Suction-controlled triaxial (SCTX) tests are considered to allow researchers to investigate influences of individual variables on unsaturated soils under specified stress path with controls of stresses, pore water and air pressures. In the past fifty years, SCTX testing method has been established as a standard approach to characterize constitutive behavior for unsaturated soils. Most important concepts for modern unsaturated soil mechanics were developed upon results from the SCTX tests. Among these, one of the most important contributions in the constitutive modeling of elasto-plastic behavi...
