CHAI, SHAOBO, SCHOOL OF CIVIL ENGINEERING, CHANG’ AN UNIVERSITY, XI’AN, 710064, CHINA / STATE KEY LABORATORY FOR GEOMECHANICS AND DEEP UNDERGROUND ENGINEERING, CHINA UNIVERSITY OF MINING & TECHNOLOGY, XUZHOU, 221116, CHINA / SCHOOL OF RIVER & OCEAN ENGINEERING, CHONGQING JIAOTONG UNIVERSITY, CHONGQING, 400045, CHINA, China