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准确计算河床沉积物渗透系数对于河流-地下水相互关系及其流域生态系统分析具有十分重要的作用.采用水头下降竖管渗透试验法对美国内布拉斯加州埃尔克霍恩河(Elkhorn River)8个不同地点、共60个试验点位上的河床上、下两层沉积物垂向渗透系数(Kv)做了试验研究.结果表明:上层沉积物Kv值普遍高于下层沉积物的.从所有测试点来看,上层沉积物中Kv测试值在2.7～104.9m/d之间,其平均值为26.6m/d;而下层沉积物Kv测试值在0.4～73.4m/d之间,其平均值为16.1m/d.河床沉积物Kv值随深度增加而减小这一现象主要是由于河流-地下水交错带水文过程引起的.交错带中水流流出和流入的交换作用增加了河床孔隙度从而增加了沉积物渗透性.此外,生物扰动作用能够有效地破坏河床表面细小沉积物形成的淤塞层,在沉积物中产生新的孔隙空间,从而增大了河床表层沉积物渗透系数.
Accurately calculating the sediment permeability coefficient of riverbed plays a very important role in the river-groundwater interrelationship and ecosystem analysis of its watershed.Using the head-down peg penetration test, the Elkhorn River, Nebraska, United States 8 A total of 60 sites were selected to study the vertical permeability coefficient (Kv) of sediments on the upper and lower layers of the riverbed.The results show that the Kv values of the upper sediments are generally higher than those of the lower ones Test point of view, the upper sediment Kv test values ?? between 2.7 ~ 104.9m / d, with an average of 26.6m / d; while the lower sediment Kv test values ?? between 0.4 ~ 73.4m / d, the average Value of 16.1m / d.The phenomenon of Kv value of riverbed sediments decreasing with depth is mainly caused by the hydrological process of river-groundwater interlaced zone.The exchange effect of water flow out and inflow in the interlaced zone increases the river bed porosity Increasing the permeability of sediments.In addition, the bioturbation can effectively destroy the silt layers formed by the fine sediments on the river bed, creating new pore spaces in the sediments and increasing the sediment permeability coefficient of the river bed.