路堤荷载下CFG桩复合地基失稳破坏特性离心模型试验  被引量:5

Centrifugal model tests on failure characteristics of CFG pile composite foundation under embankment

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作  者:刘宏扬 罗强[1,2] 薛元[3] 程田 王腾飞 张良[1,2] 蒋良潍[1,2] LIU Hong-yang;LUO Qiang;XUE Yuan;CHENG Tian;WANG Teng-fei;ZHANG Liang;JIANG Liang-wei(School of Civil Engineering,Southwest Jiaotong University,Chengdu 610031,China;MOE Key Laboratory of High-Speed Railway Engineering,Chengdu 610031,China;China Railway Eryuan Engineering Group Co.,Ltd.,Chengdu 610031,China)

机构地区:[1]西南交通大学土木工程学院,四川成都610031 [2]高速铁路线路工程教育部重点实验室,四川成都610031 [3]中铁二院工程集团有限责任公司,四川成都610031

出  处:《岩土工程学报》2022年第8期1502-1511,F0002,共11页Chinese Journal of Geotechnical Engineering

基  金:国家自然科学基金项目(51878560,41901073);四川省科技计划项目(2021YJ0001)。

摘  要:掌握路基工程CFG桩复合地基失稳破坏特性是建立稳定分析方法的基础。针对路堤荷载作用下深厚软黏土地基,开展了3组CFG桩复合地基离心模型试验,采用自行研制的空中泄砂装置模拟路堤分层填筑过程,设计制作砂浆包裹石墨芯的模型桩监测桩体破坏时序,通过摄影测量技术获取地基土位移场云图,分析复合地基的承载与变形特性及失稳滑动形态。试验表明,随路堤荷载增加,位于坡脚附近的桩体首先发生破坏,并逐渐向路堤中心发展,呈现渐进破坏特点,复合地基发生整体失稳后滑面近似呈圆弧状;桩体破坏形态与桩周土体变形特性密切相关,地基发生隆起变形的坡脚附近桩体呈现拉弯破坏特征,承受路堤荷载较大的路肩附近桩体以压弯破坏为主;桩帽对桩土荷载分担影响显著,桩身轴力增大可提高桩体抗弯拉能力,有利于复合地基稳定性提高。Establishing a stability analysis approach for CFG pile composite foundation requires a thorough understanding of its instability and failure characteristics in subgrade engineering. For the deep soft clay foundation under embankment, three groups of centrifugal model tests are conducted in this study. The self-developed in-flight sand release device is used to simulate the staged embankment construction. In order to monitor the failure sequence of the piles, the model piles are made by wrapping graphite sticks with mortar. The photogrammetry is used to obtain the contours of foundation displacement. Finally,the bearing and deformation characteristics of the composite foundation are analyzed along with their sliding surface. The tests show that as the embankment height increases, the model piles near the embankment toe firstly fail, followed by the failure of piles beneath the shoulder and center of the embankment, exhibiting a progressive failure feature. After the global instability is triggered, the sliding surface of the composite foundation is nearly a circular slip plane. The failure modes of piles are closely linked to the deformation of the surrounding soil. Tensile bending failure is observed for the piles near the slope toe, where the foundation soil heaves, but the compressive bending failure of piles occurs near the embankment shoulder, where the embankment load is relatively large. The pile cap has a significant effect on the load distribution between the piles and the soils.As the axial force of the piles increases, the flexural tensile capacity of the piles is enhanced, which benefits the stability of composite foundations.

关 键 词:CFG桩 复合地基 离心模型试验 失稳滑动形态 渐进破坏 

分 类 号:TU473.1[建筑科学—结构工程]

 

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