降雨条件下河流冲刷型滑坡的基本特征及滑动机制分析——以四川宣汉樊哙大桥滑坡为例

以宣汉樊哙大桥滑坡为例,分析降雨条件下河流冲刷型滑坡的滑动机制。在对滑坡区的地质条件、滑坡的基本特征和滑坡的变形过程等综合分析的基础上,探讨了降雨条件下河流冲刷型滑坡发育特征及形成机理。分析表明,降水对降雨条件下河流冲刷型滑坡起到了双重作用:一方面,河水对坡脚的浸泡、冲刷;另一方面,强降雨形成的雨水沿着坡面渗入坡体,在滑体与基岩接触面上形成滞水带,受地下水的浸泡泥岩极易软化,强度大幅降低,促使坡体滑动。深入研究樊哙滑坡的基本特征和成灾机制,对西南地区临河型滑坡的预防与治理提供一定的技术支持和借鉴作用。

Analysis of the Basic Characteristics and Formation Mechanism of River Erosion-Type Landslides under Rainfal Conditions as Exemplified by Fankuai Daqiao Landslide in Xuanhan, Sichuan Province

At 21:30 p.m.of July 16, 2009, a slide took place in Dafengtan of Gufeng Village of Fankuai Town of Xuanhan, Sichuan, the volume of slide was about 50×10⁴ m³, the maximum sliding distance was 40 m, and about 10×10⁴ m³ of sliding body substances ran into the river to block more than half the river (about 40 m), sliding materials diverted the river, which caused collapse of public housing and destruction of related facilities, giving rise to large economic losses. Based on geology and precipitation data, the paper analyzed comprehensively the formation mechanism of the landslide and explained the reasons for the formation of the disaster.The landslide resulted from many factors, but the role of each factor is different.The main factors are storm water, geological conditions favorable for slide occurrence, and irrational human activities. Powerful rain played an erosion, jacking, wedge cracking, motivate role. The occurrence of landslide involves the following four steps:namely groundwater convergence-jacking the landslide body, river rise-scouring the foot, squeeze-wedge crack and collapse crack-slide. It has provided some guidance for preventing and governing disaster risks in Southwest China, so as to further study the formation conditions and presence mechanism of Gufeng Village landslide in Fankuai town.