Ground Temperature Variations Research Articles

Geocryological Conditions of Small Mountain Catchment in the Upper Kolyma Highland (Northeastern Asia)

This research presents a comprehensive environmental assessment of a small mountain permafrost catchment of the Anmangynda River in the Upper Kolyma Highland (Northeastern Asia) over the period of 2021–2023. The study reveals significant diversity in climatic, geocryological, and hydrogeological conditions within this confined area, emphasizing the need for extensive field data collection and monitoring in vast permafrost regions with limited data availability. Key findings include variations in ground temperature, maximum seasonal thaw depth, and depths of zero annual amplitudes of ground temperature at different elevations and landscape types. Groundwater and surface flow dynamics within spring aufeis basins exhibit complex geocryological regimes influenced by icing processes. The presence of aufeis and its impact on local hydrology highlight the ecological significance of this phenomenon. Future research should focus on long-term trends in permafrost dynamics and their relationship with climate change, as well as the ecological effects of aufeis formation on local ecosystems. The study underscores the importance of a multi-faceted approach to environmental assessment, incorporating various environmental parameters and processes, to gain a comprehensive understanding of the intricate interactions within the cryosphere and their responses to changing climate conditions. Such knowledge is essential for addressing broader questions related to climate change, ecosystem resilience, and sustainable resource management in Northeastern Siberia.

Research on Temperature Field of Cement-Mixing Pile-Reinforced Soft Soil Foundation

To investigate the mechanism of reinforcing soft soil with cement-mixing pile, based on ABAQUS secondary development, a numerical simulation study of the hydration reaction of cement-mixing piles was conducted. In this study, the influence of ground temperature variations on the distribution patterns of the temperature field in and around the pile was also considered. The temperature field of the pile–soil model can be primarily divided into two stages: the temperature rise stage (0~5 d) and the temperature decrease stage (5~90 d). The following observations were made: (1) The temperature of the pile body rapidly increased within the first 5 days, dissipating heat to the surrounding soil, leading to an elevation of the temperature in the soil around the pile and a decrease in soil moisture content. Around the 5th day, the temperature reached its maximum value, and the heat release rate of the pile body was higher than that of the surrounding soil. (2) With a 15% cement admixture, under the influence of 425# cement hydration, the temperature inside the pile increased by 5 °C, and the temperature in the soil around the pile increased by 4.2 °C. After considering the ground temperature, the temperature in the soil around the pile increased by 4.6 °C. (3) The maximum temperature generated during the hydration of 425# Portland cement is higher than that of 525#; the temperature of the soil around piles made with 425# cement is consistently higher than that made with 525#. (4) The hydration temperature of piles with a 10% cement admixture increased by 4.4 °C; for piles with a 15% cement admixture, the hydration temperature increased by 6.6 °C; and for piles with a 20% cement admixture, the hydration temperature increased by 9.1 °C. The temperature field of this structure gradually stabilizes after 7 days with increasing time and cement admixture. The results indicate that the hydration of cement-mixing piles raises the temperature of the soil around the piles. Additionally, the temperature resulting from the hydration of cement-mixing pile increases with the addition of cement.

Thermal stability of permafrost under U-shaped crushed rock embankment of the Qinghai‒Tibet Railway

The U-shaped crushed rock embankment (UCRE), of which widely utilized in the permafrost regions along the Qinghai‒Tibet Railway, has the capability to rapidly reduce the ground temperature of the underlying permafrost. However, there remains uncertainty regarding the adaptation of UCRE to climate change and its long-term cooling trend. This study focuses on nine UCRE monitoring sites along the Qinghai‒Tibet Railway to analyze the dynamic variations of the ground temperature underlying permafrost from 2006 to 2020. The efficiency of UCRE in stabilizing permafrost temperature in different permafrost zones is evaluated by considering the permafrost table, ground temperature, and MAGT, as well as the temperature difference between the top and bottom of the crushed rock layer and the ground temperature variation index (GTVI). The results show that UCRE is suitable for application in extremely unstable warm permafrost regions where the MAGT is higher than −0.5 °C. Moreover, UCRE effectively diminishes the disparity in permafrost thermal stability between the sunny and shaded shoulders of the embankment. The short-term and long-term effect of cooling permafrost is experiencing a change related with permafrost stability. Notably, in stable cold permafrost regions with MAGT lower than −1.5 °C, the long-term cooling effect of UCRE on permafrost seems to gradually diminishes, but UCRE continues to fulfill the role of stabilizing the underlying permafrost thermal state over the long-term. These results show that UCRE can quickly restore and stabilize the thermal state of permafrost in the early stages of construction, and adapt to the influence of future climate change. The findings provide important guidance for understanding the variations of permafrost thermal stability beneath the embankment in permafrost regions, as well as for improving the embankment stability and operational safety of the Qinghai‒Tibet Railway.

Analysis and simulation of ecological environment response of ground source heat pump system under thermal equilibrium

This work is designed to study the thermodynamic equations of groundwater source heat pump in hot summer and cold winter, and to determine the optimal operating conditions of groundwater source heat pump by means of the thermodynamic analysis of source heat pump, flow, unit, pump power, evaporation side and condensation side. Practice has proved that the equipment runs stably and with high efficiency. By comparison, the ground source heat exchangers were compared with conventional chillers and boiler. The results showed that the underground heat pump had higher energy consumption, lower primary energy consumption, reduced CO2 emissions, and reduced environmental pollution during operation, proving that the underground heat pump had obvious advantages over the conventional cooling and heating system. Meanwhile, this also shows that the long-term operation of ground heating system has caused the instability of ground heating system, the accumulation of cold and heat in ground-water, and the variation of ground temperature, which not only reduces the system efficiency, but it also affects the physical properties of soil itself and the soil heat flow, and will also cause changes in soil microbial environment and vegetation ecological environment, thus affecting the whole ecological environment.

Effects of the ground surface thermal boundary condition on the long-term thermal performance of energy diaphragm walls

Energy diaphragm walls have attracted increasing attention due to their high heat transfer performance. Thus, the factors that affect the thermal performance of energy walls have been investigated to provide insights for further practical applications. Numerical simulation is widely used in energy wall analysis due to the complexity of conducting field tests. Therefore, the choice of boundary conditions in the simulations is crucial; it refers to whether the model reflects reality and has a significant impact on the results. In most cases, the assumed ground surface thermal boundary is not the same (e.g., thermal insulation, constant temperature), and the ground temperature is also assumed to be constant with depth, which may result in a large loss of thermal energy or inaccurate assessment of thermal performance for the energy wall. In this respect, this paper investigates the long-term differences in thermal performance under these boundaries and considers the ground temperature that varies with depth and time, which has not been comprehensively considered before in the analysis of energy walls. The results show that accounting for air temperature or ground temperature variations with depth and time can result in a great increase in thermal performance, e.g., a 34% increase in the cooling thermal load compared with the thermal insulation boundary. In the performed parametric analysis, the results highlight the significant influence of the thermal load and wall height on the thermal differences between these boundaries. These findings provide a reference for choosing ground surface thermal boundaries and better thermal design of energy diaphragm walls.

Research on the long-term operation performance of deep borehole heat exchangers array: Thermal attenuation and maximum heat extraction capacity

The long-term operation performance and thermal attenuation of deep borehole heat exchangers (DBHEs) array are important for their stable and safe operation. This paper proposed a semi-analytical method to quantitatively evaluate the 100-years operation performance of DBHEs array. Numerical simulation was utilized to determine the heat flux per depth of DBHE, while the finite line heat source model was modified to calculate the ground temperature variation. This allowed to obtain the ground borehole wall temperature, serving as a boundary condition for calculating the water temperature distribution in DBHE using an analytical solution. The results revealed that the line space of DBHEs array directly affected the allowed maximum accumulated heat extraction per DBHE per heating season (Qa,max). With line space decreasing from 100 m to 10 m, the Qa,max decreased from 0.3% to 19.1% compared to the single DBHE. Therefore, a line space larger than 30 m was recommended. Considering practical project with limited space, the inclined DBHEs were recommended in depth direction. For DBHEs array with a line space of 10 m at the surface ground and 100 m at a depth of 2500 m, Qa,max was only 3.2% smaller compared to the single DBHE, which showed an improvement over DBHEs array with a line space of 50 m. The proposed semi-analytical method could be applied in system design, to ensure the long-term safety and stability of DBHEs array.

The silent impact of underground climate change on civil infrastructure

Urban areas increasingly suffer from subsurface heat islands: an underground climate change responsible for environmental, public health, and transportation issues. Soils, rocks, and construction materials deform under the influence of temperature variations and excessive deformations can affect the performance of civil infrastructure. Here I explore if ground deformations caused by subsurface heat islands might affect civil infrastructure. The Chicago Loop district is used as a case study. A 3-D computer model informed by data collected via a network of temperature sensors is used to characterize the ground temperature variations, deformations, and displacements caused by underground climate change. These deformations and displacements are significant and, on a case-by-case basis, may be incompatible with the operational requirements of civil structures. Therefore, the impact of underground climate change on civil infrastructure should be considered in future urban planning strategies to avoid possible structural damage and malfunction. Overall, this work suggests that underground climate change can represent a silent hazard for civil infrastructure in the Chicago Loop and other urban areas worldwide, but also an opportunity to reutilize or minimize waste heat in the ground.

Monitoring of Seasonal Variations in Ground Temperature

The paper considers the problem of monitoring seasonal changes in soil temperature in northern and mountainous areas in the light of ongoing climate changes. To study seasonal changes in soil temperature, a model site of the Moscow State University Meteorological Observatory was used with the ability to monitor air temperature, snow cover thickness, and ground freezing temperature and depth, which was a prototype of a system for monitoring the state of permafrost soils used in the Arctic and mountain territories. The paper presents the results of monitoring seasonal changes in soil temperature based on the results of numerical modeling of the penetration of seasonal fluctuations in soil temperature in 2014-2017 in MATLAB environment at the model site of the MSU Meteorological Observatory. The results of numerical simulation of the penetration of seasonal temperature fluctuations in the ground at the MSU meteorological site in 2014-2017 in the MATLAB environment are in good agreement with the thermometry data and, therefore, the developed calculation scheme shows fairly good simulation results. This makes it possible to use the calculation scheme to assess the thermal state of frozen soils and assess the stability of foundations and buildings and linear structures located on them in the conditions of the North and mountainous territories. Therefore, the presented methodology can serve as a good help for monitoring and preventing the destruction of the studied structures in the conditions of climate warming.

Monitoring of seasonal variations in ground temperature at the observation site of Lomonosov MSU

The paper considers the problem of monitoring seasonal variations of ground temperature in northern and mountainous areas in the light of ongoing climate changes. To study seasonal variations of ground temperature, a model site of the Moscow State University Meteorological Observatory was used with the ability to monitor air temperature, snow cover thickness, and ground freezing temperature and depth, which was a prototype of a system for monitoring the state of permafrost soils used in the Arctic and mountain territories. The paper presents the results of monitoring seasonal variations of ground temperature based on the results of numerical modelling of the propagation of seasonal fluctuations of ground temperature in 2014-2017 in MATLAB environment which are in good agreement with the thermometry data and, therefore, the developed calculation scheme shows fairly good simulation results. This makes it possible to use the calculation scheme to assess the thermal state of frozen grounds and the stability of foundations and buildings and linear constructions located on them in the conditions of the North and mountainous territories. Therefore, the presented methodology can serve as a good help for monitoring and preventing the destruction of the observed structures in the conditions of climate warming.

Geology, Structure, Ground Temperature and Groundwater Level in Aquifer Taliks in the Shestakovka River Basin, Eastern Siberia

The objective of this study was to evaluate subaerial taliks’ geology, configuration, ground temperature and groundwater level in the continuous permafrost environment of Central Yakutia (Eastern Siberia). The study included geophysical surveys, borehole drilling and measurements of ground temperature and groundwater level variation in a talik aquifer in the Shestakovka research watershed. The talik occupies a gentle, sandy slope covered by a sparse pine forest. Its thickness varies from 3 to 17 m. The talik has several water-conducting branches along its slope. The seasonal thaw layer outside the talik and the talik itself form a single aquifer at the end of the summer. Water-saturated deposits in the talik have a temperature of about 0 °C throughout the year and do not freeze because of the constant filtration of water through the pores and convective heat transfer. Although the groundwater level is relatively close to the land surface, at a depth of just 1–3 m, it has very weak response to snowmelt and precipitation events. The maximum groundwater level occurs in February under cryogenic pressure due to deep seasonal ground freezing above the talik aquifer. Complicated relations between the landscape and the groundwater in the given geological conditions lead to the long-term existence of talik aquifers in the continuous permafrost environment.

Can deep borehole heat exchangers operate stably in long-term operation? Simulation analysis and design method

Deep borehole heat exchanger (DBHE) extracts heat from medium-depth geothermal energy through heat transfer process, and its annual accumulative heat extraction directly influences the stability and safety in long-term operation. To calculate the maximum annual accumulative heat extraction ( Q a,max ) per DBHE rapidly and accurately at design stage, a method combining numerical simulation, modified finite linear heat source model (FLM), and analytical solutions is proposed in this paper. Based on the superposition feature of ground excess temperature, this method divides heat flow of DBHE to one constant value and one extra periodic value. The effect of constant heat flow on ground temperature is calculated by modified FLM rapidly, and the extra periodic effect in first year is calculated by numerical simulation. Then the actual ground temperature variation at any time can be rapidly calculated with the superposition of these two effects. After obtaining ground temperature, the water temperature distribution in DBHE is directly calculated by analytical solutions. Results show that Q a,max per DBHE with depth of 2500 m and normal conditions could reach about 3000 GJ per heating season. However, the specific value is significantly influenced by geothermal conditions, DBHE parameters and heating season duration. This paper then studies the effects of these key factors quantitatively and further raises a system design method for DBHE based on Q a,max , so as to guarantee the stability, safety, and feasibility in long-term operation. • Long-term operational performance of deep borehole heat exchanger (DBHE) is studied. • Maximum annual accumulative heat extraction ( Q a,max ) is key design parameter. • Q a,max is affected by geothermal conditions, DBHE parameters, heating season duration. • System design method based on Q a,max is raised to design the number of DBHEs.

Ground surface temperature monitoring data analysis and applications to geothermal exploration in volcanic areas, Mount Meager, western Canada

The southern Mount Meager area has been studied for its geothermal resource potential for a half century. Although attempts to commercialize the resource were unsuccessful in the past, a large volume of surface and subsurface geoscience data have been collected and made publicly available, making the Mount Meager area a unique natural laboratory for testing new ideas or tools for geothermal exploration. This study investigates the potential of using a ground surface temperature (GST) monitoring network as a tool in geothermal resource exploration. Twenty-two temperature data loggers were deployed in, and surrounding, the core area of the geothermal prospect for nearly one year. The collected temperature time series were analyzed statistically, and machine learning methods such as hierarchical clustering and k-means classification, were applied to data interpretation. The temporal variation of measured temperature can be divided into four segments: 1) snow free, 2) snow affected, 3) snow curtain, and 4) snow melt seasons. The intensity of daily ground temperature variation in the snow free season shows clear environmental and topographic footprints and is complicated by soil properties. The sites with a short period of near zero GST during the snow curtain period is spatially coincident with high heat flow areas. The measured mean GST shows a close affinity with subsurface heat flow and shallow ground water circulation, suggesting that GST time series contain information indicative of subsurface geothermal anomalies and that a GST monitoring network could be an effective tool for geothermal resource exploration in high latitude and/or elevation areas with seasonal snow cover.

Numerical analysis of permafrost heat transfer for small module reactor installation in northern areas

Permafrost degradation amplified by climate change is one of the key issues to consider when attempting to install a small modular reactor (SMR) in remote towns and communities of northern Canada. If the thermal disturbance of permafrost occurs, the ground's strength may be significantly reduced, resulting in structural settlement and stability problems. Therefore, when constructing an SMR on permafrost soils or bedrocks, local permafrost conditions must be protected around the foundations. In the present work, a permafrost heat transfer model has been developed, including the mechanisms of the transient heat conduction, convection and phase change between the solid (ice) and liquid (water) in a porous medium (subsurface soil or sand), to predict the ground temperature variation with depth. The model was assessed by comparing against the available analytical solutions, and then applied to an underground SMR structure (using the Russian-ELENA design) and a civic building foundation (Igloo Church in Inuvik) to forecast the influence of construction heating and seasonal change on the thawing fronts, especially below the structure foundations. The climate data of Inuvik, Northwest Territories, Canada was used as typical weather conditions of northern areas. The numerical results concluded that there is no significant difference of the thawing front penerations adjacent to the underground SMR structure between the summer and winter times, except the active layer. This study will help to ensure the long-term performance of SMR structures under changing environmental conditions.

Stability analysis of Shiwei-Labudalin Highway in Inner Mongolia, Northeastern China using Sentinel-1 InSAR

Permafrost in Northeastern China has significantly degraded due to global warming, deforestation and urbanization in the last few decades. The frost heave and thaw subsidence induced by freeze-thaw cycles of deep seasonal frozen ground have caused serious damage to infrastructures. The Shiwei-Labudalin (Shi-La) Highway is an important infrastructure connecting Shiwei town and Labudalin town of Argun city, Inner Mongolia, which passes through the areas covered by deep seasonal frozen ground or isolated patchy permafrost. In this paper, we mapped the long-term linear displacement trend and amplitude of seasonal displacement of the Shi-La Highway and its nearby areas, with an ascending Sentinel-1 dataset acquired from September 2016 to April 2020. Seasonal displacement amplitudes of 5–20 mm are widely detected in low-lying areas (e.g., the basin of the Gen and Derbugan rivers). The time lags between frozen ground displacement and temperature variations generally range from 10 to 80 days while larger values of 100–120 days caused by soil moisture or land cover difference are also observed. Linear creep displacement rates greater than −20 mm/yr are detected on mountainous slopes and sections of the Shi-La Highway in the line-of-sight (LOS) direction. Our results provide a method for evaluating highway stability in cold regions, which is helpful to highway route selection and design in Northeastern China.

Heat transfer performance of new efficient coaxial casing heat exchanger based on thermostatic thermal response test

Ground-source heat pump (GSHP) systems are helpful for reducing building-sector heating and cooling energy consumption. As the core part of the GSHP system, the underground heat exchanger has a large influence on the heat transfer performance (HTP) of the system. The ground temperature variation characteristics of a new efficient coaxial casing heat exchanger (ECCHE) for heat extraction or rejection were investigated. The study was based on dynamic analysis of linear thermostatics used in the thermal response test and the HTP of the ECCHE. The influences of drilled borehole depth, circulation flow rate, and exchanger structure were considered. Results show that the HTP of the ECCHE is 1.61 (1.46) times that of the doublet U-pipe heat exchangers during heat extraction (heat rejection), and the radius thermal influence distance of the ECCHE is > 10 m. The spiral ribs of the ECCHE extended the heat transfer time between the fluid and surrounding rock, and the heat transfer in the upper part of the borehole was greater than that near the deeper part, so it is easy to produce continuous heat or cold accumulation near the borehole tops. Higher thermal conductivity rock, such as gneiss, has shown a faster recovery rate of the ground temperature after heat extraction. This work provides a theoretical basis for the optimization of the design and installation of GSHPs equipped with ECCHEs.

Soil Thermal Response to Temperature Cycles and End Boundary Conditions of Energy Piles

This paper explores the influence of building cover and pile toe boundary conditions on ground temperature distributions surrounding energy piles. Experimental and numerical studies were conducted on two isolated cast-in-place energy piles installed in dense unsaturated sand, one exposed to the atmosphere at the ground surface (diameter=0.6 m and length=16.1 m) and the other installed under a six-story building (diameter=0.6 m and length=10 m). Investigations were conducted for monotonic heating and daily cyclic temperature changes of the piles ranging between 10°C and 35°C. The changes in ground temperature decreased as radial distance increased from the edge of both piles. Cyclic temperatures in both piles induced lower ground temperature changes and decreased the radial thermal influence zone compared with monotonic heating. However, the radial thermal zone in cyclic operating mode can be influenced by different ratios of heating to cooling times and hence should be selected carefully to avoid unexpected ground temperature changes. Atmospheric effects were observed up to a depth of 2 m for the energy pile exposed to the atmosphere. The insulation provided by the building footprint slightly decreased the impacts of ground-atmosphere interaction on the soil temperature distribution with depth near the surface compared to the energy pile exposed to the atmosphere. The ground temperature variations were dominant along the length of the heat exchanger loops for both piles. However, they were negligible near the pile toe below the heat exchanger loops for both piles.

Monitoring of Seasonal Variations in Ground Temperature

The paper considers the problem of monitoring seasonal changes in soil temperature in northern and mountainous areas in the light of ongoing climate changes. To study seasonal changes in soil temperature, a model site of the Moscow State University Meteorological Observatory was used with the ability to monitor air temperature, snow cover thickness, and ground freezing temperature and depth, which was a prototype of a system for monitoring the state of permafrost soils used in the Arctic and mountain territories. The paper presents the results of monitoring seasonal changes in soil temperature based on the results of numerical modeling of the penetration of seasonal fluctuations in soil temperature in 2014-2017 in MATLAB environment at the model site of the MSU Meteorological Observatory. The results of numerical simulation of the penetration of seasonal temperature fluctuations in the ground at the MSU meteorological site in 2014-2017 in the MATLAB environment are in good agreement with the thermometry data and, therefore, the developed calculation scheme shows fairly good simulation results. This makes it possible to use the calculation scheme to assess the thermal state of frozen soils and assess the stability of foundations and buildings and linear structures located on them in the conditions of the North and mountainous territories. Therefore, the presented methodology can serve as a good help for monitoring and preventing the destruction of the studied structures in the conditions of climate warming.

An hourly ground temperature dataset for 16 high-elevation sites (3493–4377 m a.s.l.) in the Bale Mountains, Ethiopia (2017–2020)

Abstract. Tropical mountains and highlands in Africa are under pressure because of anthropogenic climate and land-use change. To determine the impacts on the afro-alpine environment and to assess the potential socio-economic consequences, the monitoring of essential climate and environmental variables at high elevation is fundamental. However, long-term temperature observations on the African continent above 3000 m are very rare. Here we present a consistent multiannual dataset of hourly ground temperatures for the Bale Mountains in the southern Ethiopian Highlands, which comprise Africa's largest tropical alpine area. The dataset covers the period from January 2017 to January 2020. To characterise and continuously monitor the mountain climate and ecosystem of the Bale Mountains along an elevation gradient from 3493 to 4377 m, ground temperature data loggers have been installed at seven sites at 2 cm depth; at four sites at 10 cm depth; and at five sites at 2, 10, and 50 cm depth. The statistical analysis of the generated time series reveals that ground temperatures in the Bale Mountains are subject to large daily fluctuations of up to 40 ∘C and minor seasonal variations on the order of 5 to 10 ∘C. Besides incoming short-wave radiation, ground moisture, and clouds at night, slope orientation and the type of vegetation coverage seem to be the main factors controlling daily and seasonal ground temperature variations. On the central Sanetti Plateau above 3800–4000 m, the mean annual ground temperature ranges from 9 to 11 ∘C. However, nocturnal ground frost down to a depth of 5 cm occurs frequently during the dry season from November to February. At the five sites where ground temperature is measured at three depths, the monitoring will be continued to trace long-term changes. To promote the further use of the ground temperature dataset by the wider research community dealing with the climate and geo-ecology of tropical mountains in eastern Africa, it is made freely available via the open-access repository Zenodo: https://doi.org/10.5281/zenodo.6047457 (Groos et al., 2022).

Real-time and Multi-physics Fiber Optic Monitoring of Landslides in Three Gorges Reservoir Area

Accurate and real-time measurement of the evolution of landslides has become a great concern in recent years. Fiber Bragg grating (FBG), as a popular quasi-distributed fiber optic sensing technology, has been successfully applied to geotechnical and geohazard monitoring. In this paper, an FBG-based real-time monitoring system has been developed to capture the multi-physics evolution of creeping landslides. The system was employed to monitor the performance of the Majiagou and Xinpu landslides in the Three Gorges Reservoir (TGR) area of China, respectively. The results show that the FBG monitoring system can accurately obtain the variations of ground temperature, soil moisture, and deep displacements, which provides valuable information for evaluating the landslide deformation and failure mechanisms during the operation of the reservoir. In this way, real-time stability analysis and early warning can be achieved.

Ground temperature variation and its response to climate change on the northern Tibetan Plateau

Ground temperature variation and its response to climate change on the northern Tibetan Plateau