敦煌阳关西土沟流域高含沙洪水河道入渗特征分析

为明确无控制性工程地区的洪水入渗过程,提高洪灾防治能力和洪水资源化利用程度。选取敦煌阳关西土沟流域下游高含沙洪水河道,通过野外试验和实验室样品测定,测算了该河道下游上段到下段河床断面不同压力水头下的导水率,拟合得到饱和入渗速率,并通过实验室测样得到不同深度的饱和入渗速率,分析河床断面不同位置和不同深度土层的饱和入渗速率的变化规律。结果表明:饱和入渗速率:上段(0.003 1 cm/s)中段(0.002 9 cm/s)下段(0.002 6 cm/s);0—120 cm不同深度的饱和入渗速率上段大于中下段,中段和下段不同深度饱和入渗速率差异较小。整体上,河床两侧饱和入渗速率随深度的增加呈增大趋势,河床中心饱和入渗速率随深度增加呈减小趋势,主要是高含沙洪水流动时泥沙沿程分选沉积造成的。粗颗粒泥沙先沉积,细颗粒泥沙后沉积导致的上下段泥沙沉积层的孔隙度差异引起饱和入渗速率在河床断面和上下段以及不同深度的变化规律。由不同压力水头下测定的地表入渗速率来表征不同洪水水位下的入渗速率,经过趋势拟合发现随洪水水位升高,地表入渗率呈线性增长。

Analysis on Infiltration Characteristics of Hyper-concentrated Flood River Channel in Xitugou Watershed of Yangguan, Dunhuang

In order to clarify the flood infiltration process in the uncontrolled engineering area, and improve the ability of flood prevention and control and the degree of flood resource utilization, the hyper-concentrated flow channel downstream of the Xitugou watershed in Yangguan, Dunhuang was selected. The field experiment and laboratory analysis were conducted to measure the different pressure heads of the river section from the upper section to the lower section of the river. Under the infiltration rate, the saturated infiltration coefficient was obtained by fitting, and the saturated infiltration coefficients at different depths were obtained by laboratory measurements. The variation of saturated infiltration coefficients of the left and right banks, centers and different depths of the riverbed was analyzed. The results showed that the saturated infiltration coefficients:upper section (0.003 1 cm/s) > middle section (0.002 9 cm/s) > lower section (0.002 6 cm/s); the saturated infiltration coefficient at different depths in the upper part was larger than that in the middle and lower sections, and the difference between the middle and lower sections was small. On the whole, the saturated infiltration coefficients on both sides of the riverbed increased with the increase of depth, and the saturated infiltration coefficients of the riverbed decreased with the increase of depth. The reason for the above results was that the sediments were deposited along the hyper-concentrated flood, the coarse sediments were deposited first, and then the fine sediments were deposited, resulting in the difference in porosity of the upper and lower sediments, and the variation of saturated infiltration coefficients in river sections and different depths. The infiltration rate was determined by different pressure heads to characterize the infiltration rate under different flood levels, the trend fitting showed that the surface infiltration rate increased linearly with the increase of flood water level.