Question

23. What is the most appropriate method for downhole testing to compute a friction angle in the soil?

a) Standard Penetration Test (SPT)

b) Thin-Walled Tube

c) Borehole Shear Test (BST)

Can BST be used to measure cohesion for fine-grained soils?

What can commonly cause refusal of the split spoon sampler during the SPT?

Answer 1

Standard Penetration Test (SPT) is the most appropriate method for downhole testing to compute a friction angle in the Soil.

STP are performed in unsaturated residual soil Layers.

Borehole Shear Test is the method of estimating the Drained Shear Strength of the Soil. The name of the Test is quiet Clear as this test is conducted inside a Drilled Boring.

The Borehole Shear Test is mainly considered for the Cohesionless soil with high Permeability and can be considered as Consolidated Drained test.

The value of N based on the over burden pressure can commonly cause refusal of the split spooon sampler during the Standard Penetration Test.

Where N= no. of blows required for 150mm penetration in SPT.

As there is some hard surface the value of N exceeds.