三峡地区奉节县城缓倾层状岸坡变形破坏模式及成因机制

Mechanism and model for deformation of bank slope with slightly inclined soil layers in Fengjie County of Three Gorges

结合奉节缓倾层状岸坡的特点,分析认为软硬相间的岩性组合、近水平的岸坡结构,加之垂直层面的密集短小节理的切割构成了奉节地区独特的岸坡结构形式。岸坡变形破坏主要以压致拉裂、差异卸荷、重力蠕变-滑移-倾倒和结构沉陷等4种模式进行。巴东组第二段(T2b2)紫红色泥岩的易风化,崩解特性以及第三段(T2b3)泥灰岩的脆性,易溶蚀特性使得该区边坡岩体结构被深度改造,导致岩体结构沉陷,使得岸坡出现了似滑非滑、似塌非塌的变形破坏特征,存而导致了关于其破坏模式认识上出现了很大争议。

Many explanations were proposed for the deformation mode of the bank slope. The geological background of Three Gorges was introduced generally at first, and then the unique deformation phenomenon of the slope was serib. Through comprehensive study, it was pointed out that the unique deformation mode of the slope was controlled by the unique structure of the slope. The slope consisted of nearly horizontal layer, with soft layer and hard layer interbedded and perpendicular joints well developed. The strata outcropped in the slope were the second formation and the third formation of Badong group, which belong to middle Triassic system （T）. The second formation of Badong group （T2b2） was purplish-red mudstone, which was vulnerable to weather and disintegration, and the third formation of Badong group was brittle and vulnerablion to dissolution. These characteristics of the strata led to deeply remonlding of the structure of the rock mass in the slope, and induced collapse of the structure of the rock mass. Thus, the slope took on some phenomena like slide or slump, and made the deformation mode of the slope complicated.