三峡库区黄土坡滑坡体原岩结构特征及演化模式研究

Research on landslide's original rock structure characteristics and evolution model of the Huangtupo landslide in the Three Gorges Reservoir area

三峡库区黄土坡滑坡是一个大型复合变形体,地质条件非常复杂,其演化过程还需要进一步研究。本文对黄土坡滑坡勘察及白土坡库岸深部监测钻孔岩芯资料进行了综合对比研究,结果表明巴东组第三段上亚段岩体相对下亚段岩体夹层发育密集,黄土坡滑坡滑床中可能仍有贯通性夹层发育,取样夹层已泥化为砾类土。根据巴东组第三段岩体中软弱夹层发育特点恢复了黄土坡滑坡体的原岩结构,滑体分布特征与原岩结构对比研究表明黄土坡滑坡体是复合牵引式滑坡多次滑动的产物。黄土坡斜坡前缘巴东组第三段上亚段岩体中夹层密集,易泥化为滑坡滑带发生深层蠕变,并且受F3断层切割和次级褶皱发育影响岩体破碎,先期发生了滑坡。继而引发斜坡中部巴东组第三段下亚段表层风化破碎岩体坠覆或滑动并超覆于前缘崩滑体之上,最后引发园艺场滑坡使斜坡后部巴东组第二段表层风化破碎岩体滑动超覆于中部岩体之上,受三峡水库蓄水影响黄土坡滑坡崩滑体深部滑带及滑床夹层蠕滑将进一步加剧。这种演化模式能较好地解释黄土坡滑坡复杂滑体结构的成因及变化特征。

The Huangtupo landslide in the Three Gorges Reservoir area is a large compound deformable body, and its evolution model needs to be further examined. Data of investigation of the Huangtupo landslide and the Baitupo deep-monitoring borehole core data are analyzed by comparison in this paper and it is found that the weak interlayers in the upper submember of the third member of the Badong Formation have developed more densely than those in the lower submember, and interpenetrant interlayers have developed in the sliding bed of Huangtupo landslide. Interlayers have been mudded into the type of gravel clay. The original rock structure of the Huangtupo landslide is recovered according to the weak interlayers＇ distribution characteristics in the third member of the Badong Formation, from which it can be concluded that the Huangtupo landslide is the product of many times＇ sliding of compound retrogressive landslide. Because interlayers have developed densely and are easy to be mudded into sliding zone in the upper submember rockmass of the third member of the Badong Formation, the front of the Huangtupo slope cut by F3 and broken by subsidiary fold fault is likely to slide after deep-seated creep in advance. The weathered and broken rockmass of lower submember of the third member of the Badong Formation in the middle of the Huangtupo slope slided （or failed over） and overlaped on the slumped mass in the front of the Huangtupo slope. Finally, the Garden landslide occurred and pushed the surface weathering broken rock of the second member of the Badong Formation in the back of the Huangtupo slope to overlap on the middle rockmass of the Huangtupo slope. Affected by the Three Gorges Reservoir＇s impoundment, the deep creep of slumped mass and deep interlayers of the Huangtupo landslide will further intensify. This evolution model can explain the cause of formation of the complicated sliding structure in the Huangtupo landslide and its change.