Surendra K. Saxena

Constitutive modeling of cemented sand

A true triaxial testing apparatus was developed and used by the authors to test uncemented and cemented sands under different stress paths. This test data are used in this paper to examine the applicability of two constitutive models which have been developed by other researchers. The first model, due to Lade (known as Lades model), is an elasto-plastic model with single yield surface and plastic potential. The second model, due to Valanis and co-workers (known as endochronic model), is reminiscent to (Bolzmann) nonlinear viscoelasticity, where ordinary time is replaced by a weighted arc length of the plastic strain in plastic strain space. The procedures for determining 13 and 12 material parameters for the respective models are explained. Predictions based on the two models are obtained and compared with experimental data for simple loading histories composed of initial hydrostatic prestress and subsequent proportional loading.

Development of a true triaxial testing apparatus

A stress-controlled, flexible boundary, true (or cubical) triaxial apparatus has been developed to investigate the behavior of cemented sand under various stress paths which are not achievable using conventional axisymmetric triaxial apparatus. The apparatus components, specimen preparation, and test procedure are described. Tests were performed on cemented sand along different stress paths which included hydrostatic compression, conventional triaxial compression, and along different directions on octahedral planes. The test results indicate that stress-strain and volumetric response of cemented sand depends on stress path.