挑角对淹没丁坝附近河床变形影响的试验

Experimental study of effects of spur-dike angle on local river bed deformation near a submerged spur-dike

挑角对淹没丁坝和非淹没丁坝坝头附近床面冲淤变形的影响不同.目前的研究成果多集中于非淹没丁坝,涉及淹没丁坝的研究成果相对偏少.为了研究淹没丁坝附近床面冲淤变形对挑角的响应,对粗、细2组非均匀沙,45°、90°、135°3个挑角进行了交叉水槽试验.通过图像对冲刷坑形态进行了对比;将冲刷坑长度、宽度、最大深度、体积等特征参数试验成果进行了统计分析;将挑角对冲刷深度的影响折算成挑角因子,与前人的挑角因子及试验资料进行了对比.试验成果表明,挑角对淹没丁坝坝头附近床面冲刷坑形态、位置、尺寸均有影响,而床沙粒度则主要影响冲刷坑的尺寸.

The effect of spur-dike angle on local bed scouring and silting deformation near the head is differ- ent to submerged spur-dike and un-submerged spur-dike. The present researches are more concentrated on the un-submerged spur dikes, and the researching achievements of submerged spur dikes are relatively few. In order to study the response of the local bed deformation near a submerged spur dike to the angles, cross flume experiments were arranged according different spur-dike angles and different bed sand sizes. The plane shapes were compared through the images of scour pits. The length, width, extreme depth and capacity of local scour pits were analyzed statistically. In this paper, the angle effects on scour depth were converted to angle factors, and compared with the previous angle factors and test data. Test results show that the angle of submerged spur dikes has all effects on the shapes, positions and dimensions of the bed scour pits near the head; but the bed grain size just has an important influence on the scour hole dimen- sions.