A set of tools have been developed to monitor shear stresses and shear strains (distortions) within a soil mass as it undergoes loading. The tools have been used in monotonic and cyclic conditions and were developed to be inherently waterproof with the response of a soil element to earthquake loading.

The same set of tools has been used in element testing.  In the figure below a shear stress sensor and a shear distortion sensor (local sensors) were planted within a large direct simple shear specimen.  Testing has shown that the shear stiffness at the sample core is significantly higher when based on the local measures in comparison to that determined from the generic (global) measures of shear load and shear deformation.

This is not magic, simply the transfer of stress and strain to the simple shear specimen is not as trivial as we would like to think.

See below the development of local shear stress and local shear strain in a set of strain controlled cycles of simple shear.