基于桩-土界面剪切特性的单桩沉降和承载问题研究  

Settlement and bearing capacity of single pile based on shear characteristics of pile-soil interface

作　　者：叶帅华[1,2] 辛亮亮 YE Shuai-hua;XIN Liang-liang(Key Laboratory of Disaster Mitigation in Civil Engineering of Gansu Province,Lanzhou University of Technology,Lanzhou,Gansu 730050,China;Western Center of Disaster Mitigation in Civil Engineering,Ministry of Education,Lanzhou University of Technology,Lanzhou,Gansu 730050,China)

机构地区：[1]兰州理工大学甘肃省土木工程防灾减灾重点实验室,甘肃兰州730050 [2]兰州理工大学西部土木工程防灾减灾教育部工程研究中心,甘肃兰州730050

出　　处：《岩土力学》2024年第5期1457-1471,共15页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.52168050)。

摘　　要：近年来,西北地区出现了许多高填方场地,为减小建筑物基础的不均匀沉降,基础类型广泛使用桩基础。与一般场地不同,黄土填方场地中的单桩桩周土受力后仍会产生较大的变形,该类场地单桩沉降机制复杂。桩顶总沉降计算是桩基设计的重要依据,为此,建立了高填方黄土场地单桩桩顶总沉降计算模型。基于传统的荷载传递法和剪切位移法,分别考虑桩-土界面的桩-土相互作用和桩-土界面外剪切带土体的剪切变形。依据桩端边界,将单桩类型分为摩擦桩和端承摩擦桩,分别建立桩周土弹性阶段和塑性阶段的桩身位移控制微分方程,结合边界条件进行求解,得到桩身位移、轴力、侧摩阻力,并通过弹塑性理论求解了桩周土剪切带土体剪切变形,进而通过叠加原理求得桩顶总沉降。用桩长与桩周土塑性发展深度的比值,定义了桩基承载力安全系数K。通过算例分析与现场试验数据对比分析,研究结果表明:使用新的模型计算得到的桩顶总沉降与现场试验结果相近;当桩顶荷载较小、桩周土处于弹性阶段时,桩端边界对桩身轴力、位移和侧摩阻力影响很小,但桩周土进入塑性滑移阶段后,桩端边界的影响开始变大,考虑桩端土的承载能力会极大提高单桩极限承载力;建立了将荷载传递法和剪切位移法综合起来的计算模型,不仅可以考虑桩-土界面的相对滑移,还可以计算桩-土界面外土体剪切带的剪切变形,使得桩顶总沉降计算更加精确,可为类似场地中单桩沉降的分析与控制提供一定的参考。In recent years,the northwest region has seen an increase in high embankment sites,leading to widespread use of pile foundations to mitigate uneven settlement of building foundations.However,in loess embankment sites,single piles experience significant deformation in the surrounding soil after loading,complicating the settlement mechanism of such single piles.As pile head settlement calculation is crucial for pile foundation design,this paper establishes a calculation model for pile head settlement of single piles in high embankment loess sites.The proposed model considers the interaction between piles and soil at the pile-soil interface and the shear deformation of the soil in the shear zone outside the pile-soil interface,based on the traditional load transfer method and shear displacement method.It classifies single pile types into friction piles and end-bearing friction piles based on the pile end boundary and establishes differential equations for pile body displacement control in both the elastic and plastic phases of the surrounding soil.Solving these equations with boundary conditions yields pile body displacement,axial force,and lateral friction resistance.Additionally,the model calculates the shear deformation of the soil in the pile-soil interface zone using elastoplastic theory and determines the total settlement at the pile head using the superposition principle.The ratio of pile length to the plastic development depth of the surrounding soil is defined as the pile bearing capacity safety factor,denoted as K.Results from case studies and comparisons with field test data demonstrate that the pile head total settlement calculated using the model proposed in this paper aligns closely with the field test results.When the pile head load is relatively small and the surrounding soil is in the elastic phase,the influences of the pile end boundary on pile body axial force,displacement,and lateral friction resistance are minimal.However,as the surrounding soil enters the plastic slip phase,the effect of the pi

关 键 词：荷载传递法 剪切位移法 桩-土界面 桩-土剪切带 桩顶沉降 承载特性分析 

分 类 号：TU473[建筑科学—结构工程]