基坑开挖对旁侧隧道影响及隔断墙作用离心模型试验研究

开展了干砂地层中基坑开挖对旁侧隧道影响及隔断墙保护作用的三维离心模型试验和数值分析,获得了隧道上浮、隧道内力、隧道周围土压力、地表沉降等变化规律以及隧道空间位置和基坑开挖深度的影响。试验结果表明,基坑回弹量与采用Boussinesq解计算的回弹量比较接近;地表沉降量与文献报道的试验结果相近,而明显小于现场实测沉降;靠近基坑一侧的隧道周围土压力有所减小,而远离基坑一侧的隧道周围土压力则有所增加。隔断墙的设置可以一定程度上减小地表沉降、隧道外土压力变化、围护墙水平位移以及隧道上浮和弯矩。数值计算结果表明,隧道上浮量和水平位移随着隧道埋深及其与围护墙距离的增大而减小,而随着基坑开挖深度的增大而增大。

Three-dimensional centrifuge modeling of influence of nearby excavations on existing tunnels and effects of cut-off walls

Centrifuge modeling and numerical simulation are conducted in dry sand to investigate the influence of nearby excavations on the existing tunnels as well as the effectiveness of cut-off walls. The tunnel heaves, internal forces, earth pressures and ground settlements are analyzed as well as the influences of the relative position and excavation depth. As indicated by the tests, the soil heaves at the excavation base are close to the results from the Boussinesq equation. The measured ground settlements are similar to those of the centrifuge modeling by other researchers, while obviously lower than the field measurements. The earth pressures at the excavation side are reduced due to the excavation, while those at the other side increase. The cut-off walls can reduce the ground settlements, change of earth pressures, lateral displacements of diaphragm wall, and uplifts and bending moments of tunnels. The numerical simulation indicates that the tunnel heaves and horizontal displacements decrease as the burial depth of the tunnel and its distance from the diaphragm wall increase, while increases with the increasing excavation depth.