云南虎跳峡两家人松散堆积体的基本特征及成因探讨

ANALYSIS OF THE BASIC FEATURES AND THE FORMATION MECHANISM OF LIANGJIAREN LOOSE DEPOSITS IN TIGER-LEAPING-GORGE, YUNNAN

两家人松散堆积体位于金沙江中虎跳峡左岸,为第四纪岩土体混杂堆积体,规模巨大,结构无序,透水性 强。文章通过野外调查和资料对比分析,揭示了该松散堆积体的发育特征和形成机制,认为两家人堆积体成因具 有复合性,是一种由滑坡、崩塌和崩坡积多期次形成的复合地质体,为典型的内外动力耦合作用的产物。最后对松 散堆积体的稳定性进行了初步评价,表明两家人堆积体整体式破坏可能性不大,局部性质脆弱,在地震、降雨和人

Liangjiaren large-scale loose deposits are located on the left bank of the middle Tiger-Leaping-Gorge of the Jinsha River. The deposits consist of a heterogeneous and incoherent mixture of Quaternary soil and rock fragments ranging in size from clay particles to rocks several centimeters or more in diameter, and more than sixty percent of the deposits are rock fragments. The area of this deposits is about 1.5km 2 and the total volume is estimated to be more than 1.8×10 8 m 3. Based on the detail field investigation and available data contrast analysis of typical loose deposits, the basic features and origin types of Liangjiaren loose deposits were investigated. Owing to complex and special climatic conditions, geological tectonics and geomorphology, the deposits' origin types include landslide mass, collapse mass and colluvium deposits etc. Liangjiaren loose deposits resulted from long term slope evolvement, and the forming processes of the deposits are very complex, which reflected the evolvement process of endogenic geological process and the surface reconstruction action of exogenic geological process in the Tiger-Leaping-Gorge area. Hereby, this paper put forward a coupling model of the Earth's endogenic and exogenic geological processes of Liangjiaren loose deposits. The analysis showed that Liangjiaren large-scale loose deposits resulted from many landslides, collapses, and detritus flow under the coordinate processes of crust uplift and river incision. They belong to composite geological body of the coupling of Earth's endogenic and exogenic geological processes. This paper analyzed and evaluated the stability of Liangjiaren large-scale loose deposits. The study indicated that these loose deposits can not form a integer unit for their loose structure; they will not deform and failure in a whole, but the stability of local part of Liangjiaren loose deposits is relatively lower and large-scale loose deposits failure can likely occur under the influence of earthquake, rainfall and human activities such as road excavating, impounding, flood discharge and pulverization. Thus, further study should emphasize on the deformation monitor and the local stability of Liangjiaren loose deposits. The large-scale complex loose deposits prevail in the Three-Gorge and the Tiger-Leaping-Gorge; they are prone to deform and failure, so the study of basic features, formation mechanism and qualitative evaluation of stability on Liangjiaren loose deposits will provide with a practice example of prevention and remediation of geo-hazards in above-mentioned areas.