Hydraulic bridges are critical components in infrastructure network. One of the major causes of its collapse is due to local SCOURing of its foundations. Hence in this study, the mechanism and various factors affecting local SCOUR around bridge piers was analyzed. For this, a software platform Hydrologic Engineering Center River Analysis System (HEC-RAS) was used to evaluate local SCOURing around piers of spillway bridge with radial gates of Telengiri Irrigation Project located in Koraput district of Odisha, India. Soil samples were collected at the site and tested in the laboratory to determine various properties required for model inputs and assess the vulnerability of soil for SCOURing. Geometric data and design specifications of radial-gated bridge structure along with soil properties of the case study were used to build HEC-RAS model and then steady-state flow profiles were given to calculate local SCOUR DEPTH. Analytical methods such as Kothyari, Richardson, and IRC equations were used to corroborate local SCOUR DEPTH values with the model. The model predicted SCOURing of 8.29m which is close enough to values predicted by Richardson equation (8.95 m). This small discrepancy was due to not accounting for bed conditions and armoring of bed material. Parameters were varied in the model such as discharge, width and geometry of piers, skew angle of bridge and piers, angle of attack, and different bed configurations to simulate their effect on local SCOUR DEPTH. The soil was found to be highly erodible as per the soil erodibility factor obtained from the Wischmeier equation.

Grade control structures are hydraulic structures used to stabilize a river bed. SCOUR downstream of this structure is the main cause of its failure. Studies have developed numerous empirical relations for SCOUR DEPTH prediction that designers must choose between to decide the most effective equation for a specific application. This study tested the condition of submerged jets over beds of sediments (median size=1.5, 2.4, 3.15 mm) downstream of a weir for discharges of 10, 15, 20 l/sec and tail water DEPTHs of 16, 21, 26 cm. The analysis applied multi-dimensionless group regression using Minitab software to predict maximum SCOUR DEPTH. All previous relations were compared to the data and it was found that the relations developed by Veronese A, Mason and Arumugam, Agostino and Ferro, and Chee and Padiyar predict the SCOUR DEPTH better than do other relations. In addition, a new relation was developed that produced better results at RMSE=0.015 and coefficient correlation=94%.

As a destructive process, SCOURing exposes bridge foundations to failure and disastrous consequences. Control structures of various arrangements are capable to change and manage the adverse effects. This paper aims to investigate the effect of submerged vanes of a quasi-triangular arrangement (of heights 0, 4, and 6 cm), eppi, and sills (of height 4.5 and 9 cm) on SCOUR development. All tests were executed in a rectangular slope-less flume covered with sediments of D50=1.8 mm. Temporal and equilibrium SCOUR DEPTH were mapped for Froud numbers: 0.15, 0.2, 0.25, and 0.6. Results clarified the aggregate effect of the eppies on the SCOUR DEPTH due to section contraction. Submerged vanes and sill were set up to deteriorate sediment transport. Although the vane of height 4 cm had the most superior performance, but the sill installation of height 4.5 cm greatly increased vane's effect, so that a remarkable reduction of SCOUR was occurred at the first pier foundation.

Many financial and living expenses are caused annually due to the destruction of bridges in the flood events. Studies show that changes in bridges' geometry can lead to changes in the time to reach maximum SCOURing. The purpose of this study was to investigate the time variation of SCOUR DEPTH at the bridge pier. For this purpose, a laboratory flume with a length of 14 meters, a width of 1. 5 meters and a height of 0. 7 meters was used. Four different forms of the slot were created on the rectangular pier including two rectangular (vertical and horizontal), square and diamond slots. Experiments were carried out at three levels: above the bed, on the bed and under the bed at four flow rates of 21. 2, 25. 6, 29 and 32 l/s in sediments with a mean diameter of 0. 5 mm. The results of this study showed that the SCOUR rate is higher in the first minutes of the start of the test. Over time, the intensity of changes is reduced. increasing the DEPTH and volume of the SCOUR hole, decreases the intensity of the changes. Moreover, there is a delay between Approaching the dimensionless SCOUR number to a certain degree and next changes in this parameter, which indicates that in a flood event, performing emergency measures could be effective. In addition, at a given time, placing slot at the top of bed increased the SCOURing dimensionless number by twice rather than placing under the bed.

SCOUR around piers and abutments leads to a lot of bridge failures. SCOURing around the bridge piers and abutments is one of the most important factors in bridge failure which happens over time and increases during floods, probably causing general damage to the bridge. Accordingly, the accurate estimation of SCOURing around the bridge piers and abutments can help engineers to take steps to deal with bridge destructions. Recently, data-driven models have been used widely to estimate the SCOUR DEPTH around bridge piers and abutments. Najafzadeh, Barani and Hessami-Kermani (2015) used a set of data-driven models such as the gravitational search algorithm and the particle swarm optimization algorithm to estimate the SCOUR around bridge abutments. Sediment particles size, geometric characteristics of bridge abutment and approach flow conditions were considered as effective parameters on SCOURing mechanism. The results of this research showed that data-driven models can estimate the SCOUR DEPTH with high accuracy. In the present study, M5 tree model has been used to predict maximum SCOUR DEPTH around bridge abutment. High accuracy, simplicity and understandability are considered the advantages of this algorithm. A huge amount of data from credible references have been used to build and validate the tree model...

Considering the importance of SCOURing in the design of bridges, nowadays, to increase the accuracy of SCOUR DEPTH estimation, artificial neural networks are used. In this research, a model for estimating SCOUR DEPTH around the bridge pier group was used by a new method called support vector machine. In this method, the statistical parameters of RMSE, R 2, DC, were used to evaluate the performance of the models. The results showed that using compounds of the sedimentary and hydraulic parameters in the support vector data model provided better results in estimation of SCOUR DEPTH. For example, in tripod mode, the assessment criteria values for the scenario 1 (hydraulic parameters), were R 2 = 0. 9914, DC = 0. 9758 and RMSE= 0. 0576, and for scenario two (hydraulic and sediment parameters), were to R 2 = 0. 9924, DC = 0. 9803 and RMSE = 0. 0529, which indicated better performance of the support vector machine in the second scenario. Finally, non-linear equations were presented for calculating the SCOUR DEPTH around the inclined Single and group piers.

One of the main reasons of bridge destruction is the bridge piers SCOUR. A more accurate computation of SCOUR DEPTH would lead to a more solid design of bridge piers. Empirical equations can be applied to compute the SCOUR DEPTH. In this study, the coefficients of 17 empirical equations were optimized using genetic algorithm and fieldwork values. 80% of the field data were used to optimize the equations and the rest were used to verify them. The RMSE, MAE, E and R2 criteria were applied to evaluate the optimization method where the results showed the ability of genetic algorithm in empirical equations optimization. The Froehlich (1988) equation had the highest degree of precision among the empirical equations, so the genetic algorithm has had the least effect on the optimization of this equation. The optimized Neill (1964), Melville (1975), Laursen and Toch (1956), Blench II (1962) and Hancu (1971) equations with respectively, 75, 72, 71, 71 and 71 percent showed the highest reduction in RMSE error criteria. The optimized Blench II (1962) equation with RMSE, MAE, E and R2 criteria equal to 0. 57 m,-0. 085 m, 62 and 0. 65 percent respectively, presented the highest correlation coefficient and lowest error. In the end, more equations were proposed to predict the bridge piers SCOUR DEPTH.

River channel confluences form important morphological element of every river system that are characterized by complex pattern of three-dimensional fluid motion and the most highly turbulent locations in fluvial systems. Because of variation in velocity, discharge, turbulent and finely bed load in these location a SCOUR hole is developed just downstream of the river confluence. These phenomena can accelerate the rate of bank erosion and affect the river morphology. Therefore it is necessary to clearly understand mechanism of sediment pattern in this location. In this study, first by using dimensional analysis, general non-dimensional equation were developed in which for the first time the densimetric Froude number was included. Then the total of 55 experimental tests were conducted to investigate the effect of discharge ratio, wide ratio and downstream densimetric Froude number on DEPTH SCOUR at 90 degree confluence. The result of experimental test showed that the DEPTH of SCOUR at confluence increases with increasing of discharge ratio and densimetric Froude number whereas it decreases as width ratio increasing. It was found that SCOUR DEPTH is more related to the densimetric Froude number. Finally, relationship was developed for prediction of SCOUR DEPTH.

Stilling basins are used in the outlet of channels, chutes and culverts to dissipate the excess kinetic energy of incoming flow. One of the basins in which the energy of incoming flow is dissipated by impact, is USBR VI stilling basin. The USBR VI stilling basin was first introduced by Bradely and Peterka in 1995 and then was modified by Biechley in 1978. This structure consists of a middle wall and an endsill. SCOURing around the structures that are located in the vicinity of erodible beds, such as stilling basins, has always been one of the most important problems related to these structures. Unlike other types of stilling basins, the studies carried out around this type of basin are limited, and there are still many hydraulics features of this type that have not been considered in previous researches. In this article, the effect of the shape of endsill on SCOUR DEPTH downstream of stilling basin is evaluated. Based on Beichley graph (Standard Design), the physical model of stilling basin was designed, constructed and installed in the hydraulic laboratory of Tarbiat Modares. Experiments were conducted in a 0.8 m wide, 0.9 m height, and 0.8 m length rectangular channel. The pump used in the experiments had a nominal flow rate of 400 cubic meters per hour (about 120 liters per hour), a head of 11.7 meters, a power of 22 horsepower, and an engine speed of 1450 rpm. In the design of experiments, the parameters including approach Froude number (i.e. 1, 1.5 and 2 times of standard Froude number on Beichley graph), the diameter of inlet pipe (i.e. De = 5, 8, and 12 centimeters), and endsill shapes (triangular, stepped and circular quadrant), in the form of 27 tests were assessed to study the dimensions of the SCOUR DEPTH. The observations revealed that in all three endsill shapes, the increase in Froud number has led to the decrease in SCOUR index. the circular quadrant endsill had the lowest SCOUR DEPTH in the front of endsill and the least SCOUR index, in the range of the Froude number of 2 to 6. In the range of the Froude numbers of 9 to 14, the triangular endsill causes the lowest SCOUR index. In the relative diameter of inlet pipe equals to 10.16, for Froud numbers equal to 9.27 and 13.91, the triangular shaped endsill has the least SCOUR index. in every endsills, decreasing the pipe’s diameter results in the maximum DEPTH of the SCOUR. Another important finding is that sediment bar is only formed in experiments conducted with inlet pipe’s diameter equal to 5cm for Froude number equal to Froude number on Beichley graph. The biggest amounts of the height of sediment bar and maximum SCOUR DEPTH are found for the stepped endsill and the smallest amounts of the height of sediment bar and maximum SCOUR DEPTH are found for the circular quadrant endsill. Subsequently, the non-dimensional equations according to the Froud number of incoming flow and the relative diameter of inlet pipe, were presented to estimate the maximum DEPTH of the SCOUR hole.