基于三维非连续变形分析的落石冲击动能损失机理研究

Calculation of impact force is crucial for the safety and economy of rockfall protection design. During the high-speed and dense-energy instant, the kinetic energy loss caused by impact is influenced by geometric, kinematic and other environmental factors. The basic action mechanism and influence rule remain ambiguous, which is imperative to be studied. 3D discontinuous deformation analysis (DDA) takes arbitrary shaped discrete blocks as basic elements and has a rigorous contact theory based on invasion algorithm, which shows advantage on handling large-displacement dynamic problems of complex hard rocks. But it is also limited by the precision of contact models in high-speed scenarios as well as the difficulty of determining relevant contact parameters. To promote the application of 3D DDA in simulating rock impacts, this research aims to acquire the calculation parameters through field tests. The quantitative relation between Schmidt hardness of field rock masses and dynamic coefficient of restitution is to be established through analytical, numerical methods, as well as field and laboratory tests. A novel contact model will be proposed based on local contact iteration, with the convergence criteria using dynamic rebound coefficient. The mechanism and influence factors of kinetic energy loss studied in the research will provide efficient technical and theoretical support for the design of rockfall protection.

落石冲击力计算，对边坡防护的安全和经济性至关重要。落石冲击属于高速、高能量复杂过程，其动能损失与岩体几何力学特征、运动状态及环境因素密切相关，损失机理和影响规律尚未被完全揭示，迫切需要对多变量的交叉作用机理开展深入研究。三维非连续变形分析（DDA）方法，采用任意形状的块体单元和基于拓扑几何侵入分析的接触模式判断，在复杂形状硬岩大位移动力学计算方面有着独特的优势，但也存在高动能条件下接触计算模型精度不高和参数获取困难的瓶颈，限制了在落石冲击模拟方面的应用。本课题综合运用现场测试、室内试验、理论分析和数值模拟等手段，分析现场岩体施密特硬度与动力回弹系数间的定量关系，建立通过现场测试获取三维DDA接触计算参数的方法。提出基于局部迭代的接触力计算模型，以及基于动力回弹系数的接触收敛准则。通过室内试验与数值模拟对比分析，揭示落石冲击过程动能损失机理及多因素影响规律，为落石防护设计提供理论和技术支持。

本项目的研究目标已经全部达成，包括通过三维非连续变形分析（DDA）方法的改进与程序开发，以数值模拟与室内外试验方式，综合模拟边坡落石冲击的动力学过程，分析现场实测参数与数值接触计算参数的相关规律，提出基于局部迭代的接触力计算方法，以及基于动力回弹系数的接触收敛准则，建立了一套能实用化的的三维非连续局部接触力计算模型及接触参数确定方法，提高了三维非连续变形分析方法在接触计算和参数选取方面的精度及适用性，使三维DDA方法能更高效、准确地解决落石等地质灾害动力计算问题，揭示并总结落石冲击过程动能损失机理及多因素影响规律，提高了落石防护工程设计分析方法的准确性。相关研究成果已经在川藏铁路易贡隧道和色季拉山隧道、四川峨汉高速大峡谷隧道、贵州崇遵扩容桐梓隧道等重点工程进行了示范性应用。项目发表了SCI检索论文11篇，EI检索论文4篇，授权国家发明专利2项，获得中国岩石力学与工程学会自然科学特等奖1项。