水力插板透水式丁坝群减缓流速效果试验研究

水力插板透水丁坝是一种新型丁坝。以水力插板透水丁坝群、井柱桩透水丁坝群和实体丁坝群为研究对象进行动床模型试验。先测定各丁坝坝前和坝后各5 cm横断面上测点的流速，再用每个测点的流速算出平均流速，通过对比横断面的平均流速来判断各丁坝群减缓流速的差异性，并详细分析和解释其减缓流速差异性产生的机理。研究发现：水力插板透水丁坝群和井柱桩透水丁坝群流速的减少率和减少量同实体丁坝群相比，分别提高了34%，23%和107%，84%。流速减缓会影响丁坝的局部冲刷和坝后淤积，再对各丁坝群附近的地形进行测量，并用surfer8.0绘制了各丁坝群附近的地形图。结果发现：实体丁坝群的局部冲刷情况最为严重，坝后淤积范围最小；水力插板透水丁坝群的局部冲刷情况最不严重，坝后淤积范围最大；井柱桩透水丁坝群的局部冲刷情况和坝后淤积范围介于两者之间。

Accumulative effect of hydraulic flashboard permeable spur dikes to reducing flow velocity

Hydraulic flashboard permeable spur dike is a new kind of spur dike. In this paper, we made movable bed model test for three kinds of spur dike group, the hydraulic flashboard permeable spur dike, well-column-pile permeable spur dike and entity spur dike. First, we measured the flow velocities at transverse section 5cm in front and back of every spur dikes in each dike groups and calculated the average flow velocity. Then, through the comparison of the average flow velocity in front and back of the spur dike, we analyzed the differences of reducing average flow velocity by the three kinds of spur dike group and the mechanism of the differences. The results showed that: compared with entity spur dike group, the flow velocity reduction efficiency of hydraulic flashboard permeable spur dike and well-column-pile permeable spur dike increase 34% and 23% and the flow velocity decrement increase 107% and 84%, respectively. Because the reduction of flow velocity also affects local scour of spur dike and the siltation behind dykes, we measured topography near the spur dikes and drew topographic map of the three spur dikes through surfer 8.0. The results show that the local scour and siltation of entity spur dike group is most serious, the hydraulic flashboard permeable spur dike group is the most slight, and the well-column-pile permeable spur dike group falls between them.