【作者】 徐立新；

【导师】 陈云敏；

【作者基本信息】 浙江大学 ， 岩土工程， 2007， 博士

【摘要】 桩承式加筋路堤作为一种新型的地基处理技术，其具有可快速填筑施工，施工工期短，无须预压和二次开挖，能有效地控制地基的沉降和侧向变形，而造价与常规搅拌桩地基基本相当等突出优点，为建设在软弱地基上的路堤、堤坝、挡土墙、储油罐等提供了一种即经济又有效的解决方法，其应用范围和领域正在不断扩大，特别是需快速施工或者对沉降要求较严格的高速公路工程。但因其工作机理非常复杂，研究工作相对滞后，目前我国还没有相应的设计方法及规范，主要沿用常规复合地基理论和依靠经验进行设计，往往与实际有较大的出入，影响其应用的科学性，从而严重限制了它的应用。本文首先从由路堤填料、加筋垫层、桩及桩帽、桩间土层和下卧持力层组成的桩承式加筋路堤整体受力体系分析着手，分别建立路堤填料的土拱作用、加筋垫层的兜提作用、桩土之间的摩擦作用、桩端持力层的支撑作用的分析模型及其基本微分方程，并以各部分应力连续和应变协调的边界条件，得到整体的分析模型及其联立方程组，获得了桩土沉降、荷载分担比、加筋体拉力、等沉面高度、桩身轴力、桩侧摩阻力等的计算方法。运用MATLAB计算工具，编制软件求解联立方程组，并以窗口界面的形式，快速方便求解。其次，运用建立的分析模型及编制的软件，通过大量的计算，系统分析了桩承式加筋路堤的桩和桩间土沉降及其沉降差、路堤等沉面高度、桩体荷载分担比、加筋体的拉力、中性点位置、持力层等沉面深度等随各参数的变化规律，进一步探讨了桩承式加筋路堤各组成部分的相互作用的力学性状。然后，选取三个典型的高速公路桩承式加筋路堤，埋设应力和变形的观测仪器，进行现场原型试验，通过大量的现场观测，获得了沉降，荷载分担，桩身轴力等随填筑荷载及时间的变化规律；同时应用FLAG计算软件，对其中的二个典型试验路段进行数值分析，获得其沉降、荷载分担、水平加筋体的应力与变形、桩身轴力、桩侧摩阻力等计算结果。并将分析模型、现场试验、数值分析三者的结果进行了比较分析，验证了分析模型基本能够反映桩承式路堤真实的工作性状，其计算结果具有一定的可靠性和工程实用性。最后，从实际工程的设计角度出发，探讨了桩承式加筋路堤的设计思路及应用范围，并以分析模型的计算方法为基础，提出了桩承式加筋路堤的加筋垫层、桩帽、桩布置的设计方法以及沉降、承载力、整体稳定的计算方法，形成了一套较完善的桩承式加筋路堤的实用分析计算方法，部分成果已被纳入到交通部标准《公路软土路堤设计与施工技术指南》(报批稿)。更多还原

【Abstract】 Pile-supported reinforced embankment is a new type of ground improvement technology. It has some distinctive merits in rapid construction rate, short construction time, unnecessary of preloading and additional excavation, effective control of ground settlements and lateral displacements, and basically the same construction cost as conventional soil cement mixing piles, etc. It offers an economical and effective solving method for the construction of roads, dams, retaining walls, and oil silos on soft grounds. The extents and realm of its applications are increasingly expanding, particularly to the highway projects where the rapid construction is required and the settlement is seriously controlled. The working mechanism of the pile-supported reinforced embankment is very complicated, and hence the research works are lagged behind. Currently there is no design method and specification in our country. Its design depends mainly on the compound ground theory and the practical experiences, sometimes leading to inconsistent results with the reality. This has an influence on the scientific applications, and hence restricts its applications.This dissertation analyses the global force system of the pile-supported reinforced embankment, which is composed of filled materials, reinforced cushion, pile and pile cap, soils in-between piles, and soils underlying piles. The analyzing models and the governing equations were established for the soil arching effect of the filled materials, the uplifting effect of the reinforced cushion, the frictional effect of the pile-soil interaction, the supporting effect of the pile-end bearing layer. With the boundary conditions of stress continuity and strain compatibility, the global analyzing model and the simultaneous equation groups were obtained. Also obtained were the calculation methods for the pile-soil settlement, load sharing ratio, tension force of the reinforcement, elevation of equal settlement plane, axial force and skin friction of the piles, etc. MATLAB package was used to code a program in window form for rapidly and conveniently solving the simultaneous equations.By a large amount of computations with the established analyzing model and coded program, the parametric influences were systematically analysed for the pile-supported reinforced embankment, such as the settlements and settlement differences of the piles and the soils in-between piles, the elevation of the equal settlement plane of the embankment, the load sharing ratio of the piles, the tensionforce of the reinforcement, the location of the neutral point, and the depth of the equal settlement plane of the bearing layer, etc. Further investigated is the mechanical behavior of the interactions of the composed parts of the pile-supported reinforced embankment.Three typical sections of the pile-supported reinforced embankments of a highway were selected for the field tests with the stress and strain instruments buried. By a large number of field measurements, the variation patterns with the placed load and the observation time were obtained for the settlements, the load sharing, and the axial forces of the piles. Numerical analyses were also carried out for two typical tested sections using the FLAC software. Calculated results were obtained for the settlements, load sharing, the stresses and strains of the horizontal reinforcement, and the axial forces and skin frictions of the piles. Results from the analyzing model, the field tests and the numerical analyses were compared. It verifies that the analyzing model is capable of reflecting the real working behavior of the pile-supported reinforced embankment. The calculated results are reliable and applicable to the engineering practice.Finally, from the point view of the design of the practical engineering, the design routine and its application extents were investigated. The design methods were proposed for the reinforced cushion, the pile cap, and the pile layout of the pile-supported reinforced embankment. Also proposed were the calculation methods for the settlements, the bearing capacity and the global stability. These made up of a set of practical methods for the analyses and calculation of the pile-supported reinforced embankment. They have also been included into the Technical Guide of the Design and Construction of Roads on Soft Soils, which is a standard of the Ministry of Transportation.更多还原