草地覆盖坡面流水动力参数的室内降雨试验

为研究两种典型黄土的坡面流水力特性变化规律,进行了室内人工降雨试验。以草地盖度为主要影响因子,土壤质地和雨强为辅助影响因子进行分析。结果表明:同一盖度下,随雨强逐渐增大,流量和流速也随之增加;当盖度增加时,流量和流速随之减小。流速随降雨历时的延长而逐渐增大;当雨强增大时,流速曲线整体抬高;当覆盖度逐渐增大,流速曲线整体降低。平均水深随流速增大而减小;同一雨强下,盖度增加时氟汝德数Fr随之增加,雷诺数Re降低,而Darcy-Weisbach阻力系数f及曼宁粗糙系数n均大致呈增加趋势;对同一盖度,雨强增加Fr随之减小,Re逐渐增加,同时f和n均随之减小。因此草地覆盖度增加将改善坡面流水力性质,总体上减小了坡面流速,增加了阻力和粗糙度。

Hydro-dynamic parameters of overland flow during laboratory rainfall experiments under grass coverage

Laboratory rainfall experiments were performed in order to investigate the variation of hydro-dynamic characteristics of overland flow for 2 typical loess soils under artificial grass coverage.Grass coverage was the major factor and soil texture and rainfall intensity were the minor factors in the analysis.The results showed that,for the same grass coverage,runoff rate and flow velocity both increased when rainfall intensity increased,while runoff rate and flow velocity both decreased when cover age increased.Flow velocity increased when rainfall duration was prolonged,while the curve of flow velocity variation over time was totally elevated when rainfall intensity increased.The curve of flow velocity variation over time was totally degraded when cover increased.Average flow depth decreased with increasing flow velocities.When cover age increased at the same rainfall intensity,Froude number increased,Renolds number decreased and both Darcy-Weisbach and Manning friction coefficients increased correspondingly.At the same grass coverage,when rainfall intensity increased,both the Froude and Renolds number increased,with both Darcy-Weisbach and Manning friction coefficients decreasing correspondingly.Therefore,the hydro-dynamic characteristics were improved,the flow velocities decreased and the friction and roughness increased when the grassland coverage increased.