考虑土抗力方向的p–y曲线法研究

当桩顶受到不在同一平面内的水平力—弯矩组合荷载时,桩身变形复杂,多采用三维有限元法进行分析,不方便实用。为此,文章提出了一种三维情况下土抗力弹簧可在水平面内旋转的p–y曲线法,并建立了相应的数学规划模型进行求解。根据最小势能原理,以广义势能方程为目标函数,将p–y曲线积分计算土弹簧做功,同时以桩身变形协调条件作为数学模型的约束条件,构成了一个非线性规划模型。模型假设桩身每个节点5自由度,并考虑了p–△效应。通过3个算例对该数学规划模型进行了验证,结果表明该模型整体假设条件合理,方法可行。文章同时对桩身双向不均匀弯曲下的土弹簧在水平面内旋转的情况进行分析,认为模型可有效反映出桩身在三维空间内的位移和力的协调。

An analytical p-y curve method based on compressive soil pressure model in sand soil

With the high-quality development of urban buildings,higher requirements are come up with for lateral bearing capacity of laterally loaded piles.Consequently,a more accurate analysis to predict the lateral response of the pile within an allowable displacement is an important issue.However,the current p-y curve methods cannot fully take into account the pile-soil interaction,which will lead to a large calculation difference.In this paper,a new analytical p-y curve is established and a finite difference method for determining the lateral response of pile is proposed,which can consider the separation effect of pile-soil interface and the coefficient of circumferential friction resistance.In particular,an analytical expression is developed to determine the compressive soil pressure by dividing the compressive soil pressure into two parts:initial compressive soil pressure and increment of compressive soil pressure.In addition,the relationship between compressive soil pressure and horizontal displacement of the pile is established based on the reasonable assumption.The correctness of the proposed method is verified through four examples.Based on the verified method,a parametric analysis is also conducted to investigate the influences of factors on lateral response of the pile,including internal friction angle,pile length and elastic modulus of pile.

砂土中光伏支架小直径刚性桩的修正p–y曲线模型

桩基础是地面光伏支架最常用的基础形式。地面光伏支架主要受水平荷载作用,工程中常采用美国石油学协会(API)推荐的p–y曲线法对基桩的水平承载特性进行分析。为探究API推荐的p–y曲线法在计算小直径刚性桩水平受荷变形时的适用性,依托某光伏项目,建立四种不同桩径的小直径刚性桩三维有限元数值模型,分析其水平承载特性并获得不同深度处基桩的p–y曲线,通过对比验证API推荐p–y曲线的适用性,在此基础上提出考虑桩径和深度的砂土中小直径刚性桩桩修正p–y曲线计算模型。结果表明:小直径刚性桩的水平位移与桩径成反比,桩径对桩身弯矩的影响不大。与数值模拟相比,API推荐的p–y曲线初始刚度偏大,极限土抗力偏小,不适用于小直径刚性桩的水平受荷计算。基于数值模拟结果,拟合得到了桩径、深度与初始地基刚度和极限土抗力之间的关系式,建立了地面光伏支架p–y曲线的修正模型,并结合实际工程进行验证计算,结果吻合较好。