DIRECT SHEAR TEST
Need and scope:
The value internal friction angle and cohesion of the soil are required for design of many engineering problems such as foundations, retaining walls, bridges, sheet piling. Direct shear test can predict these parameters quickly.
APPARATUS
1. Direct shear box apparatus, and Loading frame (motor attached).
2. Dial gauge, Proving ring, Balance to weigh upto 200 mg.
3. Tamper, Straight edge, Aluminum container, Spatula.
Knowledge of Equipment:
Strain controlled direct shear machine consists of shear box, soil container, loading unit, proving ring, dial gauge to measure shear deformation and volume changes. A two piece square shear box is one type of soil container used. A proving ring is used to indicate the shear load taken by the soil initiated in the shearing plane.
Procedure :
1. Check the inner dimension of the soil container, and put the parts of the soil container together.
2. Calculate the volume of the container. Weigh the container.
3. Place the soil in smooth layers (approximately 10 mm thick). If a dense sample is desired tamp the soil.
4. Weigh the soil container, and find the weight of soil. Calculate the density of soil.
5. Plane the top surface of soil, and put the upper grating stone and loading block on top of soil.
6. Measure the thickness of soil specimen.
7. Apply the desired normal load and Remove the shear pin.
8. Attach the dial gauge which measures the change of volume.
9. Record the initial reading of the dial gauge and calibration values.
10. Check all adjustments to see that there is no connection between two parts except sand/soil.
11. Start the motor. Take the reading of the shear force and volume change till failure.
12. Add 5 kg normal stress 0.5 kg/cm2 and continue the experiment till failure
13. Record carefully all the readings. Set the dial gauges zero, before starting the experiment
Data Calculation Sheet for Direct Shear Test
Normal stress = 0.5 kg/cm2 L.C=....... P.R.C=.........
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Horizontal Gauge Reading
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Vertical Dial gauge Reading |
Proving ring Reading
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Hori. dial gauge Reading Initial reading div. gauge |
Shear deformation Col.(4) x Least count of dial |
Vertical gauge reading Initial Reading
|
Vertical deformation col.6
x
L.C of dial gauge |
Proving reading Initial reading |
Shear stress = div.col.(8) x proving ring constant Area of
the specimen (kg/cm2) |
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0 |
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25 |
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50 |
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75 |
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100 |
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125 |
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150 |
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175 |
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200 |
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250 |
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300 |
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400 |
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500 |
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600 |
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700 |
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800 |
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900 |
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Normal stress = 1.0 kg/cm2 L.C=....... P.R.C=........
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Horizontal Gauge Reading
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Vertical Dial gauge Reading |
Proving ring Reading
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Hori. dial gauge Reading Initial reading div. gauge |
Shear deformation Col.(4) x Least count of dial |
Vertical gauge reading Initial Reading
|
Vertical deformation col.6
x
L.C of dial gauge |
Proving reading Initial reading |
Shear stress = div.col.(8) x proving ring constant Area of
the specimen (kg/cm2) |
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0 |
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25 |
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50 |
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75 |
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100 |
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125 |
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150 |
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175 |
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200 |
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250 |
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300 |
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400 |
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500 |
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600 |
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700 |
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800 |
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900 |
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Normal stress = 1.5 kg/cm2 L.C=....... P.R.C=........
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Horizontal Gauge Reading
|
Vertical Dial gauge Reading |
Proving ring Reading
|
Hori. dial gauge Reading Initial reading div. gauge |
Shear deformation Col.(4) x Least count of dial |
Vertical gauge reading Initial Reading
|
Vertical deformation col.6
x
L.C of dial gauge |
Proving reading Initial reading |
Shear stress = div.col.(8) x proving ring constant Area of
the specimen (kg/cm2) |
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0 |
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25 |
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50 |
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75 |
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100 |
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125 |
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150 |
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175 |
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200 |
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250 |
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300 |
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400 |
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500 |
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600 |
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700 |
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800 |
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900 |
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