刚性桩复合地基中性面深度与桩土应力比计算

刚性桩复合地基中性面深度及桩土应力比的简化计算主要基于桩侧摩阻力线性分布假设，当桩身较长时，桩端侧摩阻力的计算值会远大于实际值，致使中性面深度及桩土应力比的计算结果与实际差别较大，故有必要对线性分布模式予以修正。据此将桩侧摩阻力分布简化为分段线性模式，考虑负摩阻力作用及桩上、下刺入变形，根据褥垫层-桩-土变形协调关系推导了刚性桩复合地基中性面深度、桩顶面桩土应力比、中性面桩土应力比计算公式。最后通过模型试验与工程实例验证，计算值与实测值吻合较好。

Determination of neutral plane depth and pile-soil stress ratio of the rigid pile composite foundation

Based on the linear distribution model of the side friction of pile, the theoretical value of pile side friction will far exceed the actual value when the pile is comparatively long. Consequently, the calculation of neutral plane depth and pile-soil stress ratio of the rigid pile composite foundation is quite different from the reality and needs modification. Therefore, the distribution of pile side friction was assumed to be piecewise linear, with influence of negative friction and behavior of pile upward and downward puncture deformation taken into consideration. According to the cushion-pile-soil deformation compatibility condition, a theoretical calculation model was created to obtain the neutral plane depth and pile-soil stress ratio on the top surface and neutral surface of pile. Finally, the calculation method was verified by field measurement as well as model test results of the rigid pile composite foundation, and theoretical values agreed well with the experimental data.