活动性断裂带错动下隧道纵向响应的解析解

震害调研表明,活动性断裂带区域的隧道灾害最为严重。针对错动作用下穿越活动性断裂带隧道的纵向响应进行了研究,推导了隧道纵向力学响应的解析解并进行了验证。考虑断裂破碎带围岩力学性质较差且处于错动变形的主要影响区,将隧道沿纵向进行分区,包括错动影响区、过渡影响区和非影响区。采用Pasternak双参数弹性地基梁,假定不同分区的地基参数和计算模式不同,建立了满足变形和内力连续的隧道纵向力学解析模型并进行了求解。解析计算结果与数值模拟结果、室内试验数据基本一致,验证了解析解的正确性。结果表明:错动作用下,活动性断裂带区域的隧道内力和变形发生了显著变化;隧道纵向挠曲变形与错动方向一致,但在断裂带与上下盘交界区域发生了反向的挠曲;在正断层错动下,纵向弯矩在断裂带与上下盘交界区域达到最大值,且上、下盘区域的隧道拱顶分别出现受拉和受压区域;断裂带区域内的剪力远大于其他区域,且受到较大弯矩,隧道结构易发生破坏。上述计算结果与实际调研结果相一致,表明了提出的解析计算方法可用于活动性断裂带错动下的隧道纵向响应分析。最后,针对地基系数和断裂带宽度两个关键参数进行了敏感性分析,得到了有益规律,可为该类区域的隧道设计和施工提供技术支撑。

An analytical solution of longitudinal response of tunnels under dislocation of active fault

The site investigation on earthquake damage shows that tunnels in the active fault zone suffer the most serious disasters. To investigate the longitudinal response of tunnels crossing the active fault under the dislocation, this paper proposed and verified an analytical solution of longitudinal mechanical behavior for tunnels. The active fault zone has worse mechanical properties and is the place where the main dislocation occurs. Therefore, the tunnel is divided into three parts in the longitudinal direction, including dislocation affected zone, transient zone and non-influence zone. Assuming that these three zones have different model parameters and calculation modes, an analytical mechanical model of the tunnel is formulated based on the double-parameter Pasternak elastic foundation beam. The proposed model satisfies the continuity of deformation and stress along the longitude direction. Analytical solutions agree well with the numerical simulation results and the laboratory mock-up test observations, demonstrating its good capacity. Analytical results reveal that the tunnel internal force and deformation show a significant increase in the active fault zone under the dislocation. The longitudinal deflection of the tunnel is similar to the dislocation while it has a reverse deflection at the junction zone between the fault zone and the foot or hanging wall. For the dislocation of normal fault, the longitude moment reaches its maximum value at the junction zone between the fault zone and the foot or hanging wall, and a tensile and compressive zone appear in the crown of tunnel on the side of the foot and hanging wall respectively. Shear force in the active fault zone is also bigger than that in the foot and hanging wall. All above responses result in the serious disasters in the fault zone, which is consistent with the site investigation results. Therefore, the proposed analytical solution could be used for the tunnel longitude response analysis under the dislocation. Finally, sensitivity analyses of the ground coefficient and the fault width are performed and useful results are summarized, which can provide technical supports for the tunnel design and construction in the active fault zone.