非等压下考虑渗流和剪胀的圆巷围岩弹塑性统一解

Elastic-plastic unified solution to circular tunnel under 2-D unequal pressure considering seepage and dilatancy

对于富水地层中深埋圆形巷道,为研究多种因素影响下巷道围岩塑性区范围和洞周位移的变化规律,对巷道围岩进行了弹塑性理论分析。对围岩应力场和渗流场进行耦合分析,基于统一强度理论和非关联流动法则,推导出多种因素影响下深埋圆形巷道围岩应力、位移和塑性区半径的解析计算式。结合工程实例进行计算分析,结果表明:中间主应力参数、围岩侧压系数、初始孔隙水压和剪胀角对围岩塑性区径向位移和塑性区范围均有显著影响,但影响规律各不相同;考虑中间主应力作用时,其他各因素的影响效应减弱。综合考虑以上各因素对围岩稳定性的影响,计算结果更加接近工程实际情况。

The present paper is inclined to present an elasticplastic theoretical analysis method for finding the effects of multiple factors on the plastic zone and the displacement of the surrounding rock mass in the deep circular tunnels badly affected in the water-rich geological strata due to the effect of the seepage force. To solve the problem,we have conducted the stress and seepage field coupling analysis on the spot. As a result,we have derived the analytical equations of the plastic radius and the displacement in the said surrounding rock mass under the 2-D unequal pressure on the basis of the unified strength criteria and the non-associated flow rule. We have proposed the analytical calculation based on the project background. The results of our study prove that,with the increase of the intermediate principal stress parameter,the plastic radius and the surrounding rock displacement tends to increase significantly,too. At the same time,the self-stability and the bearing capacity of the surrounding rocks can be enhanced on account of the intermediate principal stress. In addition, the lateral pressure coefficient can also have direct effects on the shape of the plastic zone,with a vertical ellipse being as the lateral pressure coefficient bigger than 1. Nevertheless,on the contrary,the horizontal ellipse tends to be as the lateral pressure coefficient less than 1. Besides,with the increase of the lateral pressure coefficient,the displacement in the plastic region in the horizontal orientation may tend to increase,too,with the decrease of the vertical displacement in plastic region. Moreover,the plastic zone and the displacement in the plastic region may tend to increase with the increase of the initial pore pressure,which may lead to the aggravation of the seepage effect. On the other hand,since the dilatancy angle mainly influence the displacement in the plastic region,which may increase with the increase of the dilatancy angle,it would be possible to reduce the effects of the lateral pressure coefficient,the initial pore pressure and the dilatancy angle on the condition that the intermediate principal stress parameter has been taken into account. Therefore,the calculation we have done has been found much closer to the engineering practice on the condition to integrate the abovementioned influential factors,which should not be neglected.