A simplified approach to transient flow effects induced by rigid cylinder rotation in a porous medium

Drainage conditions associated with loading rate effects during rotation of elements embedded in intermediate permeability soils are fundamental factors in the assessment and analysis of in situ measured properties and foundation design systems. In that context, a simplified model for poromechanical analysis of consolidation induced by rotation of a rigid cylinder embedded within a porous medium is formulated. The approach is closely connected with the concept of deformation plasticity and relies upon the equivalence between the local behavior of a poroplastic material under monotonic loading process and that of an appropriate non-linear fictitious poroelastic behavior. The non-linear poroelastic model is conceived to capture the transient flow effects on the poromechanical response of the soil surrounding the rotating cylinder. Semi-analytical solutions are derived for pore-fluid pressure, displacement and stress distributions, allowing for the evaluation of rate effects in silty soils, with specific application to purely cohesive and frictional materials. The accuracy of the approach is assessed by comparison of model predictions with poroplastic finite element solutions. The results correlating the degree of drainage to normalized rotation velocity derived from proposed model may be a useful support for a wide range of geotechnical applications, such as laterally loaded rigid piles with rotationally pile connections, offshore wind turbines shafts subjected to torque or torsional vibration, rotation of shaft drilling tools and in situ tests subjected to shear.