ABSTRACT
The development of constitutive models for geomaterials usually relies on laboratory tests to define the material response. Typical laboratory test programs include a suite of stress path and/ or strain path tests. In terms of developing constitutive relationships, stress path tests provide information on various material properties including deformation properties, ultimate strength, residual strength, and volume compressibility. The rock simulant was composed of Ottawa sand with an epoxy binder. The resulting “rock” was of moderate strength and high permeability. Although drainage was provided for the specimen, most concretes have low permeabilities and when subjected to compression testing, the permeability can decrease further due to pore volume crushing. Under drained test conditions, the test has the additional advantage that the failure envelope defined by the biaxial unload is not affected by pore pressures that might be present in low permeability materials. In undrained test conditions, the test is just as useful provided steps are taken to minimize influence of stress relaxation.
