基于土拱效应围护桩间距的计算模型

Calculation model of spacing between guard piles based on soil arch effect

目前的围护桩设计中缺少合理计算桩距的方法。在充分考虑桩间土拱效应的基础上,建立了土拱水平受荷时土拱效应的计算模型,对土拱进行受力分析。当水平土压力作用在土拱上,拱后土体仍会受到部分应力作用;当拱后土体处于土体极限平衡状态时,不同方向的应力满足一定的关系。根据土体极限平衡状态条件、静力平衡条件和拱脚的几何条件,分别推导出了无黏性土和黏性土时桩间距计算模型,并对模型适用性进行分析。当桩后土体为无黏性土时,出于安全考虑,桩间距可取为零;当桩后土体为黏性土时,可根据所推导出的相应公式计算合理的桩间距。在使用模型计算时,应注意土体抗剪强度指标的选取,尤其是土体的内摩擦角建议取值不超过20°。

Computation method of pile spacing is in deficiency in the present design of guard piles. The computation model of soil arching under horizontal load was set up and stress analysis was carried out based on considering horizontal soil arching effect.The soil behind arch still bears part of stress when soil arch subjected to horizontal soil pressure ,when soil behind arch is in limit state, the stress in different orientation meets certain relationship. The geometric condition of arch foot and the static balance condition, the formulas of pile spacing in cohesive and cohesiveless soil were derived based on the soil limit state. The suggestion value of pile spacing is zero for the concern of safety when the soil behind pile is cohesiveless. The suggestion value of pile spacing can be computed according to the equation when the soil behind pile was cohesive. The chosen shear strength of soil is important in utilizing the equation and the value of inner friction angle should not too large（ ≤ 20°）.