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1994 | Buch

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An Introduction to Frozen Ground Engineering

verfasst von: Orlando B. Andersland, Branko Ladanyi

Verlag: Springer US

Enthalten in: Professional Book Archive

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Frozen Ground Engineering first introduces the reader to the frozen environment and the behavior of frozen soil as an engineering material. In subsequent chapters this information is used in the analysis and design of ground support systems, foundations, and embankments. These and other topics make this book suitable for use by civil engineering students in a one-semester course on frozen ground engineering at the senior or first-year-graduate level. Students are assumed to have a working knowledge of undergraduate mechanics (statics and mechanics of materials) and geotechnical engineering (usual two-course sequence). A knowledge of basic geology would be helpful but is not essential. This book will also be useful to advanced students in other disciplines and to engineers who desire an introduction to frozen ground engineering or references to selected technical publications in the field. BACKGROUND Frozen ground engineering has developed rapidly in the past several decades under the pressure of necessity. As practical problems involving frozen soils broadened in scope, the inadequacy of earlier methods for coping became increasingly apparent. The application of ground freezing to geotechnical projects throughout the world continues to grow as significant advances have been made in ground freezing technology. Freezing is a useful and versatile technique for temporary earth support, groundwater control in difficult soil or rock strata, and the formation of subsurface containment barriers suitable for use in groundwater remediation projects.

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Inhaltsverzeichnis

Frontmatter

1. Frozen Ground

Abstract

Frozen ground is soil or rock with a temperature below 0°C. The definition is based entirely on temperature and is independent of the water and ice content of the soil or rock. The large increase in soil strength on freezing has been utilized by engineers in the construction of frozen earth structures. The ice becomes a bonding agent, fusing together adjacent soil particles or blocks of rock to increase their combined strength and make them impervious to water seepage. Excavation and other work can proceed safely inside, or next to, a barrier of strong, watertight frozen earth. In cold regions, perennially frozen ground (or permafrost) remains at a temperature below 0°C continuously from year to year. Moisture in the form of water and ground ice may or may not be present. Seasonally frozen ground involves temperatures below 0°C only during the winter season. In the northern hemisphere the southern limit of cold regions extends to about the 40th parallel. Engineers identify this southern limit by the depth of seasonal ground freezing, the 300-mm depth of frost penetration.

Orlando B. Andersland, Branko Ladanyi

2. Physical and Thermal Properties

Abstract

Frozen soil is a four-component system consisting of soil particles, ice, water, and air. The particles (mineral and/or organic matter) come in various sizes and shapes with a thin film of unfrozen water coating most mineral grains. The voids are filled with ice, unfrozen water, and air. Ice may be distributed uniformly throughout the soil mass or it may have accumulated in the form of irregular or stratified ice inclusions. Larger ice masses may form as a result of processes associated with ice wedges and pingos. Frozen soil classification involves identification of the soil phase, adding characteristics associated with the frozen soil, and describing ice found in frozen ground.

Orlando B. Andersland, Branko Ladanyi

3. Heat Flow in Soils

Abstract

Ground temperatures have a significant effect on soil engineering behavior and must be considered in the design of frozen ground support systems and other constructed facilities in cold regions. In these problems, temperatures within, under, and around the structure depend on the ground surface temperatures together with the geothermal gradient for the area. In addition to dependence on variable surface factors, ground temperatures may also depend on construction activity: for example, the controlled freezing of an earth support system. Where freezing occurs in the ground, the soil latent heat, soil thermal conductivity, and heat capacity will play a part when time dependence is involved. These topics are addressed in this chapter.

Orlando B. Andersland, Branko Ladanyi

4. Thaw Behavior of Frozen Ground

Abstract

Frozen ground contains ice in several forms, ranging from coatings on soil particles and individual ice inclusions to ice with soil inclusions. On thawing, the ice will disappear and for existing overburden pressures the soil skeleton must now adapt itself to a new equilibrium void ratio. The resulting thaw settlement phenomenon is important to the design of frozen ground support systems, design of building foundations and embankments on permafrost where thaw is permitted, design of buried pipelines, and road and highway design on seasonally and perennially frozen ground. Thaw settlement due to melting of ice-rich permafrost is illustrated in Fig. 4-1. The settlement appears to follow a polygon shape, suggesting melting of ice wedges. In this chapter we introduce concepts relative to thaw settlement, thaw consolidation, and thaw behavior in layered soil systems.

Orlando B. Andersland, Branko Ladanyi

5. Mechanical Properties of Frozen Soils

Abstract

From the point of view of the science of materials, frozen soil is a natural particulate composite, composed of four different constituents: solid grains (mineral or organic), ice, unfrozen water, and gases. The most important characteristic by which it differs from other similar materials, such as unfrozen soils and the majority of artificial composites, is that under natural conditions its matrix, composed mostly of ice and water, changes continuously with varying temperature and applied stress.

Orlando B. Andersland, Branko Ladanyi

6. Construction Ground Freezing

Abstract

Controlled ground freezing for construction and mining applications has been in use for over a century. Frozen ground may be used to provide ground support, groundwater control, or structural underpinning during construction. Constructed prior to excavation, the frozen earth wall, for practical purposes, eliminates the need for sheeting of the earth, site dewatering, soil stabilization, or concern for movement of adjacent ground. It is a versatile technique that involves use of refrigeration to convert in situ soil pore water into ice. The ice becomes a bonding agent, fusing together adjacent particles of soil or blocks of rock to increase their combined strength and make them impervious to water seepage. Excavation and other work can then proceed safely inside, or next to, the barrier of strong, watertight frozen earth. It should be noted that it is essential that groundwater be present, supplied either by high water table or artificially.

Orlando B. Andersland, Branko Ladanyi

7. Foundations In Frozen Soils

Abstract

Foundation design in areas of seasonal frost depends on the choice of an appropriate foundation depth and protection of the foundation from the effects of frost, particularly where there is frost-susceptible soil. Under certain conditions, harmful frost action effects may arise. For this to occur, frost must penetrate down to frost-susceptible soil, and sufficient water must be available to sustain the formation and growth of ice lenses. The lenses usually form parallel to the frost front, producing forces or soil movements directed at a right angle to the frost front. These forces can be very large and can lead to heaving or displacement of all parts of the foundation as the soil freezes. The magnitude of heave forces is generally difficult to determine. As it is impractical to restrain heave fully, one should attempt to eliminate it by proper design. In practice, this means that any frost-susceptible soil that will affect the foundation must be either prevented from freezing by proper insulation, or the water supply to the freezing front should be reduced by drainage. Otherwise, such a soil must be excavated and replaced with a frost-stable material.

Orlando B. Andersland, Branko Ladanyi

8. Stability of Soil Masses in Cold Regions

Abstract

A soil mass located beneath a sloping ground surface has a tendency to move downward and outward under the influence of gravity. This moving mass may proceed by flowing, sliding, falling, or by a combination of these processes. Movement is counteracted by the soil shearing resistance, which can be mobilized along a potential failure surface. Materials involved in the movement may consist of naturally deposited soil (frozen or unfrozen), human-made fills, or a combination of both. The types and processes of slope movement in unfrozen soils have been identified and classified by Varnes (1978). Methods of stability analysis for various slope movements in unfrozen materials were reviewed by Morgenstern and Sangrey (1978).

Orlando B. Andersland, Branko Ladanyi

9. Earthwork in Cold Regions

Abstract

Embankment construction with frozen and unfrozen soil materials is conducted throughout the year on many engineering projects where ambient air temperatures remain below 0°C for a significant portion of the year. Construction for oil field support facilities on the Alaska North Slope required that operations proceed over a 12-month period and not wait for the short 3-month thaw season (Tart, 1983). Operation of open-pit mines requires effective and economic excavation and handling of frozen and thawed ground during the entire year. Difficult problems can be experienced depending on the material type, temperature and water content, and the time of year. Material properties of fill used on the project must be reviewed. Landform analyses, borings, and geophysical techniques help assess potential material sources. Borrow source characteristics determine the techniques required for excavation (e.g., blasting, ripping, and scraping). Material type and volumes involved determine haul equipment most suitable for the project. In addition, placement and compaction techniques are dependent on embankment use and material type.

Orlando B. Andersland, Branko Ladanyi

10. Field Investigations

Abstract

For most engineering projects in seasonal and permafrost areas, detailed information on subsurface conditions is required for design and construction purposes if structures and facilities are to perform satisfactorily (Johnston, 1963c; Linell and Johnston, 1973). Determination of the type, distribution, properties, and behavior of frozen foundation materials is essential. Sampling of the materials (soil or rock) for examination and testing in the field and the laboratory will be an important part of field investigation programs. Valuable information can also be obtained at the site using in situ test methods and geophysical techniques.

Orlando B. Andersland, Branko Ladanyi

Backmatter

Titel: An Introduction to Frozen Ground Engineering
verfasst von: Orlando B. Andersland
Branko Ladanyi
Copyright-Jahr: 1994
Verlag: Springer US
Electronic ISBN: 978-1-4757-2290-1
Print ISBN: 978-1-4757-2292-5
DOI: https://doi.org/10.1007/978-1-4757-2290-1