报告题目：Dam safety and handling of floating debris
报告内容：During extreme floods, a large quantity of floating debris can be produced due to erosion, drifting with the flood water and eventually accumulating upstream of the dam. In Sweden, the debris is typically composed of spruce and pine trees of lengths up to 25 m. The debris may clog up the spillway openings and reduce the discharge capacity. As this is a dam-safety risk, proper countermeasures need to be taken to handle the debris. An innovatively designed visor is devised to prevent the spillway from clogging with debris. It is formed to have a horizontally semi-circular shape, with sloping beams supported on a platform. In one project, a concept model is tested, while in the other, a more realistic model according to scale is examined. Taking account of prototype tree lengths, 100-130 small trees with a density of between 650-1000 m3/s are used. Without the visor, the trees block all the spillway openings from the threshold to the water surface and the discharge capacity is reduced by some 30%. The tests have shown that the visor effectively stops the floating debris and the spillway openings are kept free from the debris. Trees with low density approach the visor afloat and are intercepted in the surface water. Debris with higher density is dragged down when approaching the visor. As a result, it covers the visor height, leading to a reduction in the flow passage. The study demonstrates the use of the visor to maintain relatively free spillway flow and a marginal reduction in the discharge capacity. Even an overflow Weir was examined as a potential measure for debris handling.
Prof. James Yang’s research experiences are in the fields of open-channel and conduit hydraulics, dam refurbishment and dam-safety issues. His main research areas consist of both physical modelling and numerical computations and cover general hydraulic investigations, hydraulics of dams and spillways, river and conduit flows, including dam-break issues, two-phase flow modelling, transients in hydropower plants, seepage flow in embankment dams and river sediment transport, etc.
James Yang is board member of Executive Committee of Swedish National Committee of Large Dams (SwedCOLD), committee member forInternational Association for Hydraulic Research (IAHR) and member of International Committee on Large Dams (ICOLD), advisory board member of the journal Hydro Review Worldwide (HRW) in USA, committee member of Swedish Hydropower Centre, etc. He is also editorial committee member of a few international journals like Journal of Applied Water Engineering and Research. He has published more than 45 papers in peer-review journals, and more than 90 international conference papers as well as more than 150 technical and consulting reports.