不同影响因素下复合土钉支护的沉降变形

摘要

In this paper,some affecting factors on micropile-composite soil nailing, which include the upper loads on a micropile,embedded depth,diameter of the pile,pile spacing,the level space of soil nailing,diameter of soil nailing,are discussed and analyzed to provide reference for engineering application and design. "Quadrilateral"distribution is selected to calculate the lateral earth pressure,Midlin solution and layerwise summation method are used to solve the subsidiary stress and vertical settlement of micropile separately, and parabolic model is adopted to analyze surface subsidence of retaining structure. Deformation and surface subsidence of composite soil nailing support are calculated by MATLAB program. Variation trends of displacement along pile shaft beneath basement are obvious with the increasing embedded depth and diameter of single pile,while the lateral displacement above the basement can be affected by the diameter and transverse space of soil nailing. Surface subsidence is trending to parabola and has the same amplitude increase with upper load and pile spacing. The settlement range of surface is in accordance to cutting depth,embedded depthand internal friction angle which is related to the soil layer under the basement. Settlement deformation of composite soil nailing can be influenced hardly by the transverse space of soil nailing, which also can be neglected. Calculation factors of upper load and pile play important roles to the deformation of micropile-composite soil nailing,and subsidence of pile top depends on the lateral deformation of pile top and tip.%目的 研究微型桩桩顶荷载、埋深、桩径大小、桩间距,以及土钉的水平间距、土钉直径等计算参数时复合土钉支护中微型桩的侧向变形、竖向沉降和地表沉降的影响规律,为工程应用和设计提供参考.方法 选用“四边形”模式计算土压力,应用Midlin解和分层总和法计算竖向沉降,采用抛物线模型分析支护结构的地表沉降,通过MATLAB编程进行微型桩复合土钉支护的沉降和变形计算.结果 埋置深度和桩径对基底以下支护结构侧移的变化影响较为明显,而土钉的直径和横向间距只对基底以上的水平位移有影响;桩顶地表沉降取决于桩顶和桩底水平位移,地表沉降量呈抛物线变化并随着上部荷载和桩距的增加而同幅度增加,地表沉降范围只与基坑的开挖深度、嵌固深度以及穿越土层的内摩擦角有关:土钉的横向间距对支护结构的沉降变形影响很小,可以忽略.结论 上部荷载和桩的计算参数对支护结构的变形影响明显,桩顶地表沉降取决于桩顶和桩底水平位移.