Search

Dam overtopping failure and the resulting floods are hazardous events that highly impact the inundated areas and are less predictable. The simulation of the dam breach failure and the flood wave propagation is necessary for assessing flood hazards to provide precautions. In the present study, a two-dimensional HEC-RAS model was used to simulate the flood wave resulting from the hypothetical failure of Al-Udhaim Dam on Al-Udhaim River, Iraq, and the propagation of the resulting dam-break wave along 100 km downstream the dam site for the overtopping scenario. The main objective is to analyze the propagation of the flood wave so that the failure risk on dam downstream areas can be assessed and emergency plans may be provided. The methodology consisted of two sub-models: the first is the dam breach failure model for deriving the breach hydrograph, and the second is the hydrodynamic model for propagating the flood wave downstream of the dam. The breach hydrograph is used as an upstream boundary condition to derive the flood impact in the downstream reach of Al- Udhaim River. The flood inundation maps were visualized in RAS-Mapper in terms of water surface elevation, water depth, flow velocity, and flood arrival time. The maximum recorded values were: 105 m (a.m.s.l.), 18 m, 5.5 m/s, and, respectively. The flow velocity decreased from upstream to downstream of the terrain, which means less risk of erosion in the far reaches downstream of the study area. The inundation maps indicated that the water depth and flow velocity were categorized as Catastrophic limits on the terrain's area. The results offer a way to predict flood extent and showed that the impact of a potential dam break at Al-Udhiam Dam will be serious, therefore, suitable management is needed to overcome this risk. Moreover, the maps produced by this study are useful for developing plans for sustainable flood management. Doi: 10.28991/cej-2021-03091739 Full Text: PDF

Local scour at the piers is one of the main reasons of bridge foundation undermining. Earlier research studies focused mainly on the scour at a single bridge pier; nevertheless, modern designs of the bridges comprise wide-span and thus group of piers rather than a single pier are usually used to support the superstructure. The flow and scour pattern around group of piers is different from the case of a single pier due to the interaction effect. Reviewing the literature of local scour around bridge piers group revealed that the local scour around bridge piers group founded in cohesive soil bed was not investigated, and most of the scour studies were related to scour in cohesionless soils. The objective of the present study is to investigate the effect of the interaction between two in-line (tandem) circular bridge piers of variable spacings founded in cohesive soil on the local scour. A set of laboratory flume experiments were conducted under the clear-water scour condition to investigate this effect. This study is the first that investigates experimentally the scour around group of bridge piers in cohesive bed. It was found that the maximum scour depth at the upstream pier of the two in-line piers occurred at a spacing of two times the diameter of the pier, scour at the downstream pier was reduced due to a sheltering effect, the interference effect will be reduced for pier spacings larger than three times of the pier diameter. A recent pier scour equation was used to estimate the scour depths at the two in-line piers in cohesive soil and compare the estimated value with the measured scour depths in the laboratory. The comparison indicated that the proposed scour equation overestimates the scour depths at both the upstream and the downstream pier.

Local pier scour is one of the main causes of bridges failure. Many studies were conducted to investigate the pier scour experimentally. Most of them studied the scour at a single pier, while the scour around a group of piers is relatively less studied. Recently, the technological development and advancement in computer abilities presented the numerical models as a promising tool in engineering analysis and design. The numerical models have more flexibility than the physical models and less limitations. The predictive capability of the hydro-morphological model for the scour around bridge piers in clear water conditions have been investigated using FLOW-3D 11.2.2 as a simulation tool. The objective of the study is to investigate the effect of piers interaction at tandem piers arrangement on the resulting scour pattern. The Van Rijn sediment transport model and (RNG) k-ε turbulence model were used to simulate the scour process and sediment transport. The computations of the numerical model have been compared with experimental data from the literature. This study demonstrates that a 3D numerical model can effectively predict the scour around tandem piers, though the scour depth at the nose of the piers was underestimated. It is found that the capability of the numerical model to predict the scour depth at the tandem piers is accepted but it was not effective at estimating the accurate location of the maximum scour depth., {"references":["Saghravani, S. F., & Azhari, A. (2012). Simulation of clear water local scour around a group of bridge piers using an Eulerian 3D, two-phase model. Progress in Computational Fluid Dynamics, An International Journal, 12(5), 333-341.","Ataie-Ashtiani, B., & Aslani- Kordkandi, A. (2013). Flow field around single and tandem piers. Flow, turbulence and combustion, 90(3), 471-490.","Beg, M., & Beg, S. (2015). Scour hole characteristics of two unequal size bridge piers in tandem arrangement. ISH Journal of Hydraulic Engineering, 21(1), 85-96.","Kim, H. S., Roh, M., & Nabi, M. (2017). Computational modeling of flow and scour around two cylinders in staggered array. Water, 9(9), 654.","Keshavarzi, A., Shrestha, C. K., Melville, B., Khabbaz, H., Ranjbar- Zahedani, M., & Ball, J. (2018). Estimation of maximum scour depths at upstream of front and rear piers for two in-line circular columns. Environmental Fluid Mechanics, 18(2), 537-550.","Das, R., Das, S., Jaman, H., & Mazumdar, A. (2019). Impact of Upstream Bridge Pier on the Scouring Around Adjacent Downstream Bridge Pier. Arabian Journal for Science and Engineering, 44(5), 4359-4372.","FLOW-3D V11.2.2 documentation, 2017.","Alemi, M., & Maia, R. (2018). Numerical simulation of the flow and local scour process around single and complex bridge piers. International Journal of Civil Engineering, 16(5), 475-487.","Omara, H., Elsayed, S. M., Abdeelaal, G. M., Abd-Elhamid, H. F., & Tawfik, A. (2019). Hydromorphological numerical model of the local scour process around bridge piers. Arabian Journal for Science and Engineering, 44(5), 4183-4199.","Melville, B. W. (1975). Local scour at bridge sites (Doctoral dissertation, researchspace@ auckland)."]}