摘要
细沟水流流速是冻土和未冻土坡面水文过程的重要参数,与冻融坡面土壤侵蚀和泥沙输移密切相关。试验在长8 m、宽0.1 m、深0.12 m的土槽内填装深度为0.05 m的陕西安塞黄绵土坡面进行。设定坡度为5°、10°、15°、20°,流量为1、2、4、8 L/min,通过测量冻土与未冻土坡面细沟水流前锋流经整个土槽所用时间,计算水流的前沿流速,对比2种坡面上水流前沿流速的关系,研究冻结对水流流速的影响,同时采用电解质示踪法计算水流的优势流速,分析优势流速与前沿流速的关系。不同工况下,冻土坡面前沿流速在0.260~0.843 m/s之间,未冻土坡面水流前沿流速在0.175~0.552 m/s之间;冻土和未冻土坡面上,随坡度、流量的增大,前沿流速增大,增大率在缓坡(5°~10°、10°~15°)时逐渐减小,流量较小(1、2、4 L/min)时,流量增大,坡度对前沿流速增大率的影响也逐渐减小;坡度和流量对冻土坡面水流前沿流速的影响大于对未冻土坡面水流前沿流速的影响;冻土和未冻土坡面前沿流速均随坡度和流量的增大近似呈幂函数增大;在试验条件下,冻土坡面前沿流速和优势流速比未冻土坡面大43%和40%;冻土和未冻土坡面上优势流速和前沿流速的比值分别为0.61和0.63,表明该系数可以用于标定前沿流速。试验结果可为冻土坡面与未冻土坡面水流动力过程研究提供参考。
Water flow velocity along an eroding rill over frozen and non-frozen slopes is of great importance for understanding rill erosion hydrodynamics, which is closely related to erosion of freeze thaw soils and sediment transport. A series of flume experiments were conducted with loess soil from Ansai, Shaanxi Province. Flow velocities were measured in a stainless steel flume which was 8 m long, O. 1 m wide, and 0.12 m high. The experiments involved five slope gradients (5° , 10°, 15° and 20°) ,four flow rates (1 L/min, 2 L/min, 4 L/min and 8 L/min) , with three replicates. Time intervals for water flow running from the top of the flume to the bottom end, covering a total length of 8 m was measured to calculate the velocities under different slopes and different flow rates, for both frozen soil and non-frozen soil slopes. The peak velocities were also gained by the data of conductivity changed with time by the electrolyte tracer method during the experiment. The leading edge velocities over frozen soil were between 0. 260 m/s and 0. 843 m/s and that of non-frozen were between 0. 175 m/s and 0. 552 m/s. Leading edge velocities over frozen soil and non-frozen soil were both increased with the increase of slope gradients and flow rate, the increasing rate of leading edge velocity was decreased with the increase of slope gradient or flow rate under gentle slope(5°- 10°, 10°- 15°) and low flow rate(1 L/min , 2 L/min and 4 L/min). Over frozen and non-frozen soils, the vel9city was increased faster on gentle slopes than that on steep slopes and under low flow rate than that under high flow rate. The power function fitted the leading edge velocity very well for all the experimental conditions over frozen and non-frozen soils. The slope and the flow rate had greater effect on velocity over frozen soil slopes than over non-frozen soil. The result demonstrated that leading edge velocities and peak velocities over frozen soil were faster than that of non-frozen soil under all slopes and flowrates, the ratio of flow velocities over frozen soil and non-frozen soil was 1.43 and 1.40. The ratio of peak velocities and leading edge velocities over frozen and non-frozen slopes were 0.61 and 0.63. The experiment showed that the method for flow velocity measurement was reasonable, and it can also be widely used, The results can provide a data set for flow dynamics research over frozen soil and non-frozen soil.
作者
陈丽燕
雷廷武
班云云
高源
CHEN Liyan;LEI Tingwu;BAN Yunyun;GAO Yuan(College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China)
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2018年第4期282-289,191,共9页
Transactions of the Chinese Society for Agricultural Machinery
基金
国家自然科学基金重点项目(41230746)
关键词
黄绵土
冻土坡面
坡面径流
前沿流速
电解质示踪法
loess soil
frozen soil
sheet flow
leading edge velocity
electrolyte tracer method