Block ramps are ecofriendly drop structures, which ensure more stability in the downstream riverbed. The scouring in the stilling basin bed material generated by the rapidly varied flow transition affects the stability of the ramp structure. In the present study, a modified stilling basin bed configuration is tested along with the uniform conventional stilling basin bed arrangements to check the stability of non-cohesive beds downstream to block ramps. Uniform non-cohesive horizontal bed configurations and bed with sill arrangement are tested for varying block ramp slopes (20% ≤ i ≥ 30%). The critical particle densimetric Froude number (F_c*) is selected as the criteria to predict the hydraulic conditions for incipient sediment motion in the uniform beds and it is compared with the established literature formulations to estimate the stability of the beds under macroroughness conditions. Scour volumes from each experimental run is quantified and the intensity of sediment motion is determined and related with the critical particle densimetric Froude number. The findings of the paper also describe the effect of F_c* on dimensionless scour depth. Spatial shift in the maximum scour depth formation from the toe of the block ramp for the tested flows over the bed sill arrangement has been observed. Experimental observations and comparison of results show the effect of sill gradation pronounced for non-uniform bed configuration, which effectively reduce the scour depth henceforth it stabilizes the upstream block ramp structure relative to the uniform beds selected.

块状坡道是生态友好的下落结构，可确保下游河床的稳定性更高。急速变化的流动过渡在静水盆地床料中冲刷会影响坡道结构的稳定性。在本研究中，测试了改良的消音盆床配置以及统一的传统消音盆床布置，以检查下游无粘性床以堵塞坡道的稳定性。均匀非粘性水平床的构造和床间的门槛装置被用于改变块的斜坡的斜坡（20％≤测试 我 ≥30％）。临界粒子密度弗劳德数（F _c *）选择标准作为预测均匀床层中早期泥沙运动的水力条件的标准，并将其与已建立的文献公式进行比较，以估算宏观粗糙度条件下床层的稳定性。量化每个实验运行的冲刷量，确定泥沙运动的强度，并将其与临界粒子密度弗洛德数相关。本文的发现还描述了F _c *的作用在无因次冲刷深度。对于在床槛装置上的测试流量，已经观察到从块状坡道的趾部到最大冲刷深度的空间位移。实验观察和结果比较表明，对于不均匀的床层构造，门槛渐变效果明显，有效地减小了冲刷深度，因此相对于所选的均匀床层，它稳定了上游砌块坡道结构。