피라미드형 어초의 이격 거리에 따른 세굴 안정성에 관한 연구

Abstract

This study was reviewed about hydraulic effect caused by distance of pyramid type artificial reefs to be made of reinforced concrete and size 3.0 m × 3.0 m × 1.45 m and weight 9.65 ton. The subject is stability and scour of artificial reefs by theoretic consideration and hydraulic model test. The former is applied Morison’s equation and the latter is 2D hydraulic experiment by scale 1/20. This study results are as follow : 1) Stability of pyramid artificial reef Morison’s equation was used for theoretical analysis of pyramid artificial reef’s stability in wave-current field. The external force conditions were tidal velocity 2.0 sec , designed regular wave height 4.0 ~ 7.5 m and wave period 7.2 ~ 10.3 sec, installed seawater depth 8 ~ 10 m. As a result, the stability appeared stable with less than safety factor 1.2. Especially considering that the AR was kept stable in condition of high wave, pyramid artificial reef has characteristics which is good resistance about wave and current by low mass center. 2) One pyramid artificial reef This Experimental conditions for One pyramid artificial reef’s stability applied irregular wave with significant wave height 5.1 ~ 15.3 cm, significant wave period 1.6 sec and 2.0 sec. And the bottom sediment used sand that 50% diameter was 0.5 mm. As a results, artificial reefs appeared stably exclusive of relative its subsidence by sand ripple. At this time, Surf parameter was 0.19 ~ 0.34 and local scour depth was 0.09 ~ 2.38 and subsidence depth is 0 ~ 1.19 cm. 3) Distance between two pyramid artificial reefs This experimental condition for Distance between two pyramid artificial reef’s stability applied 4cases by depth 50 cm, distance two artificial reefs 2hAR, 3hAR, irregular wave height 9.9 ~ 15.3 cm, wave period 1.6 sec and 2.0 sec. As a result in case of distance 2hAR, local scour depth was 1.19 ~ 2.73 cm, subsidence was 0.77 ~ 1.58 cm. In case of distance 3hAR, local scour depth was 1.01 ~ 2.67 cm, subsidence was 0.23 ~ 1.93 cm. Maximum Relative scour depth(hsc/hAR)was 0.38 when Surf parameter was 0.21 in distance 2hAR. Maximum relative subsidence(hb/hAR) was 0.15 in distance 2hAR at first artificial reef. Be taken all results, relative local scour appeared 0.2, 0.28 and 0.27 each unit AR, 2hARs, 3hARs. Relative subsidence appeared 0.11, 0.15 and 0.12 each unit AR, 2hARs, 3hARs. In view of the functionality of ARs, placement distance between of ARs can be considered 2hAR ~ 3hAR in this study. But it will need further research about detailed distances of ARs and conditions of wave-current field.