隧道应力扰动区及其影响因素分析

Analysis of stress disturbed zone of tunnel and its influence factors

一般认为扰动区范围为隧道截面最大直线尺寸的3~5倍。在弹性状态下进行分析,利用已有的未考虑自重的圆形隧道解析解确定圆形隧道扰动区影响因素及扰动区范围,并总结出圆形隧道扰动区半径与隧道半径和泊松比之间的多项式关系。采用ANSYS分析考虑自重的圆形、直墙半圆拱和矩形3种截面隧道开挖后围岩应力场和扰动区范围。应用弹塑性折线理论将弹性状态所得的成果推广至弹塑性状态。研究结果表明:圆形、矩形、直墙半圆拱3种截面形式的最大扰动区范围均超出了隧道截面最大直线尺寸的5倍,即一般情况下大于现时认为的3~5倍;从减小扰动区范围的角度出发,相同高度与跨度的3种隧道截面,圆形截面最优,直墙半圆拱截面次之,矩形截面最差。研究成果可为隧道支护设计以及数值模型计算域的选取提供参考。

The range of the disturbed zone is generally considered to be 3 to 5 times the maximum linear dimension of the tunnel cross section.The existing circular tunnel analytical solution without considering its own weight was used to determine the influence factors of the circular tunnel disturbed zone and the range of the disturbed zone within the elastic state.The polynomial relationship between the radius of the circular tunnel and disturbed zone and the tunnel radius to Poisson’s ratio was obtained.ANSYS was used to analyze the stress field and disturbed zone of the tunnel’s surrounding rocks with circular,straight wall semi-circular arch and rectangular excavation respectively.With applying the new stress field solution from the broken line theory of Elastoplastic mechanics,the results of elastic state analysis were extended to elastic-plastic state.The main results are listed as follows:The maximum disturbed zone of the three different sections(circular,rectangular and straight wall semi-circular arches)all exceeds the maximum linear dimension of the tunnel section by 5 times,which is generally greater than the current 3 to 5 times.Under the same condition of height and span,the circular cross section tunnel was found to be the best to reduce the range of the disturbed zone,followed by straight wall semi-circular arch section tunnel and rectangular section tunnel.In addition,this study provides reference for tunnel support design and the selection of numerical model calculation domain.