刚性桩复合地基的桩土应力比计算方法

刚性桩的桩体刚度比较大,承担较大荷载后桩身变形较小,其桩土应力比远大于半刚性桩的桩土应力比。刚性桩复合地基设计仍沿用半刚性桩复合地基经验设计,导致刚性桩复合地基设计过于保守,问题的关键在于如何准确确定其桩土应力比。基于刚性桩荷载传递规律、桩-土-垫层变形协调条件,综合考虑了桩体的上下刺入变形、桩侧正负摩阻、桩长、桩径、土性等影响因素,推导得到了刚性桩复合地基桩土应力比简化公式,并与刚性桩复合地基室内模型试验和现场实测结果进行对比分析,该公式便于工程应用,更有利于刚性桩复合地基定量化设计和计算沉降。

Calculation Method of Stress Concentration Ratio of Pile to Soil of Rigid Pile Composite Foundation

Due to the big stiffness of rigid pile, the deformation of the rigid pile body is small when it supports large load. The stress concentration ratio of the rigid pile is greater than the semi-rigid pile’s. The design theory of the rigid pile composite foundation has still some problems in the practical engineering. Engineers used the design experience of semi-rigid pile composite foundation to design the rigid pile composite foundation, thus the design is over conservative and profuse. The key problem is how to determine the pile-soil stress concentration ratio of rigid pile composite foundation. Based on the load transfer rule of the rigid pile,the deformation coordination condition of pile-cushion-soil, considering the upward and downward puncture deformations of piles, positive and negative friction on piles,diameter and length of piles and ground soil behaviors, the pile-soil stress concentration ratio formula of rigid pile composite foundation is put out in this paper. The formula is checked by modeling test and field measurement results of the rigid pile composite foundation and can be conveniently applied to quantitative design and calculation of settlement in the engineering.