• Proceedings of the Korea Water Resources Association Conference
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• 1995.05a
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• pp.34-41
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• 1995

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.20-26
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• 2019

Where hydraulic structures are to be installed over the entire width of a river or stream, usually a bed protection structure is to be installed. However, a local scour occurs in which the river bed downstream of the river protection system is eroded due to the influence of the upstream flow characteristics. This local scour is dominant in the flow and turbulence characteristics at the boundary of the flow direction and in the material of the bed materials, and may gradually become dangerous over time. Therefore, in this study, we compared the turbulence patterns in the local scour hole at the downstream of the river bed protection with the results of the analysis of the mobile bed experiment, and compared with the application of OpenFoam, a three dimensional numerical analysis model. The distribution of depth-averaged relative turbulence intensities along the flow direction was analyzed. In addition to this result, the stabilization of scour hole was compared with the bed shear stress and Shields parameter, and the results were compared by changing the initial turbulent flow conditions. From the results, it was confirmed that the maximum depth of generation of the three-stage was dominantly developed by the magnitude of depth-averaged relative turbulence intensity rather than the mean flow velocity. This result also suggests that design, construction or gate control are needed to control the depth-averaged relative turbulence intensities in order to reduce or prevent the local scour faults that may occur in the downstream part of the bed protection.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.291-301
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• 1998

The objective of this study is to analyze the characteristics of flow and bed topography with changing bed material in a 180-degree, with constant-radius curved experimental channel. Sand($D_{50}$ = 0.56 mm, s = 2.65) and anthracite($D_{50}$ = 0.26 mm, s = 1.54) were selected as bed materials. The maximum scour depth was found to be about two times for the mean flow depth at the outer bank of bend angle $30^{\circ}~60^{\circ}$, and in case of anthracite, it was found upper part of bend angle $5^{\circ}~15^{\circ}$ than that of sand. Regardless of bed materials the path of maximum streamwise velocity is skewed inwards in the upper part of the bend, the maximum velocity shifts outwards, and it lagged downward as bed roughness increases. The maximum skewed angle of flow grows faster in the smooth bottom than in the rough one, and its value also increases. The secondary flow in anthracite bottom was measured larger than that of sand one, and two cells of secondary flow was found in this experiment.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.845-854
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• 2008

The old bridge of Woljeong-gyo, which has the fluvial history and culture, represents the ancient construction and civil engineering techniques. It is the oldest stone bridge in Korea and currently restored with its vicinities. In this study, the experimental model was used to analyze the hydraulic characteristics, the local pier-scour depth without scour protection, and the stability of riprap protection using the old grid type panels and stones for Woljeong-gyo of the study area. The water levels were increased around 30cm due to the restored bridge piers and foundations and the effects went up to 200m upstream. The maximum scour depth of 5.4m was measured and the scour protection tests were performed with the riprap size calculated using empirical equations and the existing scour protection range. The riprap of the existing scour protection in the upstream side was broken away, while the riprap of extended scour protection was very stable for the design flood condition of Woljeong-gyo area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.453-458
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• 2016

While the design of weirs requires a scour-considered strategy, research on the analysis of the effectiveness of hydraulic energy dissipaters and design criteria are scarce due to the limited experimental facilities and restraint in the experiment conduction period. The study analyzed the scour dissipation effect of multidirectional dissipaters to improve the scour problems of a weir downstream and suggests design criteria to minimize scour. A hydraulic model experiment was conducted for Nakdong River Hapcheon-Changnyeong Weir and a model in 1/25 of horizontal accumulation and 1/25 of vertical accumulation was produced. The experimental equipment was classified into channels and a flow rate supply and an underwater pump were installed to enable flow at a maximum of 2.0 m3/s. The experimental inflow was 1.3 m3/s, the upstream water level was 0.36 m, downstream water level was 0.24 m, and a cylinder wooden baffle, a dissipater, with a diameter of 0.05 m was made. A 3D scanner was also used for an accurate scour depth comparison for a length change of the baffle before and after installing the baffle. When the baffle was arranged in the shape of a V, the depth of scour decreased by 36% while the scour length decreased by 49% due to flow reduction compared to that before installing the baffle.

• Water for future
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• v.17 no.3
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• pp.197-209
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• 1984

This study has been carried out to investigate into the local scour of wall-toe and the beach deformation caused by the construction of a seal wall. It has been performed to determine the values of the marine invertigation of HAE UN DAE and two dimensional Movable bed gydraulic model test. From the results of this work approtection method of HAE UN DAE beach erosion is established to reduce the amount of topography deformation by investigating the values of the constructive position of a sea wall, seabed slope, the maximum scour depth, the first and the second influence range, the maximum quantity of beach deformation, and the distance measured from the sea will to the maximum quantity of beach deformation.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.233-233
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• 2011

This study describes the characteristics of accretion and scour around artificial reefs in Korea. The survey for accretion and scour was made at a dice reef set consisting of 137 dice reefs. The volume of a dice reef unit is 8 $m^3$. The reef set was placed on the muddy sand at 21.6 m in November of 1999. Equipment used in the survey includes Side Scan Sonar, Multi Beam Echo Sounder, Sub-Bottom Profiler and water current meter. According to the results, the artificial reefs are heaped up at two to three times (4 m) the height of the dice reef. The maximum current around the artificial reefs was 81.5 cm/sec at the ebb tide and 72.7 cm/sec at the flood tide. Scour around artificial reefs occurs upstream to the flow while accretion is formed at wake zone in the downstream. The height of accretion ranges from 2.4 to 3.0 m. The crest of the accretion is formed at the distance of about 10 m from the edge of the reef. The slope of accretion is formed steeply at the vicinity of the reef which is at right angles to the direction of main current, and grows gently lower with the increased distance from the reef. Scour is continuously caused by upwelling from the reef set and by side currents that flow parallel to side of the accretion. Also, scour takes place on the deposited sediment rather than on the remaining bottom sediments. This means that, once fully formed, the depth of scour gully on both sides to the direction of main current hardly changes.

• Journal of the Korean GEO-environmental Society
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• v.15 no.9
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• pp.37-45
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• 2014

An embedded length of monopile caused by a scouring should be evaluated to monitor the stability of offshore foundations, because offshore foundations are affected by horizontal load. The objective of this study is to evaluate the scouring around offshore foundation by using electrical resistivity and to estimate ground stiffness by using shear wave tomography. The electrical resistivity profiles and shear wave tomography were measured according to the scour depth of model ground prepared with sand and cement. Several electrodes and bender elements were used to measure the electrical resistivity and shear waves, respectively. The electrode sets are attached on the monopile surface and bender elements are arranged in $7{\times}7$ arrays by using nylone frames. The electrical resistivity profiles and shear wave tomography are acquired by laboratory experiment. Maximum scour depth was estimated by electrical resistivity profiles and the ground stiffness of model ground was estimated by shear wave tomography. This study suggests that the electrical resistivity profiles and shear wave tomography may be useful for monitoring the stability of the offshore foundations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.17-25
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• 2016

Revetments help protect levee slopes from erosion. If the design of the revetment is not appropriate, the levee may collapse as a result of scouring due to the strong flow velocity and tractive force. Therefore, when designing a revetment, it is very important to calculate the representative velocity. However, the average velocity and depth calculated by 1-D varied flow analysis are generally applied to the design, which do not reflect the increase in velocity caused by the free and force vortex. Therefore, it is necessary to correct the representative velocity in order to ensure the stability of the revetment in a meandering channel. In this study, the applicability of the method of calculating the representative velocity considering the curve and scour was studied (by comparing it with) the average and maximum velocities determined by numerical simulation. The representative velocity corrected for the effect of the curve and scour and the maximum velocity calculated by the numerical simulation were found to match quite well. In addition, the riprap size of the gabion in the meandering and straight channels were compared by applying them to the conventional design formulas. In the future, it is necessary to perform additional numerical simulations for various rivers with different characteristics, in order to propose a method of designing a suitable revetment for Korean characteristics. At this time, the results of this study are expected to be able to be used as basic data.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.43-50
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• 2002

This paper describes a simplified numerical procedure for analyzing the response of bridge pier foundations due to riverbed scouring. A computationally efficient algorithm to analyze the behavior of a pile group is proposed by considering soil-pile, pile-cap, and pile-fluid interactions. The complex phenomenon of the pile-soil interaction is modeled by discrete nonlinear soil springs (p-y, t-z and q-z curves). The pile-cap interaction is considered by geometric configuration of the piles in a group and connectivity conditions between piles and the cap. The pile-fluid interaction is incorporated into the procedure by reducing the stiffness of the soil-pile reactions as a result of nonlinearity and degradation of the soil stiffness with river bridge scouring. Through the numerical study, it is shown that the maximum bending moment increases with increasing scour depth. Thus it is desirable to check the stability elf pile groups based on soil-pile and pile-cap interactions by considering scouring depth in the riverbed.