嵌岩桩尺寸效应及深度效应的室内试验研究

Laboratory Test on the Effect of Diameter and Depth of Rock-socketed Piles

为了研究嵌岩深度超过4倍桩径的深嵌岩桩的桩径尺寸及嵌岩深度对桩基承载特性的影响,采用室内模型试验方法,通过室内3组(9根)模型试桩对其进行了研究与分析,内容包括桩径大小及嵌岩深度对深嵌岩桩基承载力的影响、嵌岩深度的变化对轴力传递的影响以及桩径尺寸及嵌岩深度效应对桩侧阻力、桩端阻力的影响等。研究结果表明:增大桩径和增加嵌岩深度对提高嵌岩桩基的极限承载力都是可行的,且增大桩径比增加嵌岩深度更为有利;从桩身轴力传递来看,随着嵌岩深度的增加,桩身轴力的分布主要集中在桩身上部;从桩侧阻力分布形态来看,桩侧阻力也主要分布在桩身的上部区域。对小直径桩基(D=50 mm)而言,随着嵌岩深度的增加,桩顶承受荷载的增大,桩身上部的极限侧摩阻力也随之增大;而对大直径桩基(D=90 mm)而言,桩侧摩阻力随桩径的增加而反而有所减小;从桩端阻力大小来看,在极限荷载作用下,桩基嵌岩深度越深、桩径越大,桩端阻力变化越小。

To study the effect of diameter size and depth of rock-socketed piles on their bearing characteristics, in case that the depth of piles embedded in rock more than four times the diameter, the bearing characteristics of three groups of model test piles had been discussed and analyzed by the use of model test methods in this article, including the bearing capacity of piles, transmission of axial force, side resistance and end resistance which influenced by the size of pile diameter and depth of the pile in rock. The results showed that it was feasible to improve the ultimate bearing capacity of rock-socketed pile by increasing the diameter of piles and their depth in rock. Furthermore, it was more beneficial to enlarge the diameter than to increase the depth in rock. From the distribution of side resistance, it was mainly distributed over the upper area of pile. For small diameter pile （ D = 50 mm） , with the increase of rocksocketed depth and load on top of pile, the ultimate side resistance was increased correspondingly. Instead, for large diameter pile （D = 90 mm）, it was decreased. From the view of end resistance, under the ultimate load, the more the depth and the larger the diameter was, the value of end resistance was more insignificant.