First Canadian Geotechnical Colloquium: Foundation design approaches in permafrost areas

1978 ◽  
Vol 15 (1) ◽  
pp. 96-112 ◽  
Author(s):  
J. F. Nixon
Keyword(s):  
Influence Factors ◽  
Frozen Soil ◽  
Case Histories ◽  
Foundation Design ◽  
Large Structures ◽  
Theoretical Predictions ◽  
Air Ventilation ◽  
Insulation Thickness ◽  
Forced Air

The design of foundations in permafrost areas for large structures involves a knowledge of the thermal and mechanical properties of frozen soil. Recent creep data for frozen soils and ice are reviewed and some secondary (steady) creep relationships are established. A design approach for pile foundations in ice-rich permafrost is proposed and compared with available field case histories. The theory is found to provide reasonable predictions of pile settlements under load. It is suggested that the limitation of long-term pile settlements will control the design loadings.The thermal aspects of ventilated pad foundations are discussed and design curves are given for required pad and insulation thickness and ventilation capacity. Case histories indicate that in order to obtain the necessary ventilation capacity, forced air ventilation using electric fans is required for most practical situations.A settlement analysis for spread footings on permafrost is established and influence factors for settlement rate are given. Again it is apparent that allowable footing loads will be controlled by limiting long-term settlements, rather than by consideration of soil shear strength alone. Field data on the creep response of a tunnel in Fairbanks provide good correlation with theoretical predictions.

Long-term association between urban air ventilation and mortality in Hong Kong

2021 ◽  
Vol 197 ◽  
pp. 111000
Author(s):  
Pin Wang ◽  
William B. Goggins ◽  
Yuan Shi ◽  
Xuyi Zhang ◽  
Chao Ren ◽  
...  
Keyword(s):  
Hong Kong ◽  
Urban Air ◽  
Air Ventilation

scholarly journals Rotor Loading Characteristics of a Full-Scale Tidal Turbine

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1035 ◽  
Author(s):  
Magnus Harrold ◽  
Pablo Ouro
Keyword(s):  
Turbulent Flows ◽  
Mechanical Loading ◽  
Full Scale ◽  
Design Stage ◽  
Flow Profile ◽  
Expected Return ◽  
Tidal Turbines ◽  
Theoretical Predictions ◽  
Tidal Turbine

Tidal turbines are subject to highly dynamic mechanical loading through operation in some of the most energetic waters. If these loads cannot be accurately quantified at the design stage, turbine developers run the risk of a major failure, or must choose to conservatively over-engineer the device at additional cost. Both of these scenarios have consequences on the expected return from the project. Despite an extensive amount of research on the mechanical loading of model scale tidal turbines, very little is known from full-scale devices operating in real sea conditions. This paper addresses this by reporting on the rotor loads measured on a 400 kW tidal turbine. The results obtained during ebb tidal conditions were found to agree well with theoretical predictions of rotor loading, but the measurements during flood were lower than expected. This is believed to be due to a disturbance in the approaching flood flow created by the turbine frame geometry, and, to a lesser extent, the non-typical vertical flow profile during this tidal phase. These findings outline the necessity to quantify the characteristics of the turbulent flows at sea sites during the entire tidal cycle to ensure the long-term integrity of the deployed tidal turbines.

Geothermal modeling of soil or mine tailings with concurrent freezing and deposition

1998 ◽  
Vol 35 (2) ◽  
pp. 234-250 ◽  
Author(s):  
JF (Derick) Nixon ◽  
Nick Holl
Keyword(s):  
Snow Cover ◽  
Mine Tailings ◽  
Frozen Soil ◽  
Freezing And Thawing ◽  
Frozen Ground ◽  
Geothermal Model ◽  
Winter Time ◽  
Upper Boundary ◽  
Good Agreement

A geothermal model is described that simulates simultaneous deposition, freezing, and thawing of mine tailings or sequentially placed layers of embankment soil. When layers of soil or mine tailings are placed during winter subfreezing conditions, frozen layers are formed in the soil profile that may persist with time. The following summer, warmer soil placement may not be sufficient to thaw out layers from the preceding winter. Remnant frozen soil layers may persist for many years or decades. The analysis is unique, as it involves a moving upper boundary and different surface snow cover functions applied in winter time. The model is calibrated based on two uranium mines in northern Saskatchewan. The Rabbit Lake scenario involves tailings growth to a height of 120 m over a period of 24 years. At Key Lake, tailings increase in height at a rate of 1.3 m/year. Good agreement between the observed position of frozen layers and those predicted by the model is obtained. Long-term predictions indicate that from 80 to 200 years would be required to thaw out the frozen layers formed during placement, assuming 1992 placement conditions continue. Deposition rates of 1.5-3 m/year give the largest amounts of frozen ground. The amount of frozen ground is sensitive to the assumed snow cover function during winter.Key words: geothermal, model, tailings, freezing, deposition.

Smoke emission and temperature characteristics of the long-term overloaded wire in space

2019 ◽  
Vol 37 (2) ◽  
pp. 99-116 ◽  
Author(s):  
Shao Xue ◽  
Wenjun Kong
Keyword(s):  
High Temperature ◽  
Fire Risk ◽  
Smoke Emission ◽  
Orbital Flight ◽  
Excess Current ◽  
Oxidative Pyrolysis ◽  
Microgravity Experiments ◽  
Insulation Thickness ◽  
First Time

We developed an experimental payload to study the overloaded characteristics of wire insulations on board the China’s SJ-10 satellite. In 2-week microgravity experiments provided by the orbital flight, the smoke emissions of overloaded wire insulations were observed in space for the first time. Two smoke emission modes, namely the end smoke jet and the bubbling smoke jet, were identified with polyethylene insulations. The results showed that the geometry of the pyrolysis front dominated the direction and the range of the end smoke jet. The non-oxidative pyrolysis that occurred between the wire core and the insulation produced the high-temperature smoke and caused the bubbling smoke jet. The bubbling jet has a significant impact on the temperatures of adjacent wires, revealing an additional fire risk in microgravity. The effects of insulation thickness and excess current on the temperature rise were also discussed.

scholarly journals Memantine in the management of affective recurrences of bipolar disorders after the discontinuation of long-term lithium treatment: three case histories

2013 ◽  
Vol 4 (1) ◽  
pp. 53-55 ◽  
Author(s):  
Giulia Serra ◽  
Lavinia De Chiara ◽  
Giovanni Manfredi ◽  
Alexia E. Koukopoulos ◽  
Gabriele Sani ◽  
...  
Keyword(s):  
Lithium Treatment ◽  
Bipolar Disorders ◽  
Case Histories

Time-dependent displacement behaviour of model adfreeze and grouted piles in saline frozen soils

1994 ◽  
Vol 31 (3) ◽  
pp. 395-406 ◽  
Author(s):  
K.W. Biggar ◽  
D.C. Sego
Keyword(s):  
Field Studies ◽  
Frozen Soil ◽  
Silty Sand ◽  
Time Dependent ◽  
Test Results ◽  
Model Pile ◽  
Laboratory Test Results ◽  
Load Carrying ◽  
Pile Deformation

The findings of a laboratory study on the time-dependent displacement of model piles in saline frozen soil are reported. The short-term time-dependent pile deformation in ice-poor saline silty sand was best described using a simple power law of time, whereas the long-term time-dependent deformations were best described using a flow law formulation similar to that used to describe the long-term time-dependent deformation of ice or ice-rich permafrost. The use of cementitious grout as a backfill resulted in doubling of the pile load carrying capacity for a given displacement rate. The laboratory test results compare well with other laboratory and field studies. Key words : frozen soil, saline, model pile, time-dependent deformation, sand backfill, grout.

Sign in / Sign up

Export Citation Format

Share Document