基于三维非连续变形分析的巨石崩塌运动研究

巨石作为一种大体积、大质量的滚石，其崩塌失稳及高速、高能远程运动往往导致沿途建筑物和交通线路的毁灭性灾难。以西藏自治区G318国道K4580典型滑坡为工程背景，基于三维非连续变形分析（three-dimensional discontinuous deformation analysis，简称3D-DDA）方法研究巨石崩塌失稳及运动全过程的特征与现象。分别建立该边坡未滑坡、浅层滑坡后和深层滑坡后3种坡形的巨石崩塌3D-DDA数值模型。采用滚石运动横向偏移经验模型，验证3D-DDA巨石运动模拟的准确性。在此基础上，分析巨石崩塌失稳机制及破坏后沿3种不同坡形边坡的运动轨迹和动能演进等运动特征。结果表明，3D-DDA能够有效模拟巨石崩塌失稳、运动发展、剧烈冲击碰撞直至最终静止等整个动力学过程。巨石崩塌表现为滑动→倾倒?滑动→倾倒→翻转?下落的失稳模式转换；巨石运动表现为碰撞、弹跳、飞跃、滚动、滑动等多种运动形式以及横向偏移、侧向偏转等三维空间运动特征，经过道路并与高架桥发生碰撞，引发巨石灾害。不同坡面几何特征下的巨石运动偏移量、弹跳高度、运动至坡底碰撞时间、最终稳定时间等均随着未滑坡、浅层滑坡后、深层滑坡后3种坡形变化而减小。通过3D-DDA巨石崩塌运动分析，预测巨石运动全过程、影响范围、冲击能量、停积位置等，可为巨石防灾减灾对策或措施制定提供依据。

Study on collapse and movement of a boulder based on 3D discontinuous deformation analysis

As a kind of rolling stone with large volume and mass, collapse, instability and long-distance movement with high-speed and high-energy for a rock boulder often lead to destructive disasters of the buildings and traffic lines along the runout pathway. The K4580 typical landslide along the G318 national road in Tibet Autonomous Region was taken as the engineering background, the characteristics and phenomena of the entire process of the collapse, instability and movement of the rock boulder were studied using 3D discontinuous deformation analysis (3D-DDA) method. The 3D-DDA numerical models of the rock boulder collapse were built for three slope shapes: slope shape without landslide, slope shape with shallow landslide, and slop shape after deep landslide. The accuracy of the 3D-DDA simulation results for the boulder movement was then verified based on an empirical model of transverse offset for the block movement. In addition, the instability mechanism of the boulder collapse was investigated; the movement trajectory and kinetic energy evolution were analyzed for the three slope shapes after failure. The results show that the 3D-DDA has the capacity to effectively simulate the whole dynamic process of the boulder collapse and instability, movement development, violent impact, collision, and terminate stages. The boulder collapse presents an instability mode that including the mode transformation of sliding→toppling-sliding→toppling→overturning-falling. The rock boulder movement is manifested by various movement forms such as collision, bouncing, flying, rolling and sliding, as well as 3D spatial movement characteristics such as transverse offset and lateral deflection. The boulder disaster may be induced once the rock boulder passing through the road and colliding with the viaduct. Under different slope geometric shapes from no landslide, to shallow landslide, and to deep landslide, the main factors all decrease as the slope shape changes such as the movement deviation, bouncing height, colliding time to the slope bottom, and final stability time of the boulder. Through the 3D-DDA analysis of the collapse and movement of the boulder, the whole movement process, influence range, impact energy, and terminate location of the boulder can be then predicted, which can provide a reference for the boulder disaster prevention and mitigation and measurement policy.