泥石流坝后侵蚀坑纵剖面形态及最大深度实验研究

Experimental Study of the Shape and the Maximum Depth of Scour Pit Below Debris Flow Sabo Dam

泥石流拦砂坝坝后侵蚀坑形态和深度是泥石流冲刷基础研究的薄弱环节。通过室内水槽实验,探讨了泥石流坝后侵蚀坑的形态和不同实验控制条件下侵蚀坑深度的变化规律等。由实验观察可知,侵蚀坑纵剖面整体上呈现两端浅中间深的形态特征,其最深点的位置随水槽坡度增大向下游方向发展;侵蚀坑坑内上游坡度较下游坡度陡,对于具有相同级配的粘性砂和无粘性砂,无粘性砂的侵蚀坑坑内坡度较粘性砂的缓;侵蚀坑的最大深度受沟床纵坡、泥石流的容重、沟床组成物质的性质(特征粒径、粘性)等因素的影响较大;泥砂粘性的存在将大大削弱侵蚀的深度。

The shape and depth of scour pit after debris flow sabo dam is one of the weak links in the research of debris flow erosion. Therefore, this paper discussed this point by a series of indoor flume experiment. The longitudinal cross-sections present shape characteristics as deep at the middle and shallow at the ends and the site of the deepest point is moving to lower reaches with the increase of the longitudinal gradient at same experimental conditions. The lower reaches＇ slope in the scour pit is slower than the upperks. Compared the slopes in the scour pit in viscous silt and non-viscous silt with the same grain composition, the former is much steeper than the later. The maximum depth of the scour pit is affected by the longitudinal slope, the volumetric weight of debris flow and the property of the silt on the bed. Under definite experimental conditions, it increases with the increase of the longitudinal slope of flume and decreases with the increase of the volumetric weight of debris flow. The results show that the viscosity of the silt reduces the depth of the scour pit greatly.