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Dredged sediments with initial water contents between 200% and 400% were treated with single and composite binders. Samples were subjected to open and semi-closed freeze-thaw (f-t) cycles to investigate the impact of f-t cycling on hydraulic conductivity (HC) and unconfined compressive strength (UCS). A grace period (GP) for thaw consolidation is included to assess healing potential of the affected stabilized mass. Findings of this study show that the impact of f-t cycles depends on initially achieved UCS and HC values prior to the f-t cycling and time of testing after f-t cycles. The HC of specimens with an initial UCS value of 87 kPa increased with number of f-t cycles. The UCS values decreased in the range of 50%-80% when specimens were tested directly after the thaw period and values decreased in the range of 14%-60% when specimens were tested at the end of the GP. The HC of specimens with an initial UCS value of 299 kPa remained almost the same. These samples experienced permanent loss in the UCS values, irrespective of time of testing. Detrimental effects of the freezing action on the UCS were greater under semi-closed than open freezing conditions. Key words: freeze-thaw cycle, dredging, hydraulic conductivity, stabilization-solidification, unconfined compressive strength, thaw weakening, thaw consolidation, durability. Dans le cadre de cette etude, on a traite des sediments dragues dont la teneur initiale en eau etait entre 200 et 400% avec un liant simple et composite. On a soumis des echantillons des cycles ouverts et semi-fermes de gel-degel (g-d) afin d'etudier les effets des successions de cycles de g-d sur la conductivite hydraulique (CH) et la resistance en compression non confinee (RCNC). On a prevu une periode de grace pour la consolidation du degel afin d'evaluer le potentiel de cicatrisation de la masse affectee stabilisee. Les resultats de cette etude montrent que les effets des cycles de g-d dependent des valeurs de la RCNC et de la CH atteintes initialement avant les successions de cycles de g-d et du moment ou les essais sont effectues apres les cycles de g-d. La CH des specimens ayant une valeur de RCNC initiale de 87 kPa a augmente avec le nombre de cycles de g-d. Les valeurs de RCNC ont diminue entre 50 et 80% lorsque les essais ont ete faits sur les specimens tout de suite apres la periode de degel et les valeurs ont baisse de 14 60% lorsqu'on a fait les essais sur les specimens la fin de la periode de grace. La CH des specimens ayant une valeur de RCNC initiale de 299 kPa est demeuree sensiblement la meme. Ces echantillons ont subi une perte permanente des valeurs de RCNC, independamment du moment ou on a fait les essais. Les effets nefastes de l'action du gel sur la RCNC ont ete plus considerables sous les conditions de systemes de gel semi-ferme qu'ouvert. [Traduit par la Redaction] Mots-cles: cycle de gel-degel, dragage, conductivite hydraulique, stabilization-solidification, resistance en compression non confinee, ramollissement du au degel, consolidation du degel, durabilite., Introduction In cold-region climates, repetitive freeze-thaw (f-t) cycles can have a detrimental effect on mechanical properties of stabilized soft soils and sediments. Researchers have shown that f-t cycling has significant [...]

A series of pilot scale freezing bed experiments were conducted to evaluate and model the freeze--thaw treatment of septic tank sludge (septage). Filtrate quality is similar to a low strength domestic wastewater and the sludge cake has a dry matter content of 25% with E. coli numbers below 2.0 x [10.sup.6] CFU/g dry solids. Experimental results showed no impact of snow cover on bed performance in a region with moderate snowfall (1.3-1.6 m) as new layers of sludge effectively melted any accumulated snow; suggesting that it is not necessary to cover the bed or remove the snow in areas where sludge dosing exceeds snowfall. Both freezing and thawing processes were successfully modelled with readily available climatic data. Model output for North American climatic conditions indicates that the freezing bed technology can be widely applied throughout the northern United States and Alaska and most of Canada with the exception of coastal areas and southern Ontario. Key words: freeze-thaw conditioning, septage treatment, sludge, freezing bed, modelling. Une serie d'experiences a l'echelle pilote de lit de congelation a ete realisee pour evaluer et modeliser le traitement par gel-degel des boues de fosses septiques. La qualite du filtrat est similaire aux eaux usees domestiques de faible intensite et le gateau de boues possede un contenu en matieres seches de 25 % et un nombre d'E. coli sous les 2.0 x [10.sup.6] CFU/g de solides secs. Les resultats experimentaux ont montre que la couverture de neige n'avait aucun impact sur la performance du lit dans une region presentant des chutes de neige moderees (1,3 a 1,6 m) alors que les nouvelles couches de boues faisaient fondre toute accumulation de neige, suggerant qu' il n' est pas necessaire de couvrir le lit ni de retirer la neige dans les zones ou le dosage de boues excede les chutes de neige. Les processus de gel et de degel ont ete modelises avec succes en utilisant des donnees climatiques facilement disponibles. Les donnees generees par le modele pour les conditions climatiques nord-americaines indiquent que la technologie du lit de congelation peut etre largement appliquee partout aux Etats-Unis et en Alaska et dans la plus grande partie du Canada, a l'exception des zones cotieres et du sud de l'Ontario. Mots-cles : conditionnement par gel-degel, traitement des boues, boues, lit de congelation, modelisation. [Traduit par la Redaction], Introduction In many jurisdictions in North America the sludge from septic tanks (septage) is routinely land applied to agricultural fields; however, land application is strictly forbidden when the ground is [...]

Previous studies have shown that 19% of dam deterioration cases are due to freezing and thawing cycles. Considering that lift joints are planes of weakness and that the mechanical properties of concrete are diminished with increasing freeze and thaw cycles, the aim of this paper is to capture the impact of these cycles on the shear resistance of lift joints. Identical concrete joint replicas were subjected to different levels of alteration prior to being sheared in accordance with the standard direct shear test method. The results found in this study showed that initially (up to 87 cycles) frost action has a positive effect on the shear resistance of lift joints due to the increase in roughness the process generates exposed surfaces of concrete joints. However, as the process continues the internal micro-cracking and loss in compressive strength of concrete is such that they offset the positive effects of the increasing roughness and a lost in shear resistance is noticeable thereafter. Key words: shear resistance, lift joints, concrete, gravity dam, durability, freeze and thaw cycles. Des etudes ont demontre que 19 % des cas de deterioration de barrages etaient dus aux cycles de gel-degel. Puisque les joints de coulee sont des plans de faiblesse et puisque les proprietes mecaniques du beton se deteriorent a mesure que celui-ci subit des cycles de gel-degel, les presentes recherches ont cherche a etablir quelle etait l'influence des cycles de gel-degel sur la resistance au cisaillement des joints de coulee. Des repliques de joints subirent un degre d' endommagement variable avant d' etre cisaille en cisaillement direct. Les resultats obtenus ont demontre qu' initialement (jusqu'au 87e cycle), l'action du gel-degel a un effet positif sur la resistance au cisaillement des joints de coulee car la rugosite des surfaces exposees au gel-degel augmentent ainsi. Cependant, a mesure que l' endommagement se poursuit, la perte de resistance a la compression est telle qu'elle neutralise l'effet benefique d'une augmentation de la rugosite et une perte de la resistance au cisaillement est decelable des lors. Mots-cles : resistance au cisaillement, joint de coulee, beton, barrage-poids, gel-degel, durabilite. [Traduit par la Redaction], 1. Introduction In 2002, the government of the Province of Quebec in Canada enacted provincial dam safety regulations as a result of the floodings that has occurred in the region [...]

Northern jurisdictions implement spring load restrictions (SLRs) on low volume roads to minimize damage during spring thaw. For this study, SLRs are applied when the thawing front depth reaches 300 mm. Spring load restrictions should be removed when the pavement structure is completely thawed and the stiffness is sufficiently restored. Thawing and freezing index and thermal numerical modelling-based SLR methods are compared. The methods were first calibrated using air temperatures and measured freezing and thawing depths from two instrumented pavement sections in northern Ontario. The calibrated methods were then tested by predicting SLR application and complete thawing for the two sites for spring 2010. Comparisons with measurements show that both methods are able to predict SLR application within several days for both sites, but were off in excess of one month for complete pavement thawing. This study indicates that a calibrated thawing-index based method is most conducive for regional scale application of SLRs. Key words: spring load restrictions, thermal numerical modelling, thawing index, freezing index, thermistors, frost and thaw depths, predictions, comparisons with measurements. Les autorites legislatives nordiques appliquent des restrictions de charges au printemps sur les routes a faible volume afin de minimiser les dommages durant le degel du printemps. Pour la presente etude, les restrictions de charges sont appliquees lorsque la profondeur de degel atteint 300 mm. Ces restrictions devraient etre retirees lorsque la structure de la chaussee est completement degelee et que la rigidite est suffisamment restauree. L'indice de gel-degel ainsi que des methodes thermiques de restrictions de charges basees sur des modeles sont comparees. Les methodes ont tout d'abord ete etalonnees en prenant des temperatures de l' air et des profondeurs mesurees de gel et de degel provenant de deux sections de chaussee instrumentees du nord de l'Ontario. Les methodes etalonnees ont ensuite ete testees en predisant l'application des restrictions de charges au printemps et le degel complet pour les deux sites au printemps 2010. Les comparaisons avec les mesures montrent que les deux methodes peuvent predire l'application de restrictions de charges au printemps a quelques jours pres pour les deux sites, mais elles depassaient de plus d'un mois le degel complet de la chaussee. Cette etude indique qu'une methode etalonnee basee sur un indice de degel est la plus propice a l'application des restrictions de charges au printemps a l' echelle regionale. Mots-cles : restrictions de charges au printemps, modelisation thermique numerique, indice de degel, indice de gel, thermistors, profondeurs de gel et de degel, previsions, comparaisons avec les mesures. [Traduit par la Redaction], Introduction In northern climates frost penetrates into a pavement structure over the winter months. The depth of frost penetration depends on climatic conditions, including air temperatures, precipitation, wind speed, and [...]

Permafrost contains an estimated 1672 Pg carbon (C), an amount roughly equivalent to the total currently contained within land plants and the atmosphere (1-3). This reservoir of C is vulnerable to decomposition as rising global temperatures cause the permafrost to thaw (2). During thaw, trapped organic matter may become more accessible for microbial degradation and result in greenhouse gas emissions (4, 5). Despite recent advances in the use of molecular tools to study permafrost microbial communities (6-9), their response to thaw remains unclear. Here we use deep metagenomic sequencing to determine the impact of thaw on microbial phylogenetic and functional genes, and relate these data to measurements of methane emissions. Metagenomics, the direct sequencing of DNA from the environment, allows the examination of whole biochemical pathways and associated processes, as opposed to individual pieces of the metabolic puzzle. Our metagenome analyses reveal that during transition from a frozen to a thawed state there are rapid shifts in many microbial, phylogenetic and functional gene abundances and pathways. After one week of incubation at 5°C, permafrost metagenomes converge to be more similar to each other than while they are frozen. We find that multiple genes involved in cycling of C and nitrogen shift rapidly during thaw. We also construct the first draft genome from a complex soil metagenome, which corresponds to a novel methanogen. Methane previously accumulated in permafrost is released during thaw and subsequently consumed by methanotrophic bacteria. Together these data point towards the importance of rapid cycling of methane and nitrogen in thawing permafrost., We collected three intact frozen permafrost soil cores with their overlying seasonally thawed active layers from Hess Creek, Alaska. This is a black-spruce forest site containing many metres of frozen [...]

This research investigated the efficacy of low-intensity, radiant, infrared heating for inducing thawing in frozen ground. Specifically, the performance characteristics of a 22 kW infrared robe heater were evaluated. A commercial building site in Park City, Utah, was instrumented with thermocouple piers for field testing over a period of approximately 5 days. The experimental data were used to calibrate a numerical model of the infrared heating process, and several numerical simulations were then performed. The simulations facilitated evaluation of the effects of radiation intensity, air temperature, and ice content on thaw penetration rates achieved using infrared heating. While ice content has a marked influence on thaw penetration rates in all the simulations, the air temperature becomes less important with increasing infrared radiation intensity. The results of the testing also indicate that the tube heater exhibits a steady reduction in emitted radiation between propane tank exchanges and that the heaters should be used in tandem to minimize spatial variations in radiation intensity. Further research is recommended to identify optimal applications of infrared heating in winter construction activities. DOI: 10.1061/(ASCE)0887-381X(2006)20:1(4) CE Database subject headings: Cold weather construction; Frozen soils; Heating; Radiation; Numerical models; Freeze-thaw.

A field study was performed at two regional airports in Wisconsin during spring thaw to determine its effects on portland cement concrete (PCC) airport pavements. This study was part of a research program to model the performance of airfield pavements for the Federal Aviation Administration. Subsurface temperature and falling weight deflection measurements of the pavement structures were taken at both airports and used to calculate the frost penetration depths, the changes in beating capacity, and the joint and load transfer efficiencies. This paper summarizes the findings of this study and includes several relationships between various engineering properties of the subsurface layers below the PCC layer, along with a procedure for evaluating pavement performance using falling weight deflection data for PCC pavements during spring thaw.

It is possible to use high hydrostatic pressure (HHP) to reduce thawing time for frozen beef without having a damaging impact on product quality, according to research designed to analyze the principles of action of HHP on frozen beef. This research also investigated colour and texture of high pressure-thawed beef. It was established that, the longer the pressure operation, the more complete the thawing of frozen beef. This is probably attributable to a better heat distribution.

Hydraulic conductivity tests were conducted in the laboratory and field on geosynthetic clay liners (GCLs) and a sand-bentonite mixture to determine if their hydraulic conductivity is affected by freezing and thawing. In the laboratory, specimens of three GCLs were frozen and thawed 20 times, and no increase in hydraulic conductivity was measured. The hydraulic conductivity of the compacted sand-bentonite also did not increase after freezing and thawing. In the field, two types of GCLs and a sand-bentonite test pad (constructed with the same mixture used in the laboratory) were exposed to one or two winters of freeze-thaw cycling. No large increase in hydraulic conductivity was measured for the field test conducted with the sand-bentonite mixture. An increase in hydraulic conductivity was observed in only one of the field tests with GCLs. Examination of thawed GCLs and specimens of the sand-bentonite mixture showed no evidence of cracking that is commonly found in thawed compacted clays.

Frozen beef treated with high hydrostatic pressure (HHP) thawed much faster than beef thawed using conventional thawing. The color and texture of HHP thawed beef were similar with controls, and thawing rate was not affected by sample size and initial temperature. These were found in an examination of HHP during thawing of frozen beef, conducted by measuring temperature changes in frozen beef and the pressurization fluid.

A microwave assisted thawing apparatus uses microwave and cold air currents, and reduces the thawing time seven folds. It also avoids run-away heating during thawing. The thawing time is reduced by circulating -3 degrees celsius air over the surface of the frozen food. Surface cooling prevents microwave attenuation and microwave power remains on longer. The thawing time is dependent on the sample thickness. Thawing time for 5.5 cm sample is three times that of 3.6 cm sample. A low ambient temperature and a large temperature gradient reduce the thawing time.

Finite-element simulations using a large-strain thaw-consolidation model, formulated by the writers, are presented and compared with the data obtained from a warm-oil test pipeline at Inuvik, Northwest Territory, Canada. Nondimensional design charts generated by the method are used to predict thaw-consolidation settlements. A good agreement is found between observed and predicted settlement values giving encouragement for future thaw-settlement predictions, based on finite-element-generated nondimensional charts.

Partial melting of the product occurs at the time of pressure loading in High Pressure-Induced Thawing (HPIT) and a temperature decrease in the sample. No melting during pressure loading takes place in High Pressure-Assisted Thawing (HPAT), the sample temperature increases due to inward heat transfer but the initial temperature of the sample for a given pressure value determines which process takes place.