In this paper, scour profiles downstream of adverse stilling basins, due to the submerged jet issuing from a sluice gate, were investigated. Experiments were conducted in a wide range of sediment sizes, incoming flow Froude numbers, tail water depths, length and slope of the stilling basin. The results showed that the scour profiles at any bed slope are similar in shape. However, the longitude evolution of scour profiles and the volume of eroded materials increased in accordance with the slope of the basin. It was observed that the maximum depth of the scour hole occurs in the vicinity of the side walls and slightly decreases towards the centerline. A polynomial equation was derived to describe the nondimensional scour profiles at different slopes. Based on experimental data, the scour characteristics have been correlated with the time of equilibrium stage by developing some empirical relationships. Finally, a power-law equation was derived and fully defined to include the dimensions of the scour hole time scale and the geometry of the sluice gate.

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.

Abutment as a hydraulic structure is used in river training, river bank protection and agricultural land conservation. In spite of protecting river banks, abutment may face with scour phenomenon due to flow concentration particularly at the abutment nose. In order to investigate the effect of contraction ratio, some experiments were conducted using short wing-wall abutments. The experiments were carried out in a clear-water condition at three different V/Vc values namely 0.9, 0.95 and 0.98. The results showed that relative dimensions of scour hole, including upstream length, downstream length and width of hole, decreased about 7, 36 and 24 percents with increasing canal contraction, respectively. Maximum scour depth occurred at the contraction ratio of 0.16 and beyond this limit, there was a reduction of up to 21.5 percents at the maximum scour depth. Maximum scour depth was also 3.27 times of the abutment length. Therefore, it may be concluded that in order to avoid contraction effect in a model abutment, the L/W ratio should be less than 0.16, otherwise scour depth decreases in respect to maximum scour depth.

The paper describes the evolution of local scour hole downstream of an adverse stilling basin. The research was conducted using a wide range of Froude number, sediment size, tailwater depth, length and slope of stilling basin. The maximum depth of scour and its distance from the stilling basin attained 87.5% in the first 24 hours and 86.3% when the experiment was continued for 54 hours. A power equation was adopted describe the characteristic dimensions of scour hole, time scale as well as geometry of stilling basin and sluice gate. The results showed a certain similarity among the scour profiles developed at different times. However, the shape of the holes was influenced with the change in length and slope of stilling basin. As the slope of stilling basin increased by 15%, the volume of sediment removed from the unit width of the hole, was increased by 30%.

The main reasons of bridge failure are local scour around the piers. In fact, they will be appeared as a scour hole in the river bed. Moreover, lack of control during the time, local scouring will threaten stability of structure. Therefore, determining of depth and dimension of the scour hole, also finding effective factors on scouring are important. Lots of researchers have studied the local scour around the bridge piers. Actually, they have proposed lots of appropriate techniques to control and to reduce scour around piers and bridge abutments. These proposed approaches are divided into two methods which are altering the flow and bed-armoring. In this research, the local scour around the bridge piers in a cohesive soils have studied. Particularly, the cohesive soils in form of mixture of Bentonite (montmorillonitic clay from 0 to 15%) and bed sediment (fine sand) used. In fact, this approach is a solution to challenge bed-armoring against existence shear stress. As a result, the proposed method will be used for controlling the scour. The experiments were carried out at the Hydraulic Laboratory of the Water Engineering Department, at Shiraz University, Iran. The laboratory flume was a rectangular cross section with 18 m length, 1. 2 m wide and 0. 4 m deep. According to channel geometry, the discharge and the depth of flow were determined to be 0. 034 ⁄ and 13 cm, respectively. In all experiments, the discharge and flow depth were constant. This study focused on the best compaction conditions, optimum clay content and the bed shear strength. The undrained shear strength of the soil was measured using an in situ miniature van shear apparatus. The best compaction conditions including optimum moisture and compaction energy. From standard Proctor test, the optimum initial water content Wopt and the optimum dry density ρ dopt was determined. The compaction was expressed as the ratio of dry density ρ d to maximum dry density ρ dopt of the mixture. Therefore three relative compaction equal to70%, 80% and 90% used. Also, three water content optimum initial water content, optimum initial water content – 3% and optimum initial water content + 3% are used. The results indicate that for smaller clay content (5%) the shape of the scour hole was similar to that in sand sediment and is regular and symmetrical. For clay content equal to10%, scour hole is geometrically much irregular compared to that observed in sand bed and it is observed that a steeper slope of the scour hole in sediment mixture. The slope became steeper whit an increase in relative compaction. In fact, the higher relative compaction and the higher clay content increases shear strength and decreases the maximum scour depth. The samples compacted at optimum water content creates a structure with the most resistant to scour. The erodibility of samples compacted dry of optimum water content is less than samples compacted on the wet side of optimum. The results showed that under conditions which the amount of Bentonite equals at least 10% of dry weight in the mixture (Bentonite and sand sediment), relative compaction equal s to 90% and and water content equals to optimum moisturesimultaneously, the local scour reduces by 100% in single pier. In addition, the influence of the compaction and type of clay mineral was investigated. The results show that Bentonite was more effective than Kaolin. If the 15% of dry weight Kaolin clay mixed with bed sand sediment to be used and relative compaction equal to 90% and water ontent equals to optimum moisture, simultaneously, the maximum scour hole was reduced only by 34%.

Time-variation of scour depth around abutments is more complicated due to the three-dimensional vortex flow. In this study, variation of the scour depth with time around abutments was investigated experimentally under clear-water conditions. The Nonlinear Regression (NLR), neuro-fuzzy inference system (ANFIS) and artificial neural networks (ANN) were employed to predict the time variation of scour depth at intermediate and short abutment. Statistical analysis showed that, although the presented regression method (R2=0.957, RMSE=0.049 and MAE=0.035) provided a better prediction compared to previous equations but the ANFIS (R2=0.961, RMSE=0.041 and MAE=0.025) produces a more accurate result. Statistical measurements showed that ANFIS as well as ANNs can be considered as a robust technique to predict the temporal scour depth at the short and intermediate abutment.

In regard to wide piers, the pile group rather than single pile is used frequently to bear the loading of the structure in a particular arrangement; piles group composed of only one column of piles in the flow direction has a great effect on supporting the bridge deck. In this study, local scour at a single column arrangement of the piles group made up of four rows of piles characterized by different piles spacing was studied for clear-water conditions with two flow discharges of 20 and 35 l/s (the effect of increasing the flow depth with the same flow intensity). The results indicated that an increase in the flow depth not only greatly enhanced the scour depth and the width of the scour hole. Besides, the investigation of the relative flow depth on scour extent showed the need for revision in deep water conditions, as reported in the literature. The results of the pile group experiments revealed the noticeable impacts of piles spacing on the local scour. The bigger pile spacing caused a feeble interaction of wake-horseshoe vortices, leading to a decrease of the scour depth; the separate view of the scour holes was generated at individual piles. Finally, the results were compared with commonly used comprehensive models. The findings of this study can be applied for the appropriate selection and positioning for the countermeasure of the scour at bridge piers...

Local scour downstream of the hydraulic structures is of great importance. In wide channels, a set of multi gates instead of a single gate may be responsible for transferring water and adjusting upstream water level due to difficulty in gate maneuvering, economic considerations, and ease of movement. Operating parallel sluice gates can create different scenarios owing to clogging or failure in some gates. This study was aimed to assess the effect of different cases of parallel sluice gates operational management, gate opening to channel width ratio, and length of the separator walls on local scour development downstream of parallel sluice gates in different operations. Five operational scenarios were investigated on three parallel sluice gates. The results of the present study showed that the dimensions of the scour hole are a function of the symmetrical and asymmetrical operation of the gates. By reducing the gate opening to channel width ratio, the dimensions of the scour hole increased compared to the classical hydraulic jump mode. Maximum scour depth in the symmetric operational management scenario (B) and the asymmetric scenario (A), increased by 120% and 43%, respectively, compared to the ABC scenario. Increasing the length of the separating walls can be a suitable option to control the dimensions of the scour hole in different operations. Owing to a 20% increase in the length of the separator walls, the maximum scour depth decreased by 68% in the maximum Froude number (8. 6) and 122% in the minimum Froude number (4. 5) in scenario B. These percentages for scenario A are equal to 17 and 58, respectively. In addition, relations were presented to estimate the dimensions of scour hole in the symmetrical and asymmetrical operation of the parallel gates.

Local scouring around bridge piers is a natural phenomenon caused by the erosive process of flowing stream on alluvial beds. The 3D flow field around bridge piers interacting with the bed materials increases complexity of local scour process. The local scour depth develops in accelerated flows and if it is not predicted correctly, the bottom level of local scour hole will exceed the original level of pier foundation. In this case the failure of bridge will occur. Using different methods of local scour countermeasure for reducing the magnitude of local scouring depth and retrofitting costs would be economically efficient. As a local scour countermeasure method, applying slots in the piers could reduce the local scour depth around circular piers. Since in natural streams the piers are skewed to flow in most cases, it is more feasible to evaluate the skew slots effects on scour reduction. The present study focuses on numerical simulation of maximum depth of scour due to the installing of slots in various angles of flow attacks by employing a 3D numerical model (SSIIM program). The results show the ability of SSIIM for modeling the local scouring around bridge piers with slots.

The main cause of concern about the stability of bridge foundation is the occurrence of scour around the piers. Therefore, there is an interest in finding reliable ways to reduce and control local scour depth. The use of slot through a pier is one of the new proposed methods for controlling and reduction of local scour at bridge piers. This study examines the effect of using rectangular slots through the pier groups at clear water condition. The results of experiments show that in pier groups, reinforcing effect causes that the scour depth at front pier is more than that at a single pier. Also, sheltering effect causes that the scour depth at rear pier is less than that at a single pier. The presence of a slot in a two and three pier groups causes the reinforcing effect increases and sheltering effect decreases. The efficacy of a slot in rear pier is more than that in front pier and single pier for three and two pier groups with S=4b. It was also found that the efficacy of slot for two and three pier groups with S=2b for all piers are almost similar and similar to the single pier. Efficacy of slot in reduction of scour depth, increased with increasing pier spacing.