In the present work,important aspects of time-dependent nonlinear 3D finite element(FE)models for deep tunnel advance by the New Austrian Tunneling Method(NATM),characterized by repeated sequences of excavation,securi...In the present work,important aspects of time-dependent nonlinear 3D finite element(FE)models for deep tunnel advance by the New Austrian Tunneling Method(NATM),characterized by repeated sequences of excavation,securing,and idle periods,are discussed on the example of a 3D finite element model of a stretch of the Brenner Base Tunnel,which is currently constructed between Austria and Italy.Nonlinear material models are utilized for representing the surrounding rock mass and the shotcrete shell.Based on the finite element model,strategies for the efficient implementation into a parallel distributed memory numerical code are proposed.They are essential to achieve reasonable computation times for numerical simulations of tunneling based on large 3D FE models.In particular,the implementation of the construction procedure,parallel computing and communication specific details,and efficient linear solvers for the global equation system within the incremental-iterative Newton–Raphson scheme are addressed.Furthermore,possible extensions of the material models for rock mass and shotcrete,used in the 3D FE model,are presented.They concern(i)a gradient-enhanced model for transversely isotropic rock and rock mass,taking into account hardening and softening behavior and(ii)the extension of the shotcrete model to nonlinear creep and damage due to creep.The possible benefits of the model extensions in numerical simulations of tunneling by the NATM are discussed.展开更多
Due to the fast growth of urban areas worldwide,the demand for tunnels in developed areas is increasing.The design and construc-tion of those tunnels are complex because of their shallow depths and their interaction w...Due to the fast growth of urban areas worldwide,the demand for tunnels in developed areas is increasing.The design and construc-tion of those tunnels are complex because of their shallow depths and their interaction with existing aboveground and buried structures,which results in rather limited allowable ground deformations induced by the tunnel excavation and support.In tropical regions,residual porous soils near the surface are common.Those soils are highly deformable;thus,tunneling may induce large ground deformations that may damage nearby structures.The new Austrian tunneling method(NATM)and the sprayed concrete lining(SCL)technique are being widely employed in several big cities in tropical regions,but little research has been conducted to assess the induced ground deformations in residual soils,common in tropical areas.This paper provides insight into this issue.A well-documented metro tunnel in Sa˜o Paulo,Brazil,in a residual red porous clay,was analyzed using 3D finite element method(FEM).The behavior of the residual red porous clay was approximated by an advanced constitutive soil model calibrated with triaxial tests on intact samples extracted at the site.Predictions of the tunnel deformations during construction matched the field data.The calibrated model was then used to explore the tunnel per-formance under different construction strategies.The influence of partial face excavation,unsupported span length,support stiffness and pipe roof umbrella were assessed.The numerical results showed that partial face excavation was effective to reduce ground deformations ahead of the face of the tunnel and to improve face stability;however,the settlements behind the face increased because of the delay in closing the primary lining.The installation of a stiffer liner closer to the face reduced the ground deformations significantly.The pipe roof umbrella was the most effective technique to reduce the ground deformations around the tunnel;however,the numerical results did not consider deformations that could be induced by the drilling and grouting operations.The results shown in this paper provide both qual-itative and quantitative information about the ground deformations induced by NATM tunneling in residual porous soils,that could help designers and contractors choose the optimum support and construction methods to minimize ground deformations.展开更多
The New Austrian Tunnelling Method(NATM)tunnel design is performed by testing support classes against the geological profile.We propose to replace this manual process with reinforcement learning,a generic framework wi...The New Austrian Tunnelling Method(NATM)tunnel design is performed by testing support classes against the geological profile.We propose to replace this manual process with reinforcement learning,a generic framework within the realm of artificial intelligence that solves control tasks.Previous studies have demonstrated this possibility,albeit with methodological simplifications.We coupled the Finite Difference Method with a Python script,used the output of the first to train the machine learning model implemented in the latter and improved the choice of the support classes.Through benchmark tests,we demonstrated that our method was capable of choosing the optimal support classes for various geological sets and showed the relation between its performance and the number of training episodes.展开更多
基金Partial financial support for Alexander Dummer and Thomas Mader by the Tyrolean Science Fund(TWF),Austria(Project Nos.F.18719 and F.18712)is gratefully acknowledged.
文摘In the present work,important aspects of time-dependent nonlinear 3D finite element(FE)models for deep tunnel advance by the New Austrian Tunneling Method(NATM),characterized by repeated sequences of excavation,securing,and idle periods,are discussed on the example of a 3D finite element model of a stretch of the Brenner Base Tunnel,which is currently constructed between Austria and Italy.Nonlinear material models are utilized for representing the surrounding rock mass and the shotcrete shell.Based on the finite element model,strategies for the efficient implementation into a parallel distributed memory numerical code are proposed.They are essential to achieve reasonable computation times for numerical simulations of tunneling based on large 3D FE models.In particular,the implementation of the construction procedure,parallel computing and communication specific details,and efficient linear solvers for the global equation system within the incremental-iterative Newton–Raphson scheme are addressed.Furthermore,possible extensions of the material models for rock mass and shotcrete,used in the 3D FE model,are presented.They concern(i)a gradient-enhanced model for transversely isotropic rock and rock mass,taking into account hardening and softening behavior and(ii)the extension of the shotcrete model to nonlinear creep and damage due to creep.The possible benefits of the model extensions in numerical simulations of tunneling by the NATM are discussed.
文摘Due to the fast growth of urban areas worldwide,the demand for tunnels in developed areas is increasing.The design and construc-tion of those tunnels are complex because of their shallow depths and their interaction with existing aboveground and buried structures,which results in rather limited allowable ground deformations induced by the tunnel excavation and support.In tropical regions,residual porous soils near the surface are common.Those soils are highly deformable;thus,tunneling may induce large ground deformations that may damage nearby structures.The new Austrian tunneling method(NATM)and the sprayed concrete lining(SCL)technique are being widely employed in several big cities in tropical regions,but little research has been conducted to assess the induced ground deformations in residual soils,common in tropical areas.This paper provides insight into this issue.A well-documented metro tunnel in Sa˜o Paulo,Brazil,in a residual red porous clay,was analyzed using 3D finite element method(FEM).The behavior of the residual red porous clay was approximated by an advanced constitutive soil model calibrated with triaxial tests on intact samples extracted at the site.Predictions of the tunnel deformations during construction matched the field data.The calibrated model was then used to explore the tunnel per-formance under different construction strategies.The influence of partial face excavation,unsupported span length,support stiffness and pipe roof umbrella were assessed.The numerical results showed that partial face excavation was effective to reduce ground deformations ahead of the face of the tunnel and to improve face stability;however,the settlements behind the face increased because of the delay in closing the primary lining.The installation of a stiffer liner closer to the face reduced the ground deformations significantly.The pipe roof umbrella was the most effective technique to reduce the ground deformations around the tunnel;however,the numerical results did not consider deformations that could be induced by the drilling and grouting operations.The results shown in this paper provide both qual-itative and quantitative information about the ground deformations induced by NATM tunneling in residual porous soils,that could help designers and contractors choose the optimum support and construction methods to minimize ground deformations.
文摘The New Austrian Tunnelling Method(NATM)tunnel design is performed by testing support classes against the geological profile.We propose to replace this manual process with reinforcement learning,a generic framework within the realm of artificial intelligence that solves control tasks.Previous studies have demonstrated this possibility,albeit with methodological simplifications.We coupled the Finite Difference Method with a Python script,used the output of the first to train the machine learning model implemented in the latter and improved the choice of the support classes.Through benchmark tests,we demonstrated that our method was capable of choosing the optimal support classes for various geological sets and showed the relation between its performance and the number of training episodes.
