密实砂土及硬黏土中圆形隧道的竖向支护压力

EARTH PRESSURE ON CIRCULAR TUNNEL IN DENSE SAND AND HARD CLAY

在Terzaghi理论假定的基础上,考虑圆形隧道侧压力系数及洞身范围斜向滑裂面作用,根据极限平衡法建立圆形隧道竖向支护压力的一般表达式,适用于密实砂土及硬黏土地层。该式表明圆形隧道的竖向支护压力随侧压力或侧压力系数λ的增大而减小,当λ=1时可得最小支护压力。为求解竖向支护压力,提出圆形隧道侧压力系数λ的计算方法,建立支护压力与衬砌刚度、地层刚度等因素的定量关系,表明随衬砌厚度的减小或地层弹性抗力系数的增大,侧压力系数增大,而竖向支护压力减小。通过对比表明,本文方法计算值与极限分析上限法、既有试验结果较接近且偏于安全,不仅适用于浅埋隧道,也适用于深埋隧道,且本文方法比极限分析上限法显著简化。

A formula is derived to calculate the vertical earth pressure of circular tunnels in dense sand and hard clay grounds. The formula considers the coefficient of lateral pressure and the effect of oblique slip surface beside the circular tunnel on the basis of the hypothesis of Terzaghi theory. A method to calculate the lateral pressure coefficient is established in order to solve the proposed formula. A quantitative relationship between the vertical pressure and the factors such as the lining stiffness and the ground stiffness is also derived. The relationship shows that the decreasing of the lining thickness or the increasing of the elastic coefficient of resistance of ground lead to the increasing of the lateral pressure coefficient and the reducing of the vertical pressure. The results from the proposed method, the upper bound of limit analysis and previous experiment results are compared and found to be close to each other. The proposed method is simpler than the upper bound method and is suitable for both shallow circular and deep tunnels.