consolidation procedure

8/3/2019 Consolidation Procedure

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Lab 10: Consolidation Test

The soil sample you will test will have been prepared before the lab starts. It was conditioned to

a certain preconsolidation stress, then allowed to relax back to a relatively unstressed condition.

The goal of this experiment is to determine the compression index, C c, the preconsolidationstress, σp, and the coefficient of consolidation, cv. To do this you will monitor the change in

height of the soil sample resulting from a sequence of vertical stresses imposed. The stress levels

will start at 1 ton per square foot (tsf), progressing to 2 tsf, 4 tsf, 8 tsf and 16 tsf. Then there willbe a progression of reduced stresses (unloading) to 8 tsf, 4 tsf and finally 1 tsf. For each stage

you should ensure that the load remains until the rate of change in height approaches zero before

going to the next load step. Using Gentest, the results at each load level will be recorded anduploaded to the CE 354L website. From there you can download the data for analysis.

CAUTION: BE AWARE OF WHAT IS GOING ON WITH THE EQUIPMENT AT ALL

TIMES. KEEP FINGERS AWAY FROM THE CONSOLIDATION DEVICE WHILE

CONNECTING OR ADJUSTING THE COMPRESSED AIR SOURCE AND THECONSOLIDOMETER CONTROLS.

Equipment

Gentest data acquisition workstation Consolidation device with soil

sample loaded in the consolidometer



Older model Newer model

The loaded consolidometer under test.

Older model: LDT sensor tip resting on edge of consolidometer wall. This photo was taken near

the end of the test.

Newer model: LDT sensor tip rest at the top center of the crosshead.

*At the beginning of the test the LDT position should be adjusted so there is ample range for the

tip to travel.

PROCEDURE

The following procedure steps assume the test setup has been prepared before the lab for thepreconsolidation phase. This means the load on the sample is less than 1 tsf and the LDT has

been installed but not yet adjusted for the test. There should be a nominal load on the sample.Have the Instructor or TA check the setup before you proceed.

1. Set the Load/Unload selector on the consolidation device to OFF. Adjust the regulator on the

consolidation device for the pressure (read on the pressure transducer's digital readout)

corresponding to 1 tsf load. DO NOT APPLY THE LOAD YET.

2. Adjust the LDT so the sensor tip has at least 0.3 inches of movement available.



Secure the LDT by tightening the locking screw. Do not overtighten.

Older model: The sensor tip rests squarely on the consolidometer wall . The tip should traveltoward the body of the LDT during the loading phase of the test so the sensor tip should be

almost fully extended.

Newer model: The LDT sensor tip should travel away from the body so the LDT position should

be adjusted so that the sensor tip is near the transducer barrel.

3. Start Gentest, select the 1-D Consolidation Test.

4. Click the Check Transducer Operation tab and observe that the computer is reading the LDT

transducer signal conditioner readout correctly. If the numbers displayed on the screen do not

coincide with the numbers on the actual transducer readout, then you need to resolve that beforecontinuing.

5. Select the Run Test tab. Verify that the small readout (black background, green numbers)

shows the correct LDT value.

6. Select Group and Course information.

7. In the textbox, enter the load increment for which Gentest will collect and store the data.

8. To start the test, simultaneously turn the Load/Unload selector switch to LOAD and click the

Begin button on Gentest to start data collection. The sampling rate is based on a rate of tensamples per log decade. This means that for each log period, e.g. 0.1 to 1.0, 1.0 to 10, and so on

about ten samples will be collected.

9. Allow the test to run until the change in LDT movement slows to about 0.0002 inch or less

between sample intervals.

10. Turn the Load/Unload selector switch to OFF. Click the STOP SAMPLING button onGentest to stop data collection and close the data file. NOTE: Do not leave the Load/Unload

selector in the OFF position for more than a few minutes. To do so would allow the applied load

to relax slightly which will introduce data errors.

11. Adjust the regulator for the next load step.

12. Repeat steps 6 through 11 for the specified load and unload values.

13. After the final unload step, remove the compressed air source and let the consolidometer base

drop to its lower position. Retrieve the soil sample and consolidometer ring and measure the finalheight of the soil sample.

14. Measure the moisture content of the soil sample.

15. Copy the data files and finish the calculations.

consolidation procedure

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