调沙库与沟滩联治

在沟道内建设调沙库可以调洪调沙,淤灌川坪农田和滩涂,达到既治沟又治滩的双重目标。实现沟滩联治的关键是调沙库的排沙能力。泥沙落淤经过自由沉降、群体沉降、浓缩沉降过程之后,在库区床面以上形成固结层、浓缩层、悬浮层、清水层。在未形成固结层之前可以高浓度自流排放,而不需要耗用大量清水。采用涡旋管排沙,可使底层含沙量大的水流进入涡旋管后形成强大的涡旋流,使泄量和挟沙能力增大,避免了泥沙的滞留淤积。涡旋管纵向开口的宽度b与涡旋管直径D的比值为0.1～0.3时,可保证管中涡旋流有足够的强度。当进库泥沙含量为200kg/m~3时,从出现清浑界面到开始形成固结层,其平均沉速为0.002cm/s,一日沉降距离只有172.8cm,设定拦蓄水深为18m,则在来洪10天内排放就可达到高含沙排放的目的。

Reservoir for Regulating Sediment and Joint Harnessment of Gully and Beach

Two-fold purposes of harnessing beach as well as gully can be realized by building reservoirs in gullies to regulate the flood and sediment and to Warp farmland and beaches. The sediment discharge capacity of the reservoir is the crux of realizing joint harnessment of gully and beach. After free settlement, mass settlement and thickening settlement of the sediment in the reservoir, layers of consolidation, suspension, and clear water are formed above river bed in the reservoir. The sediment can be discharged high density by gravity before the formation of consolidation layer without consuming large amount of water. Using vortex pipe to discharge sediment can avoid sediment accumulation, because the bottom flow with high concentration of sediment forms strong whirl after it enters the vortex pipe, increasing discharge capacity and sediment-carrying capacity. When the ratio of the width of the hole along the pipe to the diameter of the pipe is between 0. 1 to 0. 3, sufficient strength of vortex in the pipe can be ensured. When the concentration of sediment entering into the reservoir is 200kg/m3, the average settling rate is 0. 002cm/s from the appearance of interface of clear water and muddy water to the formation of consolidation layer, so the settling distance per day is 172. 8cm. It the depth of retained water were 18m, then the sediment could be discharged in high concentration in 10 days after the flood entering the reservoir.