Question

Consider the following features of direct shear test:
1. Failure takes place on the predetermined plane.
2. It is a quick test.
3. Drainage conditions cannot be changed.
4. Failure of the sample is progressive.
Which of these are the disadvantages of direct shear test?

• A. $1,2$ and $3$
• B. $1,3$ and $4$
• C. $1,2$ and $4$
• D. $3$ and $4$

Answer 1

The correct option is B $1,3$ and $4$

The most important limitation of direct shear test is that the failure plane is predetermined and this may not be the weakest plane.
There is virtually no control of drainage of soil specimen as the water content of saturated soil changes rapidly with stress.
The stress conditions across the soil sample are very complex because of nonuniform distribution of normal and shear stress on the potential surface of sliding. The stress is more at edge and less at centre. Due to this there is progressive failure of the specimen i.e., the entire strength of soil is not mobilised simultaneously.