The change in size(transverse section and longitudinal length) of a tunnel will result in variation in the temporal and spatial distribution characteristics of the tunnel temperature field, particularly in the cold re...The change in size(transverse section and longitudinal length) of a tunnel will result in variation in the temporal and spatial distribution characteristics of the tunnel temperature field, particularly in the cold region. Understanding the size effect on the temperature field is crucial for the prevention of freeze-thaw disasters in large tunnels in high-altitude frozen soil areas. This study investigates the distribution of the tunnel temperature field, considering traffic wind through numerical simulations. The research explores how changes in size affect both the temporal and spatial distribution of tunnel temperatures and freeze-thaw depths. The findings reveal that traffic wind significantly influences tunnel temperature fields, with larger amplitudes observed when accounting for traffic wind compared to no-traffic wind conditions. Additionally, peak temperature of surrounding rock decreases logarithmically with increasing tunnel diameter and depth, while freeze-thaw depth decreases logarithmically with increased section size. Furthermore, the peak temperature of surrounding rock and the freezethaw depth are inversely proportional to the tunnel length. Based on these observations regarding section size and length's impact on temperature fields, a mathematical relationship between freeze-thaw depth within surrounding rock and tunnel dimensions is established to elucidate the size effect on temperature fields. These research results could provide theoretical guidance for the design, construction, and disaster prevention of tunnels in alpine regions.展开更多
In order to study the stress characteristics of the initial support and secondary lining of the large section tunnel and to solve the problem of secondary lining cracking during operation. Taking the large section tun...In order to study the stress characteristics of the initial support and secondary lining of the large section tunnel and to solve the problem of secondary lining cracking during operation. Taking the large section tunnel in Zihong village, Qi County as the research object, a numerical simulation method was used to establish a finite element model of the large section tunnel. So as to simulate and analyze the stress characteristics of the support structure of this tunnel. Through the simulation of the initial support and second lining of this large section tunnel in terms of displacement, stress, plastic zone damage and anchor shaft force, the results show that as the excavation progresses, the stress and displacement on the surface of the newly excavated tunnel profile is faster, especially at the side walls and arch footings, the stress and displacement values are slightly larger than other characteristic points, but the final values are stable and converge, and are basically consistent with the field monitoring results, which indicates that this support system is basically in stable state. Therefore, during the tunnel excavation and support process, special attention should be paid to the stability of the sidewalls and footings, and the results of this study will be of great practical significance for tunnel construction and maintenance.展开更多
Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huangg...Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.展开更多
The shallow tunnelling method(STM)often uses temporary supports to divide large section tunnels into several closed or semiclosed sections so as to share the upper load.The complex support system composed of primary a...The shallow tunnelling method(STM)often uses temporary supports to divide large section tunnels into several closed or semiclosed sections so as to share the upper load.The complex support system composed of primary and temporary supports can ensure safety during tunnel construction.Based on the large section tunnel of Beijing Subway Line 12,the mechanical characteristics of support system by the double-side-drift method(DSDM)during excavation and demolition were analyzed through numerical simulation and monitoring.The study showed that the middle cave excavation was the most critical stage of the DSDM,during which the load on the supporting structure increased significantly.The temporary vertical support bore most of the new load during middle cave excavation.During the demolition stage,the load was redistributed,which caused arch settlement and section convergence.The removal of the temporary vertical support exerted the greatest impact in this process.The lateral temporary inverted arch changed from axial compression to axial tension after the middle and lower caves were excavated.Based on the mechanical characteristics of the support system,some engineering suggestions were proposed for large section tunnel construction.These research results can provide reference for the design and construction of similar large section tunnels.展开更多
Due to the weakness in mechanical properties of chlorite schist and the high in situ stress in Jinping II hydropower station, the rock mass surrounding the diversion tunnels located in chlorite schist was observed wit...Due to the weakness in mechanical properties of chlorite schist and the high in situ stress in Jinping II hydropower station, the rock mass surrounding the diversion tunnels located in chlorite schist was observed with extremely large deformations. This may significantly increase the risk of tunnel instability during excavation. In order to assess the stability of the diversion tunnels laboratory tests were carried out in association with the petrophysical properties, mechanical behaviors and waterlweakening properties of chlorite schist. The continuous deformation of surrounding rock mass, the destruction of the support structure and a large-scale collapse induced by the weak chlorite schist and high in situ stress were analyzed. The distributions of compressive deformation in the excavation zone with large deformations were also studied. In this regard, two reinforcement schemes for the excavation of diversion tunnel bottom section were proposed accordingly. This study could offer theoretical basis for deed tunnel construction in similar geological condition~展开更多
This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel （CBT）, which is the southern part of the fiat railway line crossing the Swiss Alps from north to so...This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel （CBT）, which is the southern part of the fiat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by cross- passages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approx- imately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast （D＆B） excavation. The support con- sisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine （TBM） was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel （with an enlarged cross-section） passed underneath the A2 Swiss highway （the major road axis connect- ing the north and south of Switzerland） at a small overburden and through soft ground. Vertical and sub- horizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D＆B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel （at a vertical distance of only 4 m） required special excavation methods through reduced sectors and special blasting techniques in order to limit the blast-induced vibrations. The application of a comprehensive risk management procedure, the execution of an intensive surface survey, and the adaptability of the tunnel design to the encountered geological conditions allowed the successful completion of the excavation works.展开更多
With the boom in deep space exploration by China since the beginning of the 21st century,the demand for high-enthalpy hypersonic shock tunnels has continued to increase.In this paper,three types of shock tunnels using...With the boom in deep space exploration by China since the beginning of the 21st century,the demand for high-enthalpy hypersonic shock tunnels has continued to increase.In this paper,three types of shock tunnels using free-piston,heated light-gas,and detonation drivers,respectively,are briefly summarized and compared.The development of large-scale hypersonic shock tunnels running in both backward and forward detonation driver modes is described in detail.A series of applications to hypersonic flow tests with engineering-scale test models demonstrate the success and advantages of this kind of shock tunnels.The challenges that arise in the operation of hypersonic tunnels are stressed,as are the requirements for precise measurement techniques in the harsh testing environments existing in these tunnels.A new approach for the development of next-generation detonation-driven high-enthalpy shock tunnels is recommended to address these challenges.展开更多
To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable su...To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force,cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve(GRC)considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel.展开更多
A full-scale experimental research is conducted on the fire fume refluence of a sloped long and large curved tunnel in the underground plant of a hydraulic and hydropower engineering project under three different fire...A full-scale experimental research is conducted on the fire fume refluence of a sloped long and large curved tunnel in the underground plant of a hydraulic and hydropower engineering project under three different fire powers.As a result,the eddy effect and pattern of the fire fume flow in the tunnel in case of fire is discovered and the refluence of the fume layers in case of fire is observed.Through analysis of the temperature measurement resulted in the course of the experiment,the main characteristics and performance of the fire fume refluence are discussed under the three different fire powers.展开更多
To improve the problem of low temperature at night in winter due to the lack of thermal storage in large-span plastic tunnels,an air thermal energy utilization system(ATEUS)was developed with fan-coil units to heat a ...To improve the problem of low temperature at night in winter due to the lack of thermal storage in large-span plastic tunnels,an air thermal energy utilization system(ATEUS)was developed with fan-coil units to heat a large-scale plastic tunnel covered with an external blanket(LPTEB)on winter nights.The ATEUS was composed of nine fan-coil units mounted on top of the LPTEB,a water reservoir,pipes,and a water circulation pump.With the heat exchange between the air and the water flowing through the coils,the thermal energy from the air can be collected in the daytime,or the thermal energy in the water can be released into the LPTEB at night.On sunny days,the collected thermal energy from the air in the daytime(E_(c))and released thermal energy at night(E_(r))were 0.25-0.44 MJ/m^(2) and 0.24-0.38 MJ/m^(2),respectively.Used ATEUS as a heating system,its coefficient of performance(COP),which is the ratio of the heat consumption of LPTEB to the power consumption of ATEUS,ranged from 1.6-2.1.A dynamic model was also developed to simulate the water temperature(T_(w)).Based on the simulation,E_(c) and E_(r) on sunny days can be increased by 60%-73%and 38%-62%,respectively,by diminishing the heat loss of the water reservoir and increasing the indoor air temperature in the period of collecting thermal energy.Then,the COP can reach 2.6-3.8,and the developed ATEUS can be applied to heating the LPTEB in a way that conserves energy.展开更多
基金the National Natural Science Foundation of China(No.52278370)the Shaanxi Natural Science Foundation(Nos.2022JM-246,2022JM-190)+1 种基金the China Postdoctoral Science Foundation(No.2019M663648)the Open Fund of State Key Laboratory of Road Engineering Safety and Health in Cold and High-Altitude Regions(No.YGY2020KYPT-03)。
文摘The change in size(transverse section and longitudinal length) of a tunnel will result in variation in the temporal and spatial distribution characteristics of the tunnel temperature field, particularly in the cold region. Understanding the size effect on the temperature field is crucial for the prevention of freeze-thaw disasters in large tunnels in high-altitude frozen soil areas. This study investigates the distribution of the tunnel temperature field, considering traffic wind through numerical simulations. The research explores how changes in size affect both the temporal and spatial distribution of tunnel temperatures and freeze-thaw depths. The findings reveal that traffic wind significantly influences tunnel temperature fields, with larger amplitudes observed when accounting for traffic wind compared to no-traffic wind conditions. Additionally, peak temperature of surrounding rock decreases logarithmically with increasing tunnel diameter and depth, while freeze-thaw depth decreases logarithmically with increased section size. Furthermore, the peak temperature of surrounding rock and the freezethaw depth are inversely proportional to the tunnel length. Based on these observations regarding section size and length's impact on temperature fields, a mathematical relationship between freeze-thaw depth within surrounding rock and tunnel dimensions is established to elucidate the size effect on temperature fields. These research results could provide theoretical guidance for the design, construction, and disaster prevention of tunnels in alpine regions.
文摘In order to study the stress characteristics of the initial support and secondary lining of the large section tunnel and to solve the problem of secondary lining cracking during operation. Taking the large section tunnel in Zihong village, Qi County as the research object, a numerical simulation method was used to establish a finite element model of the large section tunnel. So as to simulate and analyze the stress characteristics of the support structure of this tunnel. Through the simulation of the initial support and second lining of this large section tunnel in terms of displacement, stress, plastic zone damage and anchor shaft force, the results show that as the excavation progresses, the stress and displacement on the surface of the newly excavated tunnel profile is faster, especially at the side walls and arch footings, the stress and displacement values are slightly larger than other characteristic points, but the final values are stable and converge, and are basically consistent with the field monitoring results, which indicates that this support system is basically in stable state. Therefore, during the tunnel excavation and support process, special attention should be paid to the stability of the sidewalls and footings, and the results of this study will be of great practical significance for tunnel construction and maintenance.
基金supported by the NSFC HSR Fundamental Research Joint Fund (Grant No.U1934213)。
文摘Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.
基金Beijing Science and Technology Planning Project(CN),Grant/Award Number:Z201100008120013Fundamental Research Funds for the Central Universities,Grant/Award Number:2022YQLJ01Major Achievements Transformation and Industrialization Projects of Central Universities in Beijing,Grant/Award Number:ZDZH20141141301。
文摘The shallow tunnelling method(STM)often uses temporary supports to divide large section tunnels into several closed or semiclosed sections so as to share the upper load.The complex support system composed of primary and temporary supports can ensure safety during tunnel construction.Based on the large section tunnel of Beijing Subway Line 12,the mechanical characteristics of support system by the double-side-drift method(DSDM)during excavation and demolition were analyzed through numerical simulation and monitoring.The study showed that the middle cave excavation was the most critical stage of the DSDM,during which the load on the supporting structure increased significantly.The temporary vertical support bore most of the new load during middle cave excavation.During the demolition stage,the load was redistributed,which caused arch settlement and section convergence.The removal of the temporary vertical support exerted the greatest impact in this process.The lateral temporary inverted arch changed from axial compression to axial tension after the middle and lower caves were excavated.Based on the mechanical characteristics of the support system,some engineering suggestions were proposed for large section tunnel construction.These research results can provide reference for the design and construction of similar large section tunnels.
基金financial supports from the National Natural Science Foundation of China under Grant Nos.51009132,10972221,10672167 and 41172288the National Basic Research Program of China under Grant No. 2014CB046902
文摘Due to the weakness in mechanical properties of chlorite schist and the high in situ stress in Jinping II hydropower station, the rock mass surrounding the diversion tunnels located in chlorite schist was observed with extremely large deformations. This may significantly increase the risk of tunnel instability during excavation. In order to assess the stability of the diversion tunnels laboratory tests were carried out in association with the petrophysical properties, mechanical behaviors and waterlweakening properties of chlorite schist. The continuous deformation of surrounding rock mass, the destruction of the support structure and a large-scale collapse induced by the weak chlorite schist and high in situ stress were analyzed. The distributions of compressive deformation in the excavation zone with large deformations were also studied. In this regard, two reinforcement schemes for the excavation of diversion tunnel bottom section were proposed accordingly. This study could offer theoretical basis for deed tunnel construction in similar geological condition~
文摘This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel （CBT）, which is the southern part of the fiat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by cross- passages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approx- imately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast （D＆B） excavation. The support con- sisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine （TBM） was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel （with an enlarged cross-section） passed underneath the A2 Swiss highway （the major road axis connect- ing the north and south of Switzerland） at a small overburden and through soft ground. Vertical and sub- horizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D＆B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel （at a vertical distance of only 4 m） required special excavation methods through reduced sectors and special blasting techniques in order to limit the blast-induced vibrations. The application of a comprehensive risk management procedure, the execution of an intensive surface survey, and the adaptability of the tunnel design to the encountered geological conditions allowed the successful completion of the excavation works.
基金co-supported by the National Natural Sci-ence Foundation of China(Grant Nos.12172365,12072353,and 12132017)。
文摘With the boom in deep space exploration by China since the beginning of the 21st century,the demand for high-enthalpy hypersonic shock tunnels has continued to increase.In this paper,three types of shock tunnels using free-piston,heated light-gas,and detonation drivers,respectively,are briefly summarized and compared.The development of large-scale hypersonic shock tunnels running in both backward and forward detonation driver modes is described in detail.A series of applications to hypersonic flow tests with engineering-scale test models demonstrate the success and advantages of this kind of shock tunnels.The challenges that arise in the operation of hypersonic tunnels are stressed,as are the requirements for precise measurement techniques in the harsh testing environments existing in these tunnels.A new approach for the development of next-generation detonation-driven high-enthalpy shock tunnels is recommended to address these challenges.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFC0805401)the National Natural Science Foundation of China (Grant No. 51738002)+1 种基金the China Railway Corporation Research and Development Program of Science and Technology (Grant No. 2014004-C)the Fundamental Research Funds for the Central Universities (Grant No. C17JB00030)。
文摘To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force,cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve(GRC)considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel.
基金supported by the National Natural Science Foundation of China(Grant Nos.505791000,51074143,91024014 and 91024022)the China Research for the 11th Five-year Plan(Grant No.2008BAB29B06)
文摘A full-scale experimental research is conducted on the fire fume refluence of a sloped long and large curved tunnel in the underground plant of a hydraulic and hydropower engineering project under three different fire powers.As a result,the eddy effect and pattern of the fire fume flow in the tunnel in case of fire is discovered and the refluence of the fume layers in case of fire is observed.Through analysis of the temperature measurement resulted in the course of the experiment,the main characteristics and performance of the fire fume refluence are discussed under the three different fire powers.
基金financially supported by China Agriculture Research System of MOF and MARA(Grant No.CARS-23-D02)the Key Research and Development Plan,Science Technology Department of Zhejiang Province(Grant No.2019C02009).
文摘To improve the problem of low temperature at night in winter due to the lack of thermal storage in large-span plastic tunnels,an air thermal energy utilization system(ATEUS)was developed with fan-coil units to heat a large-scale plastic tunnel covered with an external blanket(LPTEB)on winter nights.The ATEUS was composed of nine fan-coil units mounted on top of the LPTEB,a water reservoir,pipes,and a water circulation pump.With the heat exchange between the air and the water flowing through the coils,the thermal energy from the air can be collected in the daytime,or the thermal energy in the water can be released into the LPTEB at night.On sunny days,the collected thermal energy from the air in the daytime(E_(c))and released thermal energy at night(E_(r))were 0.25-0.44 MJ/m^(2) and 0.24-0.38 MJ/m^(2),respectively.Used ATEUS as a heating system,its coefficient of performance(COP),which is the ratio of the heat consumption of LPTEB to the power consumption of ATEUS,ranged from 1.6-2.1.A dynamic model was also developed to simulate the water temperature(T_(w)).Based on the simulation,E_(c) and E_(r) on sunny days can be increased by 60%-73%and 38%-62%,respectively,by diminishing the heat loss of the water reservoir and increasing the indoor air temperature in the period of collecting thermal energy.Then,the COP can reach 2.6-3.8,and the developed ATEUS can be applied to heating the LPTEB in a way that conserves energy.
