长江口深水航道整治一期工程南导提丁坝群头局部冲刷试验研究

采用双向稳定水流、清水定床、局部动床的试验方法，用正态模型研究长江口深水航道整治一期工程南导堤丁坝群坝头局部冲刷问题。结果表明，航道开挖和双本坝的存在使得下游流速有所增加，影响程度落潮大于涨潮。坝头局部冲刷主要受落潮流控制，在沿深度为单一砂粉底质情况下，坝头冲刷坑深度分别达到27m和29m；考虑到原状底质下部为极难起动的粘土，实际冲刷坑底界到达粘土层后就不再刷深，此时冲刷坑深度为7．4m和4．7m，冲刷坑的平面范围有所加大。工程设计提出的护坦尺度能较好地保护坝头前沿滩地，适当缩小护坦尺度也能起到保护作用，但冲刷范围明显增大。

A physical model study on local scour in front of the south groin group of the Changjiang Estuary Waterway Project I

In order to test the effectiveness of protection devises against local scour in front of the south groins group of the Changjiang Estuary Waterway Project, a normal physical model was built in this study, covering two groins and their adjacent estuary area. By using rinsing fixed bed model as well as local mobile bed model, the experiment was undertaken under conditions of bi directional steady flow. According to the results of this experiment, waterway dredging would lead to flow velocity increase, which is greater during ebb tide than during flood tide. The upstream groin has the same influence as the downstream one. Local scour happening in front of the groin head is controlled mainly by ebb flow. When the riverbed material is totally composed silt, the depth of local scour in front of the two groin heads are 27m and 29m respectively. Actually, the lower layer of the river bed is composed of clay whose critical velocity is much higher than that of Changjiang Estuary flow. Therefore, the local scour can not excedd the depth of up silt layer and is 7 4m and 4 7m respectively. With the designed size, the apron over the riverbed in front of groin head is very effective in preventing the scour. The apron of slightly smaller size can also reach the aim of protection, however, the scope of local scour may increase dramatically.