Ninth International Conference on Permafrost ... - IARC Research

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A Permafrost and Building Foundation Monitoring System toHelp Design Adaptable Foundation Structures in a Changing ClimateMichael R. LillyGW Scientific, Fairbanks, Alaska, USARon F. PaetzoldGW Scientific, College Station, Texas, USADaniel ReichardtGW Scientific, Anchorage, Alaska, USAIntroductionDesigning foundations for homes and buildings innorthern regions will face many challenges in future yearsas climate changes impact permafrost regions. Permafroststability may be adversely affected by climate change, andnew buildings need to be designed to withstand or adapt forsuch changing conditions. Past approaches have focusedon stabilizing permafrost, making the assumption that thebuilding structure was the primary source for any changein permafrost. As climate changes increase, the potential forassociated impacts to foundation systems within the designlifespan of the building will become more common, and theexpense and difficulty associated with stabilizing warmingpermafrost will likely become greater.The Cold Climate Housing Research Center (CCHRC)was created to promote, develop, and test cold climatebuilding technology. The Center’s Research and TestingFacility (RTF) is a 15,000 square foot building designed asa multipurpose structure containing office space, researchlaboratories, meeting rooms, and a library. The building islocated in a setting having shallow permafrost conditions.Additional information about the Center and the RTF maybe found on their website: http://www.cchrc.org/.The RTF was built to adjust to degrading permafrost byhaving an adjustable foundation system. This is differentthan past methods, which focus on maintaining frozenconditions. With warming climatic conditions, this placesa foundation-stabilization system at odds with the naturalstate of the environment. The building’s foundation isdesigned with piers that are equipped with 50-ton jacks tokeep the building level by compensating for any differentialsettlement resulting from permafrost degradation.To help evaluate, respond, and demonstrate this type offoundation system for buildings, a permafrost and activelayer monitoring system was installed to help provide datafor the life of facility operations. The RTF and the areasbeneath and around the building have been thoroughlyinstrumented to monitor conditions, especially those relatedto temperature and moisture.The temperature monitoring network was establishedto help look at background permafrost conditions, as wellas conditions under the building and at various sections ofthe building foundations that may be impacted by seasonalfreezing. The site has a supra-permafrost, unconfined, aquiferin unconsolidated silts. The groundwater flow impacts heattransfer between the building and underlying permafrost.The water-table elevation varies seasonally with snowmeltrecharge in the spring. The general groundwater gradient isfrom west to east.Additional monitoring includes unfrozen soil-moisturesensors. While the building limits future vertical drainageinto the subsurface, annual rising and falling groundwatertables can contribute to the unsaturated moisture levels underthe building. Changing permafrost conditions may increaseor decrease groundwater fluxes and vertical changes underthe building.A better understanding of the subsurface environment andchanging permafrost conditions will be important for futureevaluations of the adjustable foundations systems and thetransferability to developing cold regions.Materials and MethodsThe depth to permafrost at the building site varies from3.7 m (12 feet) at the southwest corner to more than 8.5 m(28 feet) on the northeast corner.Construction began on the RTF in the middle of July 2005.The building was completely enclosed in January 2006 andwas completed in September of 2006. Sensors were installedduring building construction. Layout of the facility is shownin Figure 1.Several monitoring wells were drilled into permafrostand allowed to freeze back. The wells can be used for twopurposes: measurements of the top of the water-table aquiferand the top of permafrost. A background site was installedaway from the facility (weather station site), on the upgradientside of the building in shallow permafrost, and on thedownstream side of the facility, where the maximum impactshould come from thermal heat loss from the building. AFigure 1. Site location map for CCHRC facility, showing locationof observation wells and thermistor borings.187
Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tFigure 2. South Bay south foundation thermal test section sensorlocations.number of sensors were also installed under all the buildingfoundation systems to help characterize the heat loss fromthe building.Soil temperature is monitored at various points usingsensors fabricated with triplicate YSI thermistors or stringsof 12 YSI thermistors at a predetermined spacing. Thecalibration for each sensor was verified. Figure 1 showsthe location of two of the thermistor strings: CCHTH1 andCCHTH3.Soil-water content was monitored with CampbellScientific, Inc. CS616 TDR-type sensors. These sensorsindicate the volumetric amount of unfrozen water content,based on changes in soil bulk dielectric properties.Water levels in observation wells are manually recordedat selected observation intervals. The groundwater wells arelocated near the four property corners, as shown on the mapin Figure 1.Sensor readings at each station were controlled andrecorded with a Campbell Scientific, Inc. CR1000 datalogger.Data are transmitted hourly to a central processing serverthough an Internet connection.Figure 2 shows sensor locations near one of the foundationjacking pad test sections. CCHTH## sensors are temperaturesensors consisting of triplicate thermistors. CCHSM##sensors are soil-moisture sensors.Results and DiscussionThe south foundation thermal test section is taken asrepresentative. Figure 3 shows soil temperatures sinceSeptember 1, 2006, for the sensors in the gravel fill andnatural silt to 2.26 m below the top of the jacking pad. Thesoil temperature did not fall below freezing here.Figure 4 shows soil-water content since September 1,2006, for the sensors in the gravel fill and natural silt to 2.26m below the top of the jacking pad. The sensors in the naturalsilt, below the gravel fill, show the soil to be very moist, nearsaturation. The gravel fill is very dry, between about 5 to 7percent by volume. The graph shows seasonal variability insoil-water content in the silt. The driest time is in the spring.Fall 2007 shows higher soil-water content than the sameperiod in 2006. The monitoring needs to continue in orderto ascertain if this is simply seasonal variability, if the soilFigure 3. South foundation thermal test section: soil temperature inthe gravel fill and in the natural silt.Figure 4. South foundation thermal test section: soil-water contentin the gravel fill and in the natural silt.is getting wetter, or if the soil was dried during constructionand is returning to a stable state.SummaryThe CCHRC RTF is a state-of-the-art facility located onshallow permafrost. The building foundation is designed toallow compensation for any differential settlement resultingfrom permafrost degradation. The building and surroundingarea is heavily instrumented to allow soil-temperatureand soil-moisture monitoring. The monitoring system isdesigned for long-term use. Preliminary results are given,but it is too soon to tell if the ground beneath the buildinghas reached equilibrium after the disturbance resulting fromthe construction.ReferencesMurton, J.B. & French, H.M. 1994. Cryostruc tures in permafrost,Tuktoyaktuk coastlands, western Arctic Canada.Canadian Journal of Earth Sciences 31: 737-747.188
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ContentsPreface ...................
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Mapping and Modeling the Distributi
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Satellite Observations of Frozen Gr
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xiiIce Wedge Thermal Regime in Nort
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xivPermafrost Response to Dynamics
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NICOP SponsorsUniversitiesUniversit
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Deep Permafrost Studies at the Lupi
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Effect of Fire on Pond Dynamics in
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Cryological Status of Russian Soils
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Acoustical Surveys of Methane Plume
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Permafrost Delineation Near Fairban
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Preparatory Work for a Permanent Ge
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A Provisional Soil Map of the Trans
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Martian Permafrost Depths from Orbi
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Time Series Analyses of Active Micr
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Impact of Permafrost Degradation on
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DC Resistivity Soundings Across a P
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Modeling Thermal and Moisture Regim
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A Provisional Permafrost Map of the
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Alpine Permafrost Distribution at M
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Cryogenic Formations of the Caucasu
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Modeling Potential Climatic Change
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A Hypothesis: A Condition of Growth
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Modeled Continual Surface Water Sto
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Freeze/Thaw Properties of Tundra So
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Discontinuous Permafrost Distributi
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Thermal Regime Within an Arctic Was
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Seasonal and Interannual Variabilit
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Twelve-Year Thaw Progression Data f
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Continued Permafrost Warming in Nor
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Landsliding Following Forest Fire o
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A Permafrost Model Incorporating Dy
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Seasonal Sources of Soil Respiratio
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Greenland Permafrost Temperature Si
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The Importance of Snow Cover Evolut
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The Account of Long-Term Air Temper
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The Combined Isotopic Analysis of L
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Adaptating and Managing Nunavik’s
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Human Experience of Cryospheric Cha
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HiRISE Observations of Fractured Mo
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A Soil Freeze-Thaw Model Through th
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Mapping and Modeling the Distributi
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First Results of Ground Surface Tem
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Historical Changes in the Seasonall
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Rock Glaciers in the Kåfjord Area,
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Snowpack Evolution on Permafrost, N
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Climate Change in Permafrost Region
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Maximizing Construction Season in a
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Pleistocene Sand-Wedge, Composite-W
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