A master’s thesis by researcher Mustafa Awad Jatheer was defended at the Department of Civil Engineering, College of Engineering, University of Basrah. The thesis, titled "...", was supervised by Prof. Dr. Saleh Issa Khasaf and Prof. Dr. Mohammed Jawad Kadhim Issa. Experimental Study of  Scour Around Pile Groups with Different Arrangements

Local scour around pile foundations is an important soil-structure interaction phenomenon that can significantly reduce the load-carrying capacity and stability of deep foundations. This study presents an experimental investigation of local scour around single piles and pile groups under clear-water flow conditions, with particular emphasis on the effects of pile shape, flow intensity, pile-group arrangement, temporal scour development, and spatial scour distribution.
The experimental program was conducted in a dedicated laboratory facility specifically designed and constructed by the researcher, incorporating a recirculating open-channel flume with a uniform non-cohesive sand bed. In the first stage, three single-pile shapes—circular, triangular, and square—were investigated under identical hydraulic and sediment conditions. Experiments were conducted at flow intensity ratios ranging from 0.60 to 0.90, where the flow intensity ratio represents the ratio of the mean approach flow velocity to the critical velocity for the initiation of sediment motion. The temporal development of scour was also investigated to determine the time required to approach equilibrium conditions. Approximately 90–95% of the final scour depth was reached within about 2.5 hours, and a test duration of three hours was adopted for the subsequent experiments.
The results showed that scour depth increased with increasing flow intensity for all tested pile shapes. The circular pile produced the lowest scour depth values, the square pile produced the highest values, and the triangular pile produced intermediate values. Compared with the circular pile, the triangular pile increased scour depth by approximately 4–8%, whereas the square pile increased it by approximately 13–21%. Based on these results, the circular pile was selected for the subsequent pile-group experiments.
Four pile-group arrangements were investigated: tandem, 2×2, 2×3, and staggered configurations. The results demonstrated that pile-group arrangement significantly influenced both the magnitude and spatial distribution of local scour. Among the tested arrangements, the 2×3 configuration produced the highest scour depth, followed by the 2×2 and tandem arrangements, whereas the staggered arrangement produced the lowest scour depth. The location of maximum scour also varied with pile-group arrangement due to pile–pile interaction and the associated modification of the local flow field. In the tandem arrangement, the maximum scour depth occurred near the upstream pile, while the three-dimensional contour maps showed that scour was non-uniformly distributed within the pile groups and that the location of maximum scour shifted depending on the arrangement and flow intensity.
Finally, an empirical equation was developed using dimensional analysis and nonlinear regression to predict the relative scour depth. Comparison between the measured and predicted values showed strong agreement, with a coefficient of determination of 0.982, indicating that the developed model satisfactorily represents the experimental results within the limitations of the present study.