小间距平行顶管管道土压力计算方法研究

Calculation method of the earth pressure for parallel pipe jacking with small spacing

小间距顶管过程中,由于管-管相互作用的影响,使得管周土压力分布与单管顶进土压力分布模式产生差异,从而造成小间距顶管荷载确定、结构计算及顶力估算与控制等设计施工难题.结合数值模拟反分析,基于太沙基土压力理论和极限平衡理论,假设了土体松动线和上部既有顶管的支挡作用线,进一步构建了小间距平行顶管管道拱顶垂直土压力的计算方法.基于构建的土压力计算方法,分析了土体抗剪强度、管径、管间距等对新建顶管拱顶土压力的影响,并与不考虑既有顶管影响的土柱理论和太沙基理论计算值进行了对比.计算结果表明:土体抗剪强度越大,新建顶管拱顶垂直土压力越大,而其侧面的土压力越小;抗剪强度较大时,新构建方法计算拱顶土压力小于太沙基理论计算结果,抗剪强度较小时,新构建方法计算拱顶土压力大于太沙基理论计算结果;顶管埋深增加时,新建顶管拱顶土压力增加,相较于土柱理论和太沙基理论,新构建方法计算的新建顶管拱顶土压力增量最小;随着管间距增加,新建顶管拱顶土压力越来越大.

With the increase in the urban underground buildings and the limitation of underground space,there are increasing double-line or even multi-line pipe jacking projects with small spacing.In the process of pipe jacking with small spacing,due to the influence of pipe-pipe interaction,the earth pressure distribution around the pipes changes greatly,which leads to difficulties in the load determination,structure calculation,and jacking force prediction and control.Combined with the back analysis of numerical simulation,based on Terzaghi’s theory of consolidation and limit equilibrium theory,the soil loosening line and the retaining line of the existing pipe are assumed,and a new calculation method of vertical earth pressure on the vault of parallel pipe jacking with small spacing is established.The effects of soil shear strength,pipe diameter,and pipe spacing on the earth pressure are analyzed,and the calculated earth pressure on the vault of the new pipe is compared with those calculated by the soil column theory and Terzaghi’s theory without considering the influence of the existing pipe.The results show that the vertical earth pressure of the new pipe jacking vault increases with the increase in the soil shear strength,but the earth pressure on both sides of the new pipe jacking decreases.When the shear strength is large,the earth pressure on the vault calculated by this method is smaller than that calculated by Terzaghi’s theory.When the shear strength is small,the earth pressure on the vault calculated by this method is larger than that calculated by Terzaghi’s theory.When the buried depth of the pipe increases,the earth pressure on the vault of the new pipe jacking increases,but compared with the soil column theory and Terzaghi’s theory,the earth pressure increment is smaller.With the increase of the spacing between the two pipes,the earth pressure on the vault of the new pipe jacking arch increases.