既有桩基影响下隧道开挖地层变形规律研究

A study of the ground deformation law of tunnel excavation influenced by existing pile foundation

为了研究城市隧道沿线邻近既有桩基的情况下,隧道开挖导致的地层变形规律,本文通过一个透明土物理模型试验并采用基于PIV技术的土体内部断层三维变形量测系统监测变形,得到了在既有桩基影响下,隧道施工过程中的地层规律。研究结果表明:隧道开挖引起的周围土体变形区域主要位于隧道上方及上方左右两侧,变形主要以竖向沉降为主,水平变形为辅,砂土地层呈现出整体较均匀变形模式,竖直与水平方向变形均大致对应隧道轴线对称;砂土地层中,隧道掌子面在桩基-隧道中心轴线前时,隧道周围地层变形较小,即隧道开挖的影响还未到达(刚到达)该区域;掌子面位置经过桩基-隧道中心轴线切面后,该切面上地层发生持续变形,直至掌子面位置距离该面约2倍直径后重新达到稳定平衡状态,变形基本完成。

In order to study the law of ground deformation caused by tunnel excavation in the case of adjacent existing pile foundation along urban tunnel,a physical model test of transparent soil and a three-dimensional deformation measurement system of internal faults of soil based on PIV technology are used to monitor the deformation,and the ground deformation law in the process of tunnel construction under the influence of existing pile foundation is obtained.The result shows that the surrounding soil deformation area caused by tunnel excavation is mainly located in the upper and upper sides of the tunnel,and the deformation is mainly vertical settlement,supplemented by horizontal deformation.The sand layer presents a more uniform overall deformation mode,and the vertical and horizontal deformation are roughly symmetrical with the tunnel axis.In the sand layer,when the tunnel face is in front of the pile foundation-tunnel central axis,the stratum deformation around the tunnel is small,that is the influence of tunnel excavation has not reached(just arrived)the area;after the face position passes through the section of the pile foundation-tunnel central axis,the stratum on the section will continue to deform until the face position is about 2 times the diameter of the tunnel,then reaching a stable equilibrium state.So the deformation is basically completed.