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FOUNDATIONS WITH FROST HEAVE. By Derek Xia, M.Sc., P.Eng., M.CSCE, M.ASCE , M.AISC. derek.xia@ualberta.ca. Contents. Introduction Soil Classification Freezing in Ground Engineering Issues Summary. Introduction. Introduction.

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foundations with frost heave

FOUNDATIONS WITH FROST HEAVE

By Derek Xia, M.Sc., P.Eng.,

M.CSCE, M.ASCE , M.AISC

derek.xia@ualberta.ca

contents
Contents
  • Introduction
  • Soil Classification
  • Freezing in Ground
  • Engineering Issues
  • Summary
introduction4
Introduction
  • Many engineering projects are located in areas where the ground experiences sub-zero conditions.
  • Frozen ground is also caused by artificial freezing such as chilled gas pipelines, refrigerated cold storage rooms, and freezing ground in civil and mining engineering.
  • Freezing and subsequent thaw induce engineering problems for most projects in areas with frost condition.
  • It is geotechnical engineer’s responsibility to solve most frozen ground problems. However, it’s always good for a civil engineer working on other areas to know some basic issues about frozen ground.
soil classification6
Soil Classification

Soils

Finegrained soils

Coarse grained soils

According to

particle size

Silts, Clays

Sands, Gravels, Cobbles, Boulders

soil classification7
Soil Classification

Frost Susceptible soils

Non-frost susceptible soils

Response

to Frost

Soils

Finegrained soils

Coarse grained soils

According to

particle size

Silts, Clays

Sands, Gravels, Cobbles, Boulders

freezing in ground9
Freezing in Ground

Temperature profiles in ground

Seasonal frost Area

Permafrost Area

freezing in ground10
Freezing in Ground

Phases of Un-frozen and Frozen Soils

freezing in ground11
Freezing in Ground

Unfrozen water in coarse-grained soil

  • Most water exists in pore as free water in unfrozen soil.
  • Unfrozen water exists in pore surrounding by ice in frozen zone.
  • Therefore, no path for water migration to frozen zone.

Soil Grain

Unfrozen

water

Ice

freezing in ground12
Freezing in Ground

Freezing in coarse-grained soils

  • Most pore water freezes in frozen zone as frost penetrates into soil.
  • Pore water expands by ~9% volumetrically when freezing.
  • This 9% expansion usually pushes the water downward into the unfrozen zone and drains away.
  • Normally, it does NOT change the soil structure. No frost heave takes place in these soils.
freezing in ground13
Freezing in Ground

Unfrozen water in fine-grained soil

  • Water in fine-grained soil exists simultaneously as
    • free water in bulk,
    • capillary water,
    • film water,
    • and hygroscopic water.
  • Each has different freezing point due to different stresses.
  • Water coexists with ice as thin films in frozen soil through which moisture migration may occur.
freezing in ground14
Freezing in Ground

Unfrozen water in fine-grained soil

freezing in ground16
Freezing in Ground

Freezing in fine-grained soils

  • Freezing of a fine-grained soil is a very complicated process including both mass and heat transfer.
  • Ice crystals initiate in frozen zone with frost penetrating into a fine-grained soil.
  • While frost penetrates into soil, water is drawn from the unfrozen zone towards the ice crystals through the frozen fringe, forming ice lenses.
  • The warmest ice lens grows until the next ice lens forming during transient heat flow.
  • Final ice lens can grow forever during the thermal steady state if there is enough water supply.

Frozen

Fringe

freezing in ground transient freezing
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

02h19

freezing in ground transient freezing18
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

02h36

freezing in ground transient freezing19
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

02h52

freezing in ground transient freezing20
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

03h08

freezing in ground transient freezing21
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

03h24

freezing in ground transient freezing22
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

03h40

freezing in ground transient freezing23
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

03h56

freezing in ground transient freezing24
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

04h12

freezing in ground transient freezing25
Freezing in Ground – Transient Freezing

Top plate: -5oC, Bottom plate 2oC

04h28

freezing in ground steady state
Freezing in Ground – Steady State

Top plate: -5oC, Bottom plate 2oC

21h45

freezing in ground steady state27
Freezing in Ground – Steady State

Top plate: -5oC, Bottom plate 2oC

32h00

freezing in ground steady state28
Freezing in Ground – Steady State

Top plate: -5oC, Bottom plate 2oC

42h00

freezing in ground steady state29
Freezing in Ground – Steady State

Top plate: -5oC, Bottom plate 2oC

52h00

freezing in ground steady state30
Freezing in Ground – Steady State

Top plate: -5oC, Bottom plate 2oC

62h00

freezing in ground steady state31
Freezing in Ground – Steady State

Top plate: -5oC, Bottom plate 2oC

72h00

freezing in ground steady state32
Freezing in Ground – Steady State

Top plate: -5oC, Bottom plate 2oC

82h00

freezing in ground frozen soil structure

Frozen zoneNo visible ice lens

Final ice lens

Vertical ice lens

Frozen fringe

Frost front

Unfrozen zone

Freezing in Ground – Frozen Soil Structure

Frozen Soil (fine)

MC redistribution

engineering issues37
Engineering Issues

Saturated fine grained soil

Uplifts and Frost-jacking

Bearing Capacities

Freezing

Engineering Problems

Settlements

Frost heave

Stabilities

Others

Thaw

engineering issues38
Engineering Issues

Shallow Foundation

  • In Ft. McMurray, Alberta the typical amount of frost heave is 50-75mm.
  • Uplift force due to frost heave can be up to 2MPa if the heave is confined.
  • Burying the foundation below the frost depth (approximately 4m in Ft. Mc.) is a normal approach.
  • This approach can also solve the problem due to thaw weakening and extensive settlement.
engineering issues39
Engineering Issues

Shallow Foundation for Heated Buildings

  • Shallow foundations for heated buildings need to be insulated to eliminate frost penetrating below the foundations.
  • Therefore, avoid frost heave.

Heated building interior

Exterior

engineering issues40
Engineering Issues

Uplift force through voidform on piles

  • Uplift force due to frost heave can be up to 2MPa if the heave is confined.
  • Voidform, an expanded polystyrene product, should be used to allow this upward movement.
  • For a known thickness of voidform and a predicted amount of frost heave, the uplift pressure on the bottom of the pile cap can be calculated.
engineering issues41
Engineering Issues

Uplift force through voidform on piles

  • Uplift force due to frost heave can be up to 2MPa if the heave is confined.
  • Voidform, an expanded polystyrene product, should be used to allow this upward movement.
  • For a known thickness of voidform and a predicted amount of frost heave, the uplift pressure on the bottom of the pile cap can be calculated.
engineering issues42
Engineering Issues

Adfreeze forces on piles

  • Adfreeze is a bond of frozen moisture between the foundation sides and the soil.
  • The value of adfreeze is typically 55-140kPa.
  • Using bond breakers can eliminate the adfreeze forces around the cap.
  • Adfreeze forces can induce frost jacking on a pile.
engineering issues43
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues44
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing.
  • The pile can be jacked out of the ground after several cycles.
engineering issues45
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues46
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues47
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues48
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues49
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues50
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues51
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues52
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues53
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues54
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues55
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues56
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues57
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues58
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues59
Engineering Issues

Frost Jacking

  • Frost jacking occurs when a pile is not embedded well.
  • Pile goes up with frozen soil during winters.
  • Soil settles down during summers when thawing
  • The pile can be jacked out of the ground after several cycles.
engineering issues60
Engineering Issues

Permafrost area

  • Frozen soil is very strong material.
  • Embed piles into permafrost and elevate structures above the grade to minimize heat transfer into soil.
  • Allow convection between structure and grade to cool down the piles.
  • Key issue is to avoid thawing permafrost to preserve its strength.

Active layer

Permafrost

summary
Summary

Frost Heave Requires

  • Freezing temperatures (temperature gradient) for a prolonged period of time.
  • Fine grained soil particles allowing ice lenses initiation and moisture migration.
  • Water supply.

Engineering Issues

  • Frost heave and subsequent thaw weakening and settlement.
  • Uplift forces through voidform and adfreezing.
  • Frost-jacking.
  • Engineering in permafrost.