Degradation effects at microstructural scale and their consequences on macroscopic behaviour of a slightly weathered siltstone.

Abstract

A systematic experimental programme was performed on a slightly weathered siltstone of Weald facies (Cretaceous period) to study the degradability of the material due to hydraulic and mechanical processes. The paper addresses weathering processes induced by drying/wetting cycles at low and high confining stresses, which were performed under relative humidity controlled conditions in an oedometer cell. Loading/unloading paths at different hydraulic states were also carried out. The evolution of the degradation at microscale was evaluated by pore size distribution changes using mercury intrusion porosimetry. Simultaneously, the evolution of the material stiffness was studied by ultrasonic wave propagation tests. In this way, the overall micro and macrostructural behaviour is observed, allowing for a better understanding of the hydro-mechanical coupled interactions at different structural levels.