汶川震区滑坡堆积体土石混合坡面细沟水流曼宁系数特征研究

Research on Manning Roughness Coefficient Characteristics of Earth-rock Mixed Landslide Deposition Slope in Wenchuan Earthquake Area

为研究汶川震区滑坡堆积体土石混合坡面细沟水流曼宁系数的变化过程及其影响因素,在两级坡面(坡度为34°、36°)、三级流量(4、8、12L/min)、四种石土比(质量比为0∶1、1∶3、1∶2、1∶1)的组合条件下,进行室内放水冲刷试验。结果表明,曼宁系数n随冲刷历时呈先缓慢增大、再迅速增大、最后急速减小的变化趋势。不同石土比条件下,n平均值大小顺序为n(1∶3)>n(1∶2)>n(1∶1)>n(0∶1)。n随流量的增大而减小,但变幅不大。水深h与n呈幂函数正相关关系。雷诺数Re与n关系不显著,弗劳德数Fr与n呈显著的幂函数负相关关系。n/h与Re呈显著的幂函数负相关关系,n/h与Fr关系不显著。研究结果为建立汶川震区滑坡堆积体坡面土壤侵蚀模型提供了理论依据。

According to the field investigation,the changes and influencing factors of Manning coefficients of earthrock mixed landslide deposition slope in Wenchuan earthquake area were studied under four rates of rock fragment and soil（0∶1,1∶3,1∶2,1∶1）,two angles of sloping surfaces（34°,36°）and three flow discharges（4,8,12L/min）by indoor scouring experiment.The results show that the Manning coefficients n increased slowly at first,then increased rapidly,and decreased sharply with the scouring times.The average values of n were sorted the following ranks：n（1∶3）n（1∶2）n（1∶1）n（0∶1）,and it decreased insignificantly with the increasing of flow discharge.There was significant positive power relationship between flow depth（h）and n values.The n values had insignificant relationship with Reynolds number（Re）but negative power relationship with Froude number（Fr）.The rate of Manning roughness coefficient to flow depth（n/h）had also significant negative power relationship with Re while had no significant relationship with Fr.The study provided important basis for establishing soil erosion model in the landslide deposition slope of Wenchuan earthquake area.