Permafrost Foundation Research Articles

Culvert device on permafrost soils

The report provides the study of culvert thermophysical state working together with the railway embankment soil of a on a permafrost foundation and taking the load from the own weight of the embankment soil and also the temporary load from the rolling stock. The culvert, which has stiffness characteristics in accordance with regulatory requirements, satisfies the conditions of strength and deformability under dynamic influences. In this research the use of centrifugal casting culverts on a polyester binder, fiberglass reinforced, with mineral fillers in the body of the railroad track embankment in the permafrost area was studied. Numerical modeling of the processes of freezing and thawing of permafrost soil in the zone of the culvert for a long period of time in a nonlinear formulation of changes in the thermophysical properties of the soils of the embankment and foundation in the annual cycle has been carried out.

Assessment of Hazardous Cryogenic Processes Impact on Engineering Facilities in the Arctic

Comprehensive studies of the state of the infrastructure in the Russian Arctic were carried out. The degree of deformation of objects and the impact of dangerous cryogenic and nival-glacial processes on the stability of build- ings and constructions were assessed. It was established that a number of cryogenic processes that are dangerous for the infrastructure were developing in urbanized areas of the permafrost zone. They are caused (or activated) by anthropogenic impact or by climatic changes. Thermokarst, thermal erosion and thermal abrasion of banks, icings formation are activating. The tangential forces of frost heaving increase due to the increase of the active layer depth. Almost all the buildings and the life support systems at the territories of the national settlements of the Polar re- gion are in an emergency or pre-emergency state. The percentage of deformation of the engineering infrastructure varies from 20% to 80% in industrial centers, which is often caused by the development of dangerous cryogenic processes. A methodic was developed to assess the negative impact of the most destructive processes on the infra- structure of settlements. It takes into account the degree of damage to the territory, the duration, and repeatability of processes. The risk assessment was carried out for one and a half dozen settlements in the Russian Arctic, with special attention paid to the infrastructure of the north of Western Siberia. The impact of waste disposal on the infrastructure of the Arctic was analyzed. A classification was proposed based on the degree of their influence on permafrost foundations. Proposals on stabilization of geotechnical situation in Arctic cities are given.

Thermal control performance of the embankment with L-shaped thermosyphons and insulations along the Gonghe-Yushu Highway

In permafrost regions, the climate warming and construction of engineering will change the energy exchange process between the original ground surface and the ambient, and warm the permafrost stratum. The degradation of permafrost stratum will endanger the stability of the infrastructures built on it. To protect permafrost from degradation, the embankment combined with L-shaped thermosyhons and insulations was adopted in the construction of the first high-grade highway in permafrost regions of the Qinghai-Tibet Plateau, namely the Gonghe-Yushu Highway. In this study, we field investigated the energy budget process of the embankment. The results indicated that the embankment can efficiently cool the warm permafrost stratum under the embankment in cold seasons. The net annual energy budget can reach approximately 1117 MJ. The composite embankment can cool the deep ground (13.0 m below the pavement layer) with the average speed of about 0.02 °C/year in the first few years. Meanwhile, it can adjust the asymmetric geotemperature distributions under two slopes. Thus, the long-term service performance of the embankment will be significantly improved. It is expected that the research can supply support for the design and construction of other high-grade highways in permafrost regions by reasonably using natural cool energy to protect permafrost foundation.

Cooling performance enhancement of a new expressway embankment in the Tibetan Plateau permafrost zone

The crushed-rock interlayer (CRI), as typical cooling technique used in the Qinghai-Tibet Railway, cannot be directly applied in expressways traversing permafrost areas because of the intense heat-absorption asphalt pavement. Sufficient cooling of permafrost foundation to meet the demand of engineering stability is an important issue. In this study, a CRI embankment combined with vertical ventilation ducts (VVDs) was designed to strengthen the convective cooling of wide expressways. To assess the performance of the combination design, a field experiment was conducted in the Tibet Plateau by building a full-scale expressway section. A numerical model was then developed and validated to analyze the heat transfer process and to predict its long-term thermal regimes considering climate warming. Results show that the new structure can produce an obviously increased convection cooling on permafrost foundation by enhancing the winter cold-energy utilization. The VVDs at the centerline play an effective role in dissipating heat accumulation in embankment center and can eliminate thermal asymmetry caused by plateau's prevalent wind direction. The combination of CRI and VVDs is effective to control ground temperature to improve expressway embankment stability. This new design could be considered for application in expressways built on permafrost stratum.

Potential applications of solar refrigeration systems for permafrost cooling in embankment engineering

This paper presents the results of an evaluation of two solar-assisted refrigeration systems in protecting permafrost foundations in railway and roadway engineering. A technical comparison was conducted between two types of traditional permafrost cooling measures and refrigeration systems: vapor compression and heat-driven adsorption. The investigated refrigeration systems have better real-time performance and effectiveness than traditional passive heat regulation measures. Moreover, the permafrost regions in China have good potential for solar energy, addressing the issue of decentralized power supply for refrigeration. Two special permafrost cooling systems were designed, manufactured, and tested; the solar photovoltaic vapor compression refrigeration system (SPV-VCRS) and the solar photothermal adsorption refrigeration system (SPT-ARS). The SPV-VCRS prototype exhibits greater potential for permafrost protection, with a consecutive average temperature of −23.55 °C and a coefficient of performance (COP) of 0.41 in the warm season. The SPT-ARS prototype is characterized by an intermittent refrigeration temperature of −1.83 °C and a significantly lower COP of 0.054 per day. Based on the results, suggestions have been given for the selection of solar refrigeration systems for application in the protection of the permafrost under embankments.

Prediction Model of Thermal Thawing Sensibility and Thaw Depth for Permafrost Embankment along the Qinghai-Tibet Engineering Corridor Using MODIS Data

The aim of this paper was to reveal the distribution law of permafrost thermal thawing sensibility and thaw depth caused by road construction in Qinghai-Tibet engineering corridor (QTEC). The prediction models of permafrost thermal thawing sensibility and thaw depth have been developed by incorporating the MODIS and in situ soil temperature observation data. The comprehensive earth-atmosphere-coupled numerical models of different embankment structures have been utilized to calculate the thaw depth of the underlying permafrost foundation. Finally, using the given data and above developed prediction models, the distribution maps of permafrost thermal thawing sensibility and thaw depth in QTEC are obtained by grid calculation. The results show the following: (1) Insensitive permafrost of QTEC mainly distributes in the large-scale mountain and high latitude area, and highly sensitive permafrost is located in the perennial river bed, flood plain, and terrace regions. (2) Road construction has a strong thermal disturbance to underlying permafrost, and the proportion of large thaw depth area of separate embankment is obviously smaller than that of 26 m full-width embankment. (3) Increase of subgrade interval reduces the proportion of large thaw depth areas, and the application of separate embankment structure is an effective engineering means for the Qinghai-Tibet expressway.

Statistical characteristics and probabilistic analysis of uncertain settlement of subgrade in permafrost regions

The settlement characteristics of permafrost subgrade are uncertain on account of the random thermal regime and mechanical parameters. This can affect the stability of permafrost foundation. In this study, the uncertain settlement behaviors of permafrost subgrade under global warming conditions are computed by Monte Carlo (MC) method. After that, the distributing fitting inspection of the samples of uncertain settlement characteristics are carried out. A probabilistic analysis methodology of the uncertain settlement of subgrade in permafrost regions is presented. The statistical characteristics and reliability of uncertain settlement for the subgrade center and shoulder are analyzed and predicted. This study presents a novel approach to estimate the stability of uncertain roadbed settlement. The results indicate that the uncertain settlement characteristics of embankment follow a normal distribution on the condition that significance level is 0.1. The reliability of subgrade center and subgrade shoulder varies with time, which imply railway operation have different risk in different seasons. The global warming can promote the thawing of permafrost foundations and it reduces the reliability. This study clearly clarifies the statistical characteristics and reliability of uncertain settlement characteristics of permafrost subgrade and the results can provide a reasonable basic data for the stability evaluation of permafrost subgrade.

Numerical evaluation for protecting and reinforcing effect of a new designed crushed rock revetment on Qinghai–Tibet Railway

Crushed rock revetment (CRR) has been widely implemented to mitigate the geothermal disturbance from the embankment construction and global warming. The cooling effect and air convective mode of the traditional CRR (TCRR) and a new designed solar−shading CRR (SSCRR) were comparatively studied based on a developed and verified heat and mass transfer model. The results indicate that TCRR used as a protecting measure cannot eliminate the geothermal disturbance in warm permafrost regions, but can preserve the permafrost foundation in cold permafrost regions, while SSCRR can further cool the permafrost foundation. If TCRR is added to reinforce a 10 years operated general embankment, it can only grudgingly keep the thermal disturbed state for about 35 years and 45 years in warm and cold permafrost regions, respectively. SSCRR, by contrast, can refrigerate the operation–disturbed permafrost foundation. Wind−forced dominated convection for TCRR in warm season dissipates the ‘cold energy’ accumulated in cold season, however, synthetic reaction for SSCRR with a longer and higher efficiency cooling process in cold season and better heat insulating effect in warm season conducts a superior cooling effect. These results provide a basis for the optimization of cold energy utilization systems for the embankments in the degenerating permafrost regions.

Thaw Settlement and Mechanical Properties of Admixture-Stabilized Frozen Soil

Abstract Roads and other infrastructure in Western Alaska are difficult to design and build owing to the high cost of construction materials and the ice-rich permafrost foundation. The present stud...

Criteria of the Influence of Climatic Factors on the Condition of Frozen Foundations by Geophysical Data

Apparent resistivity in the frequency range of 100-1000 kHz and soil electromagnetic emission parameters in the frequency range of 1-300 kHz are proposed to be used as criteria for assessing the influence of climatic factors on the condition of permafrost foundations. The addition of traditional measurements of soils temperature by measurements of their apparent resistivity raises information maintenance of monitoring. The joint consideration of effective resistance and temperatures gives more complete representation about changes of a soils condition, climatic factors, occurring as result of influence. By monitoring apparent resistivities, it is possible not only to assess the degree of soil freezing, but also to take into account changes in volumetric ice content (moisture content) and other physical properties. Apparent resistivity can also be used to detect and estimate the influence of such climatic factors, as rainfall and snow depth. The phenomenon of electromagnetic emission in frozen ground is shown to be an indicator of on-going processes of thawing or freezing. Electromagnetic emission parameters are thus useful for assessing intensity and duration of soil thawing and freezing.

Feasibility study on use of cellular concrete for air convection embankment on permafrost foundations in Fairbanks, Alaska

Abstract The crushed-rock air convection embankment (ACE) is an excellent technique to protect the permafrost from thawing in road construction in cold regions due to its superb cooling effect in winter and excellent thermal resistance performance in summer. However, the desired materials needed for ACE are not readily available, which prevents its extensive use in Alaska. To overcome the limitation (shortage of suitable crushed rocks) of traditional ACE and further improve the cooling effect of ACE, this study investigated the feasibility of using cellular concrete as an alternative material for ACE in cold regions. The finite element method was used to predict the heat transfer patterns of the sand/gravel embankment, the crushed-rock ACE, and the cellular concrete ACE. The results of the present study showed that the cooling performance of both the cellular concrete ACE and the crushed-rock ACE was superior to the conventional sand/gravel embankment. The cellular concrete ACE had better heat insulation property in the summer, and the crushed-rock ACE had stronger natural convection in winter. For the yearly cooling efficiency of the two different ACE techniques, the proposed cellular concrete ACE had a better cooling effect on the foundation soil than the crushed-rock ACE. The results presented in the isotherms and velocity vectors plots for different months of the year also indicated that the thermal conductivity and specific heat capacity of the construction materials had a significant impact on the performance of the ACE. The preliminary cost analyses showed that the cost of the cellular concrete ACE was close to that of the conventional sand/gravel embankment but much lower than that of the crushed-rock ACE.

Impact of spatial variability of geotechnical properties on uncertain settlement of frozen soil foundation around an oil pipeline

The spatial variability of geotechnical properties can lead to the uncertainty of settlement for frozen soil foundation around the oil pipeline, and it can affect the stability of permafrost foundation. In this paper, the elastic modulus, cohesion, angle of internal friction and poisson ratio are taken as four independent random fields. A stochastic analysis model for the uncertain settlement characteristic of frozen soil foundation around an oil pipeline is presented. The accuracy of the stochastic analysis model is verified by measured data. Considering the different combinations for the coefficient of variation and scale of fluctuation, the influences of spatial variability of geotechnical properties on uncertain settlement are estimated. The results show that the stochastic effects between elastic modulus, cohesion, angle of internal friction and poisson ratio are obviously different. The deformation parameters have a greater influence on stochastic settlement than the strength parameters. The overall variability of settlement reduces with the increase of horizontal scale of fluctuation and vertical scale of fluctuation. These results can improve our understanding of the influences of spatial variability of geotechnical properties on uncertain settlement and provide a theoretical basis for the reliability analysis of pipeline engineering in permafrost regions.

Experimental study on performance of crushed-rock embankment with heat-induced asphalt pavement

Abstract Previous numerical and field studies have confirmed effectiveness of the crushed-rock embankment (CRE) in protecting permafrost foundations in cold regions. However, some recent field monitoring data indicated that the CRE was not effective enough to prevent the permafrost foundations from thawing in some highway applications. The undermined effectiveness of the CRE was attributed to the strong heat absorption associated with the black asphalt pavement which absorbed more heat compared with lighter-colored surfaces. In order to strengthen the cooling effect of CRE in highway application, the composite CRE section with the heat-induced asphalt pavement (the composite CRE section) was presented. And then, the indoor laboratory model tests were performed to investigate the cooling performances of two sections: one is the composite CRE section, the other is the control CRE section with the conventional asphalt pavement (the control CRE section). Various sensors were installed at different locations of the two test sections to monitor the temperature, wind speed, and heat flux in order to better understand the working mechanisms of the different CRE structures. The test results showed that: (1) the heat-induced asphalt pavement increased the heat release in cold cycles, which was conducive to generate natural convection of the CRE. The cooling effect of the composite CRE section on the foundation was better than that of the control CRE section. (2) The maximum velocity of natural convection of crushed-rock layer in the composite CRE section was bigger than that of the control CRE section. The duration of the convection stage in the composite CRE section was longer than that of the control CRE section. (3) In warming cycles, the heat flux in the composite CRE section was slightly larger than that in the control CRE section. In cooling cycles, the heat flux in the composite CRE section was much smaller than that in the control CRE section. By comparing the cooling effects, air convective characteristics, and transient heat flux in the two CRE sections, the composite CRE section has a good cooling effects comparing with the control CRE section.

Pipeline–permafrost interaction monitoring system along the China–Russia crude oil pipeline

In-situ monitoring system is absolutely necessary for a long-distance linear pipeline infrastructure in permafrost regions due to the complicated interaction between buried pipeline and its harsh permafrost environment. To study this complex problem, a comprehensive in-situ monitoring system has been designed and established along the China–Russia Crude Oil Pipeline (CRCOP), which is one of vital energy channels for importing crude oil from Russia to China. This monitoring system can record the meteorological data, ground temperature and water content within the permafrost foundation, vertical settlement of the oil pipe, ground surface deformation on the pipeline right-of-way (on-ROW), as well as the thaw bulb around the pipeline at four sites with different engineering geological conditions. In this paper, the layout and instrumentation of the whole monitoring system and monitoring methods are described in detail, and then the thermal regime of permafrost on-ROW and off-ROW and cooling performance of the mitigative measures on foundation soils are evaluated. Results show that heat dissipated from the CRCOP lead to the rapid degradation of permafrost on-ROW and produce different sizes of thaw bulb around the oil pipelines. The mitigative measures, including insulation layer, two-phase closed thermosyphon and U-shaped air-ventilated pipes, are effective to minimize permafrost degradation and ensure the thermal stability of permafrost foundation along the CRCOP. Some recommendations are proposed for future research and for the monitoring system to be improved. This monitoring system can provide multi-field data to clarify the interaction between pipeline and permafrost degradation under different geological conditions, and guide the design and maintenance of the buried warm pipeline in permafrost regions.

Large-Strain Nonlinear Thaw Consolidation Analysis of the Inuvik Warm-Oil Experimental Pipeline Buried in Permafrost

AbstractThe large strain nonlinear thaw consolidation model developed by Dumais and Konrad is used to analyze the Inuvik experimental warm-oil pipeline built on ice-rich permafrost foundations. The...

Study of the time-dependent thermal behavior of the multilayer asphalt concrete pavement in permafrost regions

Asphalt concrete is one of the widespread pavement materials. The multilayer asphalt concrete pavement (MACP) has strong heat-absorption capacity. The thermal behavior of the MACP can affect the energy exchange between atmosphere and embankment, especially for the permafrost ground which is sensitive to temperature. To investigate the thermal behavior of the MACP, an in-situ experiment was performed firstly to investigate the effect of MACP on the cooling performance of an air convection embankment used in permafrost region. Subsequently, a mathematical model was developed and validated to describe the thermal behavior. Finally, series of simulations were carried out to evaluate the time dependence of the thermal behavior. The results indicate that, (1) the asphalt pavement can alter the energy exchange between permafrost foundation and atmosphere, and reduce the cooling performance of the embankment; (2) the construction interval of MACP can strengthen the convective cooling capacity and accelerate the heat dissipation of the permafrost foundation; (3) an optimized construction interval was proposed for the simulated air convection embankment to maintain its long-term stability. The study can contribute to the construction control of air convection embankment with MACP in permafrost regions.

Analysis of thermal regime under riverbank in permafrost region

A riverbank was constructed on ice-rich permafrost in the far north of China in 2015, and its performance is closely related to the thermal stability of the permafrost foundation. To investigate the thermal regime evolution of the foundation, a numerical simulation using a coupled hydro-thermal model that involves concrete hydration, heat transfer by conduction and convection is performed over 20years in this paper. The monitored ground temperatures help confirm the accuracy of the simulation. A dramatic thaw penetration in the permafrost foundation is anticipated in the future under current geological and structural conditions. Moreover, this paper highlights the importance of concrete hydration, backfilled soil temperature, seepage and the mean annual ground temperature in effecting the geothermal evolution. These discussions suggest a requirement for some measures in construction and maintenance of hydraulic structures over permafrost.

Experimental study on heat transfer of upright pipes in cold regions

Laboratory experiments are conducted to investigate the heat transfer characteristics of upright pipes under periodic ambient temperatures. The results provide evidence to support the use of upright pipes in permafrost engineering. This paper presents two models with different inlet pipe diameters. The results indicate that the mean periodic temperatures at the bottom of the pipe and soil decrease with increasing freeze-thaw cycles and ultimately remain in a frozen state. Natural convection is the dominant mode of conducting heat exchange between the upright pipe and air. The inlet diameter greatly affects both the cold energy accumulation at the pipe bottom and the cooling efficiency. Furthermore, the lateral thermal disturbance distance of the upright pipe is approximately more than one fold of the inlet diameter. Therefore, the upright pipe enhances the cooling effect to the surrounding soil and is recommended for the cooling of permafrost foundations.

Evaluation on the influences of lakes on the thermal regimes of nearby tower foundations along the Qinghai-Tibet Power Transmission Line

Lakes/ponds in permafrost regions may have strong thermal influences on the foundation of adjacent infrastructures such as railways, highways, and transmission lines. To assess the thermal influences of lakes on the stability of tower foundations along the Qinghai-Tibet Power Transmission Line (QTPTL), field works were conducted during mid- to late-April 2015 to investigate the distribution of lakes along the QTPTL. The results showed that the majority of the lakes are either too far from tower foundation (∼200m) or too small (less than 50m in diameter) or too shallow (shallower than 0.7m) to make considerable thermal influence on the tower foundation soils. The lake K-1047 in Kaixinling region may be the most possible one to make influence on the thermal stability of nearby tower foundation. A series of numerical simulations were conducted to evaluate the influence of the lake on a nearby shallow foundation. The results show that the lake influences the thermal regimes of permafrost soils 30m away from the lake, speeding the degradation process of the permafrost foundation soils. This thermal influence will shorten the operational duration of the tower foundation, especially in condition of climate warming. This study may provide some insights into the future design and construction of the similar engineered infrastructures in permafrost regions.

Geohazards and thermal regime analysis of oil pipeline along the Qinghai–Tibet Plateau Engineering Corridor

This paper investigates the influence of geohazards on the existing oil pipeline and the potential interaction between the proposed new oil pipeline and preexisting transportation structures along the Qinghai–Tibet Plateau Engineering Corridor. The current Golmud–Lhasa oil pipeline has been seriously affected by retrogressive thaw slumps caused by surface water being channeled through culverts causing serious erosion problems. Climate data show that the air temperature increased at a rate of 0.0281 °C/a for the past 60 years along the corridor. To design the new pipeline, the effects of revegetation, climate warming and pipe insulation on permafrost have been simulated using numerical modeling. A warm oil pipeline would potentially lead to significant thawing of the permafrost foundation. When climate warming is not considered, insulation of the buried pipe could keep the permafrost stable. Revegetation and the use of utilidors could counteract the influence of heat input from the oil pipe, and even a 1.1 °C/50a climate-warming rate. However, for the 2.6 °C/50a climate-warming-rate scenario, they are inadequate to keep the permafrost stable. Vegetation cover is important to reduce the effect of climate warming on both the natural and the human-impacted permafrost. Revegetation after construction is important to protect the permafrost environment as well as the oil pipeline itself.