Influence of the fluid polarity on shear strength of sodium montmorillonite clay: A steered molecular dynamics study

Smectite clay minerals such as sodium montmorillonite (NaMt) are some of the main constituents of expansive clays. This work evaluated the mechanical response of NaMt intercalated with fluids having a wide range of polarities under various magnitudes of compression and fluid content using steered molecular dynamics (SMD) simulations. The shear strength parameters of the clay at the molecular scale, cohesion, and friction angle were quantitively evaluated. The simulation results indicated that the polarity of the fluids and the fluid content in the clay interlayer space played a vital role in shear stress versus shear strain response, the shear strength parameters, and nonbonded interactions energies upon mechanical loading of externally applied compressive stresses followed by shearing. The expansive clay's shear stress versus shear strain response depended on the normal stress and fluid polarity. This study showed the profound influence of the polarity of the fluids on the molecular shear strength behavior of swelling clays. Incorporating the clay-fluid molecular interactions and their role in shear response at the molecular scale is crucial for developing robust theories and tools for accurately predicting the shear strength properties of swelling clays for geotechnical and geoenvironmental applications.