柔性接头地铁隧道穿越地裂缝的地震响应

采用振动台模型试验, 模拟地震荷载和地裂缝场地沉降, 分析了穿越地裂缝区域且设置柔性接头的分段地铁隧道的动力响应, 研究了地裂缝场地沉降、裂缝发育特征、地铁隧道加速度响应特征、土压力与隧道各区段不同部位的应变规律。分析结果表明: 由地裂缝场地沉降与地震荷载耦合作用所产生的差异沉降和裂缝多集中于柔性接头部位; 各区段地铁隧道间的运动具有一定独立性, 上盘靠近地裂缝的地铁隧道的加速度峰值是下盘隧道的3.2倍; 距离地裂缝越近土压力越大, 且在耦合荷载作用下, 上盘土压力是下盘土压力的6.7倍; 地铁隧道各区段左右拱腰应变较大, 底板处应变次之, 拱顶部位应变较小; 柔性接头设置后各区段应变增率减小, 在距离地裂缝较近部位未出现明显的应变增加现象。可见, 在地震荷载与地裂缝场地沉降耦合作用下, 柔性接头能够减小地铁隧道地裂缝位置处的集中应力与地裂缝场地的变形。

Seismic response of segmented metro tunnel with flexible joints passing through ground fissures

Earthquake load and site settlement near ground fissures were simulated by shaking table model test.The dynamic responses were studied in sectional metro tunnel with flexible joints passing through active ground fissures.The characterises of uneven settlements, crack development, tunnel accelerations, earth pressures and sectional tunnel strains were studied.Analysis result shows that the site cracks and uneven settlement resulted from the coupling load of site settlement and earthquake load mainly distribute around flexible joints.Each part movement of tunnel with flexible joints is independent.The tunnel located in hanging wall has3.2times peak acceleration of the value in foot wall.The soil pressures near the ground fissure are larger.The soil pressure in hanging wall is 6.7times of the value in foot wall under the coupling load.The strains at the middle of tunnel arch are bigger, the strains at the bottom of thefloor are secondary, and the strains on the top of the arch are less.The strain rate of each section decreases because flexible joints are designed in metro tunnel, and the strains increase little near the ground fissures.The result indicates that the flexible joints can decrease the site deformation and stress concentration of metro tunnel in ground fissure area under the coupling load of site settlement and earthquake load.