Nanoscale Stick-Slip Behavior and Hydration of Hydrated Illite Clay

The present work is to shed light on the hydration and stick–slip behavior during shear process in interlayer region between clay sheets, because this region is the main location for the diffusion of water and ions, adsorption, hydration, slip, etc. Molecular Dynamics (MD) simulation method has been performed to investigate the interlayer hydration, diffusion, and shear behavior of various hydrated illites. The stick–slip effect found during shear process was explained by the potential energy surface of crystal layers. Simulation results indicated that water film in hydrated illite could be divided into multiple types of water layers. Moreover, the typical stick–slip effect was significantly related to the potential energy surface of illite crystal layers. The higher the hydrostatic pressure or the lower the water content, the more significant stick–slip effect, and the higher the average shear stress. The interlayer bound water played a bonding role during shear process, while free water was mainly for a lubricating role. The friction coefficient and internal friction angle of 10.2 % ∼ 61.2 % hydrated illite system in nanoscale are 0.023 ∼ 0.095 and 1.335° ∼ 5.438°, respectively.