Maximum scour depth around bridge pier in gravel bed streams

Self Cite

Flume experiments have been carried out under clear water scour conditions to analyze the maximum equilibrium scour depth and scour processes in armored streambeds. A total of 85 experiments have been carried out using different diameters of circular piers and non-uniform gravels. A graphical approach for dimensionless scour depth in equilibrium condition around the circular pier in armored streambeds has been developed. As per this curve, the maximum dimensionless scour depth variation with dimensionless armor particle size depends on the densimetric particle Froude number (Frd50), and the decreasing rate of dimensionless scour depth decreases with the value of Frd50.

Section: Introductionmentioning

confidence: 99%

Local Scour of Armor Layer Processes around the Circular Pier in Non-Uniform Gravel Bed

Pandey

Chen

Sharma

et al. 2019

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“…Larger mass particles require more energy to remove from the scour hole [6,16]. At the same time, some sand particles are covered by the gravel particles and, gradually, this process results Maximum scour depth around spur dikes in uniform sediment beds are studied extensively compared to the sediment mixtures [9][10][11][12][13][14]. However, rivers in upper reaches or in hilly streams are mainly composed of different sediment mixtures or non-uniform sediments.…”

Section: Introductionmentioning

confidence: 99%

“…However, rivers in upper reaches or in hilly streams are mainly composed of different sediment mixtures or non-uniform sediments. Uniform sediment is defined as when the value of the geometric standard deviation σ = d 84 /d 16 is greater than 1.4 [14], where d 84 and d 16 are particle sizes at 84% and 16% finer, respectively. In non-uniform sediment mixtures, finer particles are being removed first, followed by the coarser particles trying to act as a protective layer near the bridge elements due to the complex sediment transport processes [5].…”

Section: Introductionmentioning

confidence: 99%

Scour around Spur Dike in Sand–Gravel Mixture Bed

Pandey

Lam

Cui

et al. 2019

Self Cite

Scour is the main cause of failure for spur dike. The accurate prediction of scour around spur dike is essential to design a spur dike. The present study focuses on the maximum scour depth in equilibrium condition and parameters, which influence it in a sand–gravel mixture bed. Outcomes of the present experimental study showed that the non-dimensional maximum equilibrium scour depth increases with critical velocity ratio (U/Uca), water depth-armour particle ratio (h/da), Froude number for sediment mixture (Frsm), water depth-spur dike length ratio (h/l), and decreases with increase in armour particle-spur dike length ratio (da/l). The maximum scour depth is proportional to dimensionless parameters of U/Uca, h/da, Frsm, h/l, but the scour depth is inverse proportional to da/l. Scour around spur dike in a sand–gravel mixture is mainly influenced by the property of the sediment mixture. The scour increases with decrease in non-uniformity of the sediment mixture. A non-linear empirical equation is proposed to estimate the maximum scour depth at an upstream nose of rectangular spur dike with a maximum error of 15%. The sensitivity analysis indicates that the maximum non-dimensional equilibrium scour depth depends on Frsm, followed by the secondary sensible parameters da/l, h/l, and h/da.

“…Although the above literature [6,12,13] has paid attention to the morphological characteristics of scour hole profiles from the time dimension or the spatial dimension, the relevant discussion on profile area of the scour hole with time evolution has not been mentioned. It is important that this parameter is one of the important parameters which cannot be ignored in the local bed shear stress evolution model, namely, the evolution characteristics of the scour hole profile area determines the evolution trend of local bed shear stress [14][15][16][17]. At present, more of the literature has reported that the local bed shear stress gradually decreases over time [18][19][20], the scour reaches the equilibrium state, and its value is close to the constant.…”

Section: Introductionmentioning

confidence: 99%

The 3-D Morphology Evolution of Spur Dike Scour under Clear-Water Scour Conditions

Zhang

Wang

Zhang

et al. 2018

By changing the alignment angle of spur dike, this study focused on the evolution of scour hole morphology in three alignments under clear-water scour conditions, including the 3-D structure of the scour hole, 2-D profile morphological evolution process and the evolution characteristics of the local bed shear stress. The results show that the plane area and volume of the scour hole both are power functions over time, which is similar to the evolution characteristics of scour depth. Local scour includes three stages: The initial stage, development stage and balance stage. The local bed shear stress presents successively: τb > τc, τb = τc and τb < τc. Based on this characteristic, the evolution mechanism between scour hole morphology and the local bed shear stress is further clarified. Furthermore, although the alignment of the spur dike significantly affects the longitudinal and vertical dimension erosion rates of the scour hole, the scour hole morphology is not only relatively constant but also has a specific proportion, and the evolution process is orderly in the whole process of evolution. To the scouring equilibrium state, the length of the scour hole on the upstream and downstream of the spur dike is approximately in line with the golden section feature. The related results provide technical support for scour parameter design and scour hole protection of spur dike in flood period.