Seepage Characteristics and Influencing Factors of Weakly Consolidated Rocks in Triaxial Compression Test under Mining-Induced Stress Path

Abstract

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.