EPS轻质土-结构动力相互作用的宏细观机制和分析方法

EPS (Expanded Polystyrene) lightweight soil, which is usually mixed with EPS beads, cement, soil and water, is characterized by light-weight, high-strength, and certain-flexibility. How to optimize these characteristics of EPS lightweight soil is a difficult issue. In this study, EPS lightweight soil is assumed as a two-phase mixture constituted by EPS beads and the cemented soil. The static & dynamic triaxial tests, interface shear tests and micro-mechanical tests are conducted to study the cementation strength, the interface strength between EPS beads and the cemented soil, and the evolution feature of the microstructure subjected to the loadings. Based on the Particle Flow Code, the simulation method of the EPS lightweight soil is studied and the numerical tests are conducted. The three-strength action mechanism is reflected including the cementation strength, interface strength between EPS beads and the cemented soil, and the strength of EPS beads. The strength failure criterion is established and is further verified by the microscopic numerical simulation. Accordingly, the two-phase and three-strength controlling theory with regard to EPS lightweight soil is proposed. The pseudo-static test and Particle Flow Code are adopted to study the energy-dissipation characteristics of EPS lightweight soil in order to reveal the diversified energy-dissipation mechanism and eventually to establish an empirical model regarding the deformation and energy-dissipation of EPS lightweight soil. The pushover tests are conducted on the system constituted by EPS lightweight soil and cantilever retaining wall, based on which the formation mechanism of the failure plane is discussed. The simulation method of the inertia force effects of the EPS lightweight soil is studied, in which the energy-dissipation of EPS lightweight soil will be considered. Subsequently, a simplified seismic analysis method for the retaining wall is proposed, which can take into account the energy-dissipation characteristics of EPS lightweight soil. In addition, the construction method for the stress-strain skeleton curve and hysteresis loop is studied, which can consider the characteristics of the energy-dissipation ratio between EPS beads and the cemented soil. The two-phase dynamic constitutive model is put forward and the sensitivity of its parameters is analyzed. The numerical simulation method is developed to study the seismic stability of the retaining wall which is able to consider the energy-dissipation ratio between two phases. The numerical simulation on the seismic stability of the retaining wall under different initial boundary conditions is conducted, and is also compared and verified by shaking table tests. The interaction mechanism between EPS lightweight soil and the retaining wall is revealed. This will provide the theoretical principle and approach in the practical seismic design for EPS lightweight soil.

发挥EPS轻质土的轻、强、柔特性以达最优利用效益是一个难点问题。将EPS轻质土视为EPS颗粒和固化物组成的两相体，综合静动三轴、接触面剪切及细观力学试验，研究胶结强度、EPS-固化物接触面强度特征及细观结构受荷演变过程，研究EPS轻质土的颗粒流模拟方法并开展数值试验，建立强度破坏标准并提出两相三强度控制理论；开展伪静力试验并结合颗粒流模拟揭示EPS轻质土多元耗能机制，建立变形耗能经验模型；开展EPS轻质土-悬臂墙推覆试验，分析破坏面形成机制，研究考虑EPS轻质土耗能的惯性力效应模拟方法，提出挡墙抗震分析简化方法；研究考虑两相能耗比的应力应变骨干曲线和滞回圈构建方法，建立动力两相体本构模型并进行参数分析，发展EPS轻质土-挡墙地震稳定性数值模拟技术；开展不同初边值条件下挡墙地震稳定性数值模拟并以振动台试验对比验证，揭示EPS轻质土-挡墙动力相互作用机制，为工程抗震实践提供理论依据和方法。

为充分发挥EPS轻质土所具有的轻、强、柔等特性，从宏细观层面研究EPS轻质土-结构的相互作用机理以及分析方法。开展EPS轻质土室内三轴压缩试验研究其宏观力学特性，并开展颗粒流模拟分析两相体内部结构损伤机理及演变过程，建立细观结构演变过程与宏力学特性演化过程间的关系，揭示EPS混合土两相体的基本物理和力学特性及其演变过程；开展EPS材料与不同土体间接触面剪切特性的物理试验及颗粒离散元模拟，研究两相体相互作用机理，探究EPS轻质土细观裂缝、剪切带及接触力链的演化，给出强度破坏模式及标准；通过与陶粒土、砂土、水泥固化土、橡胶颗粒土对比研究EPS轻质土的变形耗能特性，引入颗粒破碎指标，建立其与破碎耗能间的关系；通过动三轴和共振柱试验，给出EPS轻质土两相耗能的应力应变骨干曲线，研究初始固结条件、配合比等对模量衰减和阻尼增长的经验模型及其机制，开展动力特性离散元数值模拟，研究细观力链与宏观力学性质的关系，验证本构模型合理性并进行参数分析；开展EPS轻质土-结构体系（挡墙、桥台、沉箱码头）的大、小振动台模型的对比试验，研究了EPS混合土回填挡墙结构体系的破坏模式及变形机理，揭示EPS轻质土-结构动力相互作用机制，给出了EPS轻质土挡墙动推力计算模式，验证了EPS轻质土-结构体系的抗震优越性；提出基于位移的回填EPS轻质土挡墙抗震性能简化分析方法，给出基于位移的土压力需求曲线与能力曲线联合估计方法用于其地震稳定性评价，为其工程抗震设计提供理论依据与支撑。在此基础上，研发了多种实用的试验仪器和设备，并开发了包括用于膨胀土地基处理、软土地基处理等在内的EPS混合土多途径应用技术。