Author(s): Rui Martins; Rita F. Carvalho
Linked Author(s): Maria Rita L. M. F. Carvalho
Keywords: Rock stability; Shields parameter; Uniform flow
Abstract: Shields criterion often serves to analyse the stability of sediments, stones and armour units under uniform or quasi-uniform conditions. It is used to calculate the initial motion of loose material in a flow. It is simple and contains physical sense as relates shear stress on the bottom with material resistance function of its dimension and density. In this work the Shields formula is analysed. We look at (1) the action, (2) the Shields parameter and (3) material resistance, separately. We consider other formulas commonly used in hydraulic engineering and safety coefficients from the practice. Then we reach to a practical formula founded on theory to evaluate block dimensions. The proposed formula takes into account tested coefficients and presents admissible velocity of the flow as being a function of material dimension, material density and water depth.
Year: 2015