Analysis of stability and kinematics of the dangerous rock mass in Zhangjiagou, Baoxing, Sichuan Province
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摘要: 张家沟危岩体于“6·1”芦山地震后被发现,稳定性差,严重威胁下方居民生命财产安全。基于稳定性计算及离散元数值分析方法对危岩体进行评价,选取稳定性最差的地震工况进行运动学分析,在上述研究基础上结合解析解与数值解成果设计相应防护措施。主要结论有:(1)张家沟危岩体结构破碎,发育顺坡向控制性结构面,破坏模式为滑移式;(2)稳定性计算与数值模拟结果皆表明张家沟危岩体在天然、暴雨、地震工况下均会失稳,其中地震工况下运动距离最长;(3)地震工况下危岩体的破坏模式为震裂—滑移式,运动过程中块石以滑移为主,跳高较小,同时坡面形态显著影响着落石运动特征;(4)落石间相互碰撞挤压会改变其运动特征及冲击动能大小,在一定程度上可增加其致灾范围。成果可为类似灾害防治提供参考。Abstract: After the “6·1” Lushan earthquake, unstable rock mass was discovered in Zhangjiagou, posing a severe threat to the safety of the residents and their property below. The dangerous rock mass was evaluated using stability calculation and the discrete element numerical analysis method, and the seismic condition with the highest threat level was selected for kinematic analysis. Based on this research, a combination of analytical solution and numerical solution was used to design corresponding protective measures. The main conclusions are as follows : (1) The structure of the unstable rock mass in Zhangjiagou is broken, and a controlling structural plane is developed along the slope. (2) The stability calculations and numerical simulations show that the Zhangjiagou unstable rock mass will become unstable under natural, rainstorm and seismic conditions, with the longest movement distance occurring during an earthquake. (3) The failure mode of the dangerous rock mass under seismic conditions is a shatter-slip type, where the rock mainly slips during movement, and the jump height is small. Additionally, the slope shape significantly affects the characteristics of rockfall movement. (4) The collision and extrusion between rockfalls can change their motion characteristics and impact kinetic energy, potentially increasing the scope of the disaster. The research results can provide a reference for similar disaster prevention and control efforts.
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表 1 岩体力学基本参数取值(天然)
Table 1. Fundamental mechanical parameters of rock mass (natural)
岩性 密度/(kg/m3) 节理刚度/(MPa) 内摩擦角/(°) 粘聚力/(MPa) 花岗岩 2750 47.5 11.2 基岩 2960 58.2 15.7 L1 2.2 30.5 0.8 L2 2.2 24.9 0.6 L3 2.2 25.3 0.7 表 2 稳定性计算参数选取
Table 2. Selection of calculation parameters for stability analysis
计算
工况重度
(Kn/m3)后缘陡倾裂隙
深度h(m)裂隙或滑面充水
高度hw(m)滑面长度
l(m)裂隙水压力
V(Kn/m)软弱结构面
倾角$ \theta $ ( °)地震水平
系数ζe结构面综合
粘聚力$ c $ (Mpa)结构面综合
内摩擦角(°)天然 26.95 6.68 1.96 25.32 19.2 45 0 0.65 31 暴雨 27.45 6.68 2.25 25.32 25.3 45 0 0.61 27 地震 26.95 6.68 1.96 25.32 19.2 45 0.16 0.65 31 表 3 稳定性计算结果
Table 3. Stability analysis calculation results
计算工况 破坏模式 稳定性系数k 稳定状态 天然 滑移式 1.18 欠稳定 暴雨 滑移式 1.00 欠稳定 地震 滑移式 0.93 欠稳定 -
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