强震下成层土盾构隧道地震响应及结构安全性分析

Seismic Response and Structural Safety Analysis of Layered Soil Shield Tunnel Under Strong Earthquake

目前盾构隧道地震响应研究大多把隧道周围岩土体做简化处理,且强震作用下成层土盾构隧道动力响应分析的相关研究较少。以昆明轨道交通某区间盾构隧道为依托,建立了土层-结构动力相互作用的成层土盾构隧道地震响应计算模型。基于动力增量分析法,开展了考虑地震波类型及地震动强度因素下成层土盾构隧道地震响应分析。结果表明:随着地震动强度的增大,管片发生最大水平位移的部位由拱肩转变至拱顶。地震动强度越大,管片轴力和弯矩均呈对称分布,但对称轴会发生偏转,与水平轴线的夹角增大,峰值加速度从0.15g增至0.6g,夹角从37.5°增至45°。管片结构的轴力和弯矩最大值均位于拱脚,而剪力最大值则位于拱底。不同地震动强度下,拱肩和拱脚处的管片结构安全系数最小,说明隧道拱肩和拱脚是结构抗震薄弱部位。与单一均质土层相比,强震和成层土层会影响结构内力最大值的出现部位。地震波的频率及脉冲特性会对盾构隧道地震响应特征及结构安全性产生影响。

At present, the seismic response research of shield tunnel mostly simplifies the rock and soil around the tunnel, and there is less research on the dynamic response analysis of layered soil shield tunnel under strong earthquake.Based on the shield tunnel in a section of Kunming Rail Transit, the seismic response calculation model of layered soil shield tunnel with soil structure dynamic interaction is established. Based on the dynamic incremental analysis method, the seismic response analysis of layered soil shield tunnel considering the types of seismic waves and the intensity of ground motion is carried out. The results show that with the increase of ground motion intensity, the position of maximum horizontal displacement of segment changes from arch shoulder to arch crown. The greater the intensity of ground motion, the axial force and bending moment of the segment are symmetrically distributed, but the axis of symmetry will deflect, the included angle with the horizontal axis will increase, the peak acceleration will increase from 0.15 g to 0.6 g, and the included angle will increase from 37.5 °to 45 °. The maximum axial force and bending moment of segment structure are located at the arch foot, while the maximum shear force is located at the arch bottom. Under different ground motion intensity, the segment structure safety factor at the arch shoulder and arch foot is the smallest, indicating that the tunnel arch shoulder and arch foot are the weak parts of the structure. Compared with single homogeneous soil layer, layered soil layer will affect the position where the maximum value of structural internal force occurs. The frequency and pulse characteristics of seismic wave will have a certain impact on the seismic response characteristics and structural safety of shield tunnel.