Shear jamming in granular experiments without basal friction

<p>Understanding past eruption dynamics at a volcano is crucial for forecasting the range of possible future eruptions and their associated hazards and risk. In this work we reconstructed pyroclastic density currents and tephra fall from three eruptions at Gede volcano, Indonesia with the aim of gaining further insight into past eruptions and identifying suitable eruption source parameters for future hazard and risk assessment. Gede has the largest number of people living within 100 km of any volcano worldwide, and has exhibited recent unrest activity, yet little is known about its eruption history. For pyroclastic density currents, we used Titan2D to reconstruct geological deposits dated at 1200 and c. 1000 years BP. An objective and quantitative multi-criteria method was developed to evaluate the fit of over 300 pyroclastic density current (PDC) model simulations to field observations. We found that the 1200 years BP geological deposits could be reproduced with either a dome collapse or column collapse as the generation mechanism although a relatively low basal friction of 6 degrees would suggest that the PDCs were markedly mobile. Lower basal frictions may reflect the occurrence of previous PDCs that smoothed the path, reducing frictional resistance and enabling greater runout for the reconstructed unit. For the 1,000 years BP PDC, a column collapse mechanism and higher basal friction was required to fit the geological deposits. In agreement with previous studies, we found that Titan2D simulations were most sensitive to the basal friction; however, we also found that the internal friction &#8211; often fixed and considered of low influence on outputs - can have a moderate effect on the simulated average deposit thickness. We used Tephra2 to reconstruct historic observations of tephra dispersed to Jakarta and other towns during the last known magmatic eruption of Gede in 1948. In the absence of observable field deposits, or detailed information from the published literature, we stochastically sampled eruption source parameters from wide ranges informed by analogous volcanic systems. Our modelling suggests that the deposition of tephra in Jakarta during the November 1948 eruption was a very low probability event, with approximately a 0.03 % chance of occurrence. Through this work, we exemplify the reconstruction of past eruptions when faced with epistemic uncertainty, and improve our understanding of past eruption dynamics at Gede volcano, providing a crucial step towards the reduction of risk to nearby populations through volcanic hazard assessment.</p>

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Marine ice sheet experiments with the Community Ice Sheet Model

The Cryosphere ◽

10.5194/tc-15-3229-2021 ◽

2021 ◽

Vol 15 (7) ◽

pp. 3229-3253

Author(s):

Gunter R. Leguy ◽

William H. Lipscomb ◽

Xylar S. Asay-Davis

Keyword(s):

Ice Sheet ◽

Ice Flow ◽

Friction Law ◽

Friction Laws ◽

Basal Friction ◽

Grounding Line ◽

Hydrological System ◽

Flow Approximation ◽

Intercomparison Project ◽

Ice Sheet Dynamics

Abstract. Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law and to the treatment of stresses and melt rates near the grounding line. We study the effects of these numerical choices on marine ice sheet dynamics in the Community Ice Sheet Model (CISM). In the framework of the Marine Ice Sheet Model Intercomparison Project 3d (MISMIP3d), we show that a depth-integrated, higher-order solver gives results similar to a 3D (Blatter–Pattyn) solver. We confirm that using a grounding line parameterization to approximate stresses in the grounding zone leads to accurate representation of ice sheet flow with a resolution of ∼2 km, as opposed to ∼0.5 km without the parameterization. In the MISMIP+ experimental framework, we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice sheet geometry, forcing, or model numerics. In both experimental frameworks, ice flow is sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of ∼2 km (arguably 4 km) when the connectivity is low or moderate and ∼1 km (arguably 2 km) when the connectivity is strong.

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Using good vibrations: Melting and controlled shear jamming of dense granular suspensions

Journal of Rheology ◽

10.1122/8.0000376 ◽

2022 ◽

Vol 66 (2) ◽

pp. 237-256

Author(s):

C. Garat ◽

S. Kiesgen de Richter ◽

P. Lidon ◽

A. Colin ◽

G. Ovarlez

Keyword(s):

Granular Suspensions ◽

Shear Jamming

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Marine ice-sheet experiments with the Community Ice Sheet Model using the MISMIP+ experimental framework.

10.5194/egusphere-egu21-6608 ◽

2021 ◽

Author(s):

Gunter Leguy ◽

William Lipscomb ◽

Xylar Asay-Davis

Keyword(s):

Ice Sheet ◽

Ice Flow ◽

Friction Law ◽

Friction Laws ◽

Basal Friction ◽

Grounding Line ◽

Hydrological System ◽

Flow Approximation ◽

Intercomparison Project ◽

Ice Sheet Dynamics

<p>Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law, and to the treatment of stresses and melt rates near the grounding line. We present the effects of these numerical choices on marine ice-sheet dynamics in the Community Ice Sheet Model (CISM). In the experimental framework of the Marine Ice Sheet Model Intercomparison Project (MISMIP+), we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice-sheet geometry, forcing, or model numerics. In the MISMIP+ framework, the ice flow is also sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of &#8764;2 km (arguably 4 km) when the connectivity is low or moderate, and &#8764;1 km (arguably 2 km) when the connectivity is strong.</p>

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Is there Shear Jamming in Frictionless Three Dimensional Granular Assemblies?

Proceedings of the 5th Asian Particle Technology Symposium ◽

10.3850/978-981-07-2518-1_059 ◽

2012 ◽

Author(s):

Kumara N. ◽

Luding S.

Keyword(s):

Three Dimensional ◽

Granular Assemblies ◽

Shear Jamming

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Variation patterns of landslide basal friction revealed from long-period seismic waveform inversion

Natural Hazards ◽

10.1007/s11069-019-03813-y ◽

2019 ◽

Vol 100 (1) ◽

pp. 313-327

Author(s):

Dan Yu ◽

Xinghui Huang ◽

Zhengyuan Li

Keyword(s):

Steady State ◽

Friction Coefficient ◽

Water Waves ◽

Waveform Inversion ◽

Time History ◽

Seismic Signals ◽

Long Period ◽

Basal Friction ◽

Seismic Waveform ◽

Variation Patterns

Abstract A catastrophic landslide struck the Xiaoba village in Fuquan, Guizhou, southwestern China at about 8:30 p.m. (Beijing Time, UTC + 8) on August 27, 2014. The landslide and induced impulse water waves destroyed two villages and killed 23 persons. By reprocessing seismic signals from a seismic network deployed in the surrounding area of the landslide, we recognized the event from low-frequency seismic signals and subsequently performed a long-period seismic waveform inversion to obtain its force–time history. The inversion results reveal that the maximum force for the landslide is 5 × 109 N, and the duration of the landslide is 38.4 s. The landslide reached its maximum velocity of 12.4 m/s at 13.2 s after its initiation, and the mass center plugged into the quarry at 24.2 s. Based on the inversion results, we estimated basal friction of the landslide. We found the friction coefficient rapidly reduces to a relatively steady-state value of ~ 0.4 at a steady-state distance of 35 m and subsequently reduces in a near-linear manner that satisfies the empirical formula $$ \mu = - 1.4d + 0.44 $$μ=-1.4d+0.44, where $$ d $$d is sliding distance in km. The reduction in friction revealed by the formula is compatible with the finding of previous studies for landslides of similar volume in landslide acceleration stage. However, our result does not make it possible for the friction coefficient to increase again in landslide deceleration stage that a velocity-dependent friction law would allow. The friction variation patterns can be used to constrain input parameters in numerical landslide simulation, which can predicate runout distance and deposit areas for massive landslides to carry out landslide hazard assessment.

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Unjamming in Dry Granular Matter: Second-Order Phase Transition between Fragile Solid and Dry Fluid (Bearing) by Intermittency.

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.172-174.1106 ◽

2011 ◽

Vol 172-174 ◽

pp. 1106-1111 ◽

Cited By ~ 2

Author(s):

Nicolas Rivier ◽

Jean Yves Fortin

Keyword(s):

Phase Transition ◽

Order Phase Transition ◽

Degrees Of Freedom ◽

Granular Matter ◽

Load Ratio ◽

Low Energies ◽

Critical Contact ◽

Shear Jamming ◽

Tangential Friction ◽

Second Order Phase Transition

Dry granular matter, with inﬁnite tangential friction, is modeled as a connected graph ofgrains linked by purely repulsive contacts. The degrees of freedom of a grain are non-slip rotationon, and disconnection from another. The material stability under shear (jamming) is ensured by oddcircuits of grains in contact that prevent the grains from rolling on each other. A dense granularmaterial with high stiffness-to-load ratio has two possible states: fragile solid, blocked by odd circuits,and dry ﬂuid or bearing, in the absence of odd circuits, that ﬂows under shear by creation and glide ofa pair of dislocations as in plasticity of continuous media. In this paper, we introduce the notions of blob, a region of the material containing only even circuits, and of critical contact that closes an oddcircuit. The granular material is then represented, at low energies and critical applied shear, as a chainof blobs connected by critical contacts. The transition between dry ﬂuid and fragile solid occurs byintermittency.

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Retreat of Thwaites Glacier, West Antarctica, over the next 100 years using various ice flow models, ice shelf melt scenarios and basal friction laws

The Cryosphere ◽

10.5194/tc-12-3861-2018 ◽

2018 ◽

Vol 12 (12) ◽

pp. 3861-3876 ◽

Cited By ~ 12

Author(s):

Hongju Yu ◽

Eric Rignot ◽

Helene Seroussi ◽

Mathieu Morlighem

Keyword(s):

Sea Level ◽

Initial Conditions ◽

Numerical Models ◽

West Antarctica ◽

Ice Shelf ◽

Flow Models ◽

Friction Laws ◽

Basal Friction ◽

Grounding Line ◽

Western Side

Abstract. Thwaites Glacier (TG), West Antarctica, has experienced rapid, potentially irreversible grounding line retreat and mass loss in response to enhanced ice shelf melting. Results from recent numerical models suggest a large spread in the evolution of the glacier in the coming decades to a century. It is therefore important to investigate how different approximations of the ice stress balance, parameterizations of basal friction and ice shelf melt parameterizations may affect projections. Here, we simulate the evolution of TG using ice sheet models of varying levels of complexity, different basal friction laws and ice shelf melt to quantify their effect on the projections. We find that the grounding line retreat and its sensitivity to ice shelf melt are enhanced when a full-Stokes model is used, a Budd friction is used and ice shelf melt is applied on partially floating elements. Initial conditions also impact the model results. Yet, all simulations suggest a rapid, sustained retreat of the glacier along the same preferred pathway. The fastest retreat rate occurs on the eastern side of the glacier, and the slowest retreat occurs across a subglacial ridge on the western side. All the simulations indicate that TG will undergo an accelerated retreat once the glacier retreats past the western subglacial ridge. Combining all the simulations, we find that the uncertainty of the projections is small in the first 30 years, with a cumulative contribution to sea level rise of 5 mm, similar to the current rate. After 30 years, the contribution to sea level depends on the model configurations, with differences up to 300 % over the next 100 years, ranging from 14 to 42 mm.

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Determination of a flow center on an ice cap

Journal of Glaciology ◽

10.1017/s0022143000002288 ◽

1992 ◽

Vol 38 (130) ◽

pp. 412-416 ◽

Cited By ~ 8

Author(s):

C.J. Van Der Veen ◽

I. M. Whillans

Keyword(s):

Central China ◽

Strain Rates ◽

Ice Flow ◽

Basal Friction ◽

Ice Cap ◽

Balance Of Forces ◽

Basal Flow

AbstractA method for identifying the center of ice flow is developed and applied using results from surveys of a strain grid near the summit of Dunde Ice Cap (central China). Strain rates are used to compute stresses. These are used with a consideration of the balance of forces to compute basal friction. The flow center at the bed occurs where this friction changes sign. For Dunde Ice Cap, the basal flow center nearly underlies the summit.

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