Collapse Mode and Mechanism of High Magmatite Rock Slope in Wenchuan Epicentral Area
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摘要: 汶川8.0级大地震触发了大量岩石边坡崩塌次生地质灾害, 不同岩性及结构的岩质高边坡, 强震作用下的破坏机理不同, 震中映秀岩浆岩高边坡在强震中破坏严重, 因此急需开展其破坏机理的研究.以震中映秀典型高边坡崩塌-虎嘴崩塌为研究对象, 在工程地质条件研究的基础上, 采用结构面统计模拟方法, 深入分析岩浆岩边坡的结构面组合特征, 通过赤平投影法初步确定了该类边坡的破坏模式: 由3组主控结构面相互贯通的双平面滑动.恢复老虎嘴岩质边坡在地震前的原始坡形, 采用2DUDEC再现地震作用下老虎嘴岩质高边坡的破坏过程, 得出在地震作用下的破坏规律: 老虎嘴边坡在地震作用下的渐进破坏过程主要表现为边坡前缘岩体首先破坏, 坡顶岩体沿着3组结构面的切割贯通面也产生拉裂破坏发生崩塌, 最终整个边坡溃塌.在重力和地震的双重作用下坡顶破坏呈现出抛射状.Abstract: Wenchuan earthquake of magnitude of 8.0 triggered a large amount of rock slope collapse. In Yingxiu, many high magmatite rock slopes collapsed when Wenchuan earthquake struck, which resulted in huge damage. So it is urgent to study the collapse mechanism. This study takes Laohuzui collapse, a typical high slope collapse located at Yingxiu, the Wenchuan earthquake epicenter, as the object of this research. The engineering geological condition was investigated and the physical and mechanical parameters of rockmass and structural plane was determined. With the stereographic projection method using the discontinuity network simulation results, the basic failure modes of the slope was obtained, which is dual-plane sliding mainly due to the interconnected three group joints. Re-establishing the Laohuzui high slope model before earthquake, the process of dynamic response on the rock slope under earthquake was simulated by using 2DUDEC, and the destruction and collapse mechanism was analyzed. The main conclusion is that the Laohuzui slope collapse is a progressive failure. At first, the tensile failure took place in the slope toe, then the slope top would be subject to tensile failure followed by the front surface failure along the cut-through plane by three group joints, which resulted in the whole slope collapse. The slinging failure took place at the slope top under the seismic and gravity action condition.
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图 5 地震波加速度谱和速度谱
a.东西向地震波0.1~10Hz滤波、线性基线校准后加速度谱；b.竖向地震波0.1~10Hz滤波、线性基线校准后速度谱
Fig. 5. Accelerated velocity curve and velocity curve of earthquake wave
图 7 坡脚和坡顶位移变化
a.坡脚x方向；b.坡脚y方向；c.坡顶x方向；d.坡顶y方向
Fig. 7. Displacement curve with time at slope bottom and slope top
表 1 岩石力学参数
Table 1. Mechanical parameters of rock
岩性 密度(g/cm3) 变形模量(GPa) 体积模量(GPa) 内摩擦角(°) 内聚力(MPa) 剪胀角(°) 拉伸强度(MPa) 蚀变细粒闪长岩 2.88 35.53 21.32 55 25 10 8 
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表 2 结构面强度参数
Table 2. Mechanical parameters of structural surface
岩性 法向刚度(MPa/cm) 切向刚度(MPa/cm) 内摩擦角(°) 内聚力(MPa) 剪胀角(°) 拉伸强度(MPa) 结构面 51 46 38 0.06 0 0
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