预应力加固强化铁路路基的机理与设计理论研究

Subgrade accounts for more than 70% of traditional and heavy hual railways. Most of subgrade (embankment) works under conditions of no lateral constraint and low confining pressure, resulting in many problems during railway operation. Motivated by theses inherent causes of subgrade problems, this research program aims to develop a new structure form of subgrade named Prestressed Subgrade Structure (PSS), which is designed to increase the confining pressure of subgrade soil and to restrict the slope of subgrade. The research work would be conducted as follows, (1) combining full scale model test, numerical simulation and theoretical analysis, it would be revealed that the spatial distribution of principle stress on the top and side surfaces of subgrade under self-weight and rolling compaction, and the mechanism of formation of incipient tensile cracks on these surfaces, which will provide a scientific basis for the application of lateral prestress in subgrade. (2) Static and dynamic triaxial tests are planned to perform on typical fills of subgrade under conditions of varying confining pressure, and the mechanism of increasing confining pressure on improving mechanical behavior of subgrade would be demonstrated, moreover, the characterization indexes of mechanical behavior as well as the parameters in constitutive relation of the subgrade fills will be determined. (3) By laboratory test and theoretical development, this research attempts to explore the horizontal diffusion law of prestress in subgrade and to propose a corresponding calculation method. (4) Full scale model test with PSS and numerical simulation will be performed to demonstrate the interaction between PSS and subgrade soil, and to reveal the mechanism of PSS on improving the performance of subgrade. The final objective of this research is to develop a new subgrade reinforcement method (using PSS) as well as to form its preliminary analysis theory.

普通铁路和重载铁路路基占线路长度比重大（超过70%）。绝大多数路基（路堤）侧向无约束、围压很低，这是路基易产生病害的重要 “源头”。对此提出既能增加路基土围压又能强制约束其边坡的预应力路基新结构，并开展如下研究：⑴通过路基足尺模型碾压试验、数值计算及理论分析，揭示自重和施工碾压作用下的路基顶面及边坡表层主应力空间分布规律，以及对其表面（层）初始张拉裂缝的形成及影响，为设置水平预压应力提供科学依据；⑵对典型路基填料开展一系列变围压下的静、动三轴试验，揭示提高围压即预压应力对改善路基填料力学性质的机理，并获得路基填料力学性能特征指标和本构关系参数；⑶通过试验测试和理论推导，探索所施加的侧向预压应力在路基中的横向传播、扩散规律及其计算方法；⑷开展预应力路基结构足尺模型试验和数值仿真分析，揭示预应力结构与路基土共同作用机制和提高路基结构性能的机理。形成一种新的强化路基方法并初步构建其分析理论。

路基占线路长度的比重一般都很大，往往超过70%。在线路结构物中路基是由散粒体经碾压形成的，虽然铁路和公路路基填筑都有严格的质量控制标准，但达到现行设计与施工标准的路基，使用中产生病害甚至滑垮的情况仍很常见，这与绝大多数路基无侧向约束、围压很低有密切关系。对此，本项目组创新性地提出了既能增加路基土围压又能强制约束其边坡的预应力路基新结构，并针对其预应力加固强化铁路路基的机理与设计分析方法开展了探索性研究，完成的主要研究内容及获得的重要成果如下：⑴通过数值计算和路基振动压实试验测试，研究了路堤初始应力分布状态，揭示了自重和填筑施工作用下的路基及边坡表层主应力空间分布规律，为设置水平预压应力提供科学依据；⑵对典型铁路路基填料开展一系列低、中、高围压下的静、动三轴试验，揭示提高围压即预压应力对改善路基填料力学性质的机理，并获得了路基填料力学性能特征指标和本构关系参数；⑶通过试验测试和理论推导，获得了侧向预压应力在路基中的横向传播、扩散规律及其计算方法；⑷开展预应力路基结构大比例静力模型试验和数值仿真分析，揭示了预应力结构与路基土共同作用机制和提高路基结构性能的机理。项目执行过程中，共发表相关学术论文37篇，其中SCI和EI检索33篇，获得国家专利3项。基于上述研究成果，形成了用预应力加固和强化路基的新方法，并基本构建起了其静力作用下的设计分析理论。