落石重复碰撞损伤累积及破碎特征研究

Rockfall is among the most frequent and unpredictable geological hazard. To ensure the security of people’s lives and property, simulating the trajectory of rockfall accurately to avoid the disaster of rockfall is quite significant. Currently, almost all the research work has ignored the degradation and fragmentation of rock blocks during the collisions of rockfall with slopes, and this kind of issue is really disadvantageous to the actual engineering. Hence, based on the theories of fragmentation of brittle particles under collision, damage mechanics and contact mechanics, this project focuses on the damage accumulation and fragmentation of rock blocks under repeated collisions, and aims at developing a highly-efficient simulating system to calculate the trajectory of rockfall. Firstly, the lab tests of rock spheres and irregular-shaped rock blocks under repeated collisions will be carried out, to have a deep understanding of the energy dissipation, damage accumulation, the critical conditions of breakage and the size distribution of fragment; then, the discrete element simulations of collisions of rock blocks will be conducted, based on the improved Particle Flow Code, to supplement the experimental data and reveal the microscopic mechanism of energy dissipation, damage and fragmentation of rock blocks; with the comprehensive understanding of collisions of rock blocks through indoor tests and discrete element simulations, a viscoelastic damage contact model, a model of breakage probability and a model of size distribution of fragments of rock blocks will be proposed; lastly, under the framework of discrete element modeling, considering the damage accumulation and fragmentation of rock blocks, a highly-efficient system simulating the trajectory of rockfall will be developed, to provide a strong technical support for the prevention of disaster of rockfall.

岩质边坡崩塌落石是最常见的地质灾害之一，准确模拟落石运动轨迹进而防治落石灾害，对保障人民生命财产安全具有重要意义。目前相关研究工作大多忽略了落石下落碰撞过程中的性质劣化及破碎，与工程实际存在较大差距。本项目以脆性颗粒碰撞破碎理论、损伤力学及接触力学为基础，研究落石重复碰撞损伤累积及破碎特征，开发落石运动轨迹快速分析系统。首先，开展球砾及不规则块石室内重复碰撞试验，研究块石碰撞的能量耗散、损伤累积、破碎条件及碎片的尺度分布特征；然后，基于改进的通用离散元分析平台开展块石碰撞数值模拟，补充室内试验数据，揭示块石碰撞能耗、损伤及破碎的细观机理；基于室内碰撞试验及离散元数值模拟结果，建立相应的块石碰撞粘弹性损伤接触模型、破碎概率模型和碎片尺度分布模型；最后，基于离散单元法的基本原理，考虑落石损伤累积和破碎特征，开发落石运动三维离散元快速分析系统，为有效防治边坡落石灾害提供强力支撑平台。

岩质边坡崩塌落石是最常见的地质灾害之一，准确模拟落石运动轨迹进而防治落石灾害，对保障人民生命财产安全具有重要意义。本项目以脆性颗粒碰撞破碎理论、损伤力学及接触力学为基础，研究落石重复碰撞损伤累积及破碎特征。研究内容包括碰撞过程中块石破碎前块石内部的能量耗散及损伤演化规律、块石碰撞破碎发生的临界条件和块石碰撞破碎后的碎片分布特征三个方面。本项目系统揭示了岩性、碰撞速度、尺寸、接触条件等各种复杂因素对岩石颗粒恢复系数的影响；切向恢复系数也存在显著尺寸效应和速度效应；碰撞角度越大，发生临界破碎的速度越小，破碎模式从劈裂张拉破坏逐渐转变为剪切破坏；岩石球砾尺寸越大，越容易发生破碎，碰撞次数增加，破碎概率显著增加，呈现明显的损伤劣化特征；开展了不同侧向约束条件下的球砾压缩破碎试验，揭示了球砾尺寸、配位数及侧向接触力大小对颗粒力位移曲线、破碎强度及破碎模式的影响；开展了大理岩球砾压缩破碎试验、准静态加卸载试验和动态循环加卸载试验，揭示了球砾强度的尺寸效应，加卸载试验结果阐明了球砾受载荷下的基本能耗特征及弹塑性变形规律；提出了一种粘弹性法向接触模型，提出了一种新的粘弹塑性法向接触模型，提出了一种新的弹塑性接触模型及循环加卸载经验接触模型，提出了一种新的重复碰撞条件下岩石颗粒破碎概率模型，提出了岩石球砾在重复碰撞条件下碎片尺寸分布模型；提出了一种三维随机clump单元方法，准确描述了岩石复杂的变形及强度特征；提出了一种有厚度的粘聚力单元FDEM数值模拟方法，提出了一种力学参数离散性的随机裂隙模拟方法，实现了岩石力学参数离散性的准确模拟，提出了一种具开度微裂隙的离散元模拟方法，提出了一种随机不规则几何外形的三维离散元数值试样建模方法；开展了岩石颗粒法向碰撞破碎的三维离散元模拟，开展了岩石颗粒斜向碰撞破碎的三维离散元模拟。