scholarly journals Water pressure fluctuations control variability in sediment flux and slip dynamics beneath glaciers and ice streams

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Anders Damsgaard ◽  
Liran Goren ◽  
Jenny Suckale
Keyword(s):  
Fast Moving ◽  
Continuum Model ◽  
Basal Slip ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Fluctuations ◽  
Sediment Flux ◽  
Ice Streams ◽  
Water Saturated ◽  
Dynamic Interplay

AbstractRapid ice loss is facilitated by sliding over beds consisting of reworked sediments and erosional products, commonly referred to as till. The dynamic interplay between ice and till reshapes the bed, creating landforms preserved from past glaciations. Leveraging the imprint left by past glaciations as constraints for projecting future deglaciation is hindered by our incomplete understanding of evolving basal slip. Here, we develop a continuum model of water-saturated, cohesive till to quantify the interplay between meltwater percolation and till mobilization that governs changes in the depth of basal slip under fast-moving ice. Our model explains the puzzling variability of observed slip depths by relating localized till deformation to perturbations in pore-water pressure. It demonstrates that variable slip depth is an inherent property of the ice-meltwater-till system, which could help understand why some paleo-landforms like grounding-zone wedges appear to have formed quickly relative to current till-transport rates.

Basal processes beneath an Arctic glacier and their geomorphic imprint after a surge, Elisebreen, Svalbard

2005 ◽  
Vol 64 (2) ◽  
pp. 125-137 ◽  
Author(s):  
Poul Christoffersen ◽  
Jan A. Piotrowski ◽  
Nicolaj K. Larsen
Keyword(s):  
Flow Instability ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water System ◽  
Water Drainage ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Glacier Ice ◽  
Water Saturated ◽  
Arctic Glacier

AbstractThe foreground of Elisebreen, a retreating valley glacier in West Svalbard, exhibits a well-preserved assemblage of subglacial landforms including ice-flow parallel ridges (flutings), ice-flow oblique ridges (crevasse-fill features), and meandering ridges (infill of basal meltwater conduits). Other landforms are thrust-block moraine, hummocky terrain, and drumlinoid hills. We argue in agreement with geomorphological models that this landform assemblage was generated by ice-flow instability, possibly a surge, which took place in the past when the ice was thicker and the bed warmer. The surge likely occurred due to elevated pore-water pressure in a thin layer of thawed and water-saturated till that separated glacier ice from a frozen substratum. Termination may have been caused by a combination of water drainage and loss of lubricating sediment. Sedimentological investigations indicate that key landforms may be formed by weak till oozing into basal cavities and crevasses, opening in response to accelerated ice flow, and into water conduits abandoned during rearrangement of the basal water system. Today, Elisebreen may no longer have surge potential due to its diminished size. The ability to identify ice-flow instability from geomorphological criteria is important in deglaciated terrain as well as in regions where ice dynamics are adapting to climate change.

scholarly journals Implications of the principle of effective stress

2020 ◽  
Author(s):  
Gerd Gudehus
Keyword(s):  
Critical Phenomena ◽  
Pore Water ◽  
Effective Stress ◽  
Critical Points ◽  
Pore Water Pressure ◽  
Numerical Models ◽  
Water Pressure ◽  
Shear Bands ◽  
Triaxial Tests ◽  
Water Saturated

AbstractWhile Terzaghi justified his principle of effective stress for water-saturated soil empirically, it can be derived by means of the neutrality of the mineral with respect to changes of the pore water pressure $$p_w$$ p w . This principle works also with dilating shear bands arising beyond critical points of saturated grain fabrics, and with patterns of shear bands as relics of critical phenomena. The shear strength of over-consolidated clay is explained without effective cohesion, which results also from swelling up to decay, while rapid shearing of water-saturated clay can lead to a cavitation of pore water. The $$p_w$$ p w -neutrality is also confirmed by triaxial tests with sandstone samples, while Biot’s relation with a reduction factor for $$p_w$$ p w is contestable. An effective stress tensor is heuristically legitimate also for soil and rock with relics of critical phenomena, particularly for critical points with a Mohr–Coulomb condition. Therein, the $$p_w$$ p w -neutrality of the solid mineral determines the interaction of solid fabric and pore water, but numerical models are questionable due to fractal features.

scholarly journals Pore-water pressure fluctuations in some landslide areas.

Landslides ◽  
1991 ◽  
Vol 28 (3) ◽  
pp. 9-16 ◽  
Author(s):  
Daisuke HIGAKI ◽  
Kiyoteru MARUYAMA ◽  
Katsumi YOSHIDA ◽  
Hiroyuki YOSHIMATSU
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Fluctuations

scholarly journals Proof-of-concept for a probe to measure pore water pressure in oil-water saturated porous rock

2021 ◽  
Vol 198 ◽  
pp. 108183
Author(s):  
Anastasia Capotosto ◽  
Bruna de Carvalho Faria Lima Lopes ◽  
Alessandro Tarantino
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Proof Of Concept ◽  
Porous Rock ◽  
Oil Water ◽  
Water Saturated

A slip law for glaciers on deformable beds

Science ◽  
2020 ◽  
Vol 368 (6486) ◽  
pp. 76-78 ◽  
Author(s):  
Lucas K. Zoet ◽  
Neal R. Iverson
Keyword(s):  
Slip Velocity ◽  
Water Pressure ◽  
Ice Sheet ◽  
Ice Streams ◽  
Threshold Velocity ◽  
West Antarctic Ice Sheet ◽  
Flow Models ◽  
West Antarctic ◽  
Slip Resistance ◽  
Water Saturated

Slip of marine-terminating ice streams over beds of deformable till is responsible for most of the contribution of the West Antarctic Ice Sheet to sea level rise. Flow models of the ice sheet and till-bedded glaciers elsewhere require a law that relates slip resistance, slip velocity, and water pressure at the bed. We present results of experiments in which pressurized ice at its melting temperature is slid over a water-saturated till bed. Steady-state slip resistance increases with slip velocity owing to sliding of ice across the bed, but above a threshold velocity, till shears at its rate-independent Coulomb strength. These results motivate a generalized slip law for glacier-flow models that combines processes of hard-bedded sliding and bed deformation.

scholarly journals Analytical method of forecasting the settlement of water-saturated soils over time

2018 ◽  
Vol 251 ◽  
pp. 04030
Author(s):  
Irina Yudina
Keyword(s):  
Pore Water ◽  
Function Method ◽  
Source Function ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Saturated Soils ◽  
Exponential Functions ◽  
Degree Of Consolidation ◽  
Water Saturated ◽  
Over Time

The paper deals with the formulation and solution of the consolidation problem for weak water-saturated soil bases by using exponential functions to describe the initial pore water pressure with zero boundary conditions on the surface of the base and at infinity. The solution of this problem was obtained in closed form by the source function method. Expressions are given for the pore water pressure and degree of consolidation, as well as an example of such calculation.

A slip law for glaciers on deformable beds

2020 ◽  
Author(s):  
Lucas Zoet ◽  
Neal Iverson
Keyword(s):  
Slip Velocity ◽  
Water Pressure ◽  
Ice Sheet ◽  
Ice Streams ◽  
Threshold Velocity ◽  
West Antarctic Ice Sheet ◽  
Flow Models ◽  
West Antarctic ◽  
Slip Resistance ◽  
Water Saturated

<p>Slip of marine-terminating ice streams over beds of deformable till is responsible for most of the contribution of the West Antarctic Ice Sheet to sea-level rise. Flow models of the ice sheet and till-bedded glaciers elsewhere require a law that relates slip resistance, slip velocity, and water pressure at the bed. We present results of the first experiments in which pressurized ice at its melting temperature is slid of over a water-saturated till bed. Steady-state slip resistance increases with slip velocity owing to sliding of ice across the bed, but above a threshold velocity till shears at its rate-independent, Coulomb strength. These results motivate a generalized slip law for glacier-flow models that combines processes of hard-bedded sliding and bed deformation.</p>

TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

2019 ◽  
Vol 128 (2B) ◽  
pp. 29-41
Author(s):  
Trần Thanh Nhàn
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clayey Soils ◽  
Loading History ◽  
Cyclic Shear ◽  
Wide Range ◽  
Primary Consolidation ◽  
Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

Conjectures, Hypotheses, and Theories of Drumlin Formation (In memory of Stanislaw Baranowski)

1981 ◽  
Vol 27 (97) ◽  
pp. 503-505 ◽  
Author(s):  
Ian J. Smalley
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Stress Level ◽  
Critical Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Glacial Till ◽  
Forming Process ◽  
Stress Levels

AbstractRecent investigations have shown that various factors may affect the shear strength of glacial till and that these factors may be involved in the drumlin-forming process. The presence of frozen till in the deforming zone, variation in pore-water pressure in the till, and the occurrence of random patches of dense stony-till texture have been considered. The occurrence of dense stony till may relate to the dilatancy hypothesis and can be considered a likely drumlin-forming factor within the region of critical stress levels. The up-glacier stress level now appears to be the more important, and to provide a sharper division between drumlin-forming and non-drumlin-forming conditions.

Sign in / Sign up

Export Citation Format

Share Document