黏性地层中深埋直墙拱形隧道的支护压力及稳定性

Earth pressure and stability of deep arch tunnel with straight wall in cohesive strata

在剪切破坏理论基础上采用极限分析法对黏性地层中深埋直墙拱形隧道展开研究。首先基于加载试验提出了破裂区的理论模型,考虑隧道侧面剪切楔形体的双滑裂面作用建立了侧压力表达式,得出侧压力及竖向支护压力的近似解,并提出了隧道侧压力与竖向土压力相互作用理论。根据剪切楔形体的稳定建立无支护深埋直墙拱形隧道的稳定性定量判别条件,得出极限承载力近似解。定义了基于极限分析法的稳定安全系数,并分析深埋隧道稳定性的影响因素。研究结果表明:本文提出的破裂区理论模型、极限承载力值与试验结果接近;基于双滑裂面作用的竖向支护压力、侧压力显著小于传统理论值;在良好地层中,拱形隧道极限状态下的竖向支护压力越小则侧压力越大,侧压力或侧压力系数?越大则竖向支护压力越小;黏聚力是无支护的深埋直墙拱形隧道稳定的必要条件稳定安全系数K随黏聚力、内摩擦角的增大而增大,随隧道跨度、高度的增大而减小;黏聚力对K的影响比内摩擦角大,跨度对K的影响比高度大,而埋深越大对深埋隧道稳定安全系数的影响越小。

The limit analysis method is adopted to study deep arch tunnel with straight wall in cohesive strata based on the shear failure theory.Firstly,a theoretical model for ruptured zone in the deep arch tunnel is established based on loading tests.And then a formula for lateral pressure is proposed considering the effect of two sphenoid rupture surfaces beside tunnel sidewalls.Secondly,the approximate solutions to the lateral pressure and the vertical earth pressure are derived.The criteria for the quantitative stability of the deep arch tunnel without supports are developed,and the approximate ultimate load on the ground can be calculated according to the stability of the shear wedge beside the tunnel sidewalls.Finally,the safety factor of the deep tunnel is defined based on the limit analysis method,and the influencing factors are analyzed.The results show that the proposed model for ruptured zone and the solution to the ultimate load are close to the test results.Compared with the traditional theoretical value,the calculated vertical and lateral earth pressure is much smaller according to the proposed formula.The interaction theory between lateral pressure and vertical pressure on arch tunnels is proposed in the good strata.The smaller the vertical earth pressure is,the greater the lateral pressure is,and the greater the lateral pressure or the lateral pressure coefficient is,the smaller the vertical earth pressure is in the limit state.The safety factor of stability increases with increasing the cohesive force and internal friction angle,and it decreases with increasing the span and height of the tunnel.The cohesive force and tunnel span have larger influences on the safety factor of stability than the internal friction angle and the tunnel height respectively.However,the greater buried depth has smaller influences on the stability safety factor of the deep tunnel.