高轴向应力下围岩环状破裂模式及其影响因素

采用厚壁钢桶约束的含预制孔洞模型的轴向加载试验，研究在有围压高轴向应力条件下，洞壁围岩的环状破裂模式及其影响因素.试验结果表明:环状破裂是从洞壁剪切破坏带相互交割处开始，向远离洞壁方向开展的以拉为主的破裂，其在洞壁附近近似平行于洞壁临空面.对于近距离双洞隧道，由于两洞间应力场叠加强烈，在高轴向应力下，环状破裂将环绕两洞，呈椭圆形发展;当两洞距离较远，两洞间应力场叠加较弱时，环状破裂带将分别围绕单洞扩展.环状破裂的形成及破裂带间距与洞壁曲率、隧道断面尺寸和岩石材料非均匀性有关.

Toroidal Fracturing Mode in Surrounding Rock Mass and Its Impact Factors Under High Axial Stress

Hole containing cylindrical specimens confined by thick steel drum were compressed in the axial direction to investigate the development of toroidal fractures and its impact factors under high axial stress. Results showed that toroidal fractures develop from the intersection of shear-slip lines and propagate sub-parallelly away from tunnel boundary mainly in tension. For the close twin tunnel with overlapped concentrated stress in between， the toroidal fractures enclose the twin tunnel and take on an elliptical shape; for distant twin tunnel with little overlapped concentrated stress in between， the toroidal fractures enclose each single tunnel respectively. The shape of toroidal fractures and the distance between the fractures are affected by tunnel curvature and tunnel span as well as the heterogeneity of the rock mass.