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Overpressure

About: Overpressure is a research topic. Over the lifetime, 3236 publications have been published within this topic receiving 34648 citations.


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Journal ArticleDOI
TL;DR: In this article, the emplacement dynamics of pyroclastic flows were investigated through noninvasive measurements of the pore fluid pressure in laboratory air-particle flows generated from the release of fluidized and nonfluidized granular columns.
Abstract: [1] The emplacement dynamics of pyroclastic flows were investigated through noninvasive measurements of the pore fluid pressure in laboratory air-particle flows generated from the release of fluidized and nonfluidized granular columns. Analyses of high-speed videos allowed for correlation of the pressure signal with the flow structure. The flows consisted of a sliding head that caused underpressure relative to the ambient, followed by a body that generated overpressure and at the base of which a deposit aggraded. For initially fluidized flows, overpressure in the body derived from advection of the pore pressure generated in the initial column and decreased by diffusion during propagation. Relatively slow diffusion caused the pore pressure in the thinner flow to be larger than lithostatic at early stages. Furthermore, partial auto-fluidization, revealed in initially nonfluidized flows, also occurred and contributed to maintain high pore pressure, whereas dilation or contraction of the air-particle mixture with associated drag and/or pore volume variation transiently led the pressure to decrease or increase, respectively. The combination of all these processes resulted in long-lived high pore fluid pressure in the body of the flows during most of their emplacement. In the case of the initially fluidized and slightly expanded (∼3–4%) flows, (at least) ∼70%–100% of the weight of the particles was supported by pore pressure, which is consistent with their inertial fluid-like behavior. Dense pyroclastic flows on subhorizontal slopes are expected to propagate as inertial fluidized gas-particle mixtures consisting of a sliding head, possibly entraining basement-derived clasts, and of a gradually depositing body.

69 citations

Journal ArticleDOI
TL;DR: In this article, the authors studied the processes and mechanisms of overpressuring via numerical modeling that couples basin filling, sediment compaction, and thermal and pressure fields to approach the origin of the shallow high overpressure.
Abstract: Yinggehai Basin is an elongate Cenozoic rift basin on the northwestern margin of the South China Sea continental shelf. Its thick (17 km) basin fill is characterized by high geothermal gradient and high overpressure. Overpressure associated with nonequilibrium compaction mainly occurs at depths more than 2800 m at the basin center and more than 4000 m at the basin margin because the shallow-buried Neogene and Quaternary strata lack effective seals. This regional overpressure distribution, however, is disrupted at basin center where high overpressure occurs in permeable formations at a depth as shallow as 1400 m on top of a series of deep-seated faults and fractures. We studied the processes and mechanisms of overpressuring via numerical modeling that couples basin filling, sediment compaction, and thermal and pressure fields to approach the origin of the shallow high overpressure. Model results indicated that an increase of fluid volume due to natural-gas generation by organic cracking is not large enough to generate the overpressure because of the limited amount of organic matter. The shallow overpressure has probably been generated allogenically. Deep open faults have served as vertical hydraulic conduits and channeled the deep high pressure into shallow permeable formations.

69 citations

Journal ArticleDOI
TL;DR: Using the average aspect (length/maximum thickness) ratios of 379 mineral-filled extension (mode I) veins from an active fault zone, the fluid overpressure, during their development, with reference to the minimum compressive principal stress, σ3, is estimated at 20 MPa as discussed by the authors.
Abstract: Using the average aspect (length/maximum thickness) ratios of 379 mineral-filled extension (mode I) veins from an active fault zone, the fluid overpressure, during their development, with reference to the minimum compressive principal stress, σ3, is estimated at 20 MPa. Emplacement of such veins increases σ3 and can generate a temporary stress barrier to the propagation of subsequent hydrofractures. On meeting a subhorizontal stress barrier, vertically propagating hydrofractures may change into water sills where the fluid pressure is at or above lithostatic. In this model, stress barriers, and thus water sills, can form at any depth in, and in any type of, fault zones. For such a high fluid pressure, the product of the coefficient of sliding friction and the normal stress in the Modified Griffith Criterion becomes essentially zero and the driving stress associated with faulting equal to twice the in situ tensile strength of the host rock. For typical in situ tensile strengths of 2–3 MPa, the driving stresses for slip on overpressured fault planes is 4–6 MPa. These results are in good agreement with the commonly measured average static stress drops of 3–6 MPa during earthquakes.

69 citations

Journal ArticleDOI
TL;DR: In this paper, a fan-jet-stirred spherical explosion vessel with different hydrogen fractions (λ) and different turbulent intensities (u'rms) in a stoichiometric hydrogen/methane/air mixture was analyzed.

69 citations

Patent
Ulrich Bonne1
21 Dec 1990
TL;DR: In this article, a non membrane-based overpressure proof gas pressure microsensor was proposed, which is based on an open microbridge sensor structure and can determine gas pressure from thermal conductivity, k, and volumetric specific heat, c pu, as well as pressure, P.
Abstract: A non membrane-based overpressure proof gas pressure microsensor. It is not a membrane-based microsensor but is based on an open microbridge sensor structure. A method and apparatus is described to determine gas pressure from thermal conductivity, k, and volumetric specific heat, c pu , as well as pressure, P, using a microbridge sensor.

69 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023263
2022504
2021174
2020173
2019171
2018174