Investigation on the friction properties of montmorillonite by molecular dynamics considering the effects of water content, cation species, ion concentration and temperature

HC Ying and HF Pei and SQ Zhang, COMPUTERS AND GEOTECHNICS, 171, 106345 (2024).

DOI: 10.1016/j.compgeo.2024.106345

The friction angle, a crucial strength indicator, has been discussed and studied through various experimental methods. However, clay friction experiments are intricate, involving numerous interfering factors. There needs to be more understanding regarding the connection between friction angles and microscopic friction mechanisms. Few studies have systematically investigated the influence of various factors on friction angles at the microscopic level. This research focuses on the nanoscale friction properties and influencing mechanisms of hydrated montmorillonite (MMT) using molecular dynamics simulations. A numerical correspondence between microscopic friction coefficients and macroscopic friction angles is established. The effects of water content, cation species, and ion concentration on friction behavior from a microscopic perspective are explored. It can be found that the calculated friction angles of MMT progressively decrease with increasing water content, which is related to the viscosity of the pore water. The friction angles of four types of MMT in descending order are K+ > Na+ > Ca2+ > Mg2+, depending on the ability of the cations to hydrate and adsorb. The impact of ion concentration in the pore fluid on the friction angle is connected to the electric double layer. The temperature affects the friction behavior by changing the amount of water.

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