高聚物胶结刚性透水碎石桩复合地基承载机理与计算方法研究

With the development of railway and highway construction in China, one of the key technologies in embankment construction is to control the settlement and to reduce the consolidation period. In order to have both the high bearing capacity as rigid pile and the high water permeability as stone column, a new type of polymer cemented stone permeable rigid pile. The loading mechanism and bearing capacity of the polymer cemented stone pile are not been studied. The main properties of polymer cemented stone applied to pile will be conducted using laboratory tests, and the shear resistance and permeability will be analyzed. Based on the laboratory static load test on the single pile, the loading transfer mechanism and failure mode under the vertical loads will be studied, and the calculation methods of pile bearing capacity under the different failure modes will be proposed. The model test of polymer cemented stone pile composite foundation under embankment will be conducted as well, the performance of pile-soil interaction during embankment filling will be discussed, and the combined effects of pile reinforcement and accelerating drainage on foundation soils are analyzed. Furthermore, the analytic model of embankment-cushion-composite foundation considering the pile-soil interaction will be founded, the analytic solution will be obtained through the continuity equation of pile-soil and the boundary condition of displacement and pore water pressure, and the consolidation theory of the polymer cemented stone pile composite foundation will be proposed.

我国铁路、公路等交通基础设施持续迅猛发展，控制地基沉降、缩短沉降时间是路基建设中的关键技术之一。刚性桩的高承载力和散体桩的透水性，均有利于路基沉降控制，但两者很难兼顾。为了同时达到刚性桩的承载力和散体桩的透水性的综合效果，一种新的地基处理方法被提出——高聚物胶结刚性透水碎石桩。目前关于该碎石桩复合地基加固机理与承载特性的研究尚属空白。本课题采用室内试验手段对高聚物胶结碎石多孔材料强度与透水特性开展研究；通过室内静载试验，研究竖向荷载下刚性透水碎石桩荷载传递机理与破坏模式，建立不同破坏模式下桩体承载力计算方法；开展路堤下刚性透水碎石桩复合地基模型试验，揭示路堤填筑过程中刚性透水桩应力集中和加速排水的联合加固机理；进而建立考虑桩土相互作用的路堤-垫层-复合地基计算分析模型，通过桩土连续方程、位移与孔压等边界条件，求得复合地基固结沉降解析解或半解析解，建立复合地基固结沉降计算方法。

控制沉降是土石填筑工程中的核心工作之一，特别是工后沉降的控制更关乎工程的安全与良好运营。针对目前碎石桩复合地基沉降量大和刚性桩复合地基固结稳定周期长的不足，本文提出了一种兼顾刚性桩和碎石桩优点的刚性透水桩——高聚物-碎石桩复合地基，桩身由高聚物胶结碎石多孔材料形成，高聚物材料的加入使得碎石粘连呈具有一定刚度的整体，同时有保留碎石多孔透水特性。本文通过室内试验、数值模拟和理论分析等方法对高聚物胶结碎石多孔材料的物理力学特性和高聚物-碎石刚性桩复合地基的承载机制进行了系统研究。阐明了高聚物胶结多孔材料强度与透水特性，揭示了高聚物胶结碎石的增强机理与材料破坏机制，探究了配合比、地基围压、碎石粒径等特性对多孔材料强度的影响规律，明晰了渗透过程中水中土颗粒对多孔材料的堵塞机制与特性，确定了高聚物胶结刚性透水碎石桩的优化材料配合比。揭示了复合地基中高聚物-碎石桩应力集中和加速地基土排水的联合加固机制，阐明了桩体排水作用对减小地基工后沉降、快速消散超静孔压、提高堤身稳定、降低堤身内等沉面高度的显著作用，明确了高聚物-碎石桩复合地基适用于堤身快速填筑等工程应用特点，探究了桩型、桩径、桩间距以及桩身强度等设计参数对高聚物-碎石桩复合地基荷载传递的影响规律。基于高聚物-碎石桩与地基土的共同作用承载特点，分别采用填土单元受力平衡分析和弹性薄板大挠度理论研究了填土拱效应和垫层刚性承台效应，提出了求解填土等沉面、桩土应力以及桩土差异沉降的计算方法，并根据高聚物-碎石桩与地基土不等应变的共同作用特点，通过力学平衡和应变条件等分析，建立了刚性透水桩复合地基固结分析的控制方程，给出了特定条件下地基土超静孔压和固结度的解。