基于透明土试验和离散元分析的内管涌细观耦合机理及预测模型研究

With the rapid development of hydropower construction in China, the fluid-solid coupling mechanism of the suffusion in the deep-covering foundation or the high dam filling area is the key scientific problem to affect the dam safety. Compared with the traditional piping, the suffusion is imperceptible and harmful, so it is of great scientific significance to study the mechanism and forecast the potential disaster. First of all, in order to investigate the main controlling factors of the suffusion and to reveal the formation and development mechanism of the the suffusion from the microscopic scale, according to the nature of suffusion, series model tests of the suffusion are carried out through the integration of transparent soil experimental technique, PLIF and tracer method; Secondly, relying on the statistical information of the images processing tests, the three-dimensional discrete model is reconstructed and the pore scale coupling analysis platform is developed, the evolution trend of stress transfer network is studied, the frequency of fine particle loss, coordination number and contact force frequency are used to characterize the stress reduction factor, the role of coarse and fine materials in stress transmission under unsteady seepage is cleared, smoothly, the connection of force acting on fine particles and suffusion is revealed;Finally, by means of the mixture theory and based on the principle of conservation of mass and momentum, the mesoscopic fluid-solid coupling hydromechanical model of suffusion covering all the main factors is constructed, which can real-time predict the occurring during suffusion processes, the research results can provide scientific basis for high dam construction and safety maintenance.

我国水电建设快速发展，深厚覆盖层地基或高坝填筑区侵蚀型内管涌流固耦合机理是影响大坝安全的关键科学问题。相较于传统管涌，侵蚀型内管涌隐蔽性强、危害性大，探讨其发生机理，对潜在灾害进行预报，具有重要科学意义。本项目首先针对内管涌隐蔽性特征，通过融合透明土技术、激光诱发荧光显像技术及粒子示踪法开展系列内管涌模型试验，探讨内管涌主控因素，从细观尺度揭示内管涌发生发展机理；其次，依托试验显像统计信息重构三维离散模型，开发孔隙尺度耦合分析平台，研究应力传递网络演变趋势，依托细粒流失量、配位数及接触力频率表征应力折减系数，明确非稳定渗透作用下粗细料在应力传递中所扮演的角色，揭示细料受力与内管涌内在关联；最后，引入混合物理论，基于各组份质量、动量守恒原理，建立涵盖各主导因素的内管涌细观流固耦合流体力学分析模型，该模型能够实时预报各因素下内管涌的时空发展过程，研究成果可为高坝施工和安全维护提供科学依据。

提出一种基于透明土技术、颗粒流模拟联合开展该细观机理研究的方法，并从颗粒间接触力链的细观角度分析颗粒摩擦系数、颗粒级配和细料含量对管涌发生、发展的影响。首先结合PLIF（平面激光诱导荧光技术）与透明土技术自行设计可视化模型试验平台，其次基于MRI（磁共振成像）技术，借助Avzio软件实现对透明土样二维切片的三维重构，然后将重构模型导入PFC3D中并进行相同条件下的颗粒流模拟，通过比对模型试验与数值模拟结果，验证本方法开展管涌细观机理研究的可靠性，最后进行重构模型在不同颗粒摩擦系数、颗粒级配和细料含量条件下的数值模拟，并从力链角度论述各组试验规律。相关研究可为管涌细观机理研究提供一种置信度高、可行性好的新途径。