不同埋深盾构双隧道及开挖顺序对临近管线的影响研究

Effects of construction sequences of twin tunneling at different depths on the adjacent pipeline

以不同埋深双隧道、不同开挖顺序对临近地埋管线的影响为研究目的,在离心模型试验中同时考虑隧道开挖所致地层损失效应和质量损失效应,并采用考虑土体非线性小应变特性的HP(Hypoplasticity亚塑性)模型和基于地层损失比的位移控制法进行有限元模拟分析。研究结果表明,不同埋深双隧道、不同开挖顺序对地表沉降、管线沉降及管线弯曲应变的影响较大。双隧道开挖完成后管线下凸区(管线底部受拉区)分布范围为-2.5D_T^1.5D_T(DT为隧道外径),且管线下凸区最大弯曲应变约为管线上凸区(管线底部受压区)最大弯曲应变的2倍。不应简单采用叠加原理对不同埋深先后开挖双隧道所致地表沉降、管线沉降及管线弯曲应变进行预测,应合理考虑后继隧道开挖所致土体的累积剪切应变及管-土相对刚度对预测结果的影响。

The aim of this study is to investigate the effects of construction sequences of twin tunneling at different depths on the adjacent pipeline.A three-dimensional（3D） centrifuge model test was conducted by considering both the volume loss effect and the weight loss effect during the tunnel excavation.Moreover,the corresponding numerical simulation of this centrifuge model test was carried out,which further considered a displacement controlled method based on ground loss and an advanced hypoplastic constitutive model based on nonlinear small strain characteristics of soil.It reveals that twin tunnels at different depths with various construction sequences greatly affects the greenfield surface settlements,the pipeline settlements and the pipeline bending strain.After the twin tunneling,the sagging regions are located within the range of-2.5DT-1.5DT and the maximum bending strain within the sagging regions is around two times that within the hogging regions.The results indicate that the superposition principle cannot be simply applied to predict the surface settlements,the pipeline settlements and the pipeline bending strain caused by twin tunneling at different depths with various construction sequences.The effects of the accumulated shear strain and the relative pipe-soil rigidity should be reasonably considered.