Temperature Field In Tunnel Research Articles

Cooling effect and parameter analysis of applying heat insulation layer to tunnel regionalization in construction period based on geothermal level

The construction of high geothermal tunnels presents significant difficulties due to the abnormal rock temperature gradients, including designing a reasonable and cost-effective insulation layer as well as effective cooling measures. In this study, the rock temperature distribution, environmental temperature, and lining surface temperature of the tunnel during the construction period were analyzed through field surveys. A numerical simulation model considering ventilation and heat transfer dynamics was established based on the geothermal measurements and construction characteristics of this tunnel. After validating the 3D numerical model, the effects of installing heat insulation layers according to geothermal levels on the tunnel temperature field control were investigated. Additionally, the impacts of different insulation layer thermal conductivities (λi), ventilation air volume (Wa), and duct thermal conductivities (λd) were analyzed. The results indicate: (1) The comparison of temperature fields in tunnels with insulation layers, which is applied in the range of the rock temperature above 50 °C and without insulation layers was made. The temperature near the excavation face (TAm-1) decreases by up to 0.3% (0.5 °C), tunnel environment temperature with insulation layer applied (TAm-2) decreases by up to 4.2% (2.1 °C), the secondary lining temperature (TSec-lining) decreases by up to 10.5% (4.6 °C), and the wind temperature of air duct outlet (TAir-duct) decreases by up to 0.7% (0.5 °C). (2) The length of the insulation layer increases to the full length of the tunnel, TAm-1 continues to decline by only 0.4°C, TAm-2 by 0.5 °C, TSec-lining by 0.9 °C, and TAir-duct by 0.1 °C, which shows that it is the most economical and reasonable to apply the insulation layer only in the tunnel area where the rock temperature is higher than 50 °C. (3) As λi increases, both the tunnel environment and secondary lining temperatures exhibit linear increases, while increasing Wa and λi cause quadratic decreases and increases in tunnel temperature field parameters, respectively. (4) Range analysis of orthogonal experiments reveals that for tunnel temperature field impact level. For TAm-1, the significance order is Wa >λd >λi. And for TAm-2 and TSec-lining, the significance order is Wa >λi >λd, which can provide the more economical scheme for the insulation layer design and cooling schemes in the high ground temperature tunnel.

Distribution Pattern and Influencing Factors for the Temperature Field of a Topographic Bias Tunnel in Seasonally Frozen Regions

In seasonally frozen regions, highway tunnels are prone to shallow buried bias pressures near the inlet/outlet, which leads to highway tunnels not only bearing asymmetric loads, but also facing the threat of extreme weather. However, there is still no clear understanding of the temperature field for topographically biased tunnel in seasonally frozen regions at present. Taking the Huitougou tunnel of Hegang-Dalian expressway as the object, this paper uses on-site monitoring, theoretical analysis, and numerical simulation to study the distribution law and influence factors of temperature field for topographically biased tunnel in seasonally frozen regions. The numerical results of the temperature field are in good agreement with the on-site monitoring data, which verified the accuracy of this numerical model based on the aerodynamic principle, turbulence model, and wall function method. Meanwhile, the effect of different slope angle and overburden thickness on the temperature field of the tunnel is further analyzed. It is found that when the slope angle increases, the temperature field in the tunnel surrounding rock changes accordingly. The connecting area between the surface and the tunnel temperature field is deflected from arch crown to the arch shoulder of the tunnel, resulting in a large change in the temperature of the shallow buried side, while minor change in the temperature of the deep buried side. The freezing depth of surrounding rock decreases with the rising slope angle. As the overburden thickness gradually increases, the temperature field of the surface surrounding rock and the tunnel surrounding rock gradually change from mutual influence to non-influence. When the overburden thickness exceeds 15 m, a “isolated temperature zone” appears in the middle with a temperature of 6~7 °C, the temperature field of the tunnel surrounding rock is basically not affected by the surface air temperature. These results can provide important theoretical and engineering guidance for the evaluation, construction, and maintenance of tunnel engineering in seasonally frozen regions.

Meteorological Effect on Temperature Field of Tunnel with High Altitude in Cold Region

Meteorological Effect on Temperature Field of Tunnel with High Altitude in Cold Region

Analyses of non-aqueous reactive polymer insulation layer in high geothermal tunnel

The scenario of geothermal tunnel is commonly observed around the world, and increases with the new constructions in the long and deep tunnels, for example in China. Tunnel insulation is generally divided into active and passive insulation. In passive insulation, it is an effective way to set low thermal conductivity materials as the thermal insulation layer as the choice of insulation material mainly depends on the thermal conductivity. Polymer is a kind of material with good geothermal performance, but there are relatively few studies. In this context, the transient plane source (TPS) method was used to measure the thermal conductivity of the developed polymer. Then, the temperature field of the high geothermal tunnel insulated by the non-aqueous reactive polymer layer was simulated. With the parametric analysis results, the suggestions for the tunnel layers were proposed accordingly. It revealed that the thermal conductivity of polymer first increases and then decreases with temperature. There are two rising sections (-40–10 °C and 20–90 °C), one flat section (10–20 °C) and one descending section (>90 °C). It is observed the thermal conductivity of polymer increases with increase of the density of insulation layer and the density, and the thermal conductivity decreases when exposed to high temperatures. The temperature of the surrounding rocks increases with increase of the thermal conductivity and the thickness of polymer. Finally, a more economical thickness (5 cm) was proposed. Based on the parametric study, a thermal insulation layer with thermal conductivity less than 0.045 W/(m K), thickness of 5 cm and a density less than 0.12 g/cm 3 is suggested for practice. • The non-aqueous reactive polymer can be applied in high geothermal tunnel with good insulation performance. • The parameters (i.e., thermal conductivity, thickness and density) on the tunnel temperature field have been analyzed. • Reasonable parameters for polymer insulation layer in practice were suggested for tunnel engineering. • When the thermal conductivity is lower than 0.045 W/(m·K), the heat insulation effect is the most significant. • When thickness is about 5 cm, the polymer layer shows best heat insulation performance.

Study on large deformation and failure mechanism of deep buried stratified slate tunnel and control strategy of high constant resistance anchor cable

Aiming at the significant deformation problem of deep buried stratified soft rock tunnel, taking the No.3 inclined shaft of Muzhailing tunnel as background, the deformation and failure mechanism of the tunnel and the control strategy of high constant resistance anchor cable are studied. The deformation and failure mechanism of stratified tunnel surrounding rock is studied by physical model test, including the tunnel's temperature field, strain field, and displacement field from excavation to failure. Lateral stress significantly influences the deformation of the surrounding rock of the horizontal stratified tunnel. The surrounding rock of the tunnel forms a dumbbell-shaped tensile stress zone under the action of stress. The high tensile stress of the roof and floor leads to dislocation and layer separation, which causes floor heave failure and temperature change. The indoor tensile test verified the super strength characteristics and large deformation of the high constant resistance anchor cable. Based on the excavation compensation method and the coupling control mechanism of high constant resistance long and short anchor cables, a new high prestress constant resistance coupling control strategy is proposed. The numerical simulation and field test studies according to the new design are presented, which show that the high constant resistance anchor cable coupling support significantly reduces the tensile stress zone, effectively controls the deformation of tunnel surrounding rock, and avoids the damage of supporting structure and the cracking and deformation of the lining. The research results can provide a reference for constructing and supporting deep-buried, stratified soft rock tunnels.

Experimental investigation of tunnel temperature field and smoke spread under the influence of a slow moving train with a fire in the carriage

A series of model tests were carried out in a 1/10 reduced-scale single-tunnel double-track railway tunnel model to simulate the fire scenario of the on-fire train moving slowly in the tunnel with speeds less than 20 km/h. The influence of the piston wind generated by the slow moving train on the smoke movement was discussed, the relation between the HRR of the fire source in the carriage and the train speed was analyzed, the temperature variation characteristics of the vault and the smoke diffusion law in the tunnel were studied when the on-fire train was moving slowly. The results show that the piston wind speed increases nonlinearly with the increase of the train speed, but the piston wind speed generated by the slow moving train is no more than 10% of the train speed and the main driving force of smoke diffusion is buoyancy. Moreover, the combustion process of the fire source in the slowly moving carriage can be divided into three stages, the heat release rate of the fire source in the carriage decreases with the increase of train speed in the stable combustion stage. Besides, the temperature rising process of tunnel vault also includes three stages, the maximum temperature rising in the fire control stage accounts for 44.2% of the total temperature rising. The smoke accumulation stage is the main period of temperature rising in the tunnel, the temperature rising accounts for more than 94% of the total temperature rising when the model train speed reaches 0.6 m/s.

Numerical investigation of the temperature field and frost damages of a frost-penetration tunnel considering turbulent convection heat transfer

Accurate evaluation of tunnel temperature field plays an essential role in anti-freezing measures of cold-region tunnels. The aim of this study is to establish turbulence-based theoretical models for the temperature field of cold-region tunnels and to investigate the temperature field and frost damages of an actual cold-region tunnel with negative mean annual air temperature. A transient convection–conduction heat transfer model with turbulent flow and phase change was established. The proposed theoretical model was validated using model test results. The temperature field and frost damages of the Daban Mountain tunnel were investigated. The influence of global warming on the temperature field was also deeply discussed. The results indicate that for the Daban Mountain tunnel, the freezing circle develops to the radial surrounding rock and simultaneously develops along the longitudinal direction of the tunnel. Permafrost occurs at the tunnel entrance in the 7th year and along the whole tunnel in the 16th year. The formation rate and maximum freezing depth of permafrost is significantly influenced by the mean annual air temperature. The annual air temperature amplitude has significant effect on the formation rate of permafrost but little effect on the maximum freezing depth. Under global warming, the mean annual temperature of the surrounding rock decreases first and then increases. In the early years, the unfrozen surrounding rock freezes yearly and develops into permafrost. However, as the mean annual air temperature rises, the permafrost gradually degenerates into seasonally frozen rock and the maximum freezing depth decreases yearly.

Influence of traffic on the temperature field of tunnel in cold region: A case study on the world's longest highway spiral tunnel

The impact of the piston wind caused by vehicle traffic on the temperature field distribution of the tunnel cannot be ignored, especially in spiral tunnels, where the temperature field distribution is more complicated than that in straight tunnels. Based on the world's longest highway spiral tunnel, this study explores the influence of traffic on the temperature fields of spiral and straight tunnels, and proposes a new design method for laying length of insulation layer. The results show that traffic has a significant effect on the temperature field distribution in the tunnel. The influence degree of different traffic elements decreases in the following order: average vehicle speed > daily traffic > morning rush hour > evening rush hour. The temperature field distribution of spiral tunnels is asymmetry on the left and right compared with straight tunnels, while the influence degree of traffic on the outside of spiral tunnels is similar to that of straight tunnels. Due to the difference of wind direction and traffic direction at different tunnel openings, an asymmetric insulation layer laying method is proposed. It is suggested that the lengths of the insulation layers of the Jinjiazhuang Tunnel should be 1200 m for the right tunnel inlet, 700 m for the right tunnel outlet, 700 m for the left tunnel inlet, and 1400 m for the left tunnel outlet.

Research on the Changing Law of Tunnel Temperature Field and the Application of Air Curtain System in Cold Regions

In this study, a tunnel temperature field model test bed is built according to the similarity principle to study the variation law of temperature in the tunnel in the cold season. According to the variation law of temperature in the tunnel, a new active thermal insulation measure, namely, an air curtain system, is developed. According to the principle of flow function superposition and heat balance, the governing equation of air curtain system is obtained. Taking the Zhengpantai tunnel as an example, the feasibility of the air curtain system is verified, and the jet angle of air curtain is optimized. The research results show that outside temperature and surrounding rock temperature are the main factors affecting the temperature field of tunnels in cold regions. The calculation results show that the air curtain system can effectively prevent tunnel freezing damage. The optimal jet angle of air curtain system should be 30°–40°. When the outside temperature is extremely low, multiple air curtains can be used in series to heat the temperature in the tunnel, and it is recommended that the distance between the two air curtains is not less than 20 m.

Temperature field spatio-temporal law and frozen-depth calculation of a tunnel in a seasonally frozen region

The freezing-thawing process in seasonally frozen regions may cause damage to underground structures, especially tunnels. The temperature field and frozen depth can provide reference for tunnel frost damage treatment. Based on the Banshiling tunnel in Northeast China, the spatio-temporal distribution of the tunnel temperature field was revealed using a self-designed intelligent monitoring system. Combined with the temperature field characteristics, a modified formula for predicting frozen depth was established considering the unfrozen water content. Also, the rationality of the modified formula was verified using an example. The calculation error of the modified formula is 1.23% to 15.63%, which is highly consistent with the observed value. Comparing the spatio-temporal distribution of temperature field and frozen depth, they have high consistency. And both them are approximately symmetrically distributed along the longitudinal direction of the tunnel: the lower the temperature, the greater the frozen depth, and the smaller the longitudinal variation along the tunnel. The sensitivity of frozen depth to geographical factors and parameter factors was explored to clarify the influence of different factors on frozen depth. The results show that the sensitivity of the frozen depth to latitude is much greater than that to altitude, and the sensitivity of the frozen depth to different calculation parameters is in the order of mean annual temperature, initial ground temperature, water content, annual temperature amplitude, and thermal conductivity.

Numerical study on long-term performance of ground source heat pumps with tunnel lining heat exchangers

To investigate the long-term performance of ground source heat pump connected to the mountain tunnel lining heat exchangers in subtropical region， a three-dimensional numerical model for the coupled heat transfer of heat pumps and tunnel lining GHEs was developed under the cooling condition. The validity of the heat transfer model was verified by the measured data of field thermal response tests. Based on a tunnel in Shenzhen， the heat transfer performance of ground source heat pump system connected to the tunnel lining heat exchanger under 10 years continuous operation was calculated and analyzed. The results show that the maximum inlet and outlet temperatures of the absorber pipe in the tenth year are 36.96 ℃ and 33.46 ℃， both of which meet the normal operating temperature range of the heat pump and only increase by 0.06 ℃ compared with the first year. The minimum energy efficiency ratio （EER） of the ground source heat pump in the tenth year is 4.76， which meets the EER requirement of the ground source heat pump， and the minimum EER only decreases by 0.01 compared to the first year. After 10 years’ operation of the system， the influencing depth for the temperature field of tunnel surrounding rock reaches approximately 8 m. Under the condition of tunnel ventilation in mountain regions， the temperature field of surrounding rock around the tunnel lining GHEs can realize a self-recovery， and the ground source heat pump connected to the mountain tunnel lining GHEs is feasible for the building cooling in subtropical region.

Numerical investigation on comprehensive control system of cooling and heat insulation for high geothermal tunnel: A case study on the highway tunnel with the highest temperature in China

Solving the high temperature problem during the construction of high geothermal tunnel is of great significance to ensure the safety of workers, improve production efficiency and improve structural safety. Therefore, this paper innovatively establishes a high temperature comprehensive control system of high geothermal tunnel combining high-temperature treatment in tunnel and high-temperature heat source insulation. Based on the highway tunnel with the highest temperature in China—the Nige Tunnel, the temperature field in tunnel with various cooling measures under different surrounding rock temperatures and the temperature variation of lining structure with different thermal insulation methods and thicknesses are studied by numerical simulation. Furthermore, the selection standard of cooling measures, the laying method and the thickness of thermal insulation layer (TIL) are proposed. In the Nige Tunnel, the high temperature comprehensive control system and cooling measures are adopted based on on-site temperature monitoring, so that the temperature in the tunnel can meet the construction requirements and ensure the safety and efficiency of high geothermal tunnel construction.

Research status and progress of tunnel frost damage

The problems of frost damage in cold region tunnels have been systematically analyzed and studied by local and foreign scholars. A series of important achievements has been proposed. In this paper, the research results on mechanism of frost damage, analysis of temperature field, classification of frost damage levels, and frost prevention technologies are summarized. The principles and limitations of the three major theories of frost damage mechanism are elaborated, and the importance of structural damage research on shotcrete in cold region tunnels is emphasized. Two major defects of current research on temperature field are concluded. The present situation of research on frost damage classification of cold region tunnels is discussed. The directions of further studies for tunnel temperature field and frost damage classification are proposed. The prevention technologies for tunnel frost damage in foreign countries, and the advantages and disadvantages of the four major prevention technologies in China and their applicable conditions, are concluded and analyzed. Meanwhile, the importance of frost damage classification is highlighted. Therefore, the local and foreign research results for cold region tunnels are systematically concluded, the defects of the researches are comprehensively analyzed, and the directions of further study are proposed. They are significant to solve the problems of tunnel frost damage in the future.

Impact of Tunnel Temperature Variations on Surrounding Rocks in Cold Regions


 
 
 Temperature is an important factor in designing and maintaining tunnels, especially in cold regions. We present three-dimensional numerical simulations of tunnel temperature fields at different temperature conditions. We study the tunnel temperature field in two different conditions with relatively low and high ambient temperatures representing winter and summer of northeast China. We specifically study how these temperature conditions affect tunnel temperature and its migration to surrounding rocks. We show how placing an insulation layer could affect the temperature distribution within and around tunnels. Our results show that the temperature field without using an insulation layer is closer to the air temperature in the tunnel, and that the insulation layer has shielding effects and could plays an important role in preventing temperature migration to surrounding rocks. We further analyzed how thermal conductivity and thickness of insulation layer control the temperature distribution. The thermal conductivity and thickness of insulation layer only affect the temperature of the surrounding rocks which are located at distances below ~20 m from the lining.
 
 

Stochastic analysis for the uncertain temperature field of tunnel in cold regions

In cold regions, the temperature is important to determine the stability of tunnel construction. However, the conventional finite element methods for stability analysis are always deterministic, rather than taking stochastic parameters and conditions into account. In this paper, the boundary conditions are considered as stochastic processes and the rock properties are considered as random fields. A stochastic analysis for the uncertain temperature characteristics of tunnel is presented. The stochastic finite element formulae are obtained by Neumann stochastic finite element method (NSFEM), and the stochastic finite element program is compiled by Matrix Laboratory (MATLAB) software. Using our program, the random temperature fields of a tunnel in a cold region are obtained and analyzed. The results show that the temperature of a large quantity of frozen surrounding rock is stochastic, and it is bad for the thermal stability of actual tunnel engineering in cold regions. The distributions of mean temperature are the same and the distributions of standard deviation are similar for the two cases in this paper. The average standard deviation increases with time, which implies that the results of conventional deterministic analysis may be far from the true value. These results can improve our understanding of the random temperature field of tunnel and provide a theoretical basis for actual engineering design in cold regions.

Analysis of Temperature Field of the Tunnel Surrounding Rock in Cold Regions

Freeze-thaw disaster is an outstanding problem of geotechnical engineering in cold regions. The temperature field of tunnel surrounding rock in Qilian mountain Osaka hill was calculated according to the transient heat conduction differential equation, meanwhile the freezing conditions of tunnel surrounding rock was forecasted and analyzed after its opening. The study shows that the freeze-thaw environment has a great influence on the temperature distribution of surrounding rock. The tunnel wall and near the mouth of the cave area are more susceptible to the influence of the open ground temperature and air convection, thus the temperature changes violently , but the temperature distribution in surrounding rock tends to be dynamic stable equilibrium as time goes on. The research results can provide a reference for tunnel design and construction in cold regions.

Three-Dimensional Numerical Computation for Temperature Field and Insulator of Cold Regions Tunnel

With heat conduction differential equation of the transient temperature field, Galerkin method is adopted to deduce the three-dimensional finite element formula; based on the test result of temperature field, the actual temperature of the environment inside the tunnel shall be exerted on surface of the second lining concrete as load, thus establish the three dimensional computation model of the temperature field of tunnel in cold region. Next, on basis of the model, numerical analysis on cross section of burial depth and longitudinal direction of tunnel in cold region with and without thermal insulating layer, so as to provide theoretical basis for thickness and longitudinal length of thermal insulating layer laid in tunnel of cold region.

Model Test Study on Insulator of Cold-Region Tunnel in Northeast China: A Case Study of Gaoling Tunnel

Based on similarity theory, the systemic analysis for the distribution characteristics of tunnel temperature field in two different working conditions of having no thermal insulation and installing PU as insulator is progressed by using manufactured model test platform in order to realize the tunnel temperature field rule in cold regions with or without thermal insulation and the influence of thermal insulation layout pattern on insulating effect. The results show that the temperature variation conforms to the “tunnel freeze-thaw circle” theory without thermal insulation, and the surrounding rock maintains negative temperature all the time in the low temperature environment; the internal temperature field of surrounding rock plays a decisive role on the surface temperature of surrounding rock, which keeps above 0°C after the layout of thermal insulation with appropriate material and thickness.