The recovery process of the coastal mud after being sheared by external loads

Abstract

In muddy coastal regions, wave-seabed interaction highly depends on the mud's rheological properties, which usually exhibit thixotropic behaviors and are closely related to the recovery of the mud. To investigate the recovery process, a series of rheological experiments were conducted on the mud samples collected from the tidal flats of the Zhoushan Archipelago. After being sheared by external loads, the mud storage modulus recovers to an equilibrium value (G∞′), and the normalized equilibrium storage modulus (G∞′/G0′) was utilized to access the structural level of the recovered mud. The effects of the magnitude, frequency, and duration of the shear load on the recovery process of the mud were investigated. Experimental results revealed thatG∞′/G0′ increases with the load magnitude and eventually reaches a constant value, regardless of the density of the mud.G∞′/G0′ is insensitive to load frequencies lower than 4 Hz when the load magnitude is below the fluidic yield stress of the mud. When load magnitude exceeds the fluidic yield stress,G∞′/G0′ decreases monotonically with frequency.G∞′/G0′ is insensitive to shear durations over O(10 s) since the internal structures were destroyed within seconds. Overall, this study offers novel insights into the rheological properties of coastal mud that provide valuable scientific support for understanding wave-mud interaction and fluid mud formation processes.