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A series of laboratory experiments was conducted in a confined channel to study the effect of armor layer on the scour formation induced by a deeply submerged circular turbulent wall jet. A wide range of particle sizes was utilized to form an armor layer and the local erosion downstream of a circular wall jet was measured. The time evolution of scour dimensions was recorded and the scour profiles of the mixed bed were compared with the scour profiles of a relatively uniform sand bed with the same average particle size. Three regimes were identified as the initial stage (Regime I), the quasi-steady state (Regime II), and the steady state (Regime III). The characteristic lengths of the scour showed rapid growth at the early stage of scour development and the growth rate decreased until the scour reached the steady-state condition. The effect of armor layer on scour dimensions was pronounced, which significantly reduced the maximum scour depth due to formation of an armor layer. The characteristic parameters affecting the maximum scour depth and width were identified and empirical correlations were introduced for the prediction of scour dimensions. The scour profiles in the mixed bed showed two consecutive scour depths. It was found that the area occupied by the armor layer increased by increasing the Froude number of the jet. [ABSTRACT FROM AUTHOR]