The success of the water-preserved mining technology is closely related to the stability of the aquiclude and the aquifer, in particular, which is made of weakly cemented rock mas. This paper starts with the tri-axial compression tests on the mudstone specimens obtained from the Ili mining area, followed by the systematic numerical simulation via the Particle Flow Code (PFC) program, aiming at obtaining an in-depth understanding of the response of weakly cemented mudstone under tri-axial compression loading state. The main outcomes obtained from this research indicated that: (1) the behavior of weakly cemented mudstone is closely sensitive to the confining pressure. As the confining pressure increases, both the peak strength and plastic deformation capacity of weakly cemented mudstone will be enhanced; (2) the main feature of weakly cemented mudstone after tests is its centrosymmetric “Z” shape, mainly attributed to the progressive separation of the particle element of mudstone; (3) the behavior of weakly cemented mudstone either in terms of the axial stress-axial strain or the failure mode is sensitive to the confining pressure. If the applied confining pressure is lower than 5 MPa, the micro-cracks are in the form of the single shear band, whereas the tested specimens will tend from brittle shear to plastic shear associated with the “X” shear when the confining pressure is higher than 5 MPa; and (4) The failure of weakly cemented mudstone is mainly attributed to the continuous expansion and penetration of internal microcracks under compression. The brittle failure mode of weakly cemented mudstone tends to ductile failure with the increase of confining pressure. The main contribution of this research is believed to be beneficial in deepening the understanding of the mechanics of weakly cemented mudstone under tri-axial compression and providing the meaningful reference to the practical application of water-preserved mining in the Ili mining area.

The rock of weakly consolidated coal measure strata has the characteristics of low mechanical strength and strong water sensitivity. Under the stress and seepage disturbance caused by coal seam mining, the surrounding rock structure is prone to instability, which leads to mine safety accidents and water resources loss. In order to master the mechanical response and permeability evolution law of weakly consolidated rock under the disturbance of coal seam mining, the specimens of Jurassic mudstone, sandy mudstone, and sandstone in the Ili mining area of China were collected, and a triaxial compression seepage test was carried out. A comprehensive analysis was carried out on the mineral composition and microstructure characteristics of the rock. The results show the following: (1) Compared to the constant confining pressure condition, mining-induced stress promotes the fracture development rate of weakly consolidated rocks. The ratios of strain at the yield point of mudstone, sandy mudstone, and sandstone under mining-induced stress and constant confining pressure are 0.33, 0.43, and 0.79, respectively, and the ratios of strain at the failure point were 0.48, 0.52, and 0.72, respectively. (2) Under the condition of mining-induced stress, the permeability change range and the permeability recovery rate of the three types of rocks were different, which decreased in the order of mudstone, sandy mudstone, and sandstone. (3) In the process of the triaxial compression test, there was a strong hysteresis in the permeability change of the mudstone, and the permeability and hysteresis of the three types of rocks decreased with the increase in the clay mineral content. (4) Combined with the analysis of the rock mineral composition and microstructure characteristics, it is believed that the clay minerals in the rock after water mud and swelling are the main reasons for the hysteresis of the permeability change of weakly consolidated rock, and the content of clay minerals is the main factor affecting the permeability characteristics of the weakly consolidated rock.