黄土地区刚-柔性桩复合地基的承载机理  

Bearing mechanism of composite foundation with rigid-flexible piles in loess area

作　　者：张恩祥 何腊平 龙照 胡志平[2] ZHANG En-xiang;HE La-ping;LONG Zhao;HU Zhi-ping(Gansu CSCEC Municipal Engineering Investigation and Design Institute Co.,Ltd.,Lanzhou 730000,Gansu,China;School of Civil Engineering,Chang'an University,Xi'an 710061,Shaanxi,China)

机构地区：[1]甘肃中建市政工程勘察设计研究院有限公司,甘肃兰州730000 [2]长安大学建筑工程学院,陕西西安710061

出　　处：《交通运输工程学报》2019年第4期70-80,共11页Journal of Traffic and Transportation Engineering

基　　金：国家自然科学基金项目(41877285)

摘　　要：为了揭示湿陷性黄土地区刚-柔性桩复合地基的荷载传递机理,开展了现场原型试验,分析了桩身和桩间土的应力在不同荷载与深度下的变化规律;通过与刚性单桩的对比,总结了刚-柔性桩复合地基的桩土相互作用特点;结合已有文献,分析了湿陷性黄土地区刚-柔性桩复合地基与软土地区刚-柔性桩复合地基在力学表现上的差异。分析结果表明:湿陷性黄土地区刚-柔性桩复合地基中柔性桩的主要作用是挤密桩间土,消除其湿陷性,试验场地处理后湿陷系数基本小于0.015;由于柔性桩的挤密作用,桩间土的承载力得以充分发挥,刚性桩的荷载传递能力得以增强;软土地区柔性桩的荷载分担率一般大于桩间土,由于黄土的承载力较高及柔性桩与桩间土的模量比小,湿陷性黄土地区桩间土的荷载分担率稳定在26%左右,远大于柔性桩的7%;复合地基中的刚性桩属于端承摩擦桩,随着荷载增加,刚性桩的荷载传递能力逐渐强化,荷载分担率逐渐增加,最终稳定在67%左右;刚性桩荷载传递能力的增强并不利于刚-柔性桩复合地基承载能力的充分发挥,在设计时需要充分考虑对纯摩擦桩有效桩长的影响,以及对端承摩擦桩桩端土体承载能力的影响。In order to investigate the loading transfer mechanism of composite foundation with rigid-flexible piles in collapsible loess area,a field prototype test was conducted.The stress variation rules of piles and soil among piles with different loads and depths were analyzed.Taking the behaviors of rigid single pile as comparison,the characteristic of pile-soil interaction in composite foundation with rigid-flexible piles was summarized. Combined with existing literatures,the difference of mechanical performance between the composite foundation with rigid-flexible piles in collapsible loess area and soft soil area was analyzed.Analysis result indicates that the flexible pile of composite foundation with rigid-flexible piles in collapsible loess area is mainly used to compact the soil among piles and eliminate the collapsibility of soil,and the collapsibility coefficients are basically less than 0.015after the treatment in the test site.As a result of the compaction of flexible pile,the bearing capacity of soil among piles can be fully developed and the loading transfer ability of rigid pile can be enhanced.The load-sharing ratio of flexible pile is always larger than that of soil among piles in soft soil area.As a result of the high bearing capacity of loess and small modulus ratio between the flexible pile and soil among piles, the load-sharing ratio of soil among piles in collapsible loess area is stable at about 26%,much higher than 7%of flexible piles.The rigid pile in composite foundation pertains to an end bearing friction pile.As the loading increases,the loading transfer ability of rigid pile improves gradually,and the load sharing ratio increases and finally settles at 67%.The improvement of the loading transfer ability of rigid piles is against the development of the bearing capacity of composite foundation with rigid-flexible piles,of which effects on the valid length of pure friction pile should be taken into account in the designing process,and its effects on the bearing capacity of soil at the bottom of

关 键 词：机场工程 刚-柔性桩复合地基 现场原型试验 荷载传递机理 湿陷性黄土 素土挤密桩 

分 类 号：U416.1[交通运输工程—道路与铁道工程]