为适应地铁工程抗震防灾的要求,对隧道结构进行抗震安全评价分析。首先,基于隧道抗震性能受地质环境、隧道结构、地震力等多因素影响的特点,通过划分地层组段表征复合地层围岩;其次,采用有限元时程分析法计算衬砌的横向弯矩、剪力、轴力以及直径变形率等4项力学性能参数;再次,依据衬砌材料的强度和变形要求,确定以上参数相应的安全因子并将其作为抗震安全单项评价指标;最后,将进一步分析评价指标的抗震敏感值作为权重,得到综合评价系数,从而建立复合地层地铁隧道结构抗震的定量安全评价方法。通过工程应用分析发现: 1)相对于衬砌弯矩和轴力,直径变形率和剪力对地震动水平的敏感度更高; 2)地层组段的整体刚度越低、地层分布越均匀,则越有利于提高隧道抗震安全性。
In order to meet the requirements of earthquake
resistance and disaster prevention, seismic safety evaluation and analysis of
tunnel structure are conducted. First, based on the characteristics of
geological environment, tunnel structure, seismic force, and other factors
affecting the tunnel seismic performance, the surrounding rock of composite
strata is characterized through dividing strata groups. Second, the finite
element timehistory analysis method is used to calculate the four mechanical
performance parameters of lining, including transverse bending moment, shear
force, axial force, and diameter deformation rate. Third, according to the
strength and deformation requirements of lining materials, the safety factors
corresponding to the above parameters are determined as the single evaluation
index of seismic safety. Last, the seismic sensitivity value of the evaluation
index is further analyzed as the weight to obtain the comprehensive evaluation
coefficient, and a quantitative safety evaluation method for the seismic
resistance of metro tunnel structure in composite strata is established.
Through analysis on the engineering application, it is found that: (1) The
diameter deformation rate and shear force are more sensitive to the seismic
force level than the lining bending moment and axial force. (2) The lower the
overall stiffness of strata group and the more uniform the strata distribution,
the more conducive to the improvement of tunnel seismic safety.