Direct Shear Test
Test objective
The objective of direct shear test is to determine the shearing strength of soil using the direct shear apparatus
Scope
Direct shear test is used to predict the internal friction angle and cohesion of soil, which are required in many engineering problems such as design of foundation, retaining walls, slab
idges, pipe and sheet piling.
Apparatus
XXXXXXXXXXDirect shear box apparatus (Fig. 1)
XXXXXXXXXXTamper.
XXXXXXXXXXStraight edge.
XXXXXXXXXXBalance
XXXXXXXXXXAluminium container.
XXXXXXXXXXSpatula.
Figure 1 Direct Shear Test Apparatus (Direct Shear Apparatus/Laser Direct Shear Apparatus, Aimil Ltd, 2011. Available from: < http:
www.aimil.com/Products.aspx?Product_Id=416 >. [9 Fe
uary 2016].
Procedure
1. Assemble the shear box.
2. Measure the inner dimension of the shear box.
3. Place the soil in smooth layers with measured amount of soil.
4. Compact the soil sample until the target density is achieved.
5. Calculate the density of the soil.
6. Make the surface of the soil plane.
7. Place the loading plate on top of the upper porous plate.
8. Set the dial gauges with initial readings to zero. Remove the alignment screws which hold two halves of the shear box together.
9. Apply the desired normal load. Observe for vertical displacement (if any) and wait till the dial gauges indicate a constant reading. Reset the dial gauges to zero.
10. Start the motor to produce the desired constant rate of shearing.
11. Take the readings for shear load, shear displacement and vertical displacement.
12. Terminate the test when the shear load starts to reduce or remains constant for at least three readings.
13. Remove the soil sample and repeat the test with different normal loads at least for another two samples.
Punctual attendance and contribution - 10 marks
Laboratory Data sheet for direct shear test15 marks
Program: Bachelor of Engineering (Civil & Infrastructure) – BH077/BH088
Date:
Test type:
Test No:
Soil type:
Measurements
Unit
Value
Applied Normal Load:
kPa
Shear rate:
mm/s
initial density measurements:
Mass of dry soil + container (before sample preparation):
g
Mass of dry soil + container (after sample preparation):
g
Shear box dimensions:
Length (mm):
mm
Width (mm):
mm
Height (mm):
mm
Measurements During the test
Shear Displacement (mm)
Shear Force (N)
Shear Stress (kPa)
Vertical Displacement (mm)
Instructions for data sheet:
1.0 Please provide this data sheet for each test you conduct. (i.e. 3 data sheets for the 3 tests).
2.0 Use the ‘Excel data example’ provided to complete the above table and proceed with the other calculations
3.0 You may only select few data rows from the excel (covering full shear stress curve as showed in Figure 2 in next page) and show the table in your lab test report
Calculations 60 marks
1.0 Calculate the sample density
Show the measurements of soil weight and volume. Provide the density in kN/m3
2.0 For each normal stress, plot
2.1 Shear stress Vs Shear displacement
Figure 2 : Example plot for shear Stress Vs shear displacement (Ref. case – density 17.5kN/m3 at 12kPa confining stress from PhD work of D.J.Robert)
2.2 Vertical displacement Vs Shear displacement
Figure 3 : Example plot for vertical displacement Vs shear displacement (Ref. case – density 17.5kN/m3 at 12kPa confining stress from PhD work of D.J.Robert)
3.0 Plot shear strength and normal stress for the three specimen and calculate the shear strength parameters of soil
c
Figure 4 : Example plot for shear strength Vs normal stress (Ref. case – density 17.5kN/m3, from PhD work of D.J.Robert)
Discussion
Please include a
ief discussion of the test results including the followings;
· Importance of shear strength of soil
· Main advantages and disadvantages of shear box test
· Reliability of the results and the factors most likely to influence the reliability15 marks
XXXXXXXXXX
Shear Stress (kPa)Shear Displacement (mm)
XXXXXXXXXX202468
Vertical Displacement (mm) Shear Displacement (mm)
01 XXXXXXXXXX
Shear Stress (kPa)Normal Stress (kPa)
Direct Shear Test
Test objective
The objective of direct shear test is to determine the shearing strength of soil using the direct shear apparatus
Scope
Direct shear test is used to predict the internal friction angle and cohesion of soil, which are required in many engineering problems such as design of foundation, retaining walls, slab
idges, pipe and sheet piling.
Apparatus
XXXXXXXXXXDirect shear box apparatus (Fig. 1)
XXXXXXXXXXTamper.
XXXXXXXXXXStraight edge.
XXXXXXXXXXBalance
XXXXXXXXXXAluminium container.
XXXXXXXXXXSpatula.
Figure 1 Direct Shear Test Apparatus (Direct Shear Apparatus/Laser Direct Shear Apparatus, Aimil Ltd, 2011. Available from: < http:
www.aimil.com/Products.aspx?Product_Id=416 >. [9 Fe
uary 2016].
Procedure
1. Assemble the shear box.
2. Measure the inner dimension of the shear box.
3. Place the soil in smooth layers with measured amount of soil.
4. Compact the soil sample until the target density is achieved.
5. Calculate the density of the soil.
6. Make the surface of the soil plane.
7. Place the loading plate on top of the upper porous plate.
8. Set the dial gauges with initial readings to zero. Remove the alignment screws which hold two halves of the shear box together.
9. Apply the desired normal load. Observe for vertical displacement (if any) and wait till the dial gauges indicate a constant reading. Reset the dial gauges to zero.
10. Start the motor to produce the desired constant rate of shearing.
11. Take the readings for shear load, shear displacement and vertical displacement.
12. Terminate the test when the shear load starts to reduce or remains constant for at least three readings.
13. Remove the soil sample and repeat the test with different normal loads at least for another two samples.
Punctual attendance and contribution - 10 marks
Laboratory Data sheet for direct shear test15 marks
Program: Bachelor of Engineering (Civil & Infrastructure) – BH077/BH088
Date:
Test type:
Test No:
Soil type:
Measurements
Unit
Value
Applied Normal Load:
kPa
Shear rate:
mm/s
initial density measurements:
Mass of dry soil + container (before sample preparation):
g
Mass of dry soil + container (after sample preparation):
g
Shear box dimensions:
Length (mm):
mm
Width (mm):
mm
Height (mm):
mm
Measurements During the test
Shear Displacement (mm)
Shear Force (N)
Shear Stress (kPa)
Vertical Displacement (mm)
Instructions for data sheet:
1.0 Please provide this data sheet for each test you conduct. (i.e. 3 data sheets for the 3 tests).
2.0 Use the ‘Excel data example’ provided in the blackboard to complete the above table and proceed with the other calculations
3.0 You may only select few data rows from the excel (covering full shear stress curve as showed in Figure 2 in next page) and show the table in your lab test report
Calculations 60 marks
1.0 Calculate the sample density
Show the measurements of soil weight and volume. Provide the density in kN/m3
2.0 For each normal stress, plot
2.1 Shear stress Vs Shear displacement
Figure 2 : Example plot for shear Stress Vs shear displacement (Ref. case – density 17.5kN/m3 at 12kPa confining stress from PhD work of D.J.Robert)
2.2 Vertical displacement Vs Shear displacement
Figure 3 : Example plot for vertical displacement Vs shear displacement (Ref. case – density 17.5kN/m3 at 12kPa confining stress from PhD work of D.J.Robert)
3.0 Plot shear strength and normal stress for the three specimen and calculate the shear strength parameters of soil
c
Figure 4 : Example plot for shear strength Vs normal stress (Ref. case – density 17.5kN/m3, from PhD work of D.J.Robert)
Discussion
Please include a
ief discussion of the test results including the followings;
· Importance of shear strength of soil
· Main advantages and disadvantages of shear box test
· Reliability of the results and the factors most likely to influence the reliability15 marks
XXXXXXXXXX
Shear Stress (kPa)Shear Displacement (mm)
XXXXXXXXXX202468
Vertical Displacement (mm) Shear Displacement (mm)
01 XXXXXXXXXX
Shear Stress (kPa)Normal Stress (kPa)