To determine the consolidation properties of a soil specimen

Theory

Consolidation of a saturated soil happens because of the exclusion of water under static, sustained load. The consolidation properties of soils are necessary to forecast the magnitude and the rate of settlement. The following properties are acquired from the consolidation test.

Coefficient of compressibility,

Coefficient of volume change

Compression Index

Coefficient of consolidation

Tool and Equipment

• Water content cans
• Large container
• Steel ball
• Weighing balance, accuracy 0.01 g.
• Oven
• Desiccator
• Pressure pad
• Consolidometer with a loading device
• Specimen ring made of a non-corroding material
• Water reservoir to saturate the sample
• Porous stones
• Soil trimming tools like fine wire saw, knife, spatula, etc.
• Dial gauge, accuracy 0.002mm

Process

1. Thoroughly clean and dry the metal ring. Compute its diameter and height. Also measure the weight of the empty ring.

2. Press the ring into the soil specimen kept in a big vessel at the preferred density and water proportion. The ring has to be pressed with help of hands.

3. Eliminate the soil about the ring. The soil sample has to protude about 10mm on both sides of the ring. Any hollows in the sample because of the elimination of big size particles has to be packed back by pressing the soil casually.

4. Cut the sample flush with the top and the base of the ring.

5. Get rid of any kind of soil particles attached to the external part of the ring. Compute the weight of the ring with the sample.

6. Take a minor quantity of the soil eliminated at the time of trimming for the water content determination.

7. Immerse the permeable stones by steaming them in distilled water for approximately 15min.

8. Accumulate the Consolidometer. Position the base permeable stone, bottom filter paper, sample, top filter paper and the top permeable stone, taking one by one.

9. Place the loading block focally on the top of permeable stone. Mount the assembly on the loading frame. Position it in such that the load exerted is axial. In the instances of the lever loading system, counterpoise the system.

10. Put the dial gauge in position. Permit adequate space for the swelling of the soil.

11. Join the mould assembly to the water reservoir consisting the water level at approximately the similar as the soil sample. Permit the water to flow into the sample till it is completely saturated.

12. Mark down the original reading of the dial gauge.

13. Exert an initial setting load to provide a pressure of 5  (2.5   for very soft soils) to the assembly so that there is no inflammation. Permit the setting load to until there is no alternation in the dial gauge reading or for 24 hours.

14. Take the final gauge reading under the initial setting load.

15. Exert the first load increment to exert a pressure of 10 , and commence the stop watch. Record the dial gauge readings at 0, 0.25, 1, 2.25, 4.0, 6.25, 9.0, 12.25, 16.00, 20.25, 25.00, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256, 289, 324, 361, 400, 500, 600, and 1440 minutes.

16. Augment the load to exert a pressure of 20  and carry on the step (15). Similarly, augment the load to exert a pressure of 40, 80, 160, 320 and 640   or up to the preferred pressure.

17. After the last load augmentation had been exerted and the readings marked down, diminish the load to 1/4 of the final load and permit it to stand for at least a day. Mark down the dial gauge reading after 24 hours. Additionally, diminish the load to 1/4 of the preceding load and carry on the above process. Likewise, further reduce the load to 1/4 previous and repeat the procedure. Finally reduce the load to the initial setting load and keep it for 24 hours and take the final dial gauge reading.

18. Disassemble the assembly. Detach the ring with the sample. Thoroughly wipe out the additional surface water utilizing a blotting paper.

19. Compute the mass of the ring with the specimen.

20. Dry the sample in the oven for 24 hours and regulate the dry mass of sample.

 

 

(b) Coefficient of consolidation

Take Dial gauge readings

For every load increment, plot   as abscissa and the dial gauge reading (R) as ordinate. Assess the value of   from the plot.

Now use,

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