From direct simple shear test to soil model development and supported excavation simulation: Integrated computational-experimental soil behavior characterization framework

A constitutive model that represents soil behavior under a wide range of loading conditions is necessary for the simulation of complex boundary value problems. However, most laboratory tests are interpreted with an assumption of uniform stresses and strains within the tested soil specimen even when the specimen is known to experience nonuniform stress-strain distribution as in the direct simple shear (DSS) test. Numerous tests are often needed to fully characterize a soil's nonlinear and anisotropic behavior and to develop an appropriate soil model. This paper utilizes an evolutionary inverse analysis approach to extract nonuniform stresses and strains within K₀ consolidated-undrained direct simple shear (CK₀UDSS) test specimens on Boston blue clay (BBC) and directly develop soil constitutive models. The extracted soil behavior is consistent with known behavior of BBC including anisotropic stress-strain response and small strain nonlinearity obtained under complex laboratory loading conditions. The developed soil models from DSS tests are applied to a deep excavation case history. The analysis results show that global responses, such as lateral wall deflections and vertical ground surface settlements, approximately match measured response. The proposed approach represents a major shift in our ability to efficiently bridge numerical modeling and laboratory testing and changes the way soil characterization and constitutive model development is approached. It is possible to use very few laboratory tests to directly develop versatile material models that can be used in the solution of geotechnical field problems without the need for complex formulations or length development processes.