跨断裂地铁隧道地震动力响应特征研究

Research on the Seismic Dynamic Response Characteristics of Metro Tunnels across Faults

研究目的:活动断裂在我国分布较广,然而在长距离工程选线及设计中,线路往往会穿越或邻近活动断裂带。断裂粘滑作用常造成地震发生,加之地震动力作用下地铁隧道的地震响应和受力变形问题又是隧道设计的重点和难点,因此本文对地铁隧道跨越活动断裂进行地震荷载时程分析,从定量角度研究跨断裂地铁隧道地震动力响应特征。研究结论:(1)地表断裂位置处PGA放大系数最大,向两侧逐渐减小,具有典型的上盘效应;(2)地震作用改变了断裂附近隧道结构接触压力,在地震过程中,拱顶最大接触压力在上盘增大下盘减小,而拱底最大接触压力在上盘减小下盘增大,接触压力的主要变化范围在上盘40 m和下盘30 m范围内;(3)地震荷载下断裂附近隧道结构拱顶轴力在上盘增大下盘减小,而拱底轴力在上盘减小下盘增大,此外,在断裂位置处隧道结构弯矩和剪应力数值明显增大;(4)基于地震作用下跨断裂地铁隧道内力显著变化范围,给出了地震动力作用下跨断裂地铁隧道的纵向设防长度建议值为上盘40 m、下盘30 m,在此区域内应采取设置减震层、加固围岩和采用柔性接头等抗震设防措施;(5)本研究成果可为跨断裂地铁隧道抗震设防提供科学参考和理论依据。

Research purposes:Active faults were widely distributed in China.However,it will inevitably pass through or adjacent to the active fault zone in the long-distance engineering line selection and design.The fault stick-slip effect often caused earthquakes to occur.In addition,the seismic response and stress deformation of metro tunnels under earthquake dynamics were the key points and difficulties in tunnel design.Therefore,time history analysis of seismic loads of metro tunnels across active faults was produced.The seismic dynamic response characteristics of across-fracture metro tunnel were studied from a quantitative perspective.Research conclusions:(1)The PGA amplification factor was the largest at the surface fracture location,and it gradually decreased toward both sides,which presented a typical hanging wall effect.(2)The seismic action changed the contact pressure of the tunnel structure near the fault.During the earthquake,the maximum contact pressure of the vault was increased in the hanging wall and the footwall was reduced.The maximum contact pressure of the arch bottom was reduced in the hanging wall and the footwall was increased.The main variation range of contact pressure was within 40 m of the hanging wall and 30 m of the footwall.(3)The axial force of tunnel vault near the fault under seismic load was increased in the hanging wall and the axial force of arch bottom was increased in the footwall.In addition,the bending moment and shear stress values of the tunnel structure increased significantly at the fracture location.(4)The internal force of the cross-fracture metro tunnel varied significantly under seismic load,the recommended value of the longitudinal fortification length of the cross-fracture metro tunnel under earthquake action was 40 m on the hanging wall and 30 m on the footwall,shock absorption layer,reinforced surrounding rock and flexible joints should be set in the length range of fortification.(5)The research results can provide scientific reference and theoretical basis for seismic fortification of cross-fracture metro tunnels.