FORMATION CHARACTERISTICS AND KINEMATICS 3-D SIMULATION OF ROCKFALL EVOLVED FROM SHATTERED MOUNTAIN—CASE STUDY OF SANGUANMIAO VILLAGE ROCKFALL IN WENCHUAN COUNTY
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摘要: 三官庙村震裂山体位于汶川强震区,又于2018年7月20日和2019年8月22日发生了两次震后崩塌灾害,严重威胁坡脚居民生命财产安全。通过对震裂山体危岩现场地质调查、无人机航测和室内三维数值模拟,阐述了震裂山体-崩塌发生的成因机理和动力学过程,并对潜在危岩区的危险性进行了分析评价。研究结果认为,此类崩塌形成过程可划分为3个阶段:即潜在危岩体坡体早期构造及卸荷裂隙发育、震裂山体(危岩体)形成、崩塌失稳。崩塌源区岩体在岷江下切过程中形成卸荷裂隙,受“5·12”强震及其余震作用下形成震动拉裂缝,单薄山脊发生变形形成震裂山体,在雨季强降雨触发下发生崩塌。运用三维模拟软件RocPro3D模拟已发生崩塌块石堆积位置、优势运动路径,并与既有崩塌堆积区进行对比验证,综合得出岩土体表面特征参数。根据所得参数进一步模拟预测了危岩区可能发生崩塌的运动特征,对其优势运动路径、运动速度、运动能量和弹跳高度进行分析,得出崩塌危害影响范围和程度。论文的研究成果对强震区震裂山体灾害隐患点的减灾防灾工作具有重要的指导意义。Abstract: Sanguanmiao shattered mountain is located in Wenchuan earthquake area,where two post-earthquake rockfalls had occurred on July 20,2018 and August 22,2019,respectively. They caused considerable economic losses and threatened the safety of residents. Therefore,this paper performs a detailed analysis on study area by using field investigation of dangerous rocks in shattered mountains,unmanned aerial vehicle survey and three-dimensional numerical simulation,clarifying the mechanisms and kinematic processes of the rockfall evolved from shattered mountain. Meanwhile,the risk of potentially dangerous rock area has been assessed. The results suggest the following findings. The formation process of this type of rockfall could be divided into three stages,including early structure and unloading crack development of potentially dangerous rock slope,formation of shattered mountains(dangerous rock mass) and occurrence of post-earthquake rockfalls. Firstly,the rock masses in the source area formed unloading fissures during the incision of the Minjiang River,and then under the role of the "5.12" strong earthquake and aftershocks,tensile fissures formed and the ridge top deformed and shattered,forming shattered mountains. Eventually,heavy rainfall in the rainy season directly triggered the rockfalls. The three-dimensional simulation software RocPro3D is used to simulate the accumulation range and the dominant moving trajectory,which are compared and verified with the existing accumulation area,comprehensively obtain the rock and soil characteristic parameters,and further simulated and predicted the possibility of the dangerous rock area based on the validated parameters. The movement characteristics,dominant moving trajectory,moving velocity,energy and bounce height are analyzed to obtain the impact extent of the rockfall. The results can provide an insight into potential disasters reduction and prevention of shattered mountain failure in the strong earthquake area.
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Key words:
- Wenchuan Earthquake /
- Rockfall /
- Formation mechanism /
- Numerical simulation /
- RocPro3D
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表 1 不同危岩区内各危岩带岩体结构面特征
Table 1. Characteristics of rock mass structural plane in different dangerous rock zones
位置 结构面组数 结构面产状 Ⅰ号危岩区 ⅠW1危岩带 4 300°∠46°、331°∠82°、266°∠16°、209°∠68° ⅠW2危岩带 3 315°∠82°、156°∠60°、283°∠25° Ⅱ号危岩区 ⅡW1危岩带 5 328°∠36°、190°∠58°、137°∠86°、108°∠57°、230°∠46° ⅡW2危岩带 3 288°∠72°、210°∠70°、5°∠54° ⅡW3~5危岩带 5 274°∠60°、135°∠85°、70°∠57°、8°∠59°、350°∠42° ⅡW6危岩带 3 232°∠16°、239°∠48°、52°∠40° Ⅲ号危岩区 ⅢW1、3危岩带 4 304°∠78°、130°∠54°、298°∠22°、129°∠73° ⅢW4危岩带 3 233°∠60°、295°∠30°、129°∠73° ⅢW2、5危岩带 5 6°∠72°、288°∠72°、98°∠83°、295°∠30°、230°∠60° Ⅳ号危岩区 ⅣW1危岩带 4 290°∠70°、50°∠62°、112°∠88°、250°∠72° ⅣW2危岩带 3 260°∠84°、30°∠60°、15°∠13° ⅣW3危岩带 3 270°∠78°、86°∠74°、15°∠13° 表 2 各危岩区危岩体特征参数
Table 2. Characteristic parameters of dangerous rock mass in each dangerous rock area
危岩分区 块石密度/kg·m-3 形状 直径/m Ⅰ号危岩区 2600 球体 1.5 Ⅱ号危岩区 Ⅲ号危岩区 Ⅳ号危岩区 表 3 崩塌落石沿途岩土体表面特征参数
Table 3. Surface characteristic parameters of rock and soil along rockfall
参数 花岗闪长岩 崩坡积物 残坡积物 恢复系数 标准值Rn 0.75 0.65 0.45 正切值Rt 0.85 0.70 0.50 变化范围Δ_R/% 4 5 8 极限速度V_R(lim)/m·s-1 10 10 10 极限变化范围Δ_R(lim)/% 2 3 6 横向偏差 变化范围Δ_θh/(°) 20.0 17.5 15.0 极限速度V_θh(lim)/m·s-1 10 10 10 极限变化范围V_θh(lim)/(°) 10.0 8.5 7.5 竖向偏差 变化范围Δ_θv/(°) 2 2 2 极限速度V_θv(lim)/m·s-1 10 10 10 极限变化范围V_θv(lim)/(°) 4 4 4 摩擦系数 k值 0.40 0.75 0.80 变化范围Δ_k/% 12 15 15 极限速度V_k(lim)/m·s-1 10 10 10 极限变化范围Δ_k(lim)/% 10 10 10 转换参数 角度β_lim/(°)(锐角情况下) 2 3 4 角度β_lim/(°)(钝角情况下) 25 30 35 -
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