膨胀土地区自平衡试验负摩阻力转换系数研究  

Research on Conversion Factor of Negative Friction in Self-balance Test in Expansive Soil Region

作　　者：欧孝夺[1,2,3] 吕政凡 陆小金 江杰 李胜[4] 秦金喜 OU Xiaoduo;LYU Zhengfan;LU Xiaojin;JIANG Jie;LI Sheng;QIN Jinxi(College of Civil Engineering and Architecture, Guangxi University, Nanning,Guangxi 530004, China;Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education, Nanning,Guangxi 530004, China;Guangxi Engineering Research Center for Metallic Tailings Security Prevention and Control, Nanning,Guangxi 530004, China;College of Civil Engineering, Tongji University, Shanghai 200092, China)

机构地区：[1]广西大学土木建筑工程学院,广西南宁530004 [2]工程防灾与结构安全教育部重点实验室,广西南宁530004 [3]广西金属尾矿安全防控工程技术研究中心,广西南宁530004 [4]同济大学土木工程学院,上海200092

出　　处：《公路工程》2022年第2期180-187,共8页Highway Engineering

基　　金：国家自然科学基金项目(51768006,51978179);广西科技计划项目(桂科2019AB02005)。

摘　　要：采用自平衡试桩法确定极限承载力时,由于其受理机理与传统静压桩不同,需通过等效转换公式得到准确的自平衡桩的极限承载力,其中上段桩负摩阻力转换系数的取值大小对试桩承载力的确定影响极大。通过模型试验的方法,对膨胀土在浸水与未浸水2种工况下的自平衡试验和传统静载试验进行对比分析,同时基于温度场等效湿度场理论,采用有限差分软件FLAC3D建立传统静压桩和自平衡静载试桩的数值模型,对模型试验结果进行了对比分析,并进一步研究了膨胀土含水率与负摩阻力转换系数的关系。结果表明:膨胀土浸水后对基桩竖向承载力有影响;膨胀土未浸水时,自平衡负摩阻力转换系数取值为0.82,与黏性土取值相近;膨胀土浸水膨胀后,基桩竖向承载力减小,自平衡负摩阻力转换系数取值为0.63,与砂土取值相近;负摩阻力转换系数的取值,随膨胀土含水率的增大而减小。研究成果可为膨胀土地区自平衡试验负摩阻力转换系数γ取值提供参考。When the self-balanced test pile method is used to determine the ultimate bearing capacity,because its acceptance mechanism is different from that of traditional static pressure piles,it is necessary to obtain an accurate ultimate bearing capacity of the self-balanced pile through an equivalent conversion formula,where the upper pile negative friction resistance conversion coefficient is taken.The value has a great influence on the determination of the bearing capacity of the test pile.This paper uses the method of model test to compare and analyze the self-balance test and traditional static load test of expansive soil under both immersion and unimmersion conditions.At the same time,based on the equivalent humidity field theory of the temperature field,the finite difference software FLAC3D is used to establish the numerical model of the traditional static pressure pile and the self-balance static load test pile.The model test results were compared and analyzed,and the relationship between the water content of expansive soil and the conversion coefficient of negative friction is further studied.The results show that the expansive soil has an impact on the vertical bearing capacity of the foundation pile after being immersed in water;when the expansive soil is not immersed in water,the self-balance negative friction conversion coefficient is taken as 0.82,which is similar to that of cohesive soil;The vertical bearing capacity of the pile decreases,and the self-balancing negative friction conversion coefficient is 0.63,which is close to the value of sand;the negative friction conversion coefficient decreases with the increase of the water content of the expansive soil.The research results can provide a reference for the value of the negative friction conversion coefficientγof the self-balance test in the expansive soil area.

关 键 词：自平衡试验 膨胀土 负摩阻力 转换系数 

分 类 号：TU473.16[建筑科学—结构工程]