of Student Academic Integrity in

preparing and submitting this report.

.: _______________

Date: _______4/19/05 ________________________________________


2/19

i

Executive Summary

The objective of this report is to determine the compression index (C c), recompression

slope (Cr), the preconsolidation pressure (p), and coefficient of consolidation (cv) of two soil

samples. These properties were determined from a consolidation test. The details of the

consolidation test are provided in the report. From the consolidation test, graphs of void ratio

versus logarithm of pressure and coefficient of consolidation versus logarithm of pressure

were determined for each soil sample. The first soil sample Ccwas found to be 0.215, the Cr

was found to be 0.02, and the pwas found to be 2,700 lb/ft2. The second soil sample Ccwas

found to be 0.234, the Crwas found to be 0.03, and the pwas found to be 2,800 lb/ft2. The

results from the two tests are significant because they identified soil properties that were

within expected ranges and could be used with additional equations for settlement analysis.


3/19

ii

Table of Contents

Executive Summary......... i

Introduction 1

Procedure.... 2

Results 5

Analysis and Conclusion.... 15

References.. 16


4/19

1

Introduction

Since soil is the foundation of most structures and roads, a detailed knowledge of soil

properties is important. This report details and discusses the consolidation test which is used

to determine specific soil properties. The soil properties determined were the compression

index (Cc), recompression slope (Cr), the preconsolidation pressure (p) and the coefficient of

consolidation (cv). Using the consolidation test data, graphs of void ratio versus logarithm of

pressure and coefficient of consolidation versus logarithm of pressure can be developed. On

the void ratio curve, Ccis the slope of the virgin compression portion and Cris the slope of the

recompression portion. The pis the maximum pressure that has ever been imposed on the

soil sample and can also be determined from the void ratio curve. The cvindicates how

rapidly or slowly the consolidation process takes. These properties can be used to determine

the rate and magnitude of settlement of structures built on the soil.

Consolidation is defined as the process of compression of soil due to very slow

extrusion of water from the voids as a result of increased loading (Liu and Evett, 2003). Any

load applied to saturated soil is assumed to be initially carried by the incompressible water

contained in the voids. Over time the water will extrude out of the voids and the soil will

compress resulting in a reduced volume of voids. Measuring the time and soil deformation

during this process helps to determine the soil properties.

The consolidation test is generally performed on undisturbed fine-grain soil samples

sedimented in water. The consolidation test is detailed in the procedure section of this report

and is also given in ASTM D-2435 Test Method for One-Dimensional Consolidation

Properties of Soils (Liu and Evett, 2003).


5/19

2

Procedure

The consolidation test was performed using a consolidometer and various weights.

The consolidometer held the soil sample in a ring, provided a means of submerging the soil

sample under water, applied a vertical load to the soil sample, and measured the thickness of

the soil sample. This procedure was followed for two separate soil samples.

The lab instructor assembled the soil samples in the consolidometer and setup the dial

gauge to read the thickness of the soil samples. Samples from each test were taken and

weighed to determine the wet mass (mwet). The samples were then put into an oven at a

temperature of 110 +/- 5 degrees Celsius for 24 hours. The samples were then taken out of

the oven and weighed to determine the dry mass (mdry). The moisture content (w) of each test

was calculated using equation 1.

dry

drywet

m

mmw

)( = (1)

The lab instructor also provided the consolidometer ring diameter (DR), ring height

(H0), ring mass (MR), and the soil sample plus ring mass (MR+T0). The height of the solids

(HS) of each test was then calculated using equation 2.

+

=

+

4

****)1(

)(2

0

RWS

RTRS

DGw

MMH

(2)

The initial void ratio (e0) of each test was then calculated using equation 3.

S

S

H

HHe

=

00 (3)


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The next step was to add weights from 2kg to 32 kg to the consolidometer which

corresponded to loads (P) on the soil samples from 0.67 to 10.67 tsf. After the loads were

applied, the soil samples consolidated and the thicknesses at various times from 0.25 minutes

to 24 hours were recorded. This data was then used to create eleven time-deformation curves

(TDC) for each sample. During the loading process, the loads were also removed and

unloading TDCs were determined.

Each TDC was then used to determine the zero percent deformation (R0), the 100

percent deformation (R100), the 50 percent deformation (R50), and the time at 50 percent

deformation (t50). R100 was determined by drawing tangents to the middle portion and the

last portion of the TDC. The point where these two tangents crossed corresponded to R100.

R0 was found by arbitrarily choosing a point on the first portion of the TDC and drawing a

horizontal line. A second horizontal line was drawn at one-quarter t, where t is the time the

first horizontal line crossed the TDC. The distance (A) between the two lines was measured

and a third horizontal line was drawn at a distance A above the second horizontal line. The

deformation corresponding to the third horizontal line is R0. R50 was exactly in the middle of

R0 and R100. The time corresponding to R50 was t50.

Using the R0, R50, R100 and t50 values, the void ratio (e) and coefficient of

consolidation (cv) were calculated for each P using equations 4 and 5.

=

SH

RR

ee

)0100(

0 (4)

50

)]50(*5.0[*196.0 0

t

RHcV

= (5)


7/19

4

Graphs were then created of void ratio versus logarithm of pressure and coefficient of

consolidation versus logarithm of pressure graph. From the void ratio graph the

preconsolidation pressure (p), the compression index (Cc), and the recompression slope (Cr)

were determined for each soil sample. Ccwas the slope of the virgin compression portion of

the curve and Crwas the slope of the recompression portion of the curve. Both Ccand Crwere

reported as positive numbers. pwas determined using the Casa Grande Method (McCarthy,

2002). pwas found by drawing a tangent to the first portion of the void ratio curve. A

horizontal line was then drawn at the point the tangent touched the void ratio curve. A third

line was drawn that bisected the first two lines. Finally, the point where the third line crossed

the Ccline corresponded to p.


8/19

5

Results

The lab instructor provided the raw data used to calculate the moisture contents. This

data along with the calculated moisture contents for each soil sample are given in Tables 1

and 2.

TABLE 1

Moisture content raw and calculated data for sample 1 C1

Can ID C1-1 C2-1

Mass of can (g) 31.92 31.62

Mass of can and wet soil sample (g) 83.91 75.35

Mass of can and dry soil sample (g) 62.31 62.70Mass wet soil sample(g) 51.99 43.73

Mass of dry soil sample (g) 30.39 31.08

Moisture content (%) 71.08 40.70

Average moisture content (%) 40.70

TABLE 2

Moisture content raw and calculated data for sample 2 C2

Can ID C1-2 C2-2Mass of can (g) 31.66 32.24

Mass of can and wet soil sample (g) 76.63 85.82

Mass of can and dry soil sample (g) 62.27 70.38

Mass wet soil sample(g) 44.97 53.58


Moisture content (%) 46.91 40.48

Average moisture content (%) 43.70

The consolidometer dimensions and initial soil data were provided by the lab

instructor. This information was used to calculate the initial height of solid and initial void

ratio of the each soil sample. These values are given in Table 3.


9/19

6

TABLE 3

Consolidometer dimension and initial soil sample data

Sample 1 Sample 2

Ring diameter (in) 2.51 2.51Ring height (in) 0.79 0.79

Ring mass (g) 64.52 63.66

Ring area (in2) 4.95 4.95

Ring volume (in3) 3.91 3.91

Mass of ring and wet soil sample (g) 173.31 171.51

Mass of wet soil sample (g) 108.79 107.85


Dry density of soil sample (g/in3) 19.78 19.21

Dry unit weight of soil sample (lb/ft3) 75.32 73.11

Density of water (g/cm3) 1.0 1.0

Specific gravity of soil sample 2.65 2.65Initial volume of solids (in

3) 478.13 464.12

Initial height of solids (in) 0.36 0.349

Initial saturation of soil sample (%) 90.23 91.78

Initial void ratio of soil sample 1.20 1.26

The loads applied to the soil samples along with the dates are given in Table 4.

TABLE 4

Permeameter Diameter Results

Date Day Load (tsf) Type

15-Mar T 2/3 Load

16-Mar W 4/3 Load

17-Mar H 8/3 Load

18-Mar F 16/3 Load

19-Mar S 8/3 Unload

20-Mar Su 4/3 Unload

21-Mar M 8/3 Load

22-Mar T 16/3 Load

23-Mar W 32/3 Load24-Mar H 8/3 Unload

25-Mar F 2/3 Unload

The time-deformation curves on each date for each soil sample are given in Figures 1,

2, and 3.


10/19

7

Time-Deformation Curve 3-15 C1

0.0575

0.0576

0.0577

0.0578

0.0579

0.0580

0.0581

0.1 1 10 100 1000 10000

Log of time, (minutes)

Defotmation,

(inches)

t2 = (t1)/4

a

aR0

R100

t50

R50

t1


0.1088

0.1089

0.1090

0.1091

0.1092

0.1093

0.1094

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.0595

0.0600

0.0605

0.0610

0.0615

0.0620

0.0625

0.0630

0.0635

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1110

0.1115

0.1120

0.1125

0.1130

0.1135

0.1140

0.1145

0.1 1 10 100 1000 10000


Defotmation

,(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.0700

0.0750

0.0800

0.0850

0.0900

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1220

0.1240

0.1260

0.1280

0.1300

0.1320

0.1340

0.1360

0.1380

0.1400

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.0950

0.1000

0.1050

0.1100

0.1150

0.1200

0.1 1 10 100 1000 10000


Defotmation,

(inches

)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1400

0.1450

0.1500

0.1550

0.1600

0.1650

0.1700

0.1750

0.1 1 10 100 1000 10000


Defotmation,

(inches

)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1

Figure 1: Time-deformation curves for 3-15 through 3-18


11/19

8


0.1174

0.1176

0.1178

0.1180

0.1182

0.1184

0.1 1 10 100 1000 10000


Defotm

ation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1670

0.1675

0.1680

0.1685

0.1690

0.1 1 10 100 1000 10000


Defotm

ation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1120

0.1130

0.1140

0.1150

0.1160

0.1170

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1620

0.1630

0.1640

0.1650

0.1660

0.1670

0.1 1 10 100 1000 10000


Defotma

tion,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1140

0.1145

0.1150

0.1155

0.1160

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1635

0.1640

0.1645

0.1650

0.1655

0.1660

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1180

0.1190

0.1200

0.1210

0.1220

0.1230

0.1240

0.1250

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1680

0.1690

0.1700

0.1710

0.1720

0.1730

0.1740

0.1750

0.1 1 10 100 1000 10000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1



12/19

9


0.1250

0.1300

0.1350

0.1400

0.1450

0.1500

0.1550

0.1 1 10 100 1000 10000


Defotm

ation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1700

0.1750

0.1800

0.1850

0.1900

0.1950

0.2000

0.2050

0.2100

0.1 1 10 100 1000 10000


Defotm

ation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1400

0.1410

0.1420

0.1430

0.1440

0.1450

0.1460

0.1470

0.1480

0.1 1 10 100 1000 10000


Defotma

tion,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1920

0.1930

0.1940

0.1950

0.1960

0.1970

0.1980

0.1990

0.2000

0.1 1 10 100 1000 10000


Defotma

tion,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1340

0.1350

0.1360

0.1370

0.1380

0.1390

0.1400

0.1410

0.1420

0.1430

0.1440

0.1 1 10 100 1000


Defotmation,

(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


0.1860

0.1870

0.1880

0.1890

0.1900

0.1910

0.1920

0.1930

0.1940

0.1 1 10 100 1000


Defotmation

,(inches)

t2 = (t1)/4

a

a

R0

R100

t50

R50

t1


Using the time-deformation curves, the values of R0, R50, R100, and t50 for each soil

sample were determined and are given based on the date in Tables 5 and 6.


13/19

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TABLE 5

Load and time deformation curve data for sample 1 C1

C1 Load Load R0 R100 R50 t50

Date tsf lb/ft

2

in in in min3/15 0.67 1333.3 0.0577 0.0580 0.0578 27

3/16 1.33 2666.7 0.0602 0.0632 0.0617 14

3/17 2.67 5333.3 0.0715 0.0875 0.0795 2.5

3/18 5.33 10666.7 0.0980 0.1151 0.1066 1.1

3/19 2.67 5333.3 0.1185 0.1175 0.1180 2.1

3/20 1.33 2666.7 0.1164 0.1138 0.1151 0.9

3/21 2.67 5333.3 0.1135 0.1145 0.1140 1.8

3/22 5.33 10666.7 0.1186 0.1231 0.1209 1.5

3/23 10.67 21333.3 0.1275 0.1480 0.1378 1.1

3/24 2.67 5333.3 0.1474 0.1418 0.1446 0.6

3/25 0.67 1333.3 0.1409 0.1366 0.1388 0.6

TABLE 6

Load and time deformation curve data for sample 2 C2

C2 Load Load R0 R100 R50 t50

Date tsf lb/ft2 In in in min

3/15 0.67 1333.3 0.1089 0.1093 0.1091 20

3/16 1.33 2666.7 0.1116 0.1137 0.1126 12

3/17 2.67 5333.3 0.1241 0.1365 0.1303 2.53/18 5.33 10666.7 0.1480 0.1645 0.1563 0.9

3/19 2.67 5333.3 0.1687 0.1678 0.1683 2.3

3/20 1.33 2666.7 0.1662 0.1638 0.1650 0.75

3/21 2.67 5333.3 0.1642 0.1653 0.1648 0.65

3/22 5.33 10666.7 0.1693 0.1728 0.1711 1.2

3/23 10.67 21333.3 0.1780 0.1980 0.1880 0.68

3/24 2.67 5333.3 0.1935 0.1984 0.1960 0.45

3/25 0.67 1333.3 0.1919 0.1879 0.1899 0.65

Using the R0, R50, R100, and t50 values, the void ratio and coefficients of

consolidation were calculated for each soil sample and are given based on the date in Tables 7

and 8.


14/19

11

TABLE 7

Calculated void ratios and coefficient of consolidations for sample 1 C1

C1 H Hs e e H cv

Date in in in in

2

/min3/15 0.000 0.36 0.001 1.199 0.366 0.001

3/16 0.006 0.36 0.016 1.184 0.364 0.002

3/17 0.030 0.36 0.083 1.117 0.355 0.013

3/18 0.057 0.36 0.160 1.040 0.342 0.031

3/19 0.060 0.36 0.166 1.034 0.336 0.017

3/20 0.056 0.36 0.156 1.044 0.337 0.039

3/21 0.057 0.36 0.158 1.042 0.338 0.019

3/22 0.065 0.36 0.182 1.018 0.335 0.024

3/23 0.090 0.36 0.251 0.949 0.326 0.034

3/24 0.084 0.36 0.234 0.966 0.323 0.063

3/25 0.079 0.36 0.219 0.981 0.326 0.062

TABLE 8

Calculated void ratios and coefficient of consolidations for sample 2 C2

C2 H Hs e e H cv

Date in in in in2/min

3/15 0.000 0.349 0.001 1.259 0.395 0.002

3/16 0.005 0.349 0.014 1.246 0.394 0.003

3/17 0.028 0.349 0.079 1.181 0.392 0.0153/18 0.056 0.349 0.159 1.101 0.391 0.043

3/19 0.059 0.349 0.169 1.091 0.395 0.017

3/20 0.055 0.349 0.157 1.103 0.396 0.053

3/21 0.056 0.349 0.162 1.098 0.395 0.061

3/22 0.064 0.349 0.183 1.077 0.394 0.033

3/23 0.089 0.349 0.255 1.005 0.390 0.061

3/24 0.090 0.349 0.257 1.003 0.394 0.094

3/25 0.079 0.349 0.226 1.034 0.396 0.064

Next, using the calculated void ratios and coefficients of consolidation, the graphs of

void ratio versus logarithm of pressure and coefficient of consolidation versus logarithm of

pressure were determined and are given in Figures 4, 5, 6, and 7.


15/19

12

Void Ratio versus Logarithm of Pressure -C1

0.9

0.95

1

1.05

1.1

1.15

1.2

1.25

1000.00 10000.00 100000.00

Pressure, P [log] (lb/ft^2)

VoidRatio,e

Cc

Cr(2000,1.045)

(6000,1.075)

(20000,1.025)

(30000,0.925)

'_p

Figure 4: Void ratio versus logarithm of pressure for soil sample 1 -C1

Void Ratio versus Logarithm of Pressure - C2

0.9

0.95

1

1.05

1.1

1.15

1.2

1.25

1.3

1000.00 10000.00 100000.00


VoidRatio,e (4000,1.175)

(30000,0.97)

(20000,1.08)(2000,1.11) Cr

Cc

'_p

Figure 5: Void ratio versus logarithm of pressure for soil sample 2 - C2


16/19

13

Coefficient of Consolidation versus Logarithm of Pressure - C1

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

1000.00 10000.00 100000.00


CoefficentofConsoldiation,cv(in/min^2)

Figure 6: Coefficient of consolidation versus logarithm of pressure for soil sample 1 - C1

Coefficient of Consolidation versus Logarith of Pressure - C2

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

1000.00 10000.00 100000.00


Coe

fficentofConsoldiation,cv(in/min^2)

Figure 7: Coefficient of consolidation versus logarithm of pressure for soil sample 2 C2


17/19

14

From the void ratio graphs, the compression index (Cc) and the recompression slope

(Cr) were determined for each soil sample were determined and are given in Table 9.

TABLE 9

Compression index and recompression slope for samples 1 and 2

Points used to find slope Slope

X y x y Cror Cc

Sample 1 - Cr 2000 1.045 20000 1.025 0.020

Sample 1 - Cc 6000 1.075 30000 0.925 0.215

Sample 2 - Cr 2000 1.11 20000 1.08 0.030

Sample 2 - Cc 4000 1.175 30000 0.97 0.234

Finally from the void ratio graphs, the preconsolidation pressures (p) were

determined to be 2,700 lb/ft2and 2,800 lb/ft2for first and second soil samples, respectively.


18/19

15

Analysis and Conclusions

Based on results of the consolidation test, graphs of void ratio versus logarithm of

pressure and coefficient of consolidation versus logarithm of pressure were determined for

two soil samples. From the coefficient of consolidation graph, it is determined that the

maximum pressure was not reach to show where the curve started so come back down.

Therefore, the results from the coefficient of consolidation graphs are inconclusive. The Cc

and Crvalues from the void ratio graphs are within expected ranges. Cris also approximately

ten percent of Ccwhich is expected. The pvalues describe soil samples that have been

exposed to about 2,700 lb/ft2in the past. These properties can be used with additional

equations to determine the rate and magnitude of settlement of structures built on the soil, but

was not required for this lab.

Potential errors in these tests could be due to inexperience, misunderstanding the

procedure, and shortened time intervals. In conclusion, the results from the two tests are

significant because they identified soil properties that were within expected ranges and could

be used for further analysis.


19/19

16

References

ASTM D-2435 Test Method for One-Dimensional Consolidation Properties of Soils, 2000.

American Society and Materials, now ASTM International, W. Conshohocken, PA.

Liu, Cheng and Evett, Jack B., (2003). Soil Properties, Testing, and Measurement, and

Evaluation. 5th

Ed., Pearson Education, Inc., Upper Saddle River, New Jersey.

McCarthy, David F., (2002).Essentials of Soil Mechanics and Foundations. 6thEd., Pearson

Education, Inc., Upper Saddle River, New Jersey.

consolidation 7

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