Shear strength of a soil is its maximum resistance to shearing stresses. The shear strength is expressed as

S + C’  + σ Tan Φ’

Equipment:

Where c’ = effective cohesion, σ = effective stress,  Φ’= effective angle of shearing resistance.

The shear tests can be conducted under three different drainage conditions. The direct shear test is generally conducted on sandy soils as a consolidated drained test.

 Shear box, divided into two halves by a horizontal plane, and fitted with locking and spacing screws

2. Box container to hold the shear box

3. Base plate having cross grooves on its top surface.

4. Grid plates, perforated, 2 Nos.

5. Porous stones, 6mm thick, 2 Nos.

6. Loading pad

7. Loading frame

8. Loading yoke

9. Proving ring, capacity 2kN.

10. Dial gauges, accuracy 0.01mm, 2 Nos.

11. Static or dynamic compaction devices.

12. Spatula

Hi

For first part of your question: the commonly used procedure of direct shear is a fixed procedure in all types of materials (applying the specific normal load on a given sample and then applying the shear load until the failure be met). the apparatus and equipment for soil shear test were introduced above by Prem Baboo. one of consideration in laboratory tests is ratio of grain size related to dimension of test container (DE). well known standards recommend that the DE