基于镜像法的隧道地表沉降时间效应计算方法

随着国内各城市地下道路建设的不断发展，地下开挖引起周围结构损坏甚至塌陷的事故时有发生，因此，合理地预测地表沉降对于保护地面建（构）筑物具有重要意义。将地表沉降速度系数与三维镜像法相结合，建立了考虑时间效应的隧道地表沉降计算方法，并以深圳某地铁区间隧道为例，通过与现场监测数据进行对比分析，验证了该方法的合理性，并利用该方法进一步分析了隧道停止施工时地表横、纵向沉降随时间的变化规律，通过参数分析明确了地表沉降量与地表沉降速度的时间效应。研究结果表明：地表沉降量与地表纵向沉降最大斜率随停工时间的增加逐渐增大并最终趋于稳定；地表最大沉降速度随开挖速度与沉降速度系数的增大呈对数型函数增长，但地表最终沉降量受二者的影响较小；地表最终沉降量和地表最大沉降速度随地层损失量的增大而线性增大；地表最大沉降速度出现的时间与地层损失的大小无关。

A calculation method of the time-dependent behavior for tunneling-induced ground settlement based on virtual image technique

With the continuous development of the underground road construction in various cities in China, accidents including damage or even collapse of the surrounding structures can often happen due to the underground excavation. Therefore, it is very importannt to predict reasonably the ground settlement for the protection of ground buildings and structures. We combine the ground settlement velocity coefficiennt with the three-dimensional imaging method, and establish a new calculation method for the tunnel surface settlement considering the time effect. We take a subway tunnel in Shenzhen as an example, and demonstrate the rationality of the method by comparing it with the on-site monitorinng data. This method is then used to further analyze the variation of the ground lateral and longitudinal settlement with time during the tunnel shutdown, and the time dependencies of the ground settlement and the settlement velocity are studied through a parameter analysis. The results show that the ground settlement and the maximum slope of the longitudinal settlement increase gradually with the increase of shutdown time and eventually tend to be stable. The maximum ground settlement velocity increases following a logarithmic function with the increase of the excavation speed and the settlement velocity coefficient. In contrast, the final ground settlement is less affected by those two factors. The final ground settlement and the maximum ground settlement velocity both increase linearly with the increase of the ground loss. The time at which the ground settlement velocity reaches its maximum has nothing to do with the amount of the ground loss.