02 - dealing with permafrost degradation under airport … 13 sept/02... · 2018-09-18 ·...
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DEALING WITH PERMAFROST DEGRADATION UNDER AIRPORT
PAVEMENTS
Ludomir Uzarowski, Rabiah Rizvi, Mark Musial, Golder Associates Ltd.Susan Tighe, University of Waterloo
SWIFT, CAPTGNiagara Falls, September 13, 2018
PRESENTATION OUTLINE
September 18, 2018 2
Introduction Permafrost Impact of permafrost degradation Geotechnical investigation Possible treatments Case studies Summary
INTRODUCTION
INTRODUCTIONTypical challenges for airport pavement design and construction in the North
Severe climatic conditions Severe winters
Deep frost penetration Permafrost and frost heaving
Soil and water conditions Typically glacial till Undulating bedrock Shallow water
Difficult construction conditions Short construction season Long distances Poor roads
INTRODUCTIONTypical challenges for airport pavement design and construction in the North
Remote locations and low human population
High construction cost Few contractors available Design
New challenges Custom specifications required
Limited experience and technology? Lack of quality materials QC/QA
Difficult and expensive
Frost susceptibility – soil characteristics that promote ice segregation and heaving when soil freezes
Typically differential in nature In general, fine-grained soils are frost
susceptible and coarse-grained soils are not Heaving occurs not only from when water in
soil turns to ice and forms ice lenses, but also in fine grained soils having high capillarity, silts and fine grained sands, ice lenses form due to water migration
PERMAFROST
Permafrost – perennially frozen soil
Active layer – in an area of permafrost, the top layer of ground subject to annual freezing and thawing
PERMAFROST
TE Osterkamp, University of Alaska CR Burn, Carleton University
PERMAFROST
Glen Argue “Canadian Airfield Pavement Engineering Reference”
PERMAFROST
Glen Argue “Canadian Airfield Pavement Engineering Reference”
PERMAFROST
Glen Argue “Canadian Airfield Pavement Engineering Reference”
FAA
PERMAFROST
Glen Argue “Canadian Airfield Pavement Engineering Reference”
PERMAFROST
PERMAFROST DEGRADATION
Permafrost degradation is also more drastic due to climate change
Alaska DOT
PERMAFROST DEGRADATION
PERMAFROST DEGRADATION
Nature of ground coverDescription of observed pavement
failuresSettlements, cracking, frost heaving
Subsurface investigationDrilling or test pitsSubsurface temperature monitoringPresent thickness of active layerDescription of frozen material
Drainage conditions
PERMAFROST INVESTIGATION
Glen Argue “Canadian Airfield Pavement Engineering Reference”
PERMAFROST INVESTIGATION
ThermistorsPrecision temperature
sensing devices at various depthProbe tip includes a semi
conductorTemperature change
cause change in electrical resistance
PERMAFROST INVESTIGATION
PERMAFROST INVESTIGATION
FROST HEAVING
Pavement treatment to address permafrost degradationEmergency repairsPavement structural
rehabilitation
PERMAFROST DEGRADATION TREATMENT
Structural repairs Provide complete frost protection – install
non-frost susceptible materials (max 1.8 m)Accept reduced subgrade strength during
seasonal permafrost thaw – differential frost having to be anticipated
InsulationRelocation of airside facilities
PERMAFROST DEGRADATION TREATMENT
Pavement designs if relocation not feasibleFull depth reconstruction to a
depth of frost penetrationSoil stabilizationGeogrid structureSingle layer with underlying
geotextilePillow structure
PERMAFROST DEGRADATION TREATMENT
CASE 1
CASE 1
CASE 1
CASE 1
CASE 1
CASE 1
Airfield Pavement Roughness Guidelines (TC)
CASE 1
Pavement condition Keel and non-keel zone
Settlements, frost heaves, low to high severity cracking, low severity ravelling
Poor (bumpy) ride particularly on two sections in the keel zone
Permafrost Melted or melting
Drainage Very poor condition of surface drainage No subsurface drainage
Emergency repairs and drainage improvement Pavement rehabilitation recommended in near future
CASE 1
CASE 2
CASE 2
CASE 2
Pavement condition Low to high severity cracking, frost heaving,
settlements – severe in non-keel zones, fair ride quality in the keel zone
Permafrost Melted or melting
Drainage Poor surface drainage Failed subsurface drainage system
Emergency repairs and drainage improvement Pavement rehabilitation recommended in near future
CASE 2
Continuous, very severe apron pavement settlements and cracking
CASE 3
Tilting of buildings and foundations
CASE 3
Capacitively-coupled electrical resistivity imaging (C-CERI)
OhmMapper using C-CERI system in addition to regular investigation
Electrical resistivity of the surface – laterally and vertically
High ice content or permafrost increase resistivity (warm colors)
Lower resistivity (cool colors) –higher water content
CASE 3
OhmMapper using C-CERI system
CASE 3
Relocation of ATB, apron and access road to a new area with no permafrost
CASE 3
Large part of Canada is in the discontinuous and scattered permafrost zone
Permafrost degradations poses serious problems for airports due to differential settlements and cracking
Differential frost heaving is also typically observed in these areas
SUMMARY
Geotechnical investigation and condition monitoring are necessary
Pavement treatment to address permafrost degradation Emergency repairs Pavement structural
rehabilitationDrainage improvements
SUMMARY
