Study on Failure Mechanism of Mudstone Based on Digital Core and Digital Volume Correlation Method

Abstract

In order to study the damage evolution law and failure mechanism of mudstone under different stress states, with the help of high-resolution CT scanning equipment, in situ CT scanning experiments of mudstone under uniaxial compression were carried out. Combined with digital core technology and the digital volume image correlation method, the 3D characterization of meso-structure and the evolution process of localized damage in mudstone were analyzed. The research shows that brittle minerals such as quartz in mudstone often exist in the form of agglomerated strips, resulting in the formation of weak structural planes at the contact surfaces of different minerals. There are a large number of primary intergranular pores near the mineral accumulation zone. With the increase in axial load, the connectivity of pores will gradually increase, cracks will gradually emerge, internal pores will develop abnormally, and rocks will reach the critical state of failure; at this time, the throat number and coordination number of pores increase obviously. There was no obvious difference found in the distribution of mineral particles of different sizes, and the slip between mineral zones was mainly dominated by small particles. The accumulated mineral zone was able to easily form a weak surface, and the aggregated mineral zone under loading was easily able to produce local deformation, which is related to the mechanical properties of the mineral zone and its surrounding rock matrix, with the rock failure easily occurring along the junction of the two minerals. The displacement in the polymeric mineral zone was small, the deformation displacement of the rock skeleton dominated by clay minerals near the quartz mineral zone was larger, and the stronger quartz minerals restrained the rock skeleton deformation in the region.