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顶管工程中,由于顶力的作用具有间歇性和短暂性,且被动土压力所需的位移量远大于主动土压力所需的位移量,因此后背土体被压实至剪切破坏时,前壁土体与井壁会产生短暂性脱空,从而在计算沉井水平承载力时可以不考虑前壁主动土压力的作用,仅考虑井底、井侧摩阻力和后背土压力的作用。根据井壁后背土体剪切破坏条件,推导出了后背土压力计算公式。从该公式可以看出,圆形沉井后背土体径向土压力增量按正弦函数形式分布。通过算例分析可知,本文计算方法是可行的。
In the pipe jacking project, due to the intermittent and transient effect of the jacking force and the displacement required by the passive earth pressure is far greater than the displacement required by the active earth pressure, the back soil is compacted to the shear failure , The soil and the wall of the front wall will be short-lived, so that the active earth pressure of the front wall can be ignored when calculating the horizontal bearing capacity of the caisson, and only the bottom hole, well-side friction and back earth pressure effect. According to the shear failure conditions of the back wall of the shaft wall, the formula of back earth pressure is deduced. It can be seen from the formula that the radial earth pressure increment of the circular backfill body is distributed in the form of a sine function. Through the example analysis shows that the calculation method is feasible.