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A Model for Turbulent Hydraulic Fracture and Application to Crack Propagation at Glacier Beds
"... Abstract. Glaciological observations of underflooding suggest that fluidinduced hydraulic fracture of an ice sheet from its bed sometimes occurs quickly, possibly driven by turbulently flowing water in a broad sheet flow. Taking the approximation of a fully turbulent flow into an elastic ice mediu ..."
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Abstract. Glaciological observations of underflooding suggest that fluidinduced hydraulic fracture of an ice sheet from its bed sometimes occurs quickly, possibly driven by turbulently flowing water in a broad sheet flow. Taking the approximation of a fully turbulent flow into an elastic ice medium with small fracture toughness, we derive an approximate expression for the cracktip speed, opening displacement and pressure profile. We accomplish this by first showing that a ManningStrickler channel model for resistance to turbulent flow leads to a mathematical structure somewhat similar to that for resistance to laminar flow of a powerlaw viscous fluid. We then adapt the planestrain asymptotic crack solution of Desroches et al. [1994] and the powerlaw selfsimilar solution of Adachi and Detournay [2002] for that case to calculate the desired quantities. The speed of crack growth is shown to scale as the overpressure (in excess of ice overburden) to the power 7/6, inversely as ice elastic modulus to the power 2/3, and as the ratio of crack length to wall roughness scale to the power 1/6. We tentatively apply our model by choosing parameter values thought appropriate for a basal crack driven by the rapid drainage of a surface meltwater lake near the margin of the Greenland Ice Sheet [Das et al., 2008]. Making various approximations perhaps relevant to this setting, we estimate fluid inflow rate to the basal fracture and vertical and horizontal surface displacements, and find orderofmagnitude agreement with observations by Das et al. [2008] associated with lake drainage. Finally, we discuss how these preliminary estimates could be improved. 1.
Unrest at Campi Flegrei: A contribution to the
"... magmatic versus hydrothermal debate from inverse and finite element modeling ..."
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magmatic versus hydrothermal debate from inverse and finite element modeling
206 PUBLICATIONS 1,047 CITATIONS SEE PROFILE
, 2012
"... 4D gravity response of compacting reservoirs:Analytical approach ..."
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"... Lithospheric flexure and deformationinduced gravity changes: effect of elastic compressibility and gravitation on a multilayered, thickplate model ..."
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Lithospheric flexure and deformationinduced gravity changes: effect of elastic compressibility and gravitation on a multilayered, thickplate model
4D gravity response of compacting reservoirs: Analytical approach
"... Timelapse gravity is a technique sensitive to subsurface change in mass and in mass distribution. We attempted to devise a method to predict gravity effects caused by redistribution of subsurface mass induced by reservoir compaction. First, displacements and strains due to compaction were modeled ..."
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Timelapse gravity is a technique sensitive to subsurface change in mass and in mass distribution. We attempted to devise a method to predict gravity effects caused by redistribution of subsurface mass induced by reservoir compaction. First, displacements and strains due to compaction were modeled using a geomechanical model. Then, 4D gravity effects were derived from the displacements and the volumetric strains computed in and around the reservoir. A sensitivity study was carried out for geomechanical parameters, such as Poisson’s ratio, as well as for geometrical parameters, such as reservoir radius and depth. Finally, changes in gravity due to compaction were compared to changes induced by reservoir fluid substitution. Given a rigid basement close below a strongly compacting reservoir, our modeling case showed that the deformation itself could give gravity changes comparable to changes caused by reservoir fluid density changes, which are the changes traditionally targeted by gravity monitoring. For a homogeneous subsurface, the compaction gave negligible gravity changes for our modeling case.
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"... Relations between pressurized triaxial cavities and moment tensor distributions ..."
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Relations between pressurized triaxial cavities and moment tensor distributions
Insights from the Nisyros Caldera, Greece
"... and other research outputs On the interpretation of gravity variations in the presence of active hydrothermal systems: Insights from the ..."
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and other research outputs On the interpretation of gravity variations in the presence of active hydrothermal systems: Insights from the
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"... and other research outputs Oscillations in hydrothermal systems as a source of periodic unrest at caldera volcanoes: Multiparameter insights from Nisyros, Greece ..."
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and other research outputs Oscillations in hydrothermal systems as a source of periodic unrest at caldera volcanoes: Multiparameter insights from Nisyros, Greece
Key words Campi Flegrei – deformation – gravity
"... – finite element method – heterogeneous medium ..."