Rita Carvalho, Rui Martins
Monday 29 june 2015
17:36 - 17:39h at Amazon (level 1)
Themes: (T) Water engineering, (ST) River and coastal engineering, Poster pitches
Parallel session: Poster pitch: 3C. Coastal Engineering
Shields criterion often serves to analyse the stability of stones and blocks 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 stones/blocks 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 analyse other formulas commonly used in professional engineering to evaluate shear, block stability, turbulence influence and safety coefficients used in practise and 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.