软岩区低强度地震诱发大规模滑坡的机理——以重庆小南海地震滑坡为例

Dynamics Mechanism of Low-intensity Earthquake Triggered the Collapse of the Soft Rock:Xiao Nanhai Seismic Landslide in Chongqing of China as an Example

为研究低强度地震在软岩区诱发大规模滑坡的动力学机理,通过现场调查采样,采用单轴动循环荷载试验及离散元数值模拟分析方法,对岩体强度的动力衰减问题﹑孤立突出地形的动力响应以及滑坡形成机理研究。结果表明:1."龟裂状"泥岩的动力响应极为敏感,极易崩解裂离成碎裂岩块;2.高陡孤立状软质岩山体的动力放大效应十分强烈,山体内部最大水平及竖向加速度分别为-4.2~7.8 m/s^2及-17.0~9.0 m/s^2,远高于基岩的0~1.5 m/s^2;3.经过碎裂化处理的模型2,模拟结果与实际一致;4."龟裂状"泥岩的震动崩解碎裂,导致山体剪切滑移形式由泥岩层面控制的平面摩擦型,转变为受泥岩振动碎裂带控制的转动摩擦滑动(甚至滚动摩擦)。受此机理控制,剪切面摩阻力急剧降低,剪切位移发生突变,山体迅速崩解破坏。这种特殊的成因机理,称之为孤立山体底部"龟裂状"泥岩层的"动力触变崩解"效应。

Large-scale hard rock landslides and small-scale soft rock landslides are common, but the large scale soft rock landslide is rare. To investigate low intensity earthquake induced large-scale dynamic mechanism of soft rock landslide, this paper adopts uniaxial cyclic dynamic loading test and two-dimensional numerical simulation based on discrete element etc. , studied the dynamic-attenuating of rock strength, the dynamic response of isolated outstanding landscape and landslide formation mechanism. Results showed that： 1. The dynamic response of ＂ cracked＂ mudstone is sensitive and easy to collapse shattered into pieces;2. Dynamic response for protruding soft rock ridge is very strong, with peak horizontal and vertical accelerations at -4.2 --7.8 m/s2 and -17.0 --9.0 m/ 2 s , respectively, far above the bedrock s 0.0 -- 1.5 rn/s2 ;3. Model 2 after fragmentation process, the simulation results are consistent with the actual situation ;4. ＂Cracked＂ fractured mudstone collapsed under vibration, and the shear slip transform level control plane friction into rotation of the friction which controlled by fractured mudstoneo Controlled by the mechanism, friction resistance drastically reduced of shear plane, the shear displacement mutated and the mountain destroyed rapidly. The author will call this particular genetic mechanism is that ＂cracked＂ shale ＂power thixotropic disintegration＂ effect which at the bottom of isolated mountain.