降雨型泥石流对沟床侵蚀的水力学机理

Hydraulic mechanism of gully bed erosion by debris flow in rainfall

为解决降雨型泥石流对沟床的侵蚀和重塑机理,以水文学为基础,在科学表征泥石流流深的前提下,借助水力学理论,分析了沟床在泥石流流动剪切和渗流水压耦合作用下的侵蚀机理,研究了泥石流流动剪应力、沟床基质孔压、泥石流静压及沟床自重作用的计算方法,给出了沟床侵蚀临界深度表达;借助算例阐明了流域降雨特征、沟道几何参数以及泥石流性质对泥石流流态及侵蚀力的影响规律,展示了沟道侵蚀曲线和侵蚀量的计算方法.结果表明:(1)泥石流侵蚀能力随沟床基质埋深的增加而下降,并在临界深度处消失;(2)不同降雨条件、沟谷特征和泥石流性质下的临界侵蚀深度因流深流速的差异而不同,越利于流深流速增大的流域沟道条件则越利于侵蚀的进行.

Based on the water lever model of debris flow established according to hydrology, and by aid of hydraulic theory, the erosion mechanism of gully bed under flow shear stress and seepage hydraulic was studied. After studying the calculation methods for flow shear stress, pore water pressure, static pressure and gully bed weight, the critical erosion depth of gully bed by debris flow was proposed. By discussing the influences of rainfall pattern, gully geometric parameters and flow property to debris flow pattern and its erosion characteristics with an example, the way to calculate erosion was illustrated. The result indi- cates that the erosion becomes weak with the incensement of depth of base material, and only occurs above on a critical erosion depth in gully bed; with different rainfall conditions, gully geometric character and debris flow property, the flow depth and velocity changes greatly, which effects the gully bed erosion directly.