MODEL PREDICTION OF ANISOTROPIC BEHAVIOR OF BOSTON BLUE CLAY

This paper investigates predictive capabilities of the effective stres s soil model MIT-E3 (described in a companion paper) through detailed comparisons with laboratory test data for Boston blue clay (BBC). The main focus of these evaluations is predictions of anisotropic stress-s train behavior using data from two special laboratory shear devices: t he directional shear cell (DSC), and the multidirectional direct simpl e shear apparatus (MDSS). Input parameters are first estimated from st andard types of laboratory data, including one-dimensional (K-0) compr ession and undrained triaxial shear tests. The DSC is a plane strain a pparatus with the additional capability of controlling principal stres s directions during shear. Measurements in this device include undrain ed shear tests with principal stress rotations at OCR = 1, and with fi xed stress direction but different principal stress orientation at OCR = 4. The MIT-E3 model describes accurately the observed variations in undrained shear strength and stress-strain behavior in tests at OCR = 1, but is notably less reliable at OCR = 4. The MDSS has the same dim ensions and boundary conditions as the Geonor simple shear apparatus, but can apply horizontal shear stresses in two independent directions. Measurements in the MDSS apparatus demonstrate the anisotropic proper ties of BBC at OCR = 1 induced by consolidation under an applied shear stress. MIT-E3 predictions are in excellent agreement with measured v ariations in peak shear resistance and prepeak stress-strain response.