土钉墙面层位移和内力的计算分析

Analysis of displacement and inner force in soil-nailing walls

面层对于土钉墙的稳定以及通过土钉把土压力传递到稳定的土体中去具有非常重要的意义。土钉墙面层承受一定比例的水土压力已是不争的事实,然而,在目前的土钉墙设计中往往把面层按照构造进行配筋而不作计算,因此设计中没有体现到面层应有的作用。对土钉墙面层的受力情况进行了简化分析,把面层看作是文克尔地基上的有限长梁,将土钉作为作用在面层上的集中力系,得到了土钉墙面层位移和内力的解析解。计算结果表明,面层位移的最大值不在坡顶,而是在坡顶靠下的位置,其位置随着基坑开挖深度的增加而下移,呈现出中间大两头小的变化规律,与实测结果较为相近;位移的大小对土体的内摩擦角和黏聚力较为敏感,因此在基坑开挖过程中应做好降水工作,以防止水渗透到土体中,降低土体的物理力学性质指标。解析解也揭示了土钉墙面层内的弯矩和土压力的分布特征:面层内的弯矩随着基坑深度的增加而增加,但靠坡顶增加平缓,而在坑底稍上弯矩曲线斜率增大,同时达到最大值,且呈现出中间大两边小的现象,而靠近坑底的位置渐渐演变成为负弯矩,其原因是坑底被动区面层上作用有较大的被动土压力;而面层内的土压力分布性状与位移具有相似的分布规律和性状特征。以严谨的弹性力学理论为基础提供了研究土钉墙的实用方法,得到的结论为土钉墙的设计提供参考,并加深对土钉墙支护结构的理解和认识。

Facing is significantly important for stability of soil-nailing walls and for transferring earth pressure to stabilized soils. It is absolutely sure that the facing bear against water and earth pressure. However present designers of soil-nailing walls consider the facing as accessory structure rather than the main one. Facing isolated and considered as finite beam on winkler foundation simply, solutions of displacement and inner force of soil-nailing walls are gained through analyzing soil-nailing interaction. The results show maximal value of displacement is on the lower side of slope instead of the top. The location moves down with the pit depth. The law is that displacement is larger in the middle than the two sides in agreement with the actual measurement data. Internal friction angle and cohesive strength have large effects on the displacement, so preventing water from flowing to the vacation is very important. The analytic solutions also disclosure characteristics of moment and lateral earth pressure. Facing moment is increased with depth, the gains are small at the top slope and large at bottom of pit, and reaches its maximal value at lower side of slope. The moment is developed into negative one because of passive earth pressure at the bottom of pit. Earth pressures have similar characteristics and behaviors with inner facing displacement. The paper puts forward a method of exploring soil-nailing walls based on precise Elasticity Theory, the results are also referenced by designer and give people throughout comprehension of soil-nailing walls.