受水平循环荷载影响的斜桩p-y曲线构建及应用

p-y曲线法是分析水平受荷桩基承载变形特性的主要方法,利用p-y曲线法的关键在于构建合理的p-y曲线。在砂土地基中开展了2组共10根水平受荷斜桩模型试验,其中2根斜桩仅分级施加了水平静力荷载,其余8根斜桩先施加了不同幅值的单向水平循环荷载,然后再分级施加水平静力荷载。试验测试了10根斜桩的砂面处桩身横向位移及桩身应变,根据桩身应变计算得到了桩身弯矩,在此基础上根据Euler-Bernoulli梁理论得到了桩侧土抗力及相应的桩身水平位移,构建了承受水平单向循环荷载后再承受水平静力荷载时斜桩的双曲线型p-y曲线,并给出了斜桩初始地基反力模量及桩侧极限土抗力的确定方法。用上述构建的双曲线型p-y曲线计算了本文模型试验及文献中模型试验斜桩的响应,发现利用所构建的p-y曲线得到的计算结果与实测结果整体上吻合较好,说明本文构建的双曲线型p-y曲线是合理可行的。最后利用p-y曲线计算了承受单向水平循环荷载后再承受水平静力荷载斜桩的桩身位移及桩身内力,计算结果表明:(1)相对于斜桩桩顶自由,桩顶固支能有效地减小斜桩的桩身横向位移、桩身弯矩及剪力;(2)在单向水平循环荷载作用下,正斜桩桩顶横向位移、 桩身最大弯矩及剪力均小于负斜桩;(3)无论是正斜桩还是负斜桩,桩顶横向位移、桩身剪力随着抗弯刚度增加而减小,而桩身最大弯矩随着抗弯刚度增加而增加。

The Formation and Application of Batter Pile p-y Curve Influenced by Lateral Cyclic Load

The p-y curve method is the main method to analyze the bearing deformation characteristics of laterally loaded pile, and the key is to construct a reasonable p-y curve. Two groups, i.e., ten laterally loaded batter piles are tested. Only horizontal static load is stepped applied to 2 batter piles, and the other 8 batter piles are first applied unidirectional horizontal cyclic load with different amplitude, and then applied horizontal static load in different stages. The lateral displacement and strain of 10 batter piles at the sand surface are tested, and the bending moment of the pile is calculated according to the pile strain. The soil reaction and the corresponding horizontal displacement of pile are obtained according to the Euler-Bernoulli's beam theory. The hyperbolic p-y curve of batter piles was established by calculating results when it bears one-way laterally cyclic load and then bears the laterally static load. Then, the determination method of initial foundation reaction modulus and limit soil resistance of batter piles side is given. The responses of batter piles in model test of this paper and reference were calculated by using this hyperbolic p-y curve. It indicates that the calculated results are in good agreement with the measured results and demonstrates that the constructed hyperbolic p-y curve is reasonable. Finally, the horizontal displacement and internal force of batter piles under one-way laterally cyclic load and then laterally static load were calculated using this p-y curve. The calculation results show that: (1) the fixed batter piles top can effectively reduce the horizontal displacement, bending moment and shearing force of batter piles comparing with the free pile top. (2) Under the effect of one-way laterally cyclic load, the horizontal displacement maximum, bending moment and shearing force of positive batter pile are smaller than those of negative batter pile. (3) For both positive and negative batter piles, the horizontal displacement of batter piles top and the shearing force of batter piles decrease with increasing of bending stiffness of batter piles, while the maximum bending moment of batter piles increases with increasing of bending stiffness of batter piles.