【摘要】 城市密集地下工程结构群下进行地下空间开发遭遇复杂地质环境时，可能会导致隧道开挖面失稳从而对既有结构的安全造成巨大威胁。开展了三个离心模型试验，模拟均质粉土地基和有黏土夹层的粉土地基中多层既有地下结构，研发了模拟隧道开挖面失稳的试验技术，再现了施工扰动引发的土体破坏模式和既有结构变形破坏机理。试验表明，控制开挖面位移（0.48H,H为开挖面高度）或者开挖面附近存在黏土夹层时，其附近形成的土拱有效地控制破坏区域，显著降低既有隧道的变形和应变，最终竖向变形为0.3～0.35 m，最大拉应变为850微应变；如果开挖面位移增大至0.86H，均质粉土地基出现整体失稳，既有隧道的最终竖向变形0.48 m，最大拉应变达到1900微应变。更多还原

【Abstract】 The development of cities often involves the construction of new tunnels underneath densely distributed existing structures. When the tunnels experience complicated and difficult conditions, failure may occur at the tunnel face and pose great threat to the existing structures. The results of three centrifuge tests to simulate existing structures in a uniform silt and in the silt with a 4 m thick clay layer are introduced. A technique is developed to simulate the instability of the excavation face and reproduce the failure mode. The tests show that when the displacement of the excavation face is controlled(0.48H, where H is the excavation height) or there is a clay interlayer near the excavation surface, soil arching is formed to confine the failure and reduce the deformation and strain of the existing tunnel. When the displacement of the excavation face increases to 0.83H, an overall collapse is trigged and induce significant deformation and strain on the existing tunnel.更多还原