Abstract
The adjustment processes of mining pits in the disturbed channels by sand or gravel mining were investigated by laboratory experiments in this study. The pit migrated with speed when the river bed was steep. The pit migrated slow and steady when the pit was filling with sand, but the pit migrated with speed after the filling processes was finished. The submerged angle of repose in the pit was nearly constant during the pit was filling. The pit was filled with sand with speed as the channel slope was increased. It took time for the pit to be filled with sand as the pit dimension was increased. This meant that the disturbed channels by sand or gravel mining to adjust the new environment was dependent on the slope of the channels and the dimension of the pits. The dimensionless pit length was short and the dimensionless pit depth was shallow as the time was increased. The dimensionless pit depth was shallow, but the dimensionless pit migration speed was increased as the dimensionless shear velocity and the migration speed of the pit were increased. The dimensionless pit depth was increased with the dimensionless bar migration speed. The shape of the pit was deformed and migrated downstream in accordance with the location and shape of the biased bar front which was developed upstream.
본 연구에서는 하도준설 및 골재채취에 의한 교란하천의 적응과정을 정량적으로 파악하기 위하여 이동상 실내실험을 수행하였으며, 하상경사 및 골재채취를 위한 준설 규모의 변화에 따른 하도의 응답 특성을 분석하였다. 웅덩이의 되메우기가 진행 중일 때에는 웅덩이의 이동속도는 일정하지만, 되메우기가 완료된 후에는 웅덩이(pit)의 이동속도가 빠르게 진행된다. 또한 웅덩이가 되메워지는 동안에 웅덩이의 수중 안식각은 일정하게 유지되었다. 하상경사가 급할 경우에, 웅덩이가 되메워지는 시간과 이동속도가 증가하였다. 골재채취에 의한 하천준설의 규모가 증가하게 되면, 웅덩이의 되메워지는 시간이 증가하게 되며, 웅덩이의 규모가 증가할수록 적응시간이 증가하였다. 무차원 마찰속도가 증가하면 무차원 웅덩이 깊이는 감소하고 무차원 웅덩이 이동속도가 증가하였다. 웅덩이 이동속도가 증가하면 무차원 웅덩이 깊이가 감소하였다. 무차원 사주의 이동속도가 증가하면, 웅덩이의 이동속도가 증가하였다. 상류에서 발달한 사주의 이동이 편향되면, 흐름이 집중되는 사주의 선단부의 위치에 따라 웅덩이의 형상이 변형되어 하류로 이동하였다.
