The authors would like to acknowledge the financial support of China Scholarship Council for study in the United States,and the accommodation provided by the Department of Civil and Environmental Engineering,University of Pittsburgh.The authors would also acknowledge the funding of National Key Research and Development Program of China(2017YFC1501104);National Natural Science Foundation of China(51079092).
V-shaped breakouts,which may appear in underground opening during excavation,are the results of two different failure mechanisms:tensile spalling and shear fracturing.This study uses discrete elements in exploring the...