关键词: 深埋煤层, 直覆硬厚顶板, 破断模式, 采动应力, 多层次卸压

Abstract: Targeting the phenomenon of strong mining pressure in empty tunnels at the “three lane layout” face in deep well, the lateral fracture mode of overlying and thick-hard roof was analyzed by the methods such as theoretical analysis, similarity simulation, and on-site measurement. This analysis reveals the mechanism of strong mining pressure in empty tunnels and clarifies the characteristics of mining stress response of the working face, taking the coal seam directly overlying the hard and thick roof as the engineering background. The results indicate the formation of a lateral long cantilever-hinge structure within the working face, with the fracture line situated within the goaf subsequent to the fracturing of the overlying thick-hard roof. The rock properties and geometric configurations of the overlying and thick-hard roof layers significantly influence the magnitude of mining-induced stress in the goaf. The greater the hardness and thickness of the roof, the higher the likelihood of stress concentration occurring around the coal body within the goaf. Not only the stress concentration in the surrounding rock of the roadway is high, but also the influence range of the advance support pressure on the goaf side is wider, the degree of stress concentration is higher, and the mining pressure in the roadway is more severe, under the condition of overlying and thick-hard roof. The abutment pressure on the coal pillar exhibits a characteristic of “synchronous force and synchronous growth”. Upon reaching the stabilization phase of the goaf, the abutment pressure manifests as an L+W stress profile, featuring asymmetric stress peaks on the adjacent upcoming mining coal pillars and double stress peaks in the center of the pillars. Under the influence of high lateral stress, the middle and lower portions of the surrounding rock in the subsequent roadway section undergo significant deformation, whereas the roof remains unaffected. Based on the lateral fracture characteristics of the overlying and thick-hard roof and the mechanism of strong dynamic mining pressure manifestation, a prevention and control technology system for roof disasters is proposed, which includes advanced treatment of roof disasters and “shallow strong support+deep multi-level unloading”. This provides beneficial guidance for rock strata control in mining stope.

Key words: deep buried coal, overlying and thick-hard roof, fracture mode, mining stress, multilevel pressure relief