顶管工程中圆形沉井土体反力计算方法的研究

Research on earth counterforce calculation for circular caisson working well during pipe jacking project

对现有的圆形沉井土体反力的计算方法进行分析,假定圆形沉井产生整体位移,采用考虑位移的土压力计算方法计算后座井壁环向土体反力,竖向土体反力按朗肯被动土压力理论计算.考虑了井底摩阻力、井侧壁摩阻力和前壁主动土压力的作用,根据圆形沉井的整体受力平衡,得出其最大土体反力和允许顶力的计算公式.算例分析表明,在黏性土中采用水土压力分算和合算得到的圆形沉井最大土体反力差别很大.与其他方法相比,采用水土合算得到的允许顶力与实测最大顶力非常接近,更符合实际情况.

The current calculation methods of earth counterforce for circular caisson were analyzed. Supposing circular caisson arises in the entire displacement, the back well annular earth counterforce was calculated using earth pressure formula considering displacement, and the vertical earth counterforce using Rankine's passive earth pressure theory. Considering the effects of caisson bottom friction, caisson lateral wall friction, and active earth pressure of the front wall, the maximal earth counterforce and the permitted jacking force formulas were obtained based on the principle of circular caisson entire force balance. The analytical calculation for one project case shows that the maximal earth counterforces calculated by estimating water and earth pressure together or separately in clay soil were very different. The maximal earth counterforce calculated was much bigger compared with that obtained by other methods. The permitted jacking force calculated by estimating them together was very close to the maximal jacking force measured in the field, so it was more accordant with reality.