入湖单沙体形成及发展的实验研究

An Experimental Study on the Formation and Evolution of a Sand Body at the River Mouth

由单沙样形成入湖沙体的室内实验结果得知,含沙水流进入水盆后,沙体在河口呈舌状向前发展。上游供沙时,平面上水下沙体前积、侧积同时发育;而垂向上开始沙体叠积明显,后渐趋平衡,此时,沙体表面只有一条主河道,近河口处以淤积为主,远河口处以冲刷为主;上游不供沙时,平面上水下沙体以侧积的横向搬运为主,几乎无前积;而垂向上则主要为侵蚀,沙体平均厚度变薄,表面除主河道外还同时发育多条分支河道,近河口冲蚀,远河口淤积,河道分汊主要发生在近河口一侧。从实验中还得知,纵向上水下形成的沙体似乎存在一极限距离,横向上沙体的最大宽度均位于距河口三倍河道宽度的剖面上,这些现象与天然条件的入湖水下沙体的形成和发展一致。沙体的最大厚度点均位于沿河道中心线延伸的纵轴上。

As a sand-laden flow entering a lake, the sand body with lobate shape occurs at the entry. Feeding the sand, progradation and Lateral accretion simultaneously develop horizontally, and the aggregation is typical at first, then decreases gradually to a equibrium state. There is only one main channel on the surface of the sand body. The deposited part is near the mouth and eroded one is away from the mouth; Not feeding the sand, lateral depsition continues to develop and progradation does not, and erosion is intense vertically. There are many braided channels beside a main river on the surface of the sand body. The position of eroded and deposited occurs oppositly with feeding the sand. The main channel starts to distribute near the mouth. In all runs, the length of the sand body appears to be limited, and the position of the maximum width of the sand body is located in the cross section that occurs away from the mouth as three times as the river width, and the maximum thickness locates always in the longitudinal axis along the centre line of the flow.