Experimental Study on the Viscosity of Soft Cohesive Sediments Around A Vibrating Pillar

• Published in: China ocean engineering Vol. 36; no. 2; pp. 289 - 298
• Main Authors: Dong, Chuan-ming, Yu, Guo-liang, Zhang, Huai-xin, Zhang, Min-xi
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.04.2022; Springer Nature B.V; SKLOE,CISSE,School of Naval Architecture,Ocean&Civil Engineering,Shanghai Jiao Tong University,Shanghai 200240,China; Navigation College,Dalian Maritime University,Dalian 116026,China%SKLOE,CISSE,School of Naval Architecture,Ocean&Civil Engineering,Shanghai Jiao Tong University,Shanghai 200240,China
• Subjects: Coastal Sciences; Cohesion; Cohesive sediments; Cyclic loads; Engineering; Fluid- and Aerodynamics; Fluidization; Fluidizing; Hydrostatic pressure; Liquidity; Loads (forces); Marine & Freshwater Sciences; Numerical and Computational Physics; Oceanography; Offshore Engineering; Offshore structures; Pore pressure; Pore water; Pore water pressure; Rheological properties; Rheology; Sediments; Shear strength; Simulation; Vibration; Viscosity; Water pressure; vibration intensity; liquidity index; cohesive sediment; viscosity coefficient; fluidization
• ISSN: 0890-5487; 2191-8945
• DOI: 10.1007/s13344-022-0025-8

Offshore structures are subject to environmental loads such as waves, currents, or wind, which may induce cyclic lateral vibration at the foundations. These cyclic vibration loadings may affect the rheological property of the sediments adjacent to the foundation and the stability of the structures. This is especially true when the structures are founded on cohesive sedimentary bed. In this study, the viscosity of soft cohesive sediments adjacent to a vibrating pillar was considered, and as a primary index of the rheological characteristics of the sediments. The investigation was performed using the sinking ball method. The experimental findings indicated that the viscosity of cohesive sediments decrease with increase of the liquidity index and vibration intensity. A simple semi-empirical formula was proposed. The structures of the cohesive sediments were destroyed due to the mechanical vibration, and the sediments were fluidized during vibration loads. The shear strength of the cohesive sediments decreased with increased vibration intensity, not only because of the increased pore water pressure but also the decreased viscosity of cohesive sediments following sediment fluidization.