洞坪水库大沟湾滑坡体变形机制

Deformation Mechanism of Dagouwan Landslide in Dongping Reservoir

大沟湾滑坡是瞿家湾滑坡群中相对高差最大的滑坡体,洞坪水库蓄水后滑坡体产生了较大变形且变形机制表现出一定的特殊性.野外调查研究表明:蓄水前该滑坡体稳定性良好;蓄水至452m后,滑坡后缘堆积体与基岩交界处产生贯通滑坡两侧冲沟的连续裂缝,剪出口位于整个滑体中部580m高程附近,由于下部坡体的抗滑作用而使整个坡体仍处于稳定状态;蓄水至488m后,从整个滑体前缘到570m高程附近又形成另一滑坡体,与先前上部滑坡呈梯级分布,分析得出大沟湾滑坡为上部牵引-下部推移的复合式滑坡,两个滑坡共同作用导致整个滑体发生明显变形.分析并利用FLAC3D模拟再现整个变形过程,对滑坡体变形破坏机制做出了很好解释.

Based on engineering survey and experiments, slide mass structure and the mechanical parameters of Dagouwan landslide were obtained. FLAC3D was employed to analyze the stability and the deformation mechanism of Dagouwan landslide at different working conditions and water levels. The results of analysis show that： when the water level rose to 452 m, there showed a continuous crack at the back of the landslide from one side of gully to another, and the shear outlet of the landslide was located in the thick deposits of the slope at 580 m, but the whole slope still showed stability; when the water level rose to 488 m, another independent landslide formed from the toe of the landslide to 570 m. Interactions between two landslides caused the failure of the whole slope. The phenomenon had been confirmed during the two field explorations. The failure reasons of the landslide can be concluded as the loose structure of the landslide, high frequency of showers and the fluctuation of the water level in the reservoir, which finally led to the form of this complex retrogressive-progressive landslide.