Consolidation Test - 023

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FACULTY OF CIVIL & ENVIRONMENTAL

ENGINEERING

DEPT.OF GEOTECHNICAL AND

TRANSPORTATION ENGINEERING

GEOTECHNICAL ENGINEERING LABORATORY

REPORT

SUBJECT CODE

TEST CODE & TITLE MG001 - CONSOLIDATION TEST COURSE CODE

TESTING DATE STUDENT NAME GROUP

GROUP MEMBER NAMES

1. 2. 3. 4. 5. LECTURER/ INSTRUCTOR/ TUTOR NAME

REPORT RECEIVED DATE

MARKS ATTENDANCE/ DISCIPLINE & INVOLVEMENT /15%

DATA ANALYSIS /20%

RESULT /20%

DISCUSSION /25%

CONCLUSION /20%

TOTAL /100%

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STUDENT CODE OF ETHIC

(SCE)

DEPT. OF GEOTECHNICAL AND TRANSPOTATION ENGINEERING

FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING

I, hereby confess that I have prepared this report on my own effort. I also admit not

to receive or give any help during the preparation of this report and pledge

that everything mentioned in the report is true.

_________________

Student Signature

Name : ………

Matric No. : ………

Date : ………

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FACULTY: CIVIL & ENVIRONMENTAL ENG. PAGE NO.: 1/8 DEPARTMENT: GEOTECHNICAL AND

TRANSPORTATION ENGINEERING

EDITION: REVIEW NO.: TEST TITLE : CONSOLIDATION TEST

(MARINE CLAY AND PEAT SOIL)

EFFECTIVE

DATE: 5/12/07

AMENDMENT

DATE: 5/12/07

1.0 OBJECTIVE

TO DETERMINE THE CONSOLIDATION CHARACTERISTICS OF SOILS OF LOW PERMEABILITY

2.0 LEARNING OUTCOME

At the end of this experiment, students are able to: • Conduct one dimensional consolidation test

•

Identify the factors causes soil consolidation

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3.0 THEORY

When a fully saturated soil is subjected to a compressive stress, its volume tends to decrease. The decreasing of its volume is due to compression of the solid grains and escape of water from the voids. In a free drainage soil such as saturated sand the escape of water can take place rapidly. But in clay, due to low permeability, the movement of water occurs very much slowly and therefore, considerable time may be required for excess water to be squeezed out to permeable boundaries.

Settlement is the direct result of the decrease in soil volume and consolidation is the rate of volume decrease with time. The consolidation test is use to estimate the amount of settlement and time of consolidation. From this test some consolidation parameters such as coefficient of consolidation (cv),

coefficient of volume compressibility (mv), compression index (Cc), preconsolidation pressure (Pc) can

be determined.

There are two methods for determining the coefficient of consolidation: (i) Casagrande or log (time) or 50% consolidation

(ii) Taylor or √ time or 90% consolidation

The coefficient of consolidation can be determined by this equation,

t

H

T

c

v v 2

=

(3.1)

Where, cv = coefficient of consolidation (m2/year)

Tv = Time factor

H = Maximum length of drainage path (m)

t = Time to achieve 50% or 90% consolidation (year or minute)

FACULTY: CIVIL & ENVIRONMENTAL ENG. PAGE NO.: 2/8

DEPARTMENT: GEOTECHNICAL AND

EFFECTIVE

DATE: 5/12/07

AMENDMENT

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Figure 3.1: Settlement versus log Time

Figure 3.2:

Settlement versus square root time

FACULTY: CIVIL & ENVIRONMENTAL ENG. PAGE NO.: 3/8

EDITION: REVIEW NO.:

TEST TITLE : CONSOLIDATION TEST EFFECTIVE

DATE: 5/12/07 0 20 40 60 80 100 120 140 160 0.1 1 10 100 1000 10000 Time (minute) S et tl em en t (m m ) 100% consolidation line A B = 4A δ δ 0% consolidation line 50% consolidation line t50 0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 40

Square Root Time (minute)

S et tl em en t (m m ) x 1.15x √t90 1 2

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(MARINE CLAY AND PEAT SOIL) AMENDMENT _DATE: 5/12/07

4.0 TEST EQUIPMENTS

1. Consolidation apparatus - Consolidation ring

- Corrossion-resistant porous plate - Consolidation cell - Dial Gauge - Loading device 2. Balance readable to 0.1g 3. Vernier caliper 4. Stop-clock readable to 1 s 5.0 PROCEDURES

1. Measure the internal diameter (D) and the height of the ring, using internal vernier calipers.

2.

Weight the ring to the nearest 0.01g (mR).

3. Cutting the specimen and trimming into ring.

4. Determine the initial moisture content from trimming soil.

5.

Determine the weight of ring and specimen (m1)

6. Determine the mass of bulk specimen (m) to the nearest 0.01g using this equation m = m1 – mR

7. Place the consolidation ring and specimen (cutting edge uppermost) centrally on the porous disc.

8. Fit the ring retainer and cell body and then place the upper porous disc centrally on top of the specimen.

9. Place the consolidation cell centrally in position on the platform of the machine base. 10. Lift the end of the beam to allow the loading yoke to be raised to the vertical position

and adjust the loading stem by screwing it downwards until the end engages closely in the recess on the top of the loading cap

11. Attach the compression dial gauge to the arm on the support post. 12. Add weight (2.5 kg) carefully to the load hanger

13. Add water at room temperature to the cell and make sure that the specimen and upper porous disc are completely submerged.

14. Wind down the beam support and at the same time start the clock.

15. Observe the compression gauge readings and the clock, and record the readings on a consolidation test form at the selected time intervals.

16. Plot the readings of the compression against time to a logarithmic scale and against square-root-time.

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FACULTY: CIVIL & ENVIRONMENTAL ENG. PAGE NO.: 4/8 DEPARTMENT: GEOTECHNICAL AND

EFFECTIVE

DATE: 5/12/07

AMENDMENT

DATE: 5/12/07

6.0 CALCULATION EXAMPLE

Date started: 9/7/07 Sample No.: A1 - 1

Soil Type: Silty clay Cell No: 4

BEFORE TEST

Moisture content from trimming: 22.9 (%) S.G. (Assumed) : 2.7

Weight of ring : 439.35 (g) Diameter of ring : 74.9 (mm) Weight of sample + ring: 260.43 (g) Area of ring: 4406 (mm2₎

Weight of sample : 178.92 (g) Thickness of ring: 20.1 (mm) Weight of dry sample: 145.35 (g) Volume of ring : 88.56 (mm3₎

Weight of initial moisture: 33.57 (g) Density, ρ : 2.02 (Mg/m3₎

Initial moisture content: 23.1 (%) Dry density, ρ d : 1.64 (Mg/m3)

Initial void ratio,

−

1

d s

G

ρ

= 0.622 SETTLEMENT READINGS Elapse time Time

(min) √ time Clock time readingGauge

Cumulative compression, ∆ H (mm) hr min sec 0 0 0 8.00 am 0 0 10 0.17 0.41 21 21 x 0.002 = 0.04 20 0.33 0.57 23 23 x 0.002 = 0.05 30 0.50 0.71 25 25 x 0.002 = 0.05 40 0.67 0.82 29 29 x 0.002 = 0.06 50 0.83 0.91 35 35 x 0.002 = 0.07 1 1 1.00 8.01 am 41 41 x 0.002 = 0.08 2 2 1.41 8.02 am 49 49 x 0.002 = 0.10 4 4 2.00 8.04 am 58 58 x 0.002 = 0.12 8 8 2.83 8.08 am 66 66 x 0.002 = 0.13 15 15 3.87 8.15 am 75 75 x 0.002 = 0.15 30 30 5.48 8.30 am 86 86 x 0.002 = 0.17 1 60 9.00 am 95 95 x 0.002 = 0.19 2 120 10.00am 107 107 x 0.002 = 0.21 4 240 12.00 pm 115 115 x 0.002 = 0.23 8 480 4.00 pm 124 124 x 0.002 = 0.25 24 1440 8.00 am 126 126 x 0.002 = 0.25

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EFFECTIVE

DATE: 5/12/07

AMENDMENT

DATE: 5/12/07

7.0 RESULTS

CONSOLIDATION TEST – CALCULATION SHEET

Date started:_________________ Sample No.: _______________

Soil Type: __________________ Cell No: ________________

BEFORE TEST

Moisture content from trimming: _______(%) S.G. (Assumed) : 2.7

Weight of ring : ___________________ (g) Diameter of ring : _______________(mm) Weight of sample + ring: ____________ (g) Area of ring: ___________________(mm2₎

Weight of sample : _______________ (g) Thickness of ring: _______________(mm) Weight of dry sample: _______________(g) Volume of ring : _________________(mm3₎

Weight of initial moisture: ____________(g) Density, ρ : _____________________(Mg/m3)

Initial moisture content: ______________(%) Dry density, ρ d : _________________

(Mg/m3₎

Initial void ratio,

−

1

d

s

G

ρ

= ____________

SETTLEMENT READINGS

Elapse time _Time

(min) √ time Clock time Gauge reading Cumulative compression , ∆ H (mm) hr min sec 0 10 20 30 40 50 1 2 4 8 15 30 1 2 4 8 24

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EFFECTIVE

DATE: 5/12/07

AMENDMENT

DATE: 5/12/07

8.0 CALCULATIONS

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EFFECTIVE DATE: 5/12/07 AMENDMENT DATE: 5/12/07 9.0 DISCUSSIONS 10.0 CONCLUSIONS

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EDITION: REVIEW NO.:

TEST TITLE : CONSOLIDATION TEST EFFECTIVE DATE:

AMENDMENT DATE:

11.0 OPEN ENDED QUESTIONS QUESTIONS 1

1.

From your experimental data, determine the coefficient of consolidation, cv (m2/year) using

Casagrande Method. Please comment your answer.

2.

Clay samples collected from 5 metres deep in Batu Pahat has a unit weight (γ ) of 18 kN/m3_.

The following data were recorded during an oedometer test.

Effective Stress (kN/m2₎ ₂₅ ₅₀ ₁₀₀ ₂₀₀ ₄₀₀ ₈₀₀ ₂₀₀ ₅₀

Void ratio (e) 0.85 0.82 0.71 0.57 0.43 0.3 0.4 0.5

(i) Plot the graph of void ratio against effective stress on semi-log graph and determine the compression index (Cc), Preconsolidation pressure (Pc) and coefficient of volume

compressibility (mv).

(ii) Define whether the soil is normally consolidated or over consolidated.

QUESTIONS 2

1.

From the experimental data , determine the coefficient of consolidation, cv (m2/year) using

Taylor Method. Please comment your answer.

2.

Clay samples collected from 10 metres deep in Parit Raja has a unit weight (γ ) of 20 kN/m3_.

The following data were recorded during an oedometer test.

Effective Stress (kN/m2₎ ₅₀ ₁₀₀ ₂₀₀ ₄₀₀ ₈₀₀ ₁₆₀₀ ₄₀₀ ₁₀₀

Void ratio (e) 0.95 0.92 0.81 0.67 0.53 0.4 0.5 0.6

(i) Plot the graph of void ratio against effective stress on semi-log graph and determine the compression index (Cc), Preconsolidation pressure (Pc) and coefficient of volume

compressibility (mv).