A Simple Method for Triaxial Strain Path Testing

Abstract

A new, simple method is presented for testing triaxial soil samples along constant strain increment ratio paths. In this method, by adjusting the ratio of the diameter of the top cap at the free end to that of the soil sample before a test, strain path testing with a constant strain increment ratio (the ratio of the radial strain increment Δɛ r to the axial strain increment Δɛ a ) can be achieved using a double-cell triaxial apparatus with a simple automated control system. This is identical to the system used for consolidation and expansion tests under K 0 -conditions. Test results show that: (1) strain path testing with a constant strain increment ratio can easily be performed for a triaxial soil sample in any moisture conditions (saturated, partially saturated or dry); (2) the relationship between the deviator stress ratio q/p ' and the deviator strain ɛ s =2( ɛ a - ɛ r )/3 of sand observed in constant strain increment ratio path testing is hyperbolic in form, and the mobilized maximum deviator stress ratio depends on the magnitude of the strain increment ratio adopted in the testing; and (3) the relationship between the mobilized maximum stress ratio and strain increment ratio obtained from constant strain increment ratio path testing does not agree with that determined by Rowe's stress-dilatancy equation.