深埋黄土盾构隧道围岩压力解析
Pressure of surrounding rock of deep-buried loess shield tunnel
-
摘要: 随着盾构隧道工程的发展,越来越多的深埋黄土盾构隧道逐步出现。对其围岩压力进行准确计算对衬砌设计及服役期的安全评价具有重要意义。围绕深埋黄土盾构隧道围岩压力的计算,考虑盾构隧道衬砌与围岩的径向变形连续条件,基于芬纳公式,推导了盾构隧道衬砌内力、围岩应力及围岩变形的解析解;引入黄土结构性参数,给出了适用黄土盾构隧道的围岩压力解析解;结合隧道开挖后围岩的广义剪应变,构建了黄土隧道围岩结构性参数的求解方法;结合黄土结构性参数,讨论了围岩增湿对黄土结构性参数及围岩压力的影响。研究发现:广义剪应变在塑性区内沿径向增大,在弹性区内逐渐减小,2倍塑性区半径外基本稳定;围岩的黄土结构性参数在塑性区内可认为均匀分布;围岩含水率由2%增加至20%时,塑性区的扩大幅度约为33%,围岩压力的增幅约为10%。研究成果以期对深埋黄土盾构隧道的围岩压力计算提供思路。Abstract: With the development of shield tunnel engineering, more and more deep-buried loess shield projects have gradually appeared. The calculation of pressure of the surrounding rock is of great significance to the design of linings and safety evaluation during the service period. The aim of this study is to establish a theoretical solution for pressure of the surrounding rock of deep-buried loess shield tunnel. With the consideration of the continuous conditions of the radial deformation at the interface between the linings and the surrounding rock, the analytical solutions for forces and displacements of the linings and surrounding rock are derived based on the Fenner formula. Then, the analytical solution of pressure of the surrounding rock applicable to loess shield tunnel is given by introducing the structural parameters of loess. Considering the generalized shear strain of the surrounding rock after tunnel excavation, a solving method for the structural parameters of surrounding rock of loess tunnel is given. The influences of humidification on the structural parameters of loess and the pressure of surrounding rock are then discussed by introducing the surrounding rock structural parameters of loess. It is found that the generalized shear strain increases radially in the plastic zone and gradually decreases in the elastic zone. It is basically stable outside the twice the radius of the plastic zone. The structural parameters of loess of the surrounding rock can be recognized as evenly distributed in the plastic zone. When the water content of rock increases from 2% to 20%, the expansion of the plastic zone is about 33%, and the increase of the pressure of the surrounding rock is about 10%. The research results are expected to provide ideas for the calculation of pressure of the surrounding rock of deep-buried loess shield tunnels.