The Change Pattern Of Wave Field After The Excavation Of Waterway

The natural waters in most ports are shallow, and basins and entrance waterways in these ports have to be dredged to meet the requirements. However, with the refraction of waves, the abrupt changes of landform produce great influence upon the propagation of waves. China has now come into another high upsurge of port construction and with the ever-growing of the size of ships, most of the existing waterways and basins are being deepened and widened while artificial waterways have to be dredged for new ports. The difference of water depths inside and outside the waterways becomes greater and greater. Such changes will surely affect the wave fields closed to the waterways and the change of the wave fields will in turn produce great impact upon the design waves of a breakwater, wave conditions inside a port and sediment transportation. Waves will develop refraction when they reach the slopes of waterways and the wave energy of the refracted waves will superpose the energy of waves propagating outside the waterways, thus not only causing the height of on-coming waves to the breakwater to increase significantly, threatening the stability of the breakwater, but also causing the wave energy to amass to propagate into the port, worsening the wave conditions inside the port.Based on the results of mathematic and physical model tests, the pattern of propagation of waves after excavation of waterways and the characteristics of distribution of wave heights on both sides of waterways are analyzed. The influence of the angle of incidence of waves, water depth and width of waterways, slope of waterways, and gradient of seabed upon the propagation of waves is also studied in the paper. The range of aggregation of wave energy after a waterway is dredged is proposed in the paper, which may be of reference for the design of marine structures close to waterways. The significance of critical angle of incidence of waves in the design of waterways is also discussed.Based on the studies of the pattern of changes of wave fields after a waterway is dredged and in the light of the designs of a detached breakwater for the first phase of Dayaowan Port Complex in Dalian Port, two engineering procedures were proposed to reduce the design wave height in front of the breakwater, which have been benfit adopted in the engineering practice and have gained significant social and economic benefit by not only shortening the construction period but also cutting down the construction cost.