刚性桩复合地基桩土应力比计算方法

Calculation method of pile-soil stress ratio of rigid pile composite foundation

为了准确简便地预测路堤在荷载下发生的沉降变形,必须对桩基复合地基的桩土应力比进行合理正确的评价计算.针对高速公路地基处理中采用刚性桩复合地基的情况,假设路堤土中基底相对位移下土柱间滑移面剪应力垂直分布,考虑桩顶上刺入路堤、桩端下刺入下卧层以及桩侧负、正摩阻力非线性分布,分析了路堤-桩-地基土整体在应力与位移协调下的相互作用.通过迭代计算求得路堤内等沉面高度与加固区中性点位置,得到戴帽刚性桩复合地基在路堤荷载下的简单桩土应力比计算公式.通过2个工程实例实测数据对提出的计算方法进行了合理性验证,分析结果表明该方法对于填土路堤高度大于2倍桩净间距的工况计算结果具有较高的精度.

In order to predict embankment settlement more accurately and simply,the pile-soil stress ratio of rigid pile composite foundation should be adequately evaluated.In the load effect analysis,a vertical shearing plane due to relative displacement at embankment fill base is adopted.Then a simplified theoretical calculation model is deduced,in which the behaviour of pile upward and downward puncture deformation is considered,and the distribution of pile lateral friction above and under the neutral point is assumed to be linearly dependent on stress state.Afterwards a calculation formula of the pile-soil stress ratio of rigid pile composite foundation is proposed with pre-determination of equal settlement plane height in fill and neural point position within pile length by iterative computation.The presented method is validated by comparing analytical solutions with the observed results from a newly constructed highway project and a widening highway project.Results show that the proposed method obtains more accurate results of pile-soil stress ratio when the fill height is more than twice the pile net spacing.