The behavior at interfaces and joints in geomechanical problems such as structure-soil foundation, and structure-rock foundation systems plays a vital role in their response under static and dynamic loads. Although laboratory testing and modeling for the interface response, mostly under dry conditions, have been performed in the past, the important issue of the effect of pore water pressures at interfaces on the soil-structure response has not been fully investigated before. The response of saturated interfaces is influenced significantly by the pore pressure development and its resulting effect on deformations, failure, and load carrying capacities of the structure-foundation systems is important for safe and economical design. This research will use a newly developed shear test device that allows static and dynamic loading and pore water pressures with inclusion of factors such as roughness, normal stress, density, simple and direct shear conditions and large-sized specimens. As interfaces between sand and concrete can provide a general condition, a series of quasistatic and cyclic tests on dry and saturated Ottawa sand-concrete interfaces will be performed. Another main objective of the research is to develop the unified disturbed state concept (DSC) which allows elastic and plastic deformations, hardening, softening and degradation, and modeling of liquefaction if indicated in the test results. The model will be calibrated based on the test data, and validated with respect to independent tests. An optimization procedure will permit systematic simplification and reduction in parameters, toward practical analysis and design. Finally, guidelines for application of the model, including through nonlinear finite element procedures, will be developed.
