Normal stresses on Direct Shear test 2

[Mgcini]

Good day people. How do you decide on the proper Normal stresses values to use in a Direct shear test. Is it based on the global stresses of soil and the depth with which we extracted the sample or it is based on the induced stresses by the proposed building. Please help.

 

[GeoPaveTraffic]

There are several factors at play in determining the normal stress to use. First is the sample "undisturbed" or remolded? If undisturbed, then the normal stress should be a at least a little, say 10%, higher than the insitu stress where the sample was collected.

Otherwise, the test normal stresses should cover the range of normal stress expected to occur during the project. Typically, a minimum of three tests are conducted at different normal stresses to establish the angle of internal friction for the material.

Mike Lambert