CONSOLIDATION TEST

OBJECTIVE:

Determination of one-dimensional consolidation parameters of given remolded soil

sample.

EQUIPMENT:

Consolidation cell, Oedometer ring, Porous stones, Loading frame and dial gauge, Filter

paper, Apparatus for moisture content determination.

PROCEDURE:

1. Take the soil sample and add the (OMC-Hygroscopic water) water to soil sample and mix

it thoroughly.

2. Do the light compaction for the soil sample with 3 layers of soil sample and 25 blows for

each layer with 2.6 kg rammer.

3. Clean the consolidation ring and measure its inside diameter, height and weight.

4. Press the ring gently into the soil sample until soil projects above the top of the ring, take

the ring with extreme care, and trim the soil surfaces flush both at the top and bottom of

the ring. Remove any excess soil sticking outside, and weigh the specimen with ring.

5. Place the porous stones on the top and bottom surfaces of the soil specimen with filter

paper in between them. Press lightly to ensure that the stones adhere to the specimen.

6. Assemble the specimen carefully into the consolidation cell, mount the cell on the

loading frame, and set the dial gauge. Connect the system to a water reservoir, and allow

the water to flow into till the specimen is completely covered and saturated.

7. Adjust and record initial dial gauge reading. Apply normal load to give a pressure

intensity of 0.05 kg/cm2 on the soil specimen.

8. Note the dial gauge readings at elapsed times of 1 min and 24 hrs.

9. Increase the normal load and take dial gauge readings at the same elapsed time intervals

Use a loading sequence of 0.2, 0.4, 0.8,2, 4, 8 kg/cm2, etc.

10. On completion of the final loading stage, decrease the load to 4 kg/cm2 and allow it to

remain for 24 hours, and then note the dial gauge reading. Reduce further the load to 2

kg/cm2 and repeat the observations.

11. After recording the final time and dial reading remove water out of the consolidation cell,

release the load, quickly disassemble the cell, remove the ring, and blot the specimen

surfaces dry with paper.

12. Weigh the specimen with ring, and place in the oven for determination of final water

content.

13. Calculate the consolidation parameters by plotting the graphs between void ratio versus

effective pressure and void ratio versus logarithmic effective stress.

RESULT:

Diameter of the consolidation ring is 6cm,

Intial height of the specimen is 2cm.

Intial water content 23%

Hygroscopic water content reading for final water content R= 19.8

Applied Pressure(kg/cm²)

Initial dial gauge reading

final dial gauge reading

ΔH(Change in Height)

Height (H)

Ht. of voids (H-Hs)

Final void ratio (H-Hs)/ Hs

Log(σ)

0.05 10 10.2 0.2 20.2 7.63 0.607001 -1.30103

0.2 10 9.06 -0.94 19.26 6.69 0.53222 -0.69897

0.4 9.02 9 -0.02 19.24 6.67 0.530628 -0.39794

0.8 8.96 8.88 -0.08 19.16 6.59 0.524264 -0.09691

2 8.74 8.57 -0.17 18.99 6.42 0.51074 0.30103

4 8.45 8.23 -0.22 18.77 6.2 0.493238 0.60206

8 8.05 7.74 -0.31 18.46 5.89 0.468576 0.90309

4 8.79 8.84 0.05 18.51 5.94 0.472554 0.60206

2 8.88 9.11 0.23 18.74 6.17 0.490851 0.30103

Void ratio Vs. Effective stress plot

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 1 2 3 4 5 6 7 8 9

VO

ID R

ATI

O

PRESSURE (KG/CM^2)

Void Ratio vs Pressure Series1 Series2

Void ratio Vs. Log Effective stress plot

CALCULATION:

The consolidation parameters are Cc, av, mv, Cv

The formula for the height of solids is Hs is = Ms/G*ρw*A

Ww + Ws =118 gm (The total weight of the sample taken excluding container weight)

But, water content (W.C) = Ww/Ws =0.23. Therefore Ws = 95.94 gm and

Hence the height of the solids is 12.57 mm

From this value the void ratios can be calculated

Now, Cc = Δe/log10(σ2/σ1) , take pressure values such that log10(σ2/σ1) is 1. So the difference

in void ratio will be the Cc

For calculation of av a particular stress is taken and calculated at that difference of stresses

Mv = av/1+eo

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

-1.5 -1 -0.5 0 0.5 1 1.5

VO

ID R

ATI

O

LOG(PRESSURE)

e vs Log(σ)

As the soil was found to be low plastic clay known previously by conducting compaction test,

the permeability is assumed to be 10-6

cm/sec and Cv is calculated by using the formula

Cv=k/(mv*γw)

DISCUSSIONS:

Consolidation is a very important phenomenon in the case of saturated clays as clayey soils take

more time to consolidate and it is a time dependent phenomena and there is non-linear stress

strain relationship

Usually consolidation in clays continues over years and the settlement due to consolidation

might create unwanted stresses in the super structure

CONCLUSION:

The value of Cc was calculated to be = 0.0215

The value of av was calculated to be = 0.0119 cm2/Kg

The value of mv was calculated to be = 0.007767 cm2/Kg

The value of Cv was calculated to be = 244.9401 cm2/Year

REFERENCES:

Soil Mechanics and Foundation Engineeirng by Dr. K. R. Arora.