This study is related to the modeling of the nonlinear stress-strain behavior of frictional materials for wide range of strain. To describe both strain-hardening and also strain-softening behavior, a constitutive equation including a power term is proposed in the following. This equation is shown to offer more versatility for modeling stress-strain behavior in monotonic loading conditions, at from low- to high-strain levels. The proposed equation is relatively verified by experimental data of hollow cylindrical torsional shear tests on both sands as frictional materials, and cement-treated sands as frictional and cohesive materials. In addition, a exponential function is adopted to express the stress-dilatancy relations of cement-treated sands. A dilatancy characteristics of sands and cement-treated sands is expressed by using both functions together.
