Failures of metro tunnels that pass obliquely through ground fissures at low angles are a common problem; however, their mechanism is unknown. In the city of Xi’an, China, Line No. 3 of the Xi’an Metro intersects ground fissures at a low angle (<25°) in certain zones. In this study, particle flow numerical analysis and physical model tests were used to investigate ground-surface deformation, structural distortions, and failure characteristics caused by ground fissures. Tests revealed an integrated bend-shear-torsion failure mode of any tunnel that entered a ground fissure obliquely at an angle of 20° or less, under the action of activities associated with a ground fissure. The tunnel structure indicated damage characterized by long longitudinal cracks and multiple groups of subparallel vertical cracks. The range in failure of the tunnel was up to 3.5 times the tunnel diameter on the hanging-wall side and up to 4.5 times the tunnel diameter on the foot wall. When metro tunnels intersect ground fissures at low angles, traditional tunnel designs do not meet minimum safety standards. It is therefore necessary to explore alternative metro tunnel designs in fissure-prone areas.

《地球科学》(ISSN 1000-2383;CN42-1874/P) (原刊名《地球科学——中国地质大学学报》ISSN 1000-2383;CN42-1233/P)，创刊于1957年，是由教育部主管、中国地质大学主办的综合性地学学术理论期刊，月刊，2015年改名为《地球科学》,她以反映中国地质大学教学与科研最新的、高水平的基础地质、应用地质、资源与环境地质及地学工程技术研究成果为主要任务。