Deformation and failure characteristics and control technology of surrounding rocks in deeply gob-side entry driving

In view of such problems of large deformation, long deformation duration, and support difficulty of a deep roadway with high stress soft rock, with the gob-side entry in Kouzidong Coalmine as the engineering background, through on-site investigation, in-situ stress test, mineral composition analysis, and mechanical properties test of the surrounding rock, the research revealed that high ground pressure and strong disturbance are the main force sources for large deformation and failure of the roadway; fracture of the surrounding rock with low load resistance intensifies its structural weathering and strength degradation and, thus aggravates the dilation and deformation of the roadway, which forms the main internal cause for the large deformation of the roadway; the unreasonable cross-section and low support strength aggravate the dilation and deformation of the surrounding rock, which forms the main external cause for the large deformation of the roadway. Five typical deformation and failure characteristics and their mechanisms of roadway were analyzed from the perspective of roadway failure modes. The spatial asymmetry of the surface deformation of the roadway, the jumping of the surrounding rock deformation in different depths, and the inhomogeneity and jumping of the internal structure degradation of the surrounding rock of the roadway were revealed through field observation. It is concluded that the large deformation mechanism of the roadway is that the surrounding rock produces significant rheological and strong dilatational deformation after the degradation of the plastic zone under high stress, which accelerates the deformation and instability of the roadway. As a result, a support technology of gob-side entry driving in Kouzidong coal mine is proposed, featuring "high pre-stress active support, grouting modified reinforcement, and sidewall intensification and roof protection". Field monitoring has shown that the support scheme can effectively rein in the deformation of deep roadway with high stress soft rock. © 2021, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.