Tri Axial Test
Procedure
- Measure the Length, Diameter and Mass of sample.
- Place the specimen on the base pedestal and put top cap on specimen top.
- Place the rubber membrane on the specimen using membrane stretcher and seal membrane.
- Place the cell containing the sample in loading machine.
- Allow the operating fluid to raise the pressure to desired level.
- Adjust the loading machine ram near the seat on the top of specimen.
- Bring axial deformation gauge near the specimen.
- Select rate of axial strain that will give time to failure of bout 5-10 min normally 1-2% per min.
- Note the initial load gauge reading.
- Note the initial axial deformation gauge reading.
- Continue the compression until maximum value of load has passed or an axial strain of 20% has been reached.
- Unload the specimen and note down the final reading of the load measuring guage.
- If the difference between final and initial reading of the load gauge is more than 5% discard the readings and do the experiment again.
- Reduce the cell pressure to zero by draining the fluid in cell.
- Dismantle the cell and remove the specimen.
- Remove rubber membrane and take photograph to record mode of failure.
- Examine the specimen and check presence of stones, layers, Calcareous matter and other irregularities in specimen.
- Place the specimen in oven and determine moisture content.
(Note: If difference of initial and final mass is more than 3% note down the percentage difference and investigate any leakage in membrane)
Direct Shear Test
Procedure:
- Once the specimen of sand is prepared (i.e. consolidation is complete for cohesive soils).
- After making sure that switch is in the right position to drive the box forward in direction, switch on the motor.
- The rate of shearing for cohesive soils shall be calculated, as shear speeds should be slow enough allowing any excess pore water pressures to dissipate from the specimen. For sands, rapid shearing rate can be used.
- Record the reading of the proving ring dial gauge and the vertical movement dial gauge, after defined interval of displacement.
- Suitably take readings after every 0.1 mm of displacement.
- When load is increasing rapidly take readings more frequently.
- When load change is slow take readings less frequently.
- While using automatic recording transducers take readings at regular interval of time, but these should be regular enough to clear the pre-peak behavior for manual reading.
- When soils are cohesive take readings until four consecutive reading comes.
- If no peak shear value come, keep shearing the sample until it reached its full travel.
- If automatic data collection instrument is used, plot the shear stress vs the horizontal displacement so that we can be able to stop the test at suitable point.
- For sands, keep shearing until the ultimate shear strength is reached and take readings until the peak has been passed.
- For loose sands, peak shear strength is not observed, so carry out shearing until the ultimate shear strength is reached.
Attachment:- Assignment Files.rar