西安地铁2号线隧道穿越地裂缝带的设防参数

基于西安地裂缝成因、基本特征和未来活动趋势分析，通过几何缩比为1：5的地裂缝活动模型试验和地裂缝活动对盾构隧道影响的数值模拟计算，研究了西安地铁2号线隧道正交穿越地裂缝带的设防参数。通过分析地裂缝年平均活动速率和历史最大活动量，确定了与地铁2号线相交的各条地裂缝的最大垂直位移量的预测值和设计建议值。模型试验和数值模拟结果表明，正交条件下地铁隧道在地裂缝活动地段的设防宽度为60 m，即上盘为35 m，下盘为25 m；沿隧道纵向地裂缝两侧地层变形规律呈现台阶状突变变形，隧道纵向设计可将上盘视为整体下降来考虑；地铁隧道穿越地裂缝带必须分段设缝以适应地裂缝的变形，其分段长度在地裂缝主影响区按10 m进行设防，在一般影响区可按10～15 m进行分段设防。研究结果可为地铁隧道穿越地裂缝带的结构设计提供参考。

Design parameters of Xi’an metro line 2 tunnel passing through active ground fissure zones

Based on analyzing the genesis, essential characteristics and tendencies of ground fissures in Xi’an, the physical model tests with a geometric proportion of 1:5 for active ground fissure and numerical simulation for the effect of active ground fissure on metro tunnel are carried out to study the design parameters of Xi’an metro line 2 tunnel orthogonally passing through the active ground fissure zones. On the basis of the average annual active rate of ground fissures and compared with the historical maximum displacements of ground fissures, the predicted and suggested maximum vertical displacements design values of each active ground fissure along the metro line 2 in the design life of 100 years are put forward. The test and simulation results show that the design width of metro tunnel orthogonally passing through the active ground fissure zone could be 60 m; i.e. 35 m in the hanging wall and 25 m in the footwall of active ground fissure zone. The stratum deformation along the tunnel axis ground fissure appears stepped mutational deformation; and integral descent of the hanging wall of ground fissure could be adopted in the design of tunnel longitudinal structure. Metro tunnel passing through the active ground fissure zones should be segmented by deformation joints to adapt the deformation of active ground fissures; the design length of sectional tunnel in main influence zone is 10 m; and in the minor influence zone that is 10 to 15 m. The conclusions will provide for reference to the design of lining structure of metro tunnel passing through the active ground fissure zones.