Measuring shear strength of loose building materials

Customised engineering example

The shear strength of compacted materials (e.g. soil and sand) can be awkward to test. This is because the shear force applied is perpendicular to the main compressive force, and universal tensile testers only operate in one direction. It is the function of the fixture to redirect the load to induce shear stress.

Our client is a specialist in waste-disposal and compacts various materials for landfill. They required an affordable solution for occasional testing of shear strength based on many of the requirements of ASTM D3080.

This test standard is designed to report specific strength data, but notably not return a true engineering value for 'shear modulus' of the sample material.

Mecmesin designed a 'direct shear box' sample container into which the material could be placed and then compacted to a known force, using an AFTI digital force and torque indicator and loadcell for load measurement. The sample container is then inserted into a Mecmesin twin column tensile tester where one of 3 different profile shear-discs can be used to apply a shear force, which is measured by the tester.