DEM investigation of the mechanical response of cementation-type methane hydrate-bearing sand using an improved linear parallel bond contact model

Abstract

This study presents a DEM investigation of the deformation behaviors and mechanical responses of cementation-type methane hydrate-bearing sand (MHBS). An improved linear parallel bond (I-PB) contact model was proposed considering the tensile-compressive-shear bond failure mode of methane hydrate (MH) and implemented in a 2D DEM code. A specific parameter calibration procedure was established to calibrate the microparameters of the I-PB contact model. Subsequently, flexible membrane particle boundaries were employed to capture the deformation characteristics of MHBS samples, and biaxial shearing tests were conducted under varying MH saturation and confining pressure conditions. Various parameters, including stress, strain, particle displacement, bond breakage distribution, contact-force chain, etc., were analyzed to investigate the macro- and micromechanical properties of MHBS samples. The numerical simulation results indicate the following: (1) Increasing MH saturation improves the bearing capacity of the samples, while the contractancy during the initial stage of shearing and strain-softening becomes more distinct; (2) The elevated confining pressure significantly increases compressive bond breakages, thereby weakening the contribution of MH bonds to the bearing capacity of the MHBS samples. The deformation characteristics and stress–strain relationships under higher confining pressure conditions resemble those of MH-free sand (MHFS) samples. (3) The cohesion exhibited a linear increase with MH saturation, whereas no clear relationship existed between MH saturation and the internal friction angle.