双向地震作用下地铁车站改进截断墙抗液化上浮机制研究

Study on anti-liquefication uplift mechanism of improved cut-off wall in subway station under bidirectional earthquakes

截断墙法能减小地震过程中因地基液化导致的地下结构上浮,但难以防止地震结束后由超孔压消散引起的结构上浮。此外,已有研究未考虑竖向地震对抗上浮效果的影响。因此,在截断墙的基础上增设抗拔梁与碎石土层,采用有限元-有限差分耦合方法,分析了改进截断墙的最优参数设计及在双向地震下的响应规律。结果表明:设置碎石土层在震后的抗浮效果明显,抗拔梁的搭接长度为1.5 m时足以防止结构上浮;强震下截断墙法只能在一定程度上抑制结构上浮,在震后的上浮量也较大,而改进的截断墙法在震中能有效地抑制结构上浮,在震后结构基本不上浮;设置改进的截断墙能在一定程度上减轻地震过程中车站结构所受的内力。

The cut-off wall method can reduce the uplift of the underground structure caused by the liquefaction of the foundation during the earthquake,but it is difficult to prevent the uplift of the structure caused by the dissipation of the excess pore pressure after the earthquake.In addition,existing studies have not considered the influence of vertical seismic action against the uplift effect.Therefore,this paper adds uplift beams and gravel soil layers based on the cut-off wall.A finite element and finite different coupled method are used to analyze the optimal parameter design of the improved truncation wall and its response law under bidirectional earthquakes.The results show that the anti-uplift effect of setting the gravel soil layer is obvious after the earthquake,and the length of the anti-uplift beam is 1.5 m sufficient to prevent the structure from floating.The cut-off wall can only restrain the structure from uplifting up a certain extent under strong earthquakes,and the uplift is also larger after the earthquake,while the improved cut-off wall can effectively restrain the structure from uplift up during the earthquake,and the structure does not uplift after the earthquake.Setting the improved truncation wall can reduce the internal force of the station structure during the earthquake to a certain extent.In addition,this paper deeply analyzes the anti-uplift mechanism of the improved cut-off wall method.