水-荷共同作用下开级配碎石透水基层颗粒接触弱化及组构演变机制

The structural characteristic and working mechanism of the Open Graded Crushed Stone (OGCS) permeable base are different from the dense graded crushed stone base. It is difficult to accurately interpret the accumulated deformation of the OGCS with traditional theory of the internal erosion of fine granules under dynamic pore hydraulic pressure. This project is proposed to study the mechanism of granules contact weakening and its fabric evolution of the OGCS permeable base course under water-load coupling effect. The aggregate fretting graphs of running condition and material response under fretting wear are proposed to be developed with results of the fretting wear experiment considering the effect of water between contact faces. These fretting graphs are applied to study the fretting operation mechanism and rule of granules wearing for OGCS in service, and reveal the mechanism of formation of wear particle between aggregate contact faces. This project proposes a particle contact model including the microscopic surface texture property based on the theory of hydrodynamic lubrication, boundary lubrication, and rolling lubrication. The proposed particle model is used to investigate the effects of mixed lubrication and fluid wrapped wearing particles rolling-sliding between two aggregate contact faces, and to demonstrate the mechanism of microscopic contact weakening among aggregates under water-load coupling effect. This project is also proposed to investigate the mesoscopic time variant characteristics of topological structure of contact force chains among aggregates and the geometric fabric of aggregates, and elaborate the mechanism of accumulated deformation of the OGCS permeable base in service through numerical analysis of mesoscopic mechanical property and utilization of a laboratory mesoscopic particle migration small-scale model experiment on the OGCS permeable base. It is anticipated that this study provide theoretical foundation for optimized design of the OGCS permeable base for permeable pavements in the sponge city.

开级配碎石透水基层结构特性及工作机制与密级配碎石基层存在差异，采用传统动孔隙水压驱动细颗粒流失理论不能准确解释开级配碎石累积变形问题。本项目拟开展水-荷共同作用下开级配碎石透水基层颗粒接触弱化及组构演变机制研究。开展考虑接触面间水作用的颗粒微动磨损试验，刻画集料微动磨损运行工况和材料响应微动图，研究不同服役阶段开级配碎石颗粒微动运行机制及磨损规律，揭示集料颗粒接触面间磨粒形成机理；基于流体润滑、边界润滑及滚动润滑理论，构建考虑集料微观面理构造特性的颗粒接触模型，研究集料接触面间混合润滑效应及流体包裹磨粒滚滑效应，揭示水-荷共同作用下集料颗粒微观接触弱化机制；通过开级配碎石透水基层细观力学特性数值分析，结合室内细观颗粒迁移小模型试验，研究集料颗粒间细观接触力链拓扑结构及几何组构时变特性，阐释服役期开级配碎石透水基层累积变形机理。研究成果可为海绵城市长寿命透水路面基层优化设计提供理论基础。

大空隙率的结构特点及潮湿有水的工作环境，致使透水路面用开级配碎石透水基层服役过程中容易出现累积变形过大问题，但其结构特性及工作机制不同于普通密级配碎石基层，采用传统动孔隙水压驱动细颗粒流失理论难以准确解释其累积变形问题。因此，本项目开展了水-荷共同作用下开级配碎石透水基层颗粒接触弱化及组构演变机制研究。首先，提出了基于频谱理论的碎石微观表/界面形貌构造水平及分布特性定量表征方法，研制了开级配碎石集料微观表/界面摩擦磨损试验台，依次开展了15种主要造岩矿物及15种工程常见岩石在有/无水环境下的表/界面微观摩擦磨损试验研究，结果表明：造岩矿物及岩石表/界面动摩擦系数均呈先增大后保持稳定的时程演变趋势，表/界面32μm和2μm波长处的微观构造水平对集料颗粒间摩擦性能影响最大，正长岩、角闪石、燧石、辉石、钾长岩、磁铁矿、橄榄石这7种造岩矿物的微观摩擦磨损性能优于其它造岩矿物，水环境的存在会不同程度地降低集料颗粒间微观摩擦系数及磨损程度，进而揭示了服役过程中开级配碎石透水基层变形产生微观机理；然后，提出了基于多视角几何原理及尺度不变特征变换算法的碎石颗粒三维数值建模方法，开展了荷载作用下具有不同围压、级配、颗粒间摩擦系数及公称最大粒径的开级配碎石颗粒间细观力学特性、迁移行为及组构时程演变规律研究，揭示了服役过程中开级配碎石透水基层变形发展细观机制；最后，构建了水-荷共同作用下开级配碎石透水基层室内模型试验，提出了基于结构融合深度学习的颗粒迁移行为追踪测试方法，依次研究了外荷载大小、级配、含水状态及压实状态对开级配碎石透水基层表面宏观形变和内部细观颗粒迁移位移场、速度场及自旋角度场时程演变的影响规律，揭示了服役过程中开级配碎石透水基层宏观累积变形演变机理。本研究积极响应国家生态文明建设及绿色发展重大战略需求，研究成果为长寿命开级配碎石透水路面基层优化设计提供了理论借鉴。