【目的】对不同节点刚度形式的两类群桩(1×3普通节点群桩、1×2劲性节点群桩)进行研究。【方法】现场试验得到节点刚度与桩数对水平承载性能的影响,在此基础上,利用有限元方法研究节点刚度对其承载性能的影响,并采用不同节点形式组合群桩,研究其承载性能及荷载分配机制。【结果】结果表明:采用1×2劲性节点群桩可提高基桩平均水平极限承载力约17.63%,并改善水平位移减小41.64%;增设T形钢件后,其竖向变形能力可提高54.22%,且可改善节点转动;对于前排承压桩,可取消其锚固钢筋,采用更大的嵌固深度;采用组合节点形式群桩,其整体水平刚度可提高13.07%,同时改善其竖向变形能力,有利于加载后期水平荷载的均匀分配;基桩节点刚度应由该桩与邻桩节点刚度共同确定。

【Purposes】 Two types of pile group with different pile-cap connection forms (1×3  pile group with ordinary connection and 1×2 pile group with rigid connection) are tested in the field to  obtain and the influences of connection stiffness and the number of piles on their horizontal bearing ca⁃ pacities. 【Methods】On this basis, the finite element method was used to study the influence of con⁃ nection stiffness on its bearing capacity. Besides, the composite connection pile groups with different  connection forms were used to study their bearing capacities and load distribution mechanism. 【Find⁃ ings】The results show that the average ultimate bearing capacity of foundation piles can be increased  by about 17.63% and the horizontal displacement can be reduced by 41.64% by using 1×2 rigid con⁃ nection group piles. After adding T-shaped steel members, the vertical deformation capacity can be in⁃ creased by up to 54.22%, and the connection rotation can be improved. For the front bearing pile, the  anchoring steel bar can be cancelled and a larger embedded depth can be selected. The overall horizon⁃ tal stiffness of the pile group with composite connections can be increased by up to 13.07%, and its  vertical deformation capacity can be improved at the some time, which is conducive to the uniform dis⁃ tribution of horizontal load in the later stage of loading. The connection stiffness of pile should be deter⁃ mined by the connection stiffnesses of both the pile and its adjacent pile.