滚石坡面碰撞的破裂机理及其对运动特征的影响研究

Fragmentation upon impact is a common phenomenon during the rock falling downwards along the slope and results in a significant influence on the subsequent rockfall trajectory. Due to lack of systematic research and less corresponding knowledge about the mechanism of rock fragmentation, the existing rockfall trajectory model commonly does not account for the effects caused by rock fragmentation that makes the predicted results often quite different from the actual conditions for different specific site. To date, the present scientific understanding about fragmentation of rockfall cannot meet the practical requirement for disaster prevention. The proposed project intends to carry out research on fragmentation mechanism of rockfall upon impact with slope and its effects on subsequent trajectory characteristics. By using field investigation, in-situ test, laboratory model test, numerical simulations and theoretical analysis, the relationship between rockfall fragmentation and the complicated influence factors, such as slope mechanical properties and roughness, rock strength and stiffness, rock size and shape, fracture characteristics, velocity and incidence angle before impact, and so on, will be comprehensively studied. The effects of rock fragmentation upon the rockfall velocity change, mass loss and kinetic energy transfer will be investigated. Accordingly, the methodology to quantitatively evaluate occurrence of fragmentation and the procedure to perform uncertainty analysis of rockfall fragmentation will be established. The sensitivity of rockfall fragmentation to the major influence factors will be investigated and the rational values and their variability for velocity, mass, kinetic energy and restitution coefficients will be recommended. The expected results of this research will provide scientific supports for modifying the existing rockfall trajectory model, selecting proper parameters and evaluating the computational results and also will present theoretical references for accurately predicting rockfall hazard zone and correctly designing the protective measures.

碰撞破裂是滚石坡面运动中的常见现象，对滚石运动轨迹产生巨大影响。由于缺乏深入的研究和系统的成果，已有的滚石运动计算方法不考虑碰撞破裂的影响，是造成预测结果与实际情况差别较大的重要原因，有关科学认识已不能满足滚石灾害的防治需要。本项目围绕滚石坡面碰撞的破裂机理及其对运动特征的影响展开研究，通过现场调查、室内外试验、数值模拟和理论分析等方法，全面分析坡面力学特性、坡面粗糙度、滚石强度和刚度、大小和形状、裂隙发育情况、运动速度、入射角等因素与滚石碰撞破裂的相关关系；探求碰撞破裂对滚石速度、能量、质量的影响；建立滚石碰撞破裂的评价方法和不确定性分析方法。获得碰撞破裂的参数敏感性规律以及碰撞后的速度、质量、能量、碰撞恢复系数等参数的取值建议和变异规律。为滚石运动计算方法中计算模型修正、参数取值、计算结果评价等提供科学依据；为合理预测滚石灾害的威胁区域和避让范围，制定经济有效的防护措施提供理论参考。

滚石灾害是山区常见的地质灾害，具有突发性、破坏性、不可预见性。滚石坡面碰撞是滚石运动中最复杂的问题，碰撞破裂对滚石运动轨迹产生巨大影响。由于缺乏深入的研究和系统的成果，已有的滚石运动计算方法不考虑碰撞破裂的影响，是造成预测结果与实际情况差别较大的重要原因。.本项目围绕滚石坡面碰撞的破裂机理及其对运动特征的影响开展研究，通过现场调查、室内试验、数值模拟等方法，研究了滚石力学性质、大小、碰撞速度、坡度等因素与滚石碰撞破裂的相关关系，探讨了滚石坡面碰撞对运动特征的影响规律。.主要成果包括：（1）开发了一套滚石碰撞试验系统，为研究多因素耦合作用下滚石碰撞破裂机理和运动特征提供了试验设备；（2）提出了采用高温加热处理制备滚石试样的方法，获得了岩石密度、纵波波速、弹性模量、单轴抗压强度、劈拉强度等力学性质与加热温度的相关关系，为获取不同性质岩石试样提供了新的思路。（3）室内试验和数值模拟的结果表明，滚石碰撞破裂主要受撞击速度和滚石力学性质控制。滚石坡面碰撞破裂与否与碰撞速度密切相关，存在发生破裂的速度阈值。碰撞速度小于该阈值滚石不会破裂，大于该阈值时，随着撞击速度的增加，滚石碰撞破碎程度增加。此外，力学性质对滚石碰撞破裂影响很大，滚石的力学性质越差，滚石的碰撞破裂法向速度阈值越小，滚石越易破裂，相同碰撞速度下，滚石破碎程度越严重；（4）坡面碰撞破裂与滚石运动特征具有相关性。碰撞速度、滚石大小、力学性质对滚石碰撞恢复系数影响较小。坡面角度对滚石碰撞恢复系数影响很大，随着坡角增加，滚石碰撞恢复系数逐渐增加。现有计算忽略坡度对碰撞恢复系数的影响缺乏合理性。此外，碰撞破裂将导致滚石碰撞恢复系数下降，不考虑碰撞破裂影响将导致滚石计算偏于保守。.上述成果为滚石运动计算中模型修正、参数取值、结果评价等提供参考，为合理预测滚石灾害的影响范围，制定有效的防护措施提供依据。