Laboratory Testing to Evaluate Changes in Hydraulic Conductivity of Compacted Clays Caused by Freeze-Thaw: State-of-the-Art

2009 ◽  
pp. 227-227-28 ◽  
Author(s):  
MA Othman ◽  
CH Benson ◽  
EJ Chamberlain ◽  
TF Zimmie
Keyword(s):  
Hydraulic Conductivity ◽  
Laboratory Testing ◽  
State Of The Art ◽  
Freeze Thaw ◽  
Compacted Clays

Effect of freeze–thaw on the hydraulic conductivity and morphology of compacted clay

1993 ◽  
Vol 30 (2) ◽  
pp. 236-246 ◽  
Author(s):  
Majdi A. Othman ◽  
Craig H. Benson
Keyword(s):  
Hydraulic Conductivity ◽  
Three Dimensional ◽  
Compacted Clay ◽  
Clay Liners ◽  
Overburden Pressure ◽  
Thin Sections ◽  
Freeze Thaw ◽  
State Of Stress ◽  
Soil Liners ◽  
Compacted Clays

Several studies have shown that freeze–thaw causes changes in the hydraulic conductivity of compacted clays. Cracks formed by ice lensing and shrinkage cause the hydraulic conductivity to increase. In this paper, changes in hydraulic conductivity are related to changes in morphology. Photographs of thin sections of frozen specimens show that ice lenses form in compacted clay during freezing in a closed system. Photographs also show that similar ice structures are obtained for one- and three-dimensional freezing, which explains why similar hydraulic conductivities are obtained for both conditions. The photographs also show that a significant network of cracks forms in a single cycle of freeze–thaw. With additional cycles, new ice lenses are created and thus the hydraulic conductivity continues to increase. However, after about three cycles the number of new ice lenses becomes negligible and hence further changes in hydraulic conductivity cease. The temperature gradient and state of stress affect morphology and hydraulic conductivity of compacted clays subjected to freeze–thaw. At larger temperature gradients, more ice lenses form and hence the hydraulic conductivity increases. In contrast, application of overburden pressure inhibits the formation of ice lenses and reduces the size of the cracks remaining when lenses thaw. As a result, the hydraulic conductivity is reduced. Key words : compacted clay, hydraulic conductivity, clay liners, soil liners, freeze-thaw, ice lenses, structure.

Hydraulic conductivity and removal rate of compacted clays permeated with landfill leachate

2013 ◽  
Vol 51 (31-33) ◽  
pp. 6148-6157 ◽  
Author(s):  
Mehmet Sukru Ozcoban ◽  
Nejat Cetinkaya ◽  
Suna Ozden Celik ◽  
Guler Turkoglu Demirkol ◽  
Vildan Cansiz ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Landfill Leachate ◽  
Removal Rate ◽  
Compacted Clays

Exoskeletons

2019 ◽  
pp. 234-259
Author(s):  
Priyanshu Agarwal ◽  
Ashish D. Deshpande
Keyword(s):  
Case Studies ◽  
Energy Efficient ◽  
Laboratory Testing ◽  
Human Performance ◽  
State Of The Art ◽  
Upper Body ◽  
The Past ◽  
The Future ◽  
Human Use ◽  
Exoskeleton Design

The past few decades have witnessed a rapid explosion in research surrounding robotic exoskeletons due to their promising applications in medicine and human performance augmentation. Several advances in technology have led to the development of more energy efficient and viable prototypes of these devices. However, despite this rapid advancement in exoskeleton technology, most of the developed devices are limited to laboratory testing and a very few of them are commercially available for human use. This chapter discusses the advances in various constituting technologies including actuation, sensing, materials, and controls that made exoskeleton research feasible. Also presented are case studies on two state-of-the-art robotic exoskeletons, Harmony and Maestro, developed for rehabilitation of the upper body. The chapter concludes with a discussion on the ongoing challenges in exoskeleton design and ethical, social, and legal considerations related to the use of these devices and the future of exoskeletons.

Substrate freeze–thaw in a drained Alberta fen

1989 ◽  
Vol 19 (8) ◽  
pp. 1024-1029 ◽  
Author(s):  
L. E. Swanson ◽  
R. L. Rothwell
Keyword(s):  
Hydraulic Conductivity ◽  
Significant Delay ◽  
Freeze Thaw ◽  
Sample Points ◽  
Surface Peat

The study of ground frost levels in a drained and undrained forested fen showed a significant delay in thaw as well as lower temperatures at 40 and 60 cm depths in the drained area because of the insulating effect of drier surface peat in the drained area. The undrained area froze to greater depths than the drained area, but thawed more rapidly. Ice was present year-round at 16.7% of the sample points in the portion of the drained area of low hydraulic conductivity. Thickness of the frozen layer appeared to be related to hydraulic conductivity as well as drainage. Thawing from underneath the frozen layer accounted for 38% of total thaw in the undrained area.

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