基于桩土相对位移特征的深厚湿陷性黄土地区桩基承载力计算方法  

Calculation Method of Pile Foundation Bearing Capacity in Deep Collapsible Loess Area Based on Characteristics of Pile-Soil Relative Displacement

作　　者：陈晓广 CHEN Xiaoguang(China Railway Fifth Survey and Design Institute Group Co.Ltd.,Beijing 102600,China)

机构地区：[1]中铁第五勘察设计院集团有限公司,北京102600

出　　处：《铁道建筑》2023年第1期137-142,共6页Railway Engineering

基　　金：中兰铁路客运专线有限公司资助项目(ZLKZ-Fw-2019-18);中铁第五勘察设计院集团有限公司科研项目(T5Y2015-B04)。

摘　　要：湿陷性黄土地层桩基中性点不易准确把握,会导致部分工程实测负摩阻力高于规范参考值。针对这一问题,本文基于现场浸水试验,提出一种依据湿陷性土层厚度确定桩基负摩阻力分布新方法——相对位移法,并进行了验证。结果表明:浸水试验场地累计沉降随着深度的增大而减小,深度为0~15 m时土体湿陷较为充分,15 m处接近饱和自重应力界限,15 m以下土层湿陷不充分,土中竖向应力增长幅度较小,22 m以下土层基本不发生湿陷;经验参数法与相对位移法计算得到的桩基承载力分别为2 926.5、3 251.6 kN,相对位移法得到的桩基承载力更能反映桩基承实际载能力,用于深厚湿陷性黄土地区桩基设计能兼顾安全性与经济性。It was difficult to accurately grasp the neutral point of pile foundation in collapsible loess stratum,which would cause the measured negative friction resistance of some projects to be higher than the reference value of the specification.To solve this problem,this paper would propose a new method to determine the negative friction distribution of pile foundation according to the thickness of collapsible soil layer,the relative displacement method,was proposed and verified based on the field immersion test.The results show that the cumulative settlement of the immersion test site decreases with the increase of burial depth.When the burial depth is 0 ~ 15 m,the soil is sufficiently collapsed,the soil collapsible at 15 m is close to the limit of saturated gravity stress.The soil below 15 m is not sufficiently collapsed,the vertical stress growth rate is small,and the soil below 22 m is basically not collapsed.The bearing capacity of pile foundation calculated by the empirical coefficient method and the relative displacement method is 2 926.5 kN and 3 251.6 kN respectively.The bearing capacity of pile foundation calculated by the relative displacement method can better reflect the actual bearing capacity of pile foundation,which can be used for the design of pile foundation in deep collapsible loess area,with the consideration on both safety and economy.

关 键 词：深厚湿陷性黄土地基 现场浸水试验 桩基础 负摩阻力 单桩竖向承载力 

分 类 号：TU473.1[建筑科学—结构工程]