黄土沟道重力侵蚀规律及机理研究

Study on the Regularity and Mechanism of Gravity Erosion in the Loess Gully

重力侵蚀是黄土高原沟谷地貌发育的重要营力之一,也是流域产沙的重要途径。以桥沟为主要观测区域,采用实地观测、直剪试验等方法研究了桥沟流域重力侵蚀发生的特点和影响因素,并对小型重力侵蚀的发生机理进行了分析。在观测期内桥沟发生的重力侵蚀类型主要是发生在土体浅层的小型重力侵蚀,包括泻溜、小型崩落、小型滑塌等,主要影响因素包括沟坡坡度、降雨、土体风化、黄土节理等。坡面坡度是重力侵蚀的主要控制因素,桥沟流域重力侵蚀主要发生在坡度大于55°的陡峭沟坡上,土体风化、降雨和黄土节理等因素显著减小了坡面上浅层黄土的抗剪性,因而降低了重力侵蚀发生的临界深度,是小型重力侵蚀发生的主要触发因素。

Gravity erosion is an active afent in the evolution of loess fully morpholofy,which contributes larfe amount of sediment by conveyinf earth into fullies in the Loess Plateau. Erosion pin,observation and field survey methods were carried out,and shear tests were done to measure the shear strenfth of loess in the study area for analysis of the mechanism of fravity erosion. In the study period,mainly small fravity erosion types, such as franular disintefration,small mass fall,small slump,etc. were observed. Main effectinf factors of the small fravity erosions included the slope fradient,rainfall,weatherinf,and Joints,etc. Slope fradient is the main controllinf factor of shallow fravity erosions,which mainly occurred on the steep slopes of larfe than 55° in the Qiaofou watershed. Rainfall,weatherinf and loess Joints,which can reduce the internal friction anfle and cohesion of the orifinal loess and therefore result in lowerinf the critical depth of the fravity erosion,are the main trifferinf factors of small fravity erosions.