Permafrost foundations : state of the practice

95 Pages·2007·5.558 MB·English

by  Clarke, Edwin S

PERMAFROST
FOUNDATIONS
STA TE OF THE PRA CTICE
SPONSORED BY
Technical Council on Cold Regions Engineering
EDITED BY
Edwin S. Clarke, P.E.
ASCE
Published by the American Society of Civil Engineers
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Copyright ® 2007 by the American Society of Civil Engineers. All Rights Reserved.
ISBN 13: 978-0-7844-0947-3
ISBN 10: 0-7844-0947-1
Manufactured in the United States of America.
Cover Photo: Federal Aviation Flight Service Building at Fairbanks International Airport.
The thermoprobes are used to keep the soils under the building in a frozen condition. Photo
by Edwin S. Clarke.
Foreword
The ASCE Technical Council on Cold Regions Engineering (TCCRE) is publishing a
series of Monographs on various cold regions engineering subjects. Each monograph
reviews the state of the practice within a defined area through a set of papers written
by invited experts in the field.
This monograph is the tenth in the series and the second of the 21st century. It
focuses on the techniques used to construct foundations on permafrost, presenting the
most current techniques used to design these foundations. As building expands in the
northern latitudes, it is critical to get information about soil conditions and
geotechnical and structural issues into the hands of the next generation of engineers
and builders who will be dealing with the many challenges of building on frozen
soils. Failure to understand the complexity of technical issues involved in building
under these extreme conditions can result in a range of undesirable outcomes—
starting with settlement or jacking of the soils—and resulting in conditions ranging
from sloping buildings to swayback roofs to complete structural collapse.
This monograph includes eight chapters, which present the authors' experience in
both the design and remedial actions required for the continued successful
performance of these systems. Topics include an overview of frozen soils and
geotechnical issues, the need for geotechnical investigation, structurally enhanced
foundations, post and pad foundations, adjustable- design foundations, innovations in
arctic engineering, building on marginal permafrost, case histories of pile foundations
in permafrost, and refrigerated foundations.
Many people were involved in the preparation of this monograph. The topic of state-
of- the-practice permafrost foundations came from Tom Krzewinski, who was the
first chairman of the structures and foundation committee. The project would not
have been possible without the assistance of John Segna our ASCE contact. All of
the chapter authors are ASCE members, and they are to be given most of the credit.
These articles reflect the experience of the individual authors, who have been
expanding the knowledge and techniques used to build successful foundations in a
demanding and challenging environment. See the table of authors for a complete
listing. The early organization and coordination of the authors was handled by Edwin
S. Clarke. He was assisted in these efforts by James Charlton. The final editing and
conversion of the monograph chapters into a uniform format were performed by Janet
Scheren of Scheren Communications.
Each paper had at least one technical review. All reviewers are listed in the table
that follows; their assistance is greatly appreciated. Without them this publication
would not be of the high quality that it is.
iii
Authors
Bryan Borjesson, P.E., F.ASCE Gregory E Wyman, P.E., P.L.S., M.ASCE
Borjesson Consulting Engineers, Inc. Golden Valley Electric Association
Fairbanks, Alaska Fairbanks, Alaska
Edwin S. Clarke, P.E., F.ASCE Ed Yarmak, M.ASCE
Soils Alaska, PC Arctic Foundations, Inc.
Fairbanks, Alaska Anchorage, Alaska
Duane Miller, P.E., M.ASCE John P. Zarling, Ph.D., P.E., M.ASCE
Duane Miller & Associates Professor Emeritus
Anchorage, Alaska University of Alaska, Fairbanks
Zarling Aero and Engineering
Mark Musial, P.E., M.ASCE Fairbanks, Alaska
Golder Associates Inc.
Anchorage, Alaska
Sheldon R. Shaw, P.E., M.ASCE
Arctic Geotech Engineer
Fairbanks, Alaska
iv
Reviewers
Billy Connor Vladimir Romanovsky
University of Alaska Fairbanks University of Alaska Fairbanks
Fairbanks, Alaska Fairbanks, Alaska
Maria Kampsen Steve Saboundjian
Dowl Engineers DOT, Retired
Anchorage, Alaska Anchorage, Alaska
Scott Crowther Brian Schumaker
Crowther & Assoc. Duane Miller & Assoc.
Anchorage, Alaska Anchorage, Alaska
Bob McHattie Gregory E Wyman. P.E., P.L.S., M.ASCE
DOT, Retired Golden Valley Electric Association
Fairbanks, Alaska Fairbanks, Alaska
Eric Johnson Joey Yang
DOT, Retired University of Alaska Fairbanks
Anchorage, Alaska Fairbanks, Alaska
Tom Krzewinski
Golder Associates
Anchorage, Alaska
V
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Contents
Chapter 1
Introduction 1
Edwin S. Clarke
Chapter 2
The Need for Geotechnical Investigation 5
Edwin S. Clarke
Chapter 3
Structurally Enhanced Foundations: A Functional Solution to
Thaw Strain in Frozen Sand and Gravel 10
Sheldon R. Shaw
Chapter 4
Post and Pad 18
Edwin S. Clarke
Chapter 5
Adjustable Foundation Design Development Innovations in
Arctic Engineering 20
Bryan Borjesson
Chapter 6
Marginal Permafrost a Foundation Material in Transition 30
Mark Musial and Gregory E. Wyman
Chapter 7
Some Case Histories of Pile Foundations in Permafrost 50
Duane Miller
Chapter 8
Refrigerated Foundations 65
John P. Zarling and Ed Yarmak
Index 83
vii
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Chapter 1
Introduction
By Edwin S. Clarke, RE., F.ASCE
Permafrost is defined as soil that remains frozen for more than two years. At elevations
less than 304.8 m (1000 ft.), it is frequently encountered north of latitude 60. It may
also be found south of latitude 60 at higher elevations or in areas with colder climates. In
general, permafrost is associated with polar regions and exists as a layer of continuously
frozen soil underlying a thin, active layer of soils that undergo annual freeze/thaw cycles.
Any soil that maintains a frozen state is defined as permafrost. If the moisture content
of soil is very low, the effects of temperature change will be minimal. However, all
soil matrices contain water to some extent. While mineral soil properties are relatively
temperature stable throughout the climatic temperature range, water is another story.
Freezing and thawing of the water in soil and the subsequent changes in physical properties
of the soil matrix, such as density, hydraulic conductivity, thermal conductivity, shear
strength, and compressive strength, are phenomena that concern engineers practicing in
northern latitudes. When water freezes, its volume increases by about 9 percent. This
dramatic expansion can generate significant stress. Pressures of 14.1 km/cm (200 psi)
are possible under some conditions.
Permafrost is formed when conditions, such as climate, latitude, solar aspect, or vegetation
patterns combine to keep the soil temperature lower than the freezing point of water.
It is possible to artificially create permafrost using refrigeration systems. Naturally
occurring permafrost is in a state of equilibrium. Heat flow into frozen soils during
summer months is balanced by heat flow out of frozen soils during winter months. The
equilibrium can be disrupted by human activities, such as clearing vegetation, building
new facilities, or diverting existing drainage patterns, or by natural forces, such as global
temperature cycles, forest fires, or erosion events. After disruption, the soil temperature
profile adjusts until a new equilibrium is achieved. During the adjustment period, the
depth of permafrost may increase or decrease, ice may form or thaw, and settlement or
heaving of soils may occur. These events affect structures built on permafrost and are
the prevalent challenge for engineers involved in development of northern regions.
Continuous permafrost primarily exists north of 60° latitude in Asia and North America.
Figure 1.1 illustrates the extent of permafrost conditions in the Northern Hemisphere.
Discontinuous permafrost is found at the boundary of continuous permafrost regions.
Site-specific conditions such as vegetation, exposure, and soil types influence the ground
temperature profile and existence of permafrost in these slightly warmer areas.
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