In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult....In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult.Unfortunately,there are few studies on the failure and support mechanism of the surrounding rocks in the excavation of supported tunnel,while most model tests of super-large-span tunnels focus on the failure characteristics of surrounding rocks in tunnel excavation without supports.Based on excavation compensation method(ECM),model tests of a super-large-span tunnel excavation by different anchor cable support methods in the initial support stage were carried out.The results indicate that during excavation of super-large-span tunnel,the stress and displacement of the shallow surrounding rocks decrease,following a step-shape pattern,and the tunnel failure is mainly concentrated on the vault and spandrel areas.Compared with conventional anchor cable supports,the NPR(negative Poisson’s ratio)anchor cable support is more suitable for the initial support stage of the super-large-span tunnels.The tunnel support theory,model test materials,methods,and the results obtained in this study could provide references for study of similar super-large-span tunnels。展开更多
The study focused on the intersecting section of the Nalong Underground Interchange Tunnel in Shenzhen and investigated the deformation mechanism of the intersecting section under excavation and overloading conditions...The study focused on the intersecting section of the Nalong Underground Interchange Tunnel in Shenzhen and investigated the deformation mechanism of the intersecting section under excavation and overloading conditions using physical model tests and numerical simulation methods.First,the optimal similarity ratio was determined based on the tunnel’s actual geometric characteristics,spatial distribution,and engineering geological conditions.A physical model of the intersecting section was then established.Secondly,following the excavation compensation theory,the intersecting section was excavated and supported using scaled Negative Poisson’s Ratio(NPR)anchor cables.The analysis of tunnel stress−strain,displacement,and NPR anchor cable axial force revealed the stress redistribution characteristics of the tunnel during excavation.Subsequently,the tunnel underwent overloading tests to reveal the surrounding rock failure mechanism of the intersecting section.Finally,numerical simulations were used to compare and verify the test results.The deformation mechanism and damage mode of the similar physical model of the intersecting section of Shenzhen Nanlong Underground Interchange Tunnel under the condition of excavation support and overloading are investigated.The support effect of NPR anchors in the intersection tunnel is verified.The study provides a theoretical basis and practical guidance for the design of tunnel excavation and support with similar engineering background.展开更多
Many ongoing tunnel projects provide a favorable opportunity for the investigation and application of tunnel lining ground heat exchangers(GHEs).Tunnel lining GHEs can be connected to a heat pump to extract geothermal...Many ongoing tunnel projects provide a favorable opportunity for the investigation and application of tunnel lining ground heat exchangers(GHEs).Tunnel lining GHEs can be connected to a heat pump to extract geothermal energy for heating and cooling buildings.Numerous studies have focused on the thermal performance of tunnel lining GHEs;however,the studies on the interaction between heat pumps and tunnel lining GHEs are relatively rare.In this study,a coupled heat transfer model of heat pumps and tunnel lining GHEs was proposed and then calibrated based on in situ test results.The model was used to evaluate the energy efficiency of a heat pump with tunnel lining GHEs under different conditions.The results show that the energy efficiency ratio(EER)increases exponentially with the absorber pipe length and thermal conductivity of the surrounding rock.The EER is governed by the convection heat transfer coefficient,which varies exponentially;meanwhile,the EER decreases approximately linearly with the annual average air temperature in the tunnel.Different types of heat pumps affect the EER significantly,and the EER of a Type-3 heat pump is higher than that of a Type-1 heat pump by 27.1%.Based on the aforementioned results,an empirical formula for the EER and absorber pipe length was established.Moreover,a preliminary design method for the absorber pipe length based on this empirical formula was developed.The method was employed to determine the appropriate absorber pipe length for the tunnel lining GHEs in the Shapu tunnel in Shenzhen,China.Finally,groups of absorber pipe layouts with a pipe spacing of 0.5 m,area of 135 m2,and length of 293.5 m were preliminarily determined.展开更多
基金supported by the Innovation Fund Research Project of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK202201)the Foundation for the Opening of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK2129)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z020007)。
文摘In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult.Unfortunately,there are few studies on the failure and support mechanism of the surrounding rocks in the excavation of supported tunnel,while most model tests of super-large-span tunnels focus on the failure characteristics of surrounding rocks in tunnel excavation without supports.Based on excavation compensation method(ECM),model tests of a super-large-span tunnel excavation by different anchor cable support methods in the initial support stage were carried out.The results indicate that during excavation of super-large-span tunnel,the stress and displacement of the shallow surrounding rocks decrease,following a step-shape pattern,and the tunnel failure is mainly concentrated on the vault and spandrel areas.Compared with conventional anchor cable supports,the NPR(negative Poisson’s ratio)anchor cable support is more suitable for the initial support stage of the super-large-span tunnels.The tunnel support theory,model test materials,methods,and the results obtained in this study could provide references for study of similar super-large-span tunnels。
基金support from the National Natural Science Foundation of China(Grant No.42377154).
文摘The study focused on the intersecting section of the Nalong Underground Interchange Tunnel in Shenzhen and investigated the deformation mechanism of the intersecting section under excavation and overloading conditions using physical model tests and numerical simulation methods.First,the optimal similarity ratio was determined based on the tunnel’s actual geometric characteristics,spatial distribution,and engineering geological conditions.A physical model of the intersecting section was then established.Secondly,following the excavation compensation theory,the intersecting section was excavated and supported using scaled Negative Poisson’s Ratio(NPR)anchor cables.The analysis of tunnel stress−strain,displacement,and NPR anchor cable axial force revealed the stress redistribution characteristics of the tunnel during excavation.Subsequently,the tunnel underwent overloading tests to reveal the surrounding rock failure mechanism of the intersecting section.Finally,numerical simulations were used to compare and verify the test results.The deformation mechanism and damage mode of the similar physical model of the intersecting section of Shenzhen Nanlong Underground Interchange Tunnel under the condition of excavation support and overloading are investigated.The support effect of NPR anchors in the intersection tunnel is verified.The study provides a theoretical basis and practical guidance for the design of tunnel excavation and support with similar engineering background.
基金funded by the National Natural Science Foundation of China(Grant numbers:51778138,and 51978162).
文摘Many ongoing tunnel projects provide a favorable opportunity for the investigation and application of tunnel lining ground heat exchangers(GHEs).Tunnel lining GHEs can be connected to a heat pump to extract geothermal energy for heating and cooling buildings.Numerous studies have focused on the thermal performance of tunnel lining GHEs;however,the studies on the interaction between heat pumps and tunnel lining GHEs are relatively rare.In this study,a coupled heat transfer model of heat pumps and tunnel lining GHEs was proposed and then calibrated based on in situ test results.The model was used to evaluate the energy efficiency of a heat pump with tunnel lining GHEs under different conditions.The results show that the energy efficiency ratio(EER)increases exponentially with the absorber pipe length and thermal conductivity of the surrounding rock.The EER is governed by the convection heat transfer coefficient,which varies exponentially;meanwhile,the EER decreases approximately linearly with the annual average air temperature in the tunnel.Different types of heat pumps affect the EER significantly,and the EER of a Type-3 heat pump is higher than that of a Type-1 heat pump by 27.1%.Based on the aforementioned results,an empirical formula for the EER and absorber pipe length was established.Moreover,a preliminary design method for the absorber pipe length based on this empirical formula was developed.The method was employed to determine the appropriate absorber pipe length for the tunnel lining GHEs in the Shapu tunnel in Shenzhen,China.Finally,groups of absorber pipe layouts with a pipe spacing of 0.5 m,area of 135 m2,and length of 293.5 m were preliminarily determined.
