Estimation of compression behavior of granular soils considering initial density effect based on equivalent concept

Compressibility of granular materials depends on its initial density and is significantly affected by particle breakage, especially at high stress levels. In this study, a simple compression model for granular soils is proposed by incorporating a new equivalent concept. The initial density effect on the curvature of compression line is captured by a novel equivalent void ratio, which features a state variable for describing the evolution of grain crushing and corresponding yielding behavior. An Equivalent Compression Curve (ECC) is further established by directly implementing the equivalent void ratio into a reference compression curve. Validation has been done by comparing the simulated curves with the test data from available literature. It reveals a good linear relationship between the state variable and breakage index. Moreover, the ECC can well normalize the compression behavior of granular soils with a wide range of initial densities and stress levels. The simplified version of ECC includes only three parameters which are consistent with the reference model. The proposed model provides a basis for establishing versatile and rigorous hardening law that can be readily used in conjunction with the general elasto-plasticity theory.