Full-depth avalanche occurrences caused by snow gliding, Coquihalla, British Columbia, Canada

AbstractSnow glide is the translational slip of the entire snowpack over a sloping ground surface, and it is thought that rapid rates of snow glide precede full-depth avalanches. The nature of avalanches that release at the ground makes them difficult to predict and difficult to control using explosives.On-slope instrumentation comprised of stainless-steel "glide shoes" was used to measure rates of snow glide for two winters on a bedrock slope adjacent to the Coquihalla Highway, Cascade Mountains, British Columbia, Canada. Climate data and avalanche occurrences were recorded by the British Columbia Ministry of Transportation and Highways.Our results show that the supply of free water to the snow/ground interface by rain or snowmelt is the most important influence on full-depth avalanche release. Full-depth avalanche release responds to rainfall and snowmelt events within 12-24 hours. Occasionally, full-depth avalanches occur unexpectedly during clear, cold periods. Snowmelt by radiation is thought to contribute enough meltwater during these cold periods to induce higher rates of snow glide and full-depth avalanche release. The results also indicate that snow glide alone is not a reliable indicator for full-depth avalanche release.

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Ground thermal and geomechanical conditions in a permafrost-affected high-latitude rockslide site (Polvartinden, Northern Norway)

10.5194/tc-2016-223 ◽

2016 ◽

Author(s):

Regula Frauenfelder ◽

Ketil Isaksen ◽

Jeannette Nötzli ◽

Matthew J. Lato

Keyword(s):

Temperature Regime ◽

Laser Scanning ◽

Ground Surface ◽

Failure Zone ◽

Climate Data ◽

Conduction Model ◽

Near Surface ◽

Northern Norway ◽

Surface Temperatures

Abstract. In June 2008, a rockslide detached in the northeast facing slope of Polvartinden, a high-alpine mountain in Signaldalen, Northern Norway. Here, we report on the observed and modelled past and present near-surface temperature regime close to the failure zone, as well as on a subsequent simulation of the subsurface temperature regime, and on initial geomechanical mapping based on laser scanning. The volume of the rockslide was estimated to be approximately 500 000 m3. The depth to the actual failure surface was found to range from 40 m at the back of the failure zone to 0 m at its toe. Visible in-situ ice was observed in the failure zone just after the rockslide. Between September 2009 and August 2013 ground surface temperatures were measured with miniature temperature data loggers at fourteen different localities close to the original failure zone along the northern ridge of Polvartinden, and in the valley floor. The results from these measurements and from a basic three-dimensional heat conduction model suggest that the lower altitudinal limit of permafrost at present is at 600–650 m a.s.l., which corresponds to the upper limit of the failure zone. A coupling of our in-situ data with regional climate data since 1958 suggests a general gradual warming and that a period with highest mean near surface temperatures on record ended four months before the Signaldalen rockslide detached. A comparison with a transient permafrost model run at 10 m depth, representative for areas where snow accumulates, strengthen this findings, which are also in congruence with measurements in nearby permafrost boreholes. It is likely that permafrost in and near the failure zone is presently subject to degradation. This degradation, in combination with the extreme warm year antecedent to the rock failure, is seen to have played an important role in the detaching of the Signaldalen rockslide.

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The effects of free water on snow gliding

Journal of Geophysical Research Atmospheres ◽

10.1029/jb092ib07p06301 ◽

1987 ◽

Vol 92 (B7) ◽

pp. 6301 ◽

Cited By ~ 23

Author(s):

David M. McClung ◽

Garry K. C. Clarke

Keyword(s):

Free Water ◽

Snow Gliding

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Amplification of seismic accelerations at slope crests

Canadian Geotechnical Journal ◽

10.1139/t09-006 ◽

2009 ◽

Vol 46 (5) ◽

pp. 585-594 ◽

Cited By ~ 15

Author(s):

A. J. Brennan ◽

S. P.G. Madabhushi

Keyword(s):

Natural Frequency ◽

Soil Layer ◽

Ground Surface ◽

Surface Structures ◽

Centrifuge Modelling ◽

Sloping Ground ◽

Topographic Amplification ◽

Tensile Forces ◽

Seismic Accelerations

Earthquake accelerations can cause many problems in sloping ground. One such problem is that accelerations are greatly amplified at the crest of slopes. This topographic amplification can lead to acceleration gradients along the ground surface, which could create tensile forces in long surface structures that extend between areas of different amplifications. This paper uses centrifuge modelling to demonstrate and quantify this as a problem for a particular slope configuration. A special brittle structure has been constructed to undergo damage in the presence of large differential accelerations. The structure is seen to connect the crest to the level ground behind the crest during an earthquake, reducing the amplitude of the crest motion at the expense of structural tension. Topographic amplification is shown to be a clear function of frequency, and is especially serious for loading frequencies above the natural frequency of the soil layer.

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Three-dimensional numerical modelling of discrete piles used to stabilize landslides

Canadian Geotechnical Journal ◽

10.1139/t11-046 ◽

2011 ◽

Vol 48 (9) ◽

pp. 1393-1411 ◽

Cited By ~ 23

Author(s):

S. Kanagasabai ◽

J. A. Smethurst ◽

W. Powrie

Keyword(s):

Slip Plane ◽

Numerical Models ◽

Three Dimensional ◽

Ground Surface ◽

Lateral Force ◽

Plane Interface ◽

Single Pile ◽

Sloping Ground ◽

Stabilizing Piles ◽

Rigid Pile

Three-dimensional finite difference analyses have been carried out to investigate the behaviour of a single pile used to stabilize a slipping mass of soil by embedment into a stable stratum. Analyses were initially carried out to determine the reduction in the limiting pile–soil lateral force per metre length, pu, close to the unconfined ground surface. The analyses then explore the failure mechanisms for landslide stabilizing piles categorized by Viggiani. The effects of varying the strength of the slip plane interface between the sliding and stable strata, and of a sloping ground surface on the behaviour of the pile are then investigated. The results from numerical models with a rigid pile, a distinct plane of sliding, and a horizontal ground surface, as assumed by Viggiani, agree well with his theoretical mechanisms. Lower values of pu close to the ground surface and adjacent to the sliding plane are found to reduce the maximum shear resistance that piles can provide to the slipping mass when compared with Viggiani’s theoretical solutions. Further analyses show that the strength of the slip plane interface has a considerable influence on pile behaviour, and that the slope of the ground surface is only significant above a certain angle.

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Coquitlam Drift: a pre-Vashon Fraser glacial formation in the Fraser Lowland, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e81-135 ◽

1981 ◽

Vol 18 (9) ◽

pp. 1443-1451 ◽

Cited By ~ 25

Author(s):

Stephen R. Hicock ◽

John E. Armstrong

Keyword(s):

British Columbia ◽

Glacial Maximum ◽

Cascade Mountains ◽

Short Pulses ◽

Coast Mountains ◽

The North ◽

Glaciomarine Sediments

Coquitlam Drift is formally defined and stratotypes established for it in the Coquitlam – Port Moody area, B.C. It is a Pleistocene formation consisting of till, glaciofluvial, ice-contact, and glaciomarine sediments deposited between 21 700 and 18 700 years BP, during the Fraser Glaciation (late Wisconsin) and prior to the main Vashon glacial maximum at about 14 500 years BP. The drift was deposited in short pulses by valley and piedmont glaciers fluctuating into the Fraser Lowland from the Coast Mountains to the north and Cascade Mountains to the east.

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Grinding a Hard-to-Grind Materials with Ultrasonic-Assisted Fluid

International Journal of Automation Technology ◽

10.20965/ijat.2014.p0478 ◽

2014 ◽

Vol 8 (3) ◽

pp. 478-483 ◽

Cited By ~ 3

Author(s):

Jun Ishimatsu ◽

◽

Atsushi Iwaita ◽

Hiromi Isobe ◽

Keyword(s):

Stainless Steel ◽

Pure Titanium ◽

Ground Surface ◽

High Accuracy ◽

Grinding Force ◽

Grinding Wheel ◽

Machining Processes ◽

Fluid Supply ◽

Ultrasonic Assisted ◽

Wheel Loading

Grinding is one of the machining processes used in the manufacture of high-accuracy parts. When materials which easily adhere to the grinding wheel are used, such as aluminum, stainless steel, and titanium, wheel loading must be considered, as this could have a limiting effect. In this research, the application of ultrasonic energy to the grinding fluid is carried out with a specially-designed effector inserted into the fluid supply flow with the expectation that loading will be removed from the wheel. The experiment is carried out on stainless steel and pure titanium. The grinding force and accession of temperature are investigated during grinding, and the reduction of both grinding force and thermal escalation is confirmed. Burn marks on the ground surface of titanium are also prevented.

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Case Study Analyses of Flaw Growth and Tolerance of Stainless Steel Canisters in Marine Environment

Volume 2: Plant Systems, Structures, Components and Materials ◽

10.1115/icone25-67301 ◽

2017 ◽

Author(s):

Chang Heui-Yung

Keyword(s):

Stainless Steel ◽

Surface Temperature ◽

Power Plants ◽

Storage Systems ◽

Great Part ◽

Initiation Time ◽

Spent Fuel ◽

Climate Data ◽

Significant Difference

The majority of dry cask storage systems used in the world confine nuclear fuel within austenitic stainless steel canisters. Past experience indicates that stainless steel may become susceptible to stress corrosion cracking (SCC) in the presence of stress and chloride salts. Recently, a cracking growth rate (CGR) model was developed and applied to evaluate the flaw depth of stainless steel canisters over the timeframe of the storage at independent spent fuel storage installations. This paper presents the results of case study analyses on stainless steel canisters of dry storage systems in the 1st and 2nd nuclear power plants in Taiwan. In detail, the flaw depth was first evaluated using the CGR model, site climate data, and surface temperature at the location of interest on the canister. The critical flaw sizes and depth were then determined from the structural tolerance assessment of canister shells to flaws of varying sizes. It was found that the difference in thermal-hydraulic behaviors of drystorage canisters can cause a great variation in the SCC initiation time. But that may not cause a significant difference in the surface temperature at initial salt deliquesce (ranging from 55 to 60 °C). The CGR at the SCC initiation is greater, and the flaw growth takes a great part. The surface temperature and activation energy get low as the time increases. The total flaw depth therefore may not vary greatly with the SCC initiation time. Overall, the drystorage canisters have shown relatively high structural tolerance to flaw sizes and depths.

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