和田河干流下游河段河床沉积物渗透特性试验研究

Experimental Research on the Permeability of Sediments in the Lower Reaches of the Hotan River

准确获取河床沉积物的渗透性能及其空间分布规律,可为刻画河流与地下水之间的水量转化以及采取科学的措施改善和维持流域生态环境提供科学依据。采用原位竖管试验法获取了和田河干流下游河段河床沉积物垂向与水平向渗透系数,并采用基于土壤转换函数的人工神经网络模型预测了沉积物的综合渗透系数,对研究河段沉积物渗透系数的空间变异规律开展了系统的研究。结果表明:①试验获取的垂向渗透系数平均值在0.81~2.77 m/d之间,水平向渗透系数在4.32~10.37 m/d之间,综合渗透系数平均值在0.54~1.30 m/d之间;各测点河床沉积物水平与垂向的各向异性比平均值在3~9之间,最大值达9.09,反映出在河床沉积物剖面上呈显著各向异性。②沿河床纵断面自上游至下游方向,K_(v平均值)与K_(h)整体上均呈增大的趋势,K_(s)平均值呈先增大后减小的趋势,河床沉积物各向异性比整体呈降低的趋势。③河流水动力条件通过塑造河床的冲淤状态及沉积物颗粒排列组合特征,进而影响河床沉积物的渗透性能,研究河段河床沉积物的颗粒排列组合结构特征对渗透系数的影响较为显著,河床表层的淤积泥膜层显著降低了河床沉积物的垂向渗透性能,是引起各向异性的主要原因。

Obtaining the permeability and spatial distribution of sediments accurately can provide a scientific basis for calculating the water conversion between river and groundwater and scientific measures are taken to improve and maintain the ecological environment of the basin.The vertical and horizontal hydraulic conductivity of the sediments in the lower reaches of the Hotan River are obtained by the in-situ stand‐pipe test,and the comprehensive hydraulic conductivity of the sediments are predicted by the artificial neural network model based on the soil transfer function.The spatial variation law of sediments hydraulic conductivity in the studied river reach is systematically studied.The results show that:①The average vertical hydraulic conductivity is between 0.81 and 2.77 m/d,the horizontal hydraulic conductivity is between 4.32 and 10.37 m/d,and the average comprehensive hydraulic conductivity is between 0.54 and 1.30 m/d.The average value of the anisotropy ratio by horizontal and vertical of the riverbed sediments at each measuring point is between 3 and 9,and the maximum value is 9.09,which reflects the significant anisotropy in the profile of the riverbed sediment.②Along the longitudinal section of the riverbed from upstream to downstream,the average value of Kv and Kh show an increasing trend on the whole,the average value of Ks shows a trend of first increasing and then decreasing,and the anisotropy ratio of riverbed sediments shows a decreasing trend as a whole.The difference between Kh and Ks is much more than that between Kv and Ks.On the whole,the values of Kv and Ks are equivalent,but compared with the state without mud film,the value of Ks is closer to Kv in the sediment state covered by mud film.③The hydrodynamic conditions of the river affect the permeability of the riverbed sediments by shaping the erosion and deposition state of the riverbed and the characteristics of the arrangement and combination of sediment particles.The influence of the particle arrangement and combination structure characteristics of the riverbed sediments on the hydraulic conductivity is more significant in the river reach.These dimentary mud layer on the surface of the riverbed significantly reduces the vertical permeability of the riverbed sediments,which is the main cause for the anisotropy.The conclusion of the research provides data support for the calculation of river leakage in this reach,and provide technical guidance for taking scientific and reasonable engineering measures to improve and maintain the ecological environment of Hotan River Basin.