细颗粒对海洋桩基水平承载力的影响规律研究

摘要

This paper puts forward a theoretical calculation method for the coefficient of subgrade reaction.This method is based on the traditional m method which combined with the cavity expansion theory.At the same time,a theoretical calculation method of horizontal bearing capacity of pile foundation which based on the plastic deformation theory is proposed for analyzing the influence of the basic mechanical parameters of ground soil on the horizontal bearing capacity of pile foundation.Based on the analysis of strength and deformation characteristics of the different fine particles and illite content in marine soil foundation,the paper gives the change ruler of horizontal bearing capacity of pile foundation under the different displacement of pile tip.Studies show that under the same damage mode,the higher the content of illite in the marine foundation soil,the greater the horizontal bearing capacity of the pile foundation.Different illite content may lead to the change of failure mode of foundation soil.When the content of illite reaches 10%,the marine soil begins to transition from softening failure to hardening failure.Because of the change of deformation characteristics,the horizontal bearing capacity under different displacement control shows the nonlinear variation characteristics.When the content of illite is 5%,the horizontal bearing capacity of pile foundation allows the displacement of pile top is 5 cm and 182.9% higher than that of 1 cm.When the content of illite is 15%,the horizontal displacement capacity of pile foundation allows the displacement of pile top is 5 cm and increases by 214% compared with that of 1 cm. The specification uses a displacement control method to determine the horizontal bearing capacity of foundation soil without considering the deformation mode changes. According to offshore conditions,the paper suggests that design the horizontal bearing capacity under the multi shift control method provides a theoretical calculation method and increases the scientific design of horizontal bearing capacity of pile foundation without the field test.%在传统m法的基础上,基于塑性变形理论,建立了桩基地基反力系数理论计算公式,提出了基于塑性变形理论的桩基水平承载力理论计算方法,本方法能够有效反映地基土基本力学参数对桩基水平承载力的影响规律.结合海洋土地基不同细颗粒和伊利土含量的强度和变形特征分析,研究了不同桩顶位移下海洋性桩基水平承载力变化规律.研究显示:在同种破坏模式下,海洋地基土中伊利土含量越高,桩基水平承载力越大.但伊利土含量的不同可能导致地基土破坏模式的变化.当伊利土含量达到10%后,海洋土开始由软化型破坏向硬化型破坏转变.由于变形特性的改变,使得不同位移控制下水平承载力规律呈现非线性变化特征.当伊利土含量5%时,允许桩顶位移为5 cm的桩基水平承载力比1 cm的增大182.9%;当伊利土含量15%时,允许桩顶位移为5 cm的桩基水平承载力比1 cm的增大214%.常规设计采用一种位移控制确定水平承载力的方法没有考虑地基土层变形破坏模式的影响,无法实现科学的优化设计,针对海洋性地基建议根据外海地层变形破坏模式考虑多位移控制下的水平承载力优化设计方法.本方法为研究海洋桩基水平承载力设计提供了新的思想,并在没有现场试验的条件下增加了桩基水平承载力设计的科学性.