Kevin Stone

A Modified Triaxial Cell for Stress-Path Testing of Weak Rock (Hard Soils)

A simple conversion of a standard triaxial apparatus for stress path testing is presented and illustrated. The conversion is effected by incorporating a balanced ram arrangement into the top plate of a conventional triaxial cell, which, together with some additional modifications to the sample top cap and ram connection details, provides a cost-effective stress path testing cell. This modified triaxial cell, combined with a suitable external loading frame, allows the axial and radial stresses to be independently controlled. Consequently, any desired stress path can be applied to a specimen mounted in the modified cell. The functionality of the modified cell is demonstrated through the results of long-term stress-path tests performed as part of a creep study of intact medium porosity chalk. In this study, the modified cells were used with cantilever type loading frames, and subjected to continuous loading for periods in excess of 400 days. The performance of the modified cells was very satisfactory, and demonstrates that such an arrangement can provide a simple and a cost-effective system for conducting laboratory stress-path tests.