Hydromechanical Properties and Engineering Applications of Weakly Cemented Soft Rock in Jurassic Strata.

Abstract

The surrounding rock control of weakly cemented soft rock in the Jurassic strata roadway in the Northwest Mining Area has become one of the bottlenecks restricting mines' safety and efficient production. Based on the engineering background of the +170 m mining level West Wing main return-air roadway of Dananhu No. 5 Coal Mine (DNCM) in Hami Xinjiang, through field investigation and borehole peeping, the deformation and failure characteristics of the surface and depth of the roadway surrounding rock under the original support scheme were mastered. The geological composition features of the typical weakly cemented soft rock (sandy mudstone) in the study area were analyzed by X-ray fluorescence (XRF) and X-ray diffractometer (XRD) experiments. Through the water immersion disintegration resistance experiment, variable angle compression-shear experiment, and the theoretical calculation, the degradation trend of the weakly cemented soft rock hydromechanical properties was systematically revealed from the following three aspects: the water immersion disintegration resistance of sandy mudstone, the influence characteristics of water on sandy mudstone mechanical performance, and the plastic zone radius of the surrounding rock under the action of water-rock coupling. Based on that, the roadway surrounding rock control measures of "timely and active support, pay attention to the surface protection components and block the water inflow channels" were proposed. The support optimization scheme of "bolt mesh cable beam shotcrete grout" is designed pertinently, and the engineering application was executed on-site. The results demonstrated that the support optimization scheme had shown excellent application effectiveness, with an average reduction of 58.37% in the range of rock fracture compared to the original support scheme. The maximum relative displacement between the roof-to-floor and rib-to-rib is only 121 and 91 mm, respectively, which can ensure the long-term safety and stability of the roadway.