期刊
PHYSICAL REVIEW APPLIED
卷 8, 期 6, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevApplied.8.064029
关键词
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资金
- Engineering and Physical Sciences Research Council [EP/L013177/1]
- Ser Cymru National Research Network in Advanced Engineering and Materials [NRN141]
- Engineering and Physical Sciences Research Council [EP/L013177/1, 1696542] Funding Source: researchfish
- EPSRC [EP/L013177/1] Funding Source: UKRI
Multiphase flows in deformable porous materials are important in numerous geological and geotechnical applications; however, the complex flow behavior makes subsurface transport processes difficult to control-or even characterize. Here, we study gas-driven (pneumatic) fracturing of a wet unconsolidated granular packing confined in a Hele-Shaw cell, and we present an in-depth analysis of both pore-scale phenomena and large-scale pattern formation. The process is governed by a complex interplay among pressure, capillary, frictional, and viscous forces. At low gas-injection rates, fractures grow in a stick-slip fashion and branch out to form a simply connected network. We observe the emergence of a characteristic length scale-the separation distance between fracture branches-creating an apparent uniform spatial fracture density. We conclude that the well-defined separation distance is the result of local compaction fronts surrounding fractures and keeping them apart. A scaling argument is presented that predicts fracture density as a function of granular friction, grain size, and capillary interactions. We study the influence of the gas-injection rate and find that the system undergoes a fluidization transition above a critical injection rate, resulting in directional growth of the fractures, and a fracture density that increases with an increasing rate. A dimensionless fluidization number F is defined as the ratio of viscous to frictional forces, and our experiments reveal a frictional regime for F < 1 characterized by stick-slip, rate-independent growth, with a transition to a viscous regime (F > 1) characterized by continuous growth in several fracture branches simultaneously.
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