The Soil Rigidity Effect in the Touchdown Boundary-Layer of a Catenary Riser: Static Problem

摘要

Recently, analytical solutions, of the boundary-layer type, were developed for the static and dynamic curvature problems in the touchdown point (TDP) region of a catenary riser (Aranha, Martins & Pesce, 1997; Pesce et al., 1997). Neverthless, the analysis was restricted to the infinitely rigid soil assumption. The present paper enlarges somewhat the static boundary-layer solution, by considering the existence of a linearly elastic soil. A nondimensional soil rigidity parameter, K = kAλ~4/EJ = kλ~2/T_0 = kEJ/T_0~2 , is defined, where k is the rigidity per unit area, EJ the bending stiffness, T_0 the static tension at TDP and λ is the flexural-length parameter representing the TDP boundary-layer length scale. Nondimensional - hence generally valid - diagrams, having K as parameter, are presented, showing, K ≥ 10, the elastica, the horizontal angle, the shear effort, and the curvature, as functions of the local nondimensional arclength parameter, s/λ.