Evolution of at-rest lateral stress for cemented sands: experimental and numerical investigation

摘要

We present measurements of the evolution of the at-rest lateral stress coefficient K_0 for cemented sands in a modified oedometer and provide additional insights into material response using discrete element method (DEM) simulations. A new scheme for the measurement of K_0 is adapted to obtain horizontal stress for the entire stress history with parallel measurement of shear wave velocity. Results show that the horizontal stress of uncemented sand linearly increases, while debonding in cemented sands is characterized by a non-linear evolution of horizontal stress. Cement content governs the stress regime in which decementation initiates. The at-rest lateral stress coefficient of cemented sands increases during decementation, resulting in higher values for overconsolidated specimens. The recovery of K_0 values is manifested at the preconsolidation stress during reloading. Cemented sands collapse followed by decementation and subsequent changes in K_0 values. The DEM simulations reasonably reproduce laboratory specimen-scale response and are used to highlight the evolution of particle contact force, gradual debonding of cement, and the formation of a blocky structure in cemented sands at the particle-scale. These observations are consistent with inferred response of physical specimens at the particle scale, yet this behavior is not directly observable in the laboratory, highlighting the particular effectiveness of an integrated physical-numerical investigation. The interparticle contact stiffness of cemented sands controls the evolution of horizontal stress at low vertical stress, and the decementation causes the convergence of K_0 values towards those of uncemented sands at high vertical stress.