地铁隧道穿越地裂缝带的物理模型试验研究

 根据西安地裂缝的分布特征与活动方式，结合西安地铁2号线的走向，建立地质模型，通过物理模型试验来研究地裂缝对地铁隧道的影响。由试验结果可知：地裂缝环境下隧道结构的受力、变形模式相当于一悬臂式弹性地基梁，处于拉、压的受力状态，受拉变形区主要在固定盘距裂缝20～80 cm范围内的衬砌顶部，受压区则主要分布在下降盘距裂缝20 cm至固定盘距裂缝80 cm范围内的衬砌底部；地裂缝的活动增加了下降盘内隧道顶部的竖向围岩压力，同时减小了该范围内衬砌底部的竖向围岩压力；地裂缝环境下隧道衬砌的破坏模式以环向开裂为主，次生裂缝的发展则受张剪区的控制，主要形成阶梯形、“y”形的贯通裂缝。在试验分析的基础上，提出地铁隧道穿越地裂带时的设防范围及设防位置

RESEARCH ON PHYSICAL MODEL EXPERIMENT OF METRO TUNNEL CROSSING GROUND FISSURE BELT

According to the distribution and movement of Xi¢an ground fissure，combining the trend of metro tunnel No.2 in Xi¢an，a geological model has been built，and then the effects of the ground fissure on the metro tunnel have been studied. The experimental results show that the tunnel is in tension and compression states，and behaviors as a cantilever elastic foundation beam under the environment of ground fissure. The tensile parts mainly distribute in the range between 20 and 80 cm away from the fissure in fixed block，and the compressive parts distribute between 20 cm away from the fissure in declined block and 80 cm away from the fissure in fixed block. At the same time，the movement of the ground fissure greatly increases the vertical pressure of surrounding rock at the top of tunnel and reduces the vertical pressure of surrounding rock under the bottom of tunnel in the decline block. Under the environment of ground fissure，the failure mode is mainly circumferential crack；the secondary fissures are controlled by tension-shear areas，and step and y-shaped fissures are mainly induced. Based on the experimental results，the section and position where countermeasures should be taken are put forward when the metro tunnels cross the ground fissure region.