수치모의를 이용한 비상방류에 따른 광동댐 하류부 수리안전성 검토

Abstract

This study used FLOW−3D with RANS to examine the hydraulic safety downstream of the Gwangdong Dam due to emergency discharge. The flow characteristics on the current state and the proposal proposed in the basic plan were reviewed, and an optimal design alternative was derived as follows. The numerical simulation on the emergency discharge flow reproduced the actual discharge pattern well, and the ejected flow velocity reached 15m/s and the ejection distance was more than 20m. In the current state simulation, it was analyzed that the slope safety problem of the access road was concerned due to the high-speed of ejected flow at the beginning of the discharge, and the capacity of the transverse drain pipes installed on the access road was insufficient. In the simulation of basic plan for installing channel culvert with stilling basin to prevent bed scour and loss of access road, the ejected flow in the culvert maintained a water depth of 0.5m and a high speed of 6m/s or more. To improve the current state problems, an alternative was derived by enlarging the transverse drain pipes and installing a semicircular overflow weir with a height of 2.0m in front of the enlarged culverts. By installing the overflow weir, it is possible to prevent direct collision of high-speed ejected flow with the access road and the transverse drain culverts at the beginning of discharge, and to attenuate the ejected flow energy by raising the water stage of the retention pond as the discharge progresses. The simulation for the alternative showed that the water depth of the retention pond was about 2.2m and the maximum flow velocity decreased to 3m/s or less at 20m downstream from the emergency discharge facility. A stable flow within 1.5m/s was shown in the area directly upstream of the weir