Liquefaction and dynamic poroelasticity in soft sediments

Bachrach, Ran; Nur, Amos; Agnon, Amotz

doi:10.1029/2000jb900474

Cited by 25 publications

(27 citation statements)

References 12 publications

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“…Appendix A shows that equation (13) is equivalent to our equation (10) when we assume that r · u s occurs by elastic deformation only, and also demonstrates the equivalency between equation (13) and the formulation of Bachrach et al [2001] under the assumption of negligible inertia. Thus, any conclusion drawn from the analysis in this section applies also to the formulation discussed in section 2.…”

Section: Poroelastic Pore Fluid Pressurization and Liquefactionmentioning

confidence: 72%

“…The poroelastic view attributes PP variations to the coupling between the elastic deformation of pores and the porous flow induced by the passage of P-waves [Bachrach et al, 2001]. A Biot based model is developed by Bachrach et al [2001], which shows that compressible fluid and low shear modulus of the granular matrix may lead to PP that exceeds the loading. A similar formulation, but without inertial terms, is developed by Wang [2000] for the general study of PP response to cyclic loading from a poroelastic point of view.…”

Section: Poroelastic Path To Liquefaction: Current State Of Understanmentioning

confidence: 99%

“…[22] Formulations similar to our equations (10) or (12) arise in other works dealing with the response of PP to specific situations of granular and porous matrix deformation [Walder and Nur, 1984;Wang, 2000;Samuelson et al, 2009], some of them specifically in the context of soil liquefaction [Bachrach et al, 2001;Snieder and van der Beukel, 2004]. Appendix A demonstrates how these models may be directly compared to our formulation.…”

Section: Theoretical Modelmentioning

confidence: 99%

“…The traditional approach suggests that poroplasticity may lead to fluid pressurization and may cause liquefaction [Sawicki and Mierczynski, 2006]. More recently a different view on the mechanics of liquefaction was suggested: poroelasticity was offered to be the possible cause of liquefaction induced by earthquakes [Bachrach et al, 2001]. Sections 1.1 and 1.2 briefly review poroplastic and poroelastic approaches and demonstrate that the physical understanding of the mechanisms by which matrix deformation generates large enough PP for soils and gouge layers to liquefy is not complete.…”

Section: Introductionmentioning

confidence: 99%

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Pore pressure evolution in deforming granular material: A general formulation and the infinitely stiff approximation

Goren¹,

Aharonov²,

Sparks³

et al. 2010

J. Geophys. Res.

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[1] The physics of deformation of fluid-filled granular media controls many geophysical systems, ranging from shear on geological faults to landslides and soil liquefaction. Its great complexity is rooted in the mechanical coupling between two deforming phases: the solid granular network and the fluid-filled pore network. Often deformation of the granular network leads to pore fluid pressure (PP) changes. If the PP rises enough, the fluid-filled granular media may transition from a stress-supporting grain network to a flowing grain-fluid slurry, with an accompanying catastrophic loss of shear strength. Despite its great importance, the mechanisms and parameters controlling PP evolution by granular shear are not well understood. A formulation describing the general physics of pore fluid response to granular media deformation is developed and used to study simple scenarios that lead to PP changes. We focus on the infinitely stiff end-member scenario, where granular deformation is prescribed, and the PP responds to this deformation. This end-member scenario illustrates the two possible modes of pore fluid pressurization: (1) via rapid fluid flow when fluid drainage is good and (2) via pore volume compaction when drainage is poor. In the former case the rate of deformation controls PP evolution, while in the latter case, fluid compressibility is found to be an important parameter and the amount of pressurization is controlled by the overall compaction. The newly suggested fluid-induced mechanism (mechanism 1) may help explain observations of liquefaction of initially compact soils and shear zones.Citation: Goren, L., E. Aharonov, D. Sparks, and R. Toussaint (2010), Pore pressure evolution in deforming granular material: A general formulation and the infinitely stiff approximation,

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Section: Poroelastic Pore Fluid Pressurization and Liquefactionmentioning

confidence: 72%

Section: Poroelastic Path To Liquefaction: Current State Of Understanmentioning

confidence: 99%

Section: Theoretical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Pore pressure evolution in deforming granular material: A general formulation and the infinitely stiff approximation

Goren¹,

Aharonov²,

Sparks³

et al. 2010

J. Geophys. Res.

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“…Equations (15) and (18) were shown in Goren et al [2010] to be a general form of previous formulations in Biot [1941], Wang [2000] and Bachrach et al [2001] that assume only elastic deformation of the grains skeleton, and Walder and Nur [1984] that assume a specific law for the evolution of porosity. Similar formulations also appear in Iverson [1993], Rudnicki and Chen [1988], Miller and Nur [2000], Snieder and van der Beukel [2004] and Samuelson et al [2009].…”

mentioning

confidence: 99%

The Mechanical Coupling of Fluid-Filled Granular Material Under Shear

Goren

Aharonov

Sparks

et al. 2011

Pure Appl. Geophys.

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Abstract. The coupled mechanics of fluid-filled granular media controls the physics of many Earth systems such as saturated soils, fault gouge, and landslide shear zones. It is well established that when the pore fluid pressure rises, the shear resistance of fluid-filled granular systems decreases, and as a result catastrophic events such as soil liquefaction, earthquakes, and accelerating landslides may be triggered. Alternatively, when the pore pressure drops, the shear resistance of these geosystems increases. Despite the great importance of the coupled mechanics of grains-fluid systems, the basic physics that controls this coupling is far from understood. Fundamental questions that need to be addressed are what are the processes that control pore fluid pressurization and depressurization in response to deformation of the granular skeleton? and how do variations of pore pressure affect the mechanical strength of the grains skeleton? To answer these questions, a formulation for the pore fluid pressure and flow is developed from mass and momentum conservation, and is coupled with a granular dynamics algorithm that solves the grain dynamics, to form a fully coupled model. The pore fluid formulation reveals that the evolution of pore pressure obeys a viscoelastic rheology in response to pore space variations. Elastic-like behavior dominates with undrained conditions and leads to a linear relation between pore pressure and overall volumetric strain. Viscous-like behavior dominates under well drained conditions and leads to a linear relation between pore pressure and volumetric strain rate. Numerical simulations reveal the possibility of liquefaction under drained and initially over-compacted conditions, which were often believed to be resistant to liquefaction. Under such conditions liquefaction occurs during short compactive 1 phases that punctuate the overall dilative trend. In addition, the more established generation of elevated pore pressure under undrained compactive conditions is observed. Simulations also show that during liquefaction events stress chains are detached, the external load becomes completely supported by the pressurized pore fluid, and shear resistance vanishes.

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Liquefaction

Wang¹,

Manga²

2021

Lecture Notes in Earth System Sciences

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Liquefaction of the ground during earthquakes has long been documented and has drawn much attention from earthquake engineers because of its devastation to engineered structures. In this chapter we review a few of the best studied field cases and summarize insights from extensive experimental data critical for understanding the interaction between earthquakes and liquefaction. Despite the progress made in the last few decades, several outstanding problems remain unanswered. One is the mechanism for liquefaction beyond the near field, which has been abundantly documented in the field. This is not well understood because, according to laboratory data, liquefaction should occur only in the near field where the seismic energy density is great enough to cause undrained consolidation leading up to liquefaction. Another outstanding question is the dependence of liquefaction on the frequency of the seismic waves, where the current results from the field and laboratory studies are in conflict. Finally, while in most cases the liquefied sediments are sand or silty sand, well-graded gravel has increasingly been witnessed to liquefy during earthquakes and is not simply the result of entrainment by liquified sand. It is challenging to explain how pore pressure could build up in gravely soils and be maintained at a level high enough to cause liquefaction.

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Liquefaction and dynamic poroelasticity in soft sediments

Cited by 25 publications

References 12 publications

Pore pressure evolution in deforming granular material: A general formulation and the infinitely stiff approximation

Pore pressure evolution in deforming granular material: A general formulation and the infinitely stiff approximation

The Mechanical Coupling of Fluid-Filled Granular Material Under Shear

Liquefaction

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