Relation between molecular structure of smectite and liquefaction of mudstone

Abstract

The elements and microstructure of typical mudstone were analysed by X-ray diffraction and scanning electron microscopy. The mudstone was composed mainly of clay minerals, with granules that form clumps with a ‘fluffy’ appearance. Pores in the clumps provide channels for water penetration. Materials Studio (MS) software was applied to simulate a double unit cell structure model of smectite. We then simulated the hydration process of smectite, demonstrating that single, double, and triple layers of saturated water molecules can be inserted within the cell structure with 48, 128 and 224 adsorbed water molecules, respectively. We also studied the microscopic structural change of smectite-dominated mudstone under different degrees of water soaking, and found that an energy exchange occurs between the water molecules and skeleton molecules of the smectite. This leads to a weakening of the intermolecular forces of smectite, which reduces the bonding among the clay minerals. Thus, this process directly leads to the breakage of the smectite microstructure: the granules detach from the surface and the fissures expand, resulting in mudstone with macroscopic phenomena such as argillization and liquefaction.