Evolution of Porosity and Channelization of an Erosive Medium Driven by Fluid Flow

Kudrolli, Arshad; Clotet, Xavier

doi:10.1103/physrevlett.117.028001

Cited by 28 publications

(37 citation statements)

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“…With increasing subglacial discharge, we expect a hydraulic transition from distributed drainage to sedimentincised channels (e.g., Mahadevan and others, 2012;Kudrolli and Clotet, 2016). However, yield failure of the channel flanks imposes a limit to their cross-sectional area and hydraulic transport capacity.…”

Section: Discussionmentioning

confidence: 99%

“…Intrinsic channelization during fluid flow has been demonstrated in physical dam-breach experiments (e.g., Walder and others, 2015) and in smaller experimental studies (e.g., Catania and Paola, 2001;Mahadevan and others, 2012;Kudrolli and Clotet, 2016;Métivier and others, 2017). Channelization occurs when fluid flux is able to erode the porous medium through which it is flowing.…”

Section: Design Of Numerical Experimentsmentioning

confidence: 99%

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Sediment behavior controls equilibrium width of subglacial channels

et al. 2017

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ABSTRACT. Flow-frictional resistance at the base of glaciers and ice sheets is strongly linked to subglacial water pressure. Understanding the physical mechanisms that govern meltwater fluxes in subglacial channels is hence critical for constraining variations in ice flow. Previous mathematical descriptions of softbed subglacial channels assume a viscous till rheology, which is inconsistent with laboratory data and the majority of field studies. Here, we use a grain-scale numerical formulation coupled to pore-water dynamics to analyze the structural stability of channels carved into soft beds. Contrary to the soft-bed channel models assuming viscous till rheology, we show that the flanks of till channels can support substantial ice loads without creep closure of the channel, because the sediment has finite frictional strength. Increased normal stress on the channel flanks causes plastic failure of the sediment, and the channel rapidly shrinks to increase the ice-bed contact area. We derive a new parameterization for subglacial channelized flow on soft beds and show that channel dynamics are dominated by fluvial erosion and deposition processes with thresholds linked to the plastic rheology of subglacial tills. We infer that the described limits to channel size may cause subglacial drainage to arrange in networks of multiple closely spaced channels.

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Section: Discussionmentioning

confidence: 99%

Section: Design Of Numerical Experimentsmentioning

confidence: 99%

Sediment behavior controls equilibrium width of subglacial channels

et al. 2017

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“…For example, river networks formed due to the confluence of tributaries drawn from a wide basin as they follow the gradient of the land, are an enduring feature across the face of the earth [3][4][5]. Though less obvious, channel networks can also develop in the subsurface in natural aquifers and in enhanced oil recovery [6][7][8]. While dissolution of the medium can play an important role in the development of subterranean channels and sinkholes [9][10][11], the internal erosion of sedimentary grains by the drag of the fluid flow can by itself lead to evolution of porosity in the subsurface [8,[12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the connection of channel networks observed on the earth's surface and those that develop due to internal erosion in the subsurface remain far from clear. Recently, a model system was developed to investigate the growth of heterogeneity due to erosion when a fluid is forced across a granular bed [6]. The solubility and the cohesivity of the granular medium in these experiments are negligible by design.…”

Section: Introductionmentioning

confidence: 99%

“…The calculated fluid flow was shown to be consistent with experimental observations, and the interface between the regions with low and high porosity was observed to erode, on average, when the local fluid velocity exceeded a critical value J c corresponding to the erodibility of the medium. Building on these observations, a hybrid erosion model was also developed [6] in which the porous medium was divided into three components consisting of the immobile granular phase corresponding to the porous solid phase, mobile granular phase, and the fluid phase following Ref. [26].…”

Section: Introductionmentioning

confidence: 99%

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Headward growth and branching in subterranean channels

2017

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We investigate the erosive growth of channels in a thin subsurface sedimentary layer driven by hydrodynamic drag toward understanding subterranean networks and their relation to river networks charged by ground water. Building on a model based on experimental observations of fluid-driven evolution of bed porosity, we focus on the characteristics of the channel growth and their bifurcations in a horizontal rectangular domain subject to various fluid source and sink distributions. We find that the erosion front between low- and high-porosity regions becomes unstable, giving rise to branched channel networks, depending on the spatial fluctuations of the fluid flow near the front and the degree to which the flow is above the erodibility threshold of the medium. Focusing on the growth of a network starting from a single channel, and by identifying the channel heads and their branch points, we find that the number of branches increases sublinearly and is affected by the source distribution. The mean angles between branches are found to be systematically lower than river networks in humid climates and depend on the domain geometry.

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