摘要
桥梁挖井基础除受到桥梁上部结构自重所产生的竖向荷载外,还将承受来自列车制动和横向摇摆以及离心力所带来的侧向荷载。现有的规范主要关注挖井基础的竖向承载是否满足地基承载力,未考虑挖井基础在三维空间中的多维承载力。本文针对挖井基础所适用的典型土层条件,采用有限元方法研究了圆形挖井基础在上黏下砂地层中的多维承载特性,分析了上覆黏土层强度和挖井基础长径比两个因素对基础单向承载力和承载力包络面的影响。结果表明:由于上覆黏土的影响,挖井基础的承载力相比于砂土地基有不同程度的减小,且这种减小效应随着井端以上黏土层厚度的增加而增加,其中以水平承载力的减小幅度最为明显。基于数值计算结果,建立了上黏下砂地层中挖井基础承载力的包络面表达式,提出了包络面特征参数随挖井基础长径比和竖向荷载水平变化的实用计算公式。
In addition to the vertical load generated by the upper structure of the bridge,the cutting caisson foundation of the bridge will also bear the lateral loads caused by train braking,lateral swing and centrifugal force.The existing specifications mainly focus on whether the vertical bearing capacity of the cutting caisson foundation meets the bearing capacity of the ground,without considering the composite bearing capacity of the cutting caisson foundation in the three-dimensional space.In view of the typical soil layer conditions applicable to the cutting caisson foundation,the one-way and composite bearing characteristics of the circular cutting caisson foundation in the upper clay and lower sand layer are studied by using the finite element method.The influence of the strength of the overlying clay layer and the length-diameter ratio of the cutting caisson foundation on the one-way bearing capacity and composite bearing capacity of the foundation is analyzed.The results show that due to the influence of the overlying clay,the bearing capacity of the excavated shaft foundation is reduced to different degrees compared with the sandy soil foundation,and this reduction effect increases with the increase of the thickness of the clay layer above the shaft end,with the most obvious reduction in the horizontal bearing capacity.Based on the numerical calculation results,the envelope surface expression of the bearing capacity of the circular caisson foundation in the upper clay and lower sand strata is established.The practical calculation formula of the characteristic parameters of the envelope surface varying with the length-diameter ratio of circular cutting caisson foundation and the vertical load level is proposed.
作者
袁宇
Yuan Yu(China Railway Design Corporation,Tianjin 300142,P.R.China)
出处
《地下空间与工程学报》
CSCD
北大核心
2024年第S01期134-147,共14页
Chinese Journal of Underground Space and Engineering
基金
中国铁路设计集团有限公司科技开发课题(2023A0248005,2021B240605)。
关键词
铁路桥梁挖井基础
复合承载力
上黏下砂
数值模拟
cutting caisson
combined bearing capacity
clay-over-sand
numerical modelling
