Stress Inversion of Coal with a Gas Drilling Borehole and the Law of Crack Propagation

Tianjun Zhang 1,2,3, Lei Zhang 2,3,* ID , Shugang Li 2,3, Jialei Liu 4, Hongyu Pan 2,3 and Shuang Song 2,3 1 College of Science, Xi’an University of Science and Technology, Xi’an 710054, China; [email protected] 2 School of Safety Engineering, Xi’an University of Science and Technology, Xi’an 710054, China; [email protected] (S.L.); [email protected] (H.P.); [email protected] (S.S.) 3 Key Laboratory of Western Mine Exploitation and Hazard Prevention of the Ministry of Education, Xi’an 710054, China 4 China Gezhouba Group No.5 Engineering Co., Ltd., Yichang 443002, China; [email protected] * Correspondence: [email protected] or [email protected]; Tel.: +86-133-7923-2112