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January 3 - Febuary 28, 2021

Meeting Abstract

73-4  Sat Jan 2  Scaling of burrowing resistances with sediment depth: a geomechanical perspective Chen, Y; DeJong, JT; Jaeger, RA; Martinez, A*; University of California Davis; University of California Davis; California Department of Water Resources; University of California Davis

Burrowing by animals such as marine worms, earthworms, and clams requires overcoming sediment resistances. Two of the resistances that influence an animal’s burrowing ability are the soil penetration resistance experienced at the burrow tip and the radial expansion pressure on the burrow walls. The magnitude of these depends on the sediment properties and depth. We perform numerical simulations to investigate the dependency of the penetration and radial expansion pressures on depth in soil of varying density. We use a ‘tip and anchor’ template, where the tip is advanced longitudinally and the anchor is expanded radially. We perform simulations using a cavity expansion (CE) analytical solution and a discrete element modeling (DEM) code calibrated to model the behavior of a sandy soils. The simulation results show that the relationship between penetration resistance, anchor radial pressure, and depth can be described using power-law relationships. The radial pressure increases at a greater rate as the depth is increased (exponent of 0.74 from CE and of 0.82 from DEM) than the penetration resistance (exponent of 0.69 from CE and of 0.69 from DEM) for sediments with high density. However, as the density is decreased, the rate of increase in both pressures becomes comparable (exponent of 0.79 for both from CE in low-density sediment). These results suggest that as the ‘tip and anchor’ burrowing strategy becomes more advantageous at greater depths. These results support previously-published observations indicating that marine worms that burrow at greater depth use variations of the ‘tip and anchor’ template such as peristalsis and the so-called ‘dual-anchor’ strategy, while animals that burrow at shallower depths use different strategies.