基于颗粒接触性能演化的道砟承载机制研究

Ballast is a kind of gravel material, which has important application in the construction of railway track. Ballast would become degraded and fouled by the progressive accumulation of external impurities after a long period of service, which would weaken its bearing capacity. Geogrid is often used for the reinforcement of railway track and on the contrary, the bearing capacity would be enhanced. This project aims to solve the following two scientific problems: the micro-evolutionary disciplines of particle contact performances under the impact of geogrid reinforcement and the fouling; the macro bearing mechanism of fouled ballast. The following results would be obtained through this study:a numerical method which can be applied to both the fouling and geogrid reinforcement situation would be proposed; uncover the mechanical properties of ballast under different degree of fouling; uncover both the negative effect of contaminants and the positive effect of geogrid on ballast; establish the connection between the macro mechanical behaviors and the micro evolution of particle contact performances with dynamic triaxial test, and uncover the bearing mechanism of ballast. So it would provide theoretical support and technical guidance for railway construction.

道砟是一种碎石材料，在铁路轨道道床结构的建设中有着重要应用。在长期工作状态下道砟会发生磨损，受到外界杂质的污染，弱化道砟的承载性能；而土工格栅常被用于道床的加固，对道砟承载性能具有强化作用。本研究重点解决以下两个科学问题：污染及土工格栅影响下道砟散体细观接触性能演化规律；污染及土工格栅影响下道砟散体宏观承载机制。通过研究，可望得到以下结果：提出适用于污染弱化及土工格栅强化作用的道砟离散元数值计算方法；揭示道砟在不同污染程度下的力学性能变化规律；揭示污染物对道砟的弱化作用以及土工格栅对道砟的强化作用；结合动三轴试验，建立宏观上道砟承载性能变化与细观上颗粒运动场和接触力的分布演化之间的联系，从而揭示道砟的承载机制，为铁道建设提供理论支持与技术指导。

道砟是一种碎石材料，在铁路轨道道床结构的建设中有着重要应用。在长期工作状态下道砟会发生磨损，受到外界杂质的污染，弱化道砟的承载性能；而土工格栅常被用于道床的加固，对道砟承载性能具有强化作用。本研究重点解决以下两个科学问题：污染及土工格栅影响下道砟散体细观接触性能演化规律；污染及土工格栅影响下道砟散体宏观承载机制。本项目使用洛杉矶磨耗试验以及添加外界脏污的方式制备不同污染水平的道砟，通过冲击试验以及大型直剪试验研究污染物对土工格栅加筋道砟承载性能的弱化作用，然后，采用PFC3D离散元平台，对污染道砟的直剪试验进行了数值模拟，提出并验证了适用于污染弱化及土工格栅强化作用的道砟离散元数值计算模型，揭示了道砟在不同污染程度下的力学性能变化规律。最后，使用所提出的离散元数值模型进行了大型箱式试验模拟，从宏细观两个方面对比分析了试验数据以及模拟结果，从而揭示道砟的承载机制，为铁道建设提供理论支持与技术指导。