黄土地层浅埋暗挖隧道松散围岩压力计算

Calculation of loose surrounding rock pressure of shallow-buried undercut tunnel in loess strata

为研究黄土地层浅埋暗挖隧道松散围岩压力特征,根据既有隧道施工现场裂缝扩展情况,假定隧道开挖后的土体存在破裂区,取一半破裂区土体进行静力极限平衡分析,考虑静止土压力、侧向土压力、隧道尺寸和土层参数对半结构的影响,推导出适用于黄土地层浅埋暗挖隧道的围岩压力解析式,确定该公式下的隧道深浅埋划分界限,并结合工程实例分析隧道埋深、静止土压力系数和侧压力系数对围岩压力的影响。研究结果表明:随隧道埋深增大,围岩压力存在峰值,围岩压力曲线呈先增大后减小的趋势;围岩压力随静止土压力系数和侧压力系数的增大而减小,但静止土压力系数对围岩压力的影响较大;将新方法得到的围岩压力值分别与现场实测值和既有理论围岩压力值进行对比,计算的垂直、侧向围岩压力值均大于实测值,且新方法的计算误差相对较小。

In order to study the pressure characteristics of loose surrounding rock of shallow-buried undercut tunnels in the loess strata,according to the crack expansion at the existing tunnel construction site,it was assumed that a fracture zone existed in the soil after the tunnel excavation,and half of the soil in the fractured zone was taken for static force limit equilibrium analysis.Considering the influence of static earth pressure,lateral earth pressure,tunnel dimensions and soil layer parameters on the semi-structure,the analytical equation of the surrounding rock pressure applicable to shallow-buried undercut tunnel in loess strata was derived.The dividing limits of deep-buried and shallow-buried tunnels under this formula were determined,and the influence of tunnel buried depth,coefficients of static earth pressure and lateral pressure on the surrounding rock pressure was analyzed combining with engineering example.The results showed that with the increase of tunnel buried depth,there was a peak of surrounding rock pressure,and the curve of surrounding rock pressure presented a trend of increasing first and then decreasing.The surrounding rock pressure decreased with the increase of coefficients of static earth pressure and lateral pressure,but the coefficient of static earth pressure had slightly greater effect on the surrounding rock pressure.The values of surrounding rock pressure obtained by the new method were compared with the field measured values and the existing theoretical values of surrounding rock pressure respectively,both the calculated values of vertical and lateral surrounding rock pressure were greater than the field measured values,and the new method had the relatively small calculation error.