纤维地聚物改良粗粒填料及其冻胀效应与动力特性研究

The frost heave performance of coarse-grained soil increases with the increase of fine grains and moisture. Thus, the key to prevent frost damage of high-speed railway subgrade in cold region is to control or eliminate the content of fine grains and moisture. By proposing a stable activation design for geopolymer at normal temperature and in weak alkaline environment, this project aims to improve the strength, compactness, impermeability, and frost heave resistance of the coarse-grained soil by adding fiber and geopolymer into it. The project will explore the feasible reinforcement parameters by analyzing the relationship between the physical-mechanical indexes and the component proportion of the coarse-grained soil. The reinforcement parameters will be further optimized according to the principles of frost deformation and solidification effect on fine grains by evaluating the frost heave performance and microstructure of the reinforced coarse-grained soil under freezing and thawing condition. The frost heave deformation prediction model of the reinforced coarse-grained soil will also be discussed. The dynamic test and the numerical simulation of the reinforced coarse-grained soil under multiple freeze-thaw action and low temperature will be launched. The control standards of design parameters will be summarized by taking an acceptable cumulative deformation as the threshold value. This project will not only solve the problem of frost heave problem of coarse-grained soil and provide the scientific basis for the design of high-speed railway subgrade fillers in cold region, but also can broaden the graduation of the coarse-grained soil within an allowable frost heave rate and offer technical support for the propulsion of national and international strategies.

粗粒填料冻胀效应随细粒含量和含水率的增加而增强，如何有效控制填料细粒含量和含水率是预防寒区高铁路基发生冻害的关键。本项目拟以常温弱碱稳定激发地聚物的工艺设计为基础，进行掺合纤维和地聚物的粗粒填料无机改良，以提高填料强度、密实性、抗渗性和抗冻胀性能。项目将先对不同组分配比下的改良粗粒填料的基本物理力学指标进行分析，找寻可行的改良设计参数。然后通过对冻融条件下改良粗粒填料的冻胀效应和细观结构分析，以冻胀变形和纤维地聚物对细粒的固化效果评价为准则来优化改良设计参数，并探讨适用于改良粗粒填料的冻胀变形预测模型。最后，再通过改良粗粒填料动力特性试验与数值模拟研究，以可接受的累积变形量为阈值，归纳粗粒填料改良的设计参数控制标准。项目研究成果不仅能解决粗粒填料冻胀问题，为寒区高铁路基填料设计提供科学依据，亦可在冻胀率允许范围内拓宽填料级配要求，为国家和国际战略顺利推进提供技术支撑。

针对地聚物胶结粗粒填料物质结构特点，在考虑其胶结程度和细观结构特征基础上，开展了地聚物常温弱碱激发与粗粒填料改良试验研究、改良粗粒填料渗透性能试验研究、地聚物改良粗粒填料冻损效应试验研究、以及纤维地聚物改良粗粒填料动力特性试验研究,主要包括：对偏高岭土基地聚物改良土开展不同配比下的强度特性及扫描电镜试验，探讨了地聚物改良土最佳配比设计，分析了地聚物材料组分对改良土力学特性及固化效果的影响；以偏高岭土为前驱体、生石灰和硅酸钠为碱激发材料制备地聚物，研究了地聚物理想材料配比设计，探讨了玄武岩纤维掺量与长度对地聚物改良土性能的影响，并综合评价了地聚物、纤维对土体的固化效果；通过大型动三轴试验研究了岩块含量和围压对泥质、地聚物胶结粗粒填料动力特性的影响，探讨了动剪切模量、阻尼比经验预测公式；采用随机块体理论构建了粗粒填料随机结构模型，开展了粗粒填料随机结构极限破坏分析，探讨了结构效应对粗粒填料变形破坏规律的影响；通过室内渗透试验和数值模拟，研究了块石含量、水泥偏高岭土掺量、最大粒径以及渗压对水泥偏高岭土复合稳定粗粒填料抗渗性能的影响规律，并归纳了其渗透系数经验预测关系；围绕地聚物胶结粗粒填料冻融损伤劣化问题，开展了不同级配、压实度、冻融循环次数下的冻融循环试验，分析上述因素对其冻融损伤特征的影响，并归纳了地聚物胶结粗粒填料的冻融损伤演化模型；通过开展纤维地聚物改良粗粒填料单轴抗压强度和循环加卸载试验研究，分析了块石含量、应力水平、加载次数等对改良粗粒填料抗压强度和变形破坏的影响，剖析了纤维地聚物改良粗粒土的累积塑性变形演化规律，并归纳了考虑细观结构特征和应力水平的累积塑性变形预测模型。研究成果可为土体固化提供新方法、为交通路基填料设计及变形控制提供新的解决方案与参考依据，同时也可为纤维地聚物改良粗粒填料在寒区高铁路基工程中的应用与推广提供理论与技术参考。