The propagation of a buoyant liquid-filled fissure from a source under constant pressure: An experimental approach
Résumé
[1] We study the propagation of a buoyant liquid-filled fissure from a reservoir under constant pressure within the framework of linear elastic fracture mechanics. We conducted laboratory experiments by injecting aqueous solutions into gelatin solid: an analogue for elastic and brittle crustal rocks. Fissure velocity and injection rate of liquid were measured rather than being imposed. Our experimental results allow evaluation of how the different driving and resistive pressures evolved during fissure propagation and highlight the influence of the fracture resistance of the host solid. In an initial transient propagation regime, elastic pressure generated by the fissure is balanced by the fracture pressure; the fissure propagates radially with decreasing velocity and increasing injection rate, controlled by the source conditions. Subsequently, buoyancy overcomes the source pressure as the driving force, and vertical steady state propagation is established. The fissure develops a bulbous head and propagation is controlled by the balance in this head, between buoyancy pressure and fracture pressure. Even after this transition, the constant values of velocity, flux, and strain energy release rate reflect the source conditions. Our model suggests that greater horizontal dyke cross section reflects larger source pressure and that mafic dykes propagating from shallow magma chambers are unlikely to attain steady state. Moreover, our experiments place constraints on the mechanics of time-dependent failure of the solid as a process that resists fissure propagation: propagation velocity scales with the square of the height of the fissure head, and fracture toughness of rocks would be length scale dependent rather than a material property.
Mots clés
INDEX TERMS: 5104 Physical Properties of Rocks: Fracture and flow
8110 Tectonophysics: Continental tectonics-general (0905)
8145 Tectonophysics: Physics of magma and magma bodies
8434 Volcanology: Magma migration
KEYWORDS: dyke
fissure propagation
analogue experiments
fracture resistance
rock failure
magma migration
Domaines
Volcanologie
Origine : Fichiers éditeurs autorisés sur une archive ouverte
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