• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4845-4852
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• 2012

This research calculated the scour depth of bridge according to inflow and outflow changes of stream's flood discharge and curves by applying scour depth formula for piers and abutments, and by comparing and examining them, evaluated the applicability of scour depth formulas. Overall, if the angles of flood discharge and inflow and outflow increase, the deviation rate of scour depth in bight increased. Especially the deviation rate was 58% at the inflow and outflow angle of $105^{\circ}$ that the bridge plan for this geography need careful examination. Next, as a result of calculating the deviation rate of scour depth at the bight by scour depth formulas, in case of pier, Andru formula showed 58% deviation rate, Laursen formula showed 26% deviation rate, and CSU. formula showed 17% deviation rate. In the case of abutment, Froehlich formula shows 44% deviation rate that when applying above scour depth formulas, scour depth calculation considering repairable characteristics of bight is necessary. Finally, about inflow and outflow angles of $45^{\circ}{\sim}135^{\circ}$ that showed big deviation rate of scour depth, this research performed regression analysis of deviation rates of scour depth due to flood discharge to suggest the regression formula.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.507-520
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• 2003

A V-shaped riffle is an artificial hydraulic structure haying two wings from the streamside with a narrow opening in between. It is usually made of crushed stones or large boulders. It limits channel width and accelerates the flow through the constricted section causing a local scour just downstream. The V-shaped riffle provides with a unique aquatic habitat by forming a pool and sandbars around the pool edge, increasing local morphologic, hydraulic and sedimentological diversity. This study investigates experimentally the scour characteristics of the V-shaped riffle in the sandbed stream and proposes a predictive equation for the scour. Total 45 cases of experiments were conducted to examine the effect of hydraulic factors and configuration of V-shaped riffle on the geometry of scour holes. From the comparison of the experimental results of this study with the predictive equation of spur dike by Breusers and Raudkivi(1991), it is found that their predictive equation of spur dike underestimates the maximum scour depth downstream of the V-shaped riffle. h new predictive equation for the maximum scour depth was developed using the non-dimensional hydraulic and geometrical variables. The parameters used in the proposed equations were determined using the experimental data. The analysis reveals that the scour depth is dependent dominantly on the Froude number at the opening of the V-shaped riffle, while the angle of riffle and the opening width also affect the scour depth. The proposed equation for the scour of V-shaped riffle well agrees with the experimental data. It can be used for estimating the scour of the V-shaped riffle in sandbed streams.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.6
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• pp.470-479
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• 2009

The local scour in waves can be thought of as very complex synthetic processes which is influenced by geology of bed material, bed flow in the sea and hydraulics condition. The most research until now be targeted at the scour depth and therefore the local scour width in waves has not been investigated as well. The size of wave or bottom velocity at the bed is direct cause of the local scour among lots of the scour effect factors, and the scour depth and width can be estimated through interrelationship analysis with scour area to use the dimensionless parameters including these such as Keulegan-Carpenter number, Ursell number etc. In this paper, to find out closely relation with the dimensionless parameters and scour width, performed an experiment with the variations of pipe diameters, wave heights and wave periods and then analyzed it. As the result, while Reynolds number and period parameter were seen to disperse local scour width largely, Shields number, KC number and Ursell number appeared good interrelationship. Specially, Shields number doesn't much affect the scour depth but has good relation for the scour width.

• Ecology and Resilient Infrastructure
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• v.7 no.2
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• pp.83-89
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• 2020

This hydraulic study analyzed the scour effect at fixed downstream weirs based on the changes in the upstream bed slope. The study was performed using six different bed slopes, that is, 0%, 2%, 3%, 4%, 7%, and 10% at 0.117 ㎥/s in all cases. The scour depth, scour length, and scour volume were measured using a broadband laser scanner to quantitatively analyze the scour at the downstream weir. This study also examined the adequacy of the designed apron length by comparatively analyzing the results of the scour experiments and the apron length calculated using conventional design standard formulas. The analysis of the local scour effect at the downstream weir showed that scour length and scour depth increased as the bed slope became steeper. A comparison between the results of the scour experiment and that of the conventional design formulas showed that both formulas of the National Construction Research Institute and the Bligh were distributed within the allowable values when there was no upstream bed slope. However, as the bed slope upstream of the weir gradually increased, the scour lengths of the apron deviated slightly from the values obtained from the conventional design formulas.

• Korean Journal of Hydrosciences
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• v.6
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• pp.23-37
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• 1995

In this experimental paper, the maximum scour depth at pier was student. The model of the pier of San Gye bridge in the Bocheong stream was set for the experimental studies. Several model verification processes were conducted through the roughness comparisons between model and prototype, pursuing scour depth variations with time depending upon channel bed variation, the comparison of the ratios between falling velocities and shear velocities in the model and prototype, and the comparison of pier scour depths between experimental data and field measuring data. The experiments were conducted in the free flow conditions and pressure flow conditions. The maximum scour depth at piers in the pressure flow conditions is almost twice as much as compared to the free flow conditions. Also, the maximum scour depth variations are indicated in the figures based on the Froude numbers, opening ratios, water depths and approaching angles in the free surface flow conditions.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.287-292
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• 1998

The phenomena of local scour due to a current from a seadike closure gap which is protected by rock, then on to an erodible bed, have been studied. Based on the data of hydraulic model test, the scour characteristics have been investigated for the variation of maximum scour depth with time until reaching equilibrium stage and the shape of ultimate scour hole. A brief evaluation of DHL formula for the relationship between maximum scouring depth and time and a dimensionless form leading to time-scale introduced. On the basis of DHL formula, modified DHL formula denoted DHL-RDC formula is extend to the range of estimation of scour depth compared to DHL formula verified by model test.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.337-340
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• 2011

In this study, qualitative and quantitative evaluations are performed using the hydraulic analysis of fiber stone for bridge pier scour protection. We can consider that the effective scour protection should be suggested from the side of hydraulic stability, structure stability, and permissible tractive force. The perfect verification, however, on the fiber stone for bridge pier scour protection is not sufficient because of short literatures and experiments on the field study. The continuous research, therefore, will be needed to establish reliable verification using literatures investigation and the various experiments on the fiber stone for bridge pier scour protection.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.166-173
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• 2002

Seismic bridge failure due to the combined effects of earthquake and local scour are examined in probabilistic perspectives. The seismic responses of multi-span continuous bridge with deep foundations are evaluated with a simplified mechanical model. The probabilistic local scour depths around the deep foundations are estimated by using the Monte Carlo simulation. From the simulation results, it is found that seismic responses of a bridge slightly increase due to the local scour effect. The effect of local scour on the global motion of the continuous bridge is found to be significant under weak seismic intensity. In addition, the duration to regain its original foundation stiffness is critical in estimating the probability of foundation failure under earthquake. Therefore, the duration in recovering the foundation stiffness should be determined reasonably and the safely of the whole bridge system should be evaluated by considering the scour effect.

• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.529-536
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• 2016

The existing methods to estimate the maximum scour depth in the bend of steep gravel bed channel have been evaluated by the hydraulic movable-bed experiments. In the $90^{\circ}$ bend steep-slope channel paved with the fluvial gravels which are uniform in size and have a mean diameter of 43mm, the maximum scour depths due to the flow discharge and the gradient of bed slope have been investigated and compared with the scour depth computed from the equations. The local scour has occurred in conditions that the bed slope is steeper than 0.02 and the $F_r$ is greater than 0.95. Except Lacey's equation and Zeller's equation, the existing methods computing the maximum scour depth overestimate the maximum scour depth in the steep channel with the very coarse gravel bed. However, Lacey's equation with the bed material size and Zeller's equation considering the approach channel gradient and the bend angle may be relatively used to estimate the scour depth in bend of the steep gravel-bed river.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.667-676
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• 2005

In this research, the reasonable local scour estimates considered conditions of the bed material and the flow was accomplished on two piers P14 and P17 of Il-san bridge. Especially, the Il-san bridge was located on the lower Han-river where is influenced by the tides of In-chon, and it has hydraulic condition that can cause the bridge piers local scour because of tides at ordinary times, as well as a flood. Therefore, the local scour depth has been presented influenced by the maximum velocity of the flow when a flood after construction and the tides on construction on the basis of the standards of river design and road design, furthermore, the results was made a comparative analysis. According to the results, the local scour depth on the basis of the standards of river design was higher than it on the basis of the standards of road design(SRICOS), and the local scour depth influenced by the maximum velocity of the flow when a flood after construction was determined the final local scour depth of P14 and P17 at the Il-san bridge. It was ascertained that the local scour depth did not exceed the inserted depth of bridge foundation.