Asphalt pavements are subjected to various forms of deterioration throughout their service life due to the combined effects of traffic loading and environmental conditions. In cold regions, the coexistence of subfreezing temperatures and a high moisture content promotes the formation of ice lenses in frost-susceptible soils that may be present in the subgrade layer. This phenomenon, known as frost heave, induces differential upward movement of the ground surface, leading to cracking and surface irregularities in pavements. During the subsequent thawing period, the melting of ice lenses leads to a significant reduction in the stiffness and stability of the underlying soil, thereby compromising the structural integrity of the pavement. This cycle of frost heave and thaw settlement contributes to progressive surface degradation, a phenomenon commonly observed in countries like Sweden, where long winters and moisture-saturated soils are prevalent.

The present thesis proposes a mechanistic framework to assess the performance of asphalt pavements under frost heave and thaw settlement. To achieve this, a thermomechanical frost heave–thaw settlement model is coupled with a thermodynamics-based asphalt damage model. In the frost heave–thaw settlement component, thermal and mechanical fields are coupled through a porosity evolution function, which implicitly accounts for water seepage during frost heave. Notably, the proposed model introduces a new approach in which the formation of ice lenses during frost heave and the excess water introduced into soil composite during the thawing phase are treated analogously to the healing and damage processes in continuum damage mechanics. 

The mechanical behavior of asphalt materials is modeled using a continuum constitutive framework capturing viscoelasticity, viscoplasticity, and material degradation. The formulation is developed in the context of finite strain theory and is grounded in thermodynamic principles governing irreversible processes. In this model, damage initiation and evolution are ascribed to the restored viscoelastic energy. 

The proposed framework is implemented and evaluated across study scenarios that include both uniform and non-uniform frost heave and thaw settlement. The scenarios comprise isolated freeze-thaw cycles and full-scale cases using measured climate data from the city of Kiruna in northern Sweden. The results show that the framework effectively captures the frost action within the soil by modeling the evolution of porosity, the distribution of ice and liquid water contents, and the associated ground surface deformations. In addition, it enables the analysis of the subsequent propagation of damage within the asphalt layer. The framework also serves as a valuable tool for assessing the effectiveness of various mitigation strategies aimed at alleviating the detrimental effects of annual ground surface deformations induced by frost heave and thaw settlement.

Asfaltbeläggningar utsätts under sin livslängd för olika former av nedbrytningtill följd av den sammantagna påverkan från trafikbelastningoch miljöförhållanden. I kalla regioner främjar samtidig förekomst avtemperaturer under fryspunkten och hög fukthalt bildningen av islinser ifrostkänsliga jordar som kan förekomma i undergrunden. Detta fenomen,känt som tjällyftning, orsakar ojämn upplyftning av markytan, vilketleder till sprickbildning och ytojämnheter i beläggningar. Under denefterföljande töperioden medför smältning av islinser en avsevärd minskningav styvhet och stabilitet i den underliggande jorden, vilket försämrarbeläggningens bärförmåga. Denna cykel av tjällyftning och tösättningbidrar till successiv ytdegradering, ett vanligt förekommande problemi länder som Sverige där långa vintrar och fuktsaturerade jordar ärvanliga.

Föreliggande avhandling föreslår ett mekanistiskt ramverk för att bedömaasfaltbeläggningars prestanda under tjällyftning och tösättning. Fördetta kopplas en termomekanisk modell för tjällyftning–tösättning sammanmed en termodynamiskt baserad skademodell för asfalt. I delmodellenför tjällyftning–tösättning kopplas de termiska och mekaniskafälten via en funktion för porositetsutveckling som implicit beaktarvattengenomströmning under tjällyftning. Särskilt kan nämnas att denföreslagna modellen introducerar ett nytt angreppssätt där bildningenav islinser under tjällyftning och det överskottsvatten som tillförs jordmaterialetunder töfasen behandlas analogt med läknings- respektiveskadeprocesser inom kontinuumskademekanik.

Det mekaniska beteendet hos asfaltmaterial modelleras med ett kontinuummekaniskt konstitutivt ramverk som fångar viskoelasticitet, viskoplasticitetoch materialdegradering. Formuleringen utvecklas inom ramenför stora deformationer och vilar på termodynamiska principer för irreversiblaprocesser. I modellen kopplas initiering och utveckling av skadatill den återvunna viskoelastiska energin.

Ramverket implementeras och utvärderas i studiescenarier som omfattarbåde uniforma och icke-uniforma tjällyftningar och tösättningar. Scenariernainkluderar enstaka frys–töcykler samt fullskalefall baseradepå uppmätta klimatdata från Kiruna i norra Sverige. Resultaten visaratt ramverket effektivt fångar tjälprocesserna i jord genom att modelleraporositetsutveckling, fördelningen av is- och vattenhalter samttillhörande markdeformationer. Vidare möjliggörs analys av efterföljandeskadeutbredning i asfaltlagret. Ramverket utgör också ett värdefulltverktyg för att bedöma effektiviteten hos olika åtgärdsstrategier somsyftar till att mildra de skadliga effekterna av årliga markdeformationerorsakade av tjällyftning och tösättning.

This study presents a mechanics-based framework for evaluating the performance of asphalt pavements subjected to annual ground surface deformations induced by frost heave and thaw settlement. Within this framework, a novel thaw settlement model is developed and coupled with a thermomechanical frost heave model to represent the heaving and subsequent thawing behavior of the soil beneath pavements. In the proposed thaw settlement model, excess water generated during the melting of ice lenses is introduced as a damage parameter within a continuum mechanics formulation, resulting in a reduction of material stiffness. The frost heave–thaw settlement model is further coupled with a thermodynamics-based asphalt damage model to capture the progressive degradation of asphalt layers. The capabilities of the proposed framework are demonstrated through two study scenarios: (i) uniform frost heave and thaw settlement occurring across the entire subgrade layer. (ii) non-uniform frost heave and thaw settlement localized within a specific region of the subgrade. The results show that the proposed framework not only captures damage in the asphalt layer but also predicts temperature distributions, ice formation, and water content during freeze–thaw cycles. Furthermore, the analysis reveals that uniform heaving and settlement cause relatively minor asphalt damage but lead to surface unevenness, whereas non-uniform frost heave and settlement result in both surface irregularities and severe damage to the asphalt layer.

Asphalt materials deteriorate when used in pavements due to their continuous exposure to traffic loads and other degrading mechanisms. This paper presents an experimental investigation to capture the initiation and evolution of damage in asphalt mixtures under compressive loads, in which the material degradation is attributed to the viscoelastic energy. In order to study the influence of temperature on degradation of asphalt materials, the test is conducted at four distinct temperatures: 10C, 0C, 20C, and 40C. The obtained experimental data reveal that, at lower temperatures, the viscoelastic energy threshold required to initiate damage in the asphalt specimens considerably increases. Furthermore, the results highlight the significant impact of temperature on damage evolution in asphalt materials. This study also identifies a critical damage threshold, beyond which the rate of damage evolution experiences a substantial increase. Notably, the critical damage threshold is lower at colder temperatures.

Roads are exposed to various degradation mechanisms during their lifetime. The pavement deterioration caused by the surrounding environment is particularly severe in winter when the humidity and subfreezing temperatures prevail. Frost heave-induced damage is one of the winter-related pavement deterioration. It occurs when the porewater in the soil is exposed to freezing temperatures. The study of frost heave requires conducting a multiphysics analysis, considering the thermal, mechanical, and hydraulic fields. This paper presents the use of a coupled thermo-mechanical approach to simulate frost heave in saturated soils. A function predicting porosity evolution is implemented to couple the thermal and mechanical field analyses. This function indirectly considers the effect of the water seepage inside the soil. Different frost heave scenarios with uniform and non-uniform boundary conditions are considered to demonstrate the capabilities of the method. The results of the simulations indicate that the thermo-mechanical model captures various processes involved in the frost heave phenomenon, such as water fusion, porosity variation, cryogenic suction force generation, and soil expansion. The characteristics and consequences of each process are determined and discussed separately. Furthermore, the results show that non-uniform thermal boundaries and presence of a culvert inside the soil result in uneven ground surface deformations.

This study investigates the structural response of an asphalt pavement constructed on frost-susceptible subgrade when subjected to the climatic conditions of Kiruna, northern Sweden. A mechanistic analysis framework is employed to assess the effectiveness of two different mitigation strategies aimed at reducing frost heave and thaw settlement-induced damage. The first strategy adopts a passive approach through the use of a polymer-modified asphalt mixture, which do not impede the penetration of freezing front but enhance the mechanical resilience of the asphalt layer. The second strategy represents an active mitigation measure, involving increased subbase thickness to reduce the downward propagation of freezing temperatures into the frost-susceptible soil. The results show that polymer modification of the asphalt mixture significantly improve the load bearing and deformation resistance properties of the asphalt layer, leading to a 20% reduction in frost heave-induced damage and about 25% reduction in thaw settlement-induced degradation. The results also reveal that, although increasing the thickness of the layers above the subgrade effectively limits frost penetration, insufficient lateral extent of these layers can amplify differential heave, ultimately exacerbating surface distress. In contrast, simultaneous increases in both the thickness and width of the protective layers substantially enhance performance, resulting in approximately 60% less frost heave damage and 50\% less thaw settlement-induced deterioration. These findings underscore the essential role of a comprehensive mechanistic framework in reliably evaluating the effectiveness of different mitigation measures against frost heave and thaw settlement in cold-region pavements.

Deterioration caused by frost heave appears as cracks, localized upward deformations,or longitudinal waves on the surface of road pavements. A multiphysics modeling approach is required to predict the performance of pavement systems under frost heave-induced ground surface deformations. This involves coupling a frost heave model with a material model describing mechanistic behavior of asphalt materials. In the current study, a thermodynamics-based viscoelastic-viscoplastic damage model is introduced and calibrated for a specific asphalt mixture through conductinga series of experimental tests. The model attributes the initiation and evolution of damage to viscoelastic energy. Simulating the frost action inside soil, on the other hand, is performed by implementing a thermomechanical approach. In this method, water seepage during penetration of freezing temperatures within soil is accounted for by incorporating a porosity evolution function. The presented framework for capturing frost heave-induced damage in asphalt pavements is applied in a study scenario where a road passes over a culvert embedded in frost-susceptible soil. The results indicate that using the proposed approach provides an opportunity to simulate the frost action inside the soil, determine the ground surface deformations, and capture the subsequent damage in theasphalt layer. Additionally, it is shown that increasing thickness of pavement layers above frost-susceptible soil significantly reduces uneven frost heave and, consequently, the damage within the asphalt layer. The study also reveals that  degradation of asphalt pavements caused by frost heave progresses at a notably rapid pace.

Roads are subjected to various deteriorating mechanisms during their lifespan. The effects of the environment and climate on pavement deterioration are particularly severe in winter when humidity and subfreezing temperatures prevail. Of damages ascribed to winter conditions, frost heave occurs when the porewater in the soil is subjected to freezing temperatures. The study of frost heave requires conducting a multiphysics analysis including the thermal field, the mechanical field, and the hydraulic field. In the current study, a coupled thermo-mechanical approach is used to simulate frost heave in saturated soils. To couple the thermal and mechanical field analyses, a function predicting porosity evolution is implemented. This function implicitly takes into account the effect of the hydraulic field by ascertaining the consequence of water seepage inside the soil. To show the capabilities of the method, different case study scenarios with uniform and non-uniform boundary conditions are considered. The results of the simulations indicate that the thermo-mechanical model captures various processes involved in the frost heave phenomenon such as water fusion, porosity variation, cryogenic suction force generation, soil expansion, etc. The characteristics and consequences of each process are determined and discussed separately. Furthermore, it is shown that non-uniform thermal boundaries result in uneven ground surface deformations.