ISSN 1000-3665 CN 11-2202/P

    基岩断层错动下上覆地层破裂演化与穿断层隧道灾变机制试验研究

    Experimental study on overlying soil rupture evolution and cross-fault tunnel failure mechanism under bedrock fault dislocations

    • 摘要: 活动断层错动是诱发地下结构震损的关键致灾因素。针对城市浅埋明挖矩形地铁隧道穿越活动断层这一典型工况,基于自主设计的可调倾角错动模型箱,开展了几何相似比1∶80的半结构物理模型试验。通过设置正断层、逆断层及不同基岩断层倾角(45°、60°)共4种工况,揭示了基岩断层错动下上覆砂土的破裂延伸规律及穿断层矩形隧道的破坏机制,并将试验结果与基于对数螺旋曲线建立的破裂延伸路径预测模型进行对比。结果表明:正断层错动下上覆土层初始破裂角及地表破裂角均大于逆断层,正断层剪切带宽度小于逆断层;隧道结构的存在显著改变破裂路径和位移场,正断层条件下破裂路径趋近直线、剪切带变窄,逆断层条件下破裂路径在隧道附近显著趋缓、剪切带展宽;隧道破坏均表现为受拉断裂为主,正断层条件下破坏发生于下盘截面,逆断层条件下破坏发生于上盘截面;同一断层倾角下正断层隧道破坏所需错动量小于逆断层,且基岩断层倾角越大隧道破坏所需错动量越小。此外,基于对数螺旋曲线建立的破裂延伸路径预测模型与自由场试验结果吻合较好,初始与地表破裂角相对误差均在12%以内。研究成果可为穿越活动断层带的城市地铁隧道抗错断设计提供理论参考。

       

      Abstract: Active fault dislocation is a key disaster-causing factor for seismic damage of underground structures. A 1∶80 geometrically similar semi-structural physical model test was conducted for urban shallow-buried cut-and-cover rectangular metro tunnels crossing active faults, considering four working conditions (normal and reverse faults with dips of 45° and 60°). The rupture extension laws of overlying sand under bedrock fault dislocation and the failure mechanism of cross-fault rectangular tunnels were systematically revealed, and the test results were compared with a rupture extension path prediction model based on the logarithmic spiral curve. The results show that: (1) Under normal fault dislocation, the initial and surface rupture angles of overlying soil are larger, while the shear zone width is smaller than those under reverse faults; (2) The presence of the tunnel significantly modifies the rupture path and displacement field, with the path tending to be straight under normal faults and slowing down near the tunnel under reverse faults; (3) Tunnel failure is dominated by tensile fracture, occurring at the footwall section under normal faults and the hanging wall section under reverse faults. The critical dislocation for failure is smaller under normal faults and decreases with increasing fault dip; (4) The logarithmic spiral prediction model agrees well with free-field test results, with relative errors of rupture angles within 12%. The findings provide theoretical references for the anti-dislocation design of metro tunnels crossing active fault zones.

       

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