An Experimental-DEM Hybrid Approach for Characterizing Micromechanical Strength of Ughelli sandstone

Abstract

Landslide has occurred in Nigeria recently, this has necessitated the simulation of crack number associated with tensile failures in sandstone subjected to tri-axial compressions. The aim is to relate the crack number to microscopic deformation which is the extent of isotropic and deviatoric components of the simulated seismic crack number to the microscopic failure mechanisms. Within the rock matrix, the cataclastic collapse occurs as the granular arrangement interferes with the applied forces which initiate a strong spatial anisotropic stress field depending on the level of applied force. The onset of the micro-cracking initiates the occurrence of the rock failure. The crack number was recorded simultaneously as the grain-to grain contacts breaks the montmorillonite mineral bond between the quartz grains. Experimental data were plotted as the contact strength reduces by tri-axial stresses induced on the rock, so that within the invisible cracks, a significant fraction of isotropic percentage in all directions were captured. The stress induced on the sample by axial and radial compression affect the waveforms and the recorded crack number are simultaneous. This micro-crack numbering provided microscopic deterioration between 5MPa to 25MPa, at this stress level no visible fracture occurring in the macroscopic feature was seen. This was achieved by representing the physical sandstone grain with an assembly of clump particle during procedural simulation of the sandstone. Thus, the interactions between clumps were governed by the defined micro-properties of spheres making the clumps. The strain in the sandstone was represented by a stiffness ratio of 1 which is in agreement with experimentally determined stiffness ratio obtained from the natural sandstone.