We have proposed a methodology to assess the robustness of underground tunnels against potential failure.This involves developing vulnerability functions for various qualities of rock mass and static loading intensiti...We have proposed a methodology to assess the robustness of underground tunnels against potential failure.This involves developing vulnerability functions for various qualities of rock mass and static loading intensities.To account for these variations,we utilized a Monte Carlo Simulation(MCS)technique coupled with the finite difference code FLAC^(3D),to conduct two thousand seven hundred numerical simulations of a horseshoe tunnel located within a rock mass with different geological strength index system(GSIs)and subjected to different states of static loading.To quantify the severity of damage within the rock mass,we selected one stress-based(brittle shear ratio(BSR))and one strain-based failure criterion(plastic damage index(PDI)).Based on these criteria,we then developed fragility curves.Additionally,we used mathematical approximation techniques to produce vulnerability functions that relate the probabilities of various damage states to loading intensities for different quality classes of blocky rock mass.The results indicated that the fragility curves we obtained could accurately depict the evolution of the inner and outer shell damage around the tunnel.Therefore,we have provided engineers with a tool that can predict levels of damages associated with different failure mechanisms based on variations in rock mass quality and in situ stress state.Our method is a numerically developed,multi-variate approach that can aid engineers in making informed decisions about the robustness of underground tunnels.展开更多
In this paper, the verticalseismic effects on tunnels are studied based on a classic mass–damper–spring model. An analyticaldiscrete modelof urban underground tunnels subjected to verticalearthquake excitations is p...In this paper, the verticalseismic effects on tunnels are studied based on a classic mass–damper–spring model. An analyticaldiscrete modelof urban underground tunnels subjected to verticalearthquake excitations is proposed by considering the first verticalvibration mode. Taking a light railproject in Tianjin as an example, this study uses the proposed discrete modelto analyze the displacements of tunneland soilunder verticalearthquake excitations. The soildisplacement responses at different tunnellocations are analyzed with linear random vibration theory.The computationalcost is greatly reduced using the proposed model. It can be seen that different from the case of horizontalearthquakes, the displacement responses under verticalearthquake excitations keep growing after seismic acceleration reaches its peak for a short duration, and then,they begin to decay. The soils at different positions around the tunnels have large relative displacement under verticalearthquake excitations. Moreover, a finite-element modelis also established for displacement responses using ABAQUS.The comparison with the results of the finite-element modelshows that the results of the proposed discrete modelare available.展开更多
The spatial distribution of underground tunnels is significant to the stress redistribution in the surrounding rock masses and blast wave propagation.The field blasting tests were first carried out to study the propag...The spatial distribution of underground tunnels is significant to the stress redistribution in the surrounding rock masses and blast wave propagation.The field blasting tests were first carried out to study the propagation of blast-induced seismic waves through under-ground tunnels of the Xiluodu Hydropower Station in China.The results show that the peak horizontal particle vibration velocity can be used as a safety criterion for underground tunnels.The effects of in situ stresses and spatial distributions of the tunnel group on the vibra-tion velocities distribution is afterward investigated by numerical simulation.The results show that there is a significant amplification of the blasting vibrations in the adjacent tunnels,which depends on their vertical positions during the excavation of a tunnel.The peak vibration velocity decreases as the lateral separation between tunnels increases.When the separation between the tunnels exceeds the width of three tunnels,the impact of the blast waves on each part of the adjacent tunnel tends to be stable on the whole.In terms of the size of the tunnel,the blasting vibration velocity in the upper part of the straight wall on the front-blast side increases as the width increases(and then levels off),while the blasting vibration velocity in the lower part decreases as the width increases(and then levels off).Finally,a generalized formula of blasting vibration velocity considering the spatial distribution is established,which can well predict the vibration velocity of particles in underground tunnels.展开更多
A series solution of displacement response of the ground surface in the presence of underground twin tunnels subjected to excitation of incident plane SV waves is derived by using Fourier-Bessel series expansion metho...A series solution of displacement response of the ground surface in the presence of underground twin tunnels subjected to excitation of incident plane SV waves is derived by using Fourier-Bessel series expansion method.The numerical parametric study shows that underground twin tunnels significantly amplify the nearby surface ground motion.It is suggested that the effect of subways on ground motion should be considered when the subways are planned and designed.展开更多
In order to increase the safety of working environment and decrease the unwanted costs related to overbreak in tunnel excavation projects, it is necessary to minimize overbreak percentage. Thus, based on regression an...In order to increase the safety of working environment and decrease the unwanted costs related to overbreak in tunnel excavation projects, it is necessary to minimize overbreak percentage. Thus, based on regression analysis and fuzzy inference system, this paper tries to develop predictive models to estimate overbreak caused by blasting at the Alborz Tunnel. To develop the models, 202 datasets were utilized, out of which 182 were used for constructing the models. To validate and compare the obtained results,determination coefficient(R2) and root mean square error(RMSE) indexes were chosen. For the fuzzy model, R2 and RMSE are equal to 0.96 and 0.55 respectively, whereas for regression model, they are 0.41 and 1.75 respectively, proving that the fuzzy predictor performs, significantly, better than the statistical method. Using the developed fuzzy model, the percentage of overbreak was minimized in the Alborz Tunnel.展开更多
The application of tunneling machine to Chinese underground engineering construction is outlined,and its future prospect is forecasted in the light of the requirements for Chinese underground engineering construction ...The application of tunneling machine to Chinese underground engineering construction is outlined,and its future prospect is forecasted in the light of the requirements for Chinese underground engineering construction in the 21st century. Further suggestion is put forward on the effective use of tunneling machine.展开更多
Given the increasingly notable segmentation of underground space by existing subway tunnels, it is dif- ficult to effectively and adequately develop and utilize underground space in busy parts of a city. This study pr...Given the increasingly notable segmentation of underground space by existing subway tunnels, it is dif- ficult to effectively and adequately develop and utilize underground space in busy parts of a city. This study presents a combined construction technology that has been developed for use in underground spaces; it includes a deformation buffer layer, a special grouting technique, jump excavation by compart- ment, back-pressure portal frame technology, a reinforcement technique, and the technology of a steel portioning drum or plate. These technologies have been successfully used in practical engineering. The combined construction technology presented in this paper provides a new method of solving key techni- cal problems in underground spaces in effectively used cross-subway tunnels. As this technology has achieved significant economic and social benefits, it has valuable future applications.展开更多
Graduation project(thesis)is an important practice part in undergraduate education,which forms an organic whole with theoretical teaching link,and it is the continuation,deepening and examination of the theoretical te...Graduation project(thesis)is an important practice part in undergraduate education,which forms an organic whole with theoretical teaching link,and it is the continuation,deepening and examination of the theoretical teaching part.This paper focuses on the constitution that the lack of quality standards for undergraduate graduation design,resulting in different depth and breadth standards;the graduation design materials are scattered and lack of standardization,which leads to the lack of systematic reference materials for students,taking the tunnel and underground engineering major as an example,this paper carries out the practice research on the standardization of the graduation design of tunnel and underground engineering through investigation and combining the teaching resources accumulated in the past decades.Through the study of practice,the content of undergraduate graduation design of tunnel and underground engineering is standardized,the breadth and depth of graduation design is defined,and the“Guide for undergraduate graduation design of tunnel and underground engineering”is organized and compiled,which can provide reference for the standardization and guidance of undergraduate graduation design of tunnel and underground engineering.展开更多
Worldwide we see that the construction industry is expanding, requiring new directions, new perspectives that can help reduce time, cost, and make transportation easy, safe, and affordable. For decades now, most of th...Worldwide we see that the construction industry is expanding, requiring new directions, new perspectives that can help reduce time, cost, and make transportation easy, safe, and affordable. For decades now, most of the large cities have completed their surface infrastructure. It has become urgent to address their issues for overpopulated cities where nowadays all infrastructure is overwhelmed, these issues must be addressed, solved and have vision to build underground infrastructure. Developed countries are focused on expanding their infrastructure for road systems, subway network, railway, storm, and sanitary systems. The emergency for underground infrastructure development requires more large-scale projects to be built and it is becoming more crucial building tunnels/underground structures for the future than ever before. Engineering focus, scientific searches are looking to develop their ideas for designing and delivering project underground, but government, agencies and engineers are concerned about the safety, durability, functionality, and the lifetime of this structures planned to be functional for decades. To address all this concerns this study provides information of how to identify the risk on tunnels and underground structures by capturing data from the beginning phases of construction, to analyze, evaluate and produce bulletins and engineering reports through convergences and monitoring. Convergences are the key factor on development of infrastructure underground as it is the only way to explore and analyze the rock mass disturbance during excavation. Convergences and monitoring in infrastructure are the safety coefficient for building underground, preventing accidents, and assessing real risks associated with tunnel/mine works and ensuring progress of the construction in underground structures. This study delves into the engineering role of convergence monitoring, during construction activities on project excavated using New Austrian Tunnelling method and Sequential Excavation Method. The primary objective of convergence monitoring is to gather critical information on ground movements and disturbances, thereby enhancing safety measures during tunnel construction. The monitoring process serves as an early warning system offering evidence of the real risks associated with underground infrastructure, bringing results and engineering data to be used for the design as key coefficient for structural design, type of material, type and strength of the concrete, rebars, concrete mix design. By using the convergence and monitoring system on underground infrastructure this study represents information that can contribute to risk assessment, structural analysis, and the lifetime of a project.展开更多
The Havriliak-Negami model for dynamic viscoelastic material behavior and Biot＇s theory of poroelasticity are employed to develop an exact solution for three-dimensional scattering effect of harmonic plane P-SV waves...The Havriliak-Negami model for dynamic viscoelastic material behavior and Biot＇s theory of poroelasticity are employed to develop an exact solution for three-dimensional scattering effect of harmonic plane P-SV waves from a circular cavity lined with a multilayered fluid-filled shell of infinite length containing viscoelastic damping materials and embedded within a fluid-saturated permeable surrounding soil medium. The analytical results are illustrated with numerical examples where the effects of liner/coating structural arrangement, viscoelastic material properties, liner-soil interface bonding condition, seismic excitation frequency, and angle of incidence on the induced dynamic stress concentrations are evaluated and discussed to obtain representative values of the parameters that characterize the system. It is demonstrated that incorporating viscoelastic damping materials with a low shear modulus in the constrained layer configuration is an efficient means of enhancing the overall seismic isolation performance, especially for near-normally incident seismic shear waves where the amplitudes of induced dynamic stresses may be reduced by up to one-third of those without isolation in a relatively wide frequency range. Some additional cases are considered and good agreements with solutions available in the literature are obtained.展开更多
The dynamic soil-tunnel interaction is studied by indirect boundary element method （IBEM）, using the model of a rigid tunnel in layered half-space, which is simplified to a single soil layer on elastic bedrock, subj...The dynamic soil-tunnel interaction is studied by indirect boundary element method （IBEM）, using the model of a rigid tunnel in layered half-space, which is simplified to a single soil layer on elastic bedrock, subjected to incident plane SH waves. The accuracy of the results is verified through comparison with the analytical solution. It is shown that soil-tunnel interaction in layered half-space is larger than that in homogeneous half-space and this interaction mechanism is essentially different from that of soil-foundation-superstructure interaction.展开更多
Rock masses without pre-existing macrocracks can usually be considered as granular materials with only microcracks.During the excavation of the tunnels,microcracks may nucleate,grow and propagate through the rock matr...Rock masses without pre-existing macrocracks can usually be considered as granular materials with only microcracks.During the excavation of the tunnels,microcracks may nucleate,grow and propagate through the rock matrix;secondary microcracks may appear,and discontinuous and incompatible deformation of rock masses may occur.The classical continuum elastoplastic theory is not suitable for analyzing discontinuous and incompatible deformation of rock masses.Based on non-Euclidean model of the discontinuous and incompatible deformation of rock masses,the distribution of stresses in the surrounding rock masses in deep tunnels is fluctuant or wave-like.The stress concentration at the tips of microcracks located in vicinity of stress wave crest is comparatively large,which may lead to the unstable growth and coalescence of secondary microcracks,and consequently the occurrence of fractured zones.On the other hand,the stress concentration at the tips of microcracks located around stress wave trough is relatively small,which may lead to the arrest of microcracks,and thus the non-fractured zones.The alternate appearance of stress wave crest and trough thus may induce the alternate occurrence of fractured and non-fractured zones in deep rock masses.For brittle rocks,the dissipated energy of microcrack growth is small,but the elastic strain energy stored in rock masses may be larger than the dissipated energy growths of pre-existing microcracks and secondary microcracks.The sudden release of the residual elastic strain energy may lead to rockburst.Based on this understanding,the criteria of rockburst are established.Furthermore,the relationship between rockbursts and zonal disintegration in the surrounding rock masses around deep tunnels is studied.The influences of the in-situ stresses and the physico-mechanical parameters on the distribution of rockburst zones and the ejection velocity of rock fragments are investigated in detail.展开更多
The problem on the dynamic response of a rigid embedded foundation in the presence of an underground rigid tunnel and subjected to excitation of incident anti-plane SH waves is analyzed.By using the exact analytical s...The problem on the dynamic response of a rigid embedded foundation in the presence of an underground rigid tunnel and subjected to excitation of incident anti-plane SH waves is analyzed.By using the exact analytical solution for the two-dimensional SH-wave propagation in and around both the surface rigid foundation and subsurface rigid tunnel,those aspects of the resulting ground motions that are of special interest and importance for seismic resistant design in earthquake analyses have been examined.The computed amplitudes of the resulting periodic ground motions display a very complicated wave-interference between the surface foundation and underground tunnel that lead to observed standing wave patterns, together with abrupt changes in the wave amplitudes and large amplification of the incident motions.展开更多
The dynamic soil-tunnel interaction is studied by the model of a rigid tunnel embedded in layered half-space, which is simplified as a single soil layer on elastic bedrock to the excitation of P- and SV-waves. The ind...The dynamic soil-tunnel interaction is studied by the model of a rigid tunnel embedded in layered half-space, which is simplified as a single soil layer on elastic bedrock to the excitation of P- and SV-waves. The indirect boundary element method is used, combined with the Green＇ s function of distributed loads acting on inclined lines. It is shown that the dynamic characteristics of soil-tunnel interaction in layered half-space are different much from that in homoge- neous half-space, and that the mechanism of soil-tunnel interaction is also different much from that of soil-founda- tion-superstructure interaction. For oblique incidence, the tunnel response for in-plane incident SV-waves is com- pletely different from that for incident SH-waves, while the tunnel response for vertically incident SV-wave is very similar to that of vertically incident SH-wave.展开更多
For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this...For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this paper.The determinations of the structural critical moments when maximal deformations and internal forces in the longitudinal direction occur are deduced as well.When applying the proposed method,the static analysis of the free-field computation model subjected to the least favorable free-field deformation at the tunnel buried depth is performed first to calculate the equivalent input seismic loads.Then,the equivalent input seismic loads are imposed on the integral tunnel-foundation computation model to conduct the static calculation.Afterwards,the critical longitudinal seismic responses of the tunnel are obtained.The applicability of the new method is verified by comparing the seismic responses of a shield tunnel structure in Beijing,determined by the proposed procedure and by a dynamic time-history analysis under a series of obliquely incident out-of-plane and in-plane waves.The results show that the proposed method has a clear concept with high accuracy and simple progress.Meanwhile,this method provides a feasible way to determine the critical moments of the longitudinal seismic responses of a tunnel structure.Therefore,the proposed method can be effectively applied to analyze the seismic response of a long-line underground structure subjected to non-uniform excitations.展开更多
基金funding received by a grant from the Natural Sciences and Engineering Research Council of Canada(NSERC)(Grant No.CRDPJ 469057e14).
文摘We have proposed a methodology to assess the robustness of underground tunnels against potential failure.This involves developing vulnerability functions for various qualities of rock mass and static loading intensities.To account for these variations,we utilized a Monte Carlo Simulation(MCS)technique coupled with the finite difference code FLAC^(3D),to conduct two thousand seven hundred numerical simulations of a horseshoe tunnel located within a rock mass with different geological strength index system(GSIs)and subjected to different states of static loading.To quantify the severity of damage within the rock mass,we selected one stress-based(brittle shear ratio(BSR))and one strain-based failure criterion(plastic damage index(PDI)).Based on these criteria,we then developed fragility curves.Additionally,we used mathematical approximation techniques to produce vulnerability functions that relate the probabilities of various damage states to loading intensities for different quality classes of blocky rock mass.The results indicated that the fragility curves we obtained could accurately depict the evolution of the inner and outer shell damage around the tunnel.Therefore,we have provided engineers with a tool that can predict levels of damages associated with different failure mechanisms based on variations in rock mass quality and in situ stress state.Our method is a numerically developed,multi-variate approach that can aid engineers in making informed decisions about the robustness of underground tunnels.
基金supported by the National Natural Science Foundation of China (No. 51478311)the Natural Science Foundation of Tianjin, China (No. 14JCQNJC07400)
文摘In this paper, the verticalseismic effects on tunnels are studied based on a classic mass–damper–spring model. An analyticaldiscrete modelof urban underground tunnels subjected to verticalearthquake excitations is proposed by considering the first verticalvibration mode. Taking a light railproject in Tianjin as an example, this study uses the proposed discrete modelto analyze the displacements of tunneland soilunder verticalearthquake excitations. The soildisplacement responses at different tunnellocations are analyzed with linear random vibration theory.The computationalcost is greatly reduced using the proposed model. It can be seen that different from the case of horizontalearthquakes, the displacement responses under verticalearthquake excitations keep growing after seismic acceleration reaches its peak for a short duration, and then,they begin to decay. The soils at different positions around the tunnels have large relative displacement under verticalearthquake excitations. Moreover, a finite-element modelis also established for displacement responses using ABAQUS.The comparison with the results of the finite-element modelshows that the results of the proposed discrete modelare available.
基金supported by the National Natural Science Foundation of China(Grant Nos.52079102,52279108)the Major Science and Technology Projects of Sanya Yazhou Bay Science and Technology City Administration,China(Grant No.SKJC-KJ-2019KY02).
文摘The spatial distribution of underground tunnels is significant to the stress redistribution in the surrounding rock masses and blast wave propagation.The field blasting tests were first carried out to study the propagation of blast-induced seismic waves through under-ground tunnels of the Xiluodu Hydropower Station in China.The results show that the peak horizontal particle vibration velocity can be used as a safety criterion for underground tunnels.The effects of in situ stresses and spatial distributions of the tunnel group on the vibra-tion velocities distribution is afterward investigated by numerical simulation.The results show that there is a significant amplification of the blasting vibrations in the adjacent tunnels,which depends on their vertical positions during the excavation of a tunnel.The peak vibration velocity decreases as the lateral separation between tunnels increases.When the separation between the tunnels exceeds the width of three tunnels,the impact of the blast waves on each part of the adjacent tunnel tends to be stable on the whole.In terms of the size of the tunnel,the blasting vibration velocity in the upper part of the straight wall on the front-blast side increases as the width increases(and then levels off),while the blasting vibration velocity in the lower part decreases as the width increases(and then levels off).Finally,a generalized formula of blasting vibration velocity considering the spatial distribution is established,which can well predict the vibration velocity of particles in underground tunnels.
基金National Natural Science Foundation of China(50378063)EYTP of MOESRF for ROCS,MOE
文摘A series solution of displacement response of the ground surface in the presence of underground twin tunnels subjected to excitation of incident plane SV waves is derived by using Fourier-Bessel series expansion method.The numerical parametric study shows that underground twin tunnels significantly amplify the nearby surface ground motion.It is suggested that the effect of subways on ground motion should be considered when the subways are planned and designed.
文摘In order to increase the safety of working environment and decrease the unwanted costs related to overbreak in tunnel excavation projects, it is necessary to minimize overbreak percentage. Thus, based on regression analysis and fuzzy inference system, this paper tries to develop predictive models to estimate overbreak caused by blasting at the Alborz Tunnel. To develop the models, 202 datasets were utilized, out of which 182 were used for constructing the models. To validate and compare the obtained results,determination coefficient(R2) and root mean square error(RMSE) indexes were chosen. For the fuzzy model, R2 and RMSE are equal to 0.96 and 0.55 respectively, whereas for regression model, they are 0.41 and 1.75 respectively, proving that the fuzzy predictor performs, significantly, better than the statistical method. Using the developed fuzzy model, the percentage of overbreak was minimized in the Alborz Tunnel.
文摘The application of tunneling machine to Chinese underground engineering construction is outlined,and its future prospect is forecasted in the light of the requirements for Chinese underground engineering construction in the 21st century. Further suggestion is put forward on the effective use of tunneling machine.
文摘Given the increasingly notable segmentation of underground space by existing subway tunnels, it is dif- ficult to effectively and adequately develop and utilize underground space in busy parts of a city. This study presents a combined construction technology that has been developed for use in underground spaces; it includes a deformation buffer layer, a special grouting technique, jump excavation by compart- ment, back-pressure portal frame technology, a reinforcement technique, and the technology of a steel portioning drum or plate. These technologies have been successfully used in practical engineering. The combined construction technology presented in this paper provides a new method of solving key techni- cal problems in underground spaces in effectively used cross-subway tunnels. As this technology has achieved significant economic and social benefits, it has valuable future applications.
文摘Graduation project(thesis)is an important practice part in undergraduate education,which forms an organic whole with theoretical teaching link,and it is the continuation,deepening and examination of the theoretical teaching part.This paper focuses on the constitution that the lack of quality standards for undergraduate graduation design,resulting in different depth and breadth standards;the graduation design materials are scattered and lack of standardization,which leads to the lack of systematic reference materials for students,taking the tunnel and underground engineering major as an example,this paper carries out the practice research on the standardization of the graduation design of tunnel and underground engineering through investigation and combining the teaching resources accumulated in the past decades.Through the study of practice,the content of undergraduate graduation design of tunnel and underground engineering is standardized,the breadth and depth of graduation design is defined,and the“Guide for undergraduate graduation design of tunnel and underground engineering”is organized and compiled,which can provide reference for the standardization and guidance of undergraduate graduation design of tunnel and underground engineering.
文摘Worldwide we see that the construction industry is expanding, requiring new directions, new perspectives that can help reduce time, cost, and make transportation easy, safe, and affordable. For decades now, most of the large cities have completed their surface infrastructure. It has become urgent to address their issues for overpopulated cities where nowadays all infrastructure is overwhelmed, these issues must be addressed, solved and have vision to build underground infrastructure. Developed countries are focused on expanding their infrastructure for road systems, subway network, railway, storm, and sanitary systems. The emergency for underground infrastructure development requires more large-scale projects to be built and it is becoming more crucial building tunnels/underground structures for the future than ever before. Engineering focus, scientific searches are looking to develop their ideas for designing and delivering project underground, but government, agencies and engineers are concerned about the safety, durability, functionality, and the lifetime of this structures planned to be functional for decades. To address all this concerns this study provides information of how to identify the risk on tunnels and underground structures by capturing data from the beginning phases of construction, to analyze, evaluate and produce bulletins and engineering reports through convergences and monitoring. Convergences are the key factor on development of infrastructure underground as it is the only way to explore and analyze the rock mass disturbance during excavation. Convergences and monitoring in infrastructure are the safety coefficient for building underground, preventing accidents, and assessing real risks associated with tunnel/mine works and ensuring progress of the construction in underground structures. This study delves into the engineering role of convergence monitoring, during construction activities on project excavated using New Austrian Tunnelling method and Sequential Excavation Method. The primary objective of convergence monitoring is to gather critical information on ground movements and disturbances, thereby enhancing safety measures during tunnel construction. The monitoring process serves as an early warning system offering evidence of the real risks associated with underground infrastructure, bringing results and engineering data to be used for the design as key coefficient for structural design, type of material, type and strength of the concrete, rebars, concrete mix design. By using the convergence and monitoring system on underground infrastructure this study represents information that can contribute to risk assessment, structural analysis, and the lifetime of a project.
文摘The Havriliak-Negami model for dynamic viscoelastic material behavior and Biot＇s theory of poroelasticity are employed to develop an exact solution for three-dimensional scattering effect of harmonic plane P-SV waves from a circular cavity lined with a multilayered fluid-filled shell of infinite length containing viscoelastic damping materials and embedded within a fluid-saturated permeable surrounding soil medium. The analytical results are illustrated with numerical examples where the effects of liner/coating structural arrangement, viscoelastic material properties, liner-soil interface bonding condition, seismic excitation frequency, and angle of incidence on the induced dynamic stress concentrations are evaluated and discussed to obtain representative values of the parameters that characterize the system. It is demonstrated that incorporating viscoelastic damping materials with a low shear modulus in the constrained layer configuration is an efficient means of enhancing the overall seismic isolation performance, especially for near-normally incident seismic shear waves where the amplitudes of induced dynamic stresses may be reduced by up to one-third of those without isolation in a relatively wide frequency range. Some additional cases are considered and good agreements with solutions available in the literature are obtained.
基金National Natural Science Foundation of China under Grant 51378384Key Project of Natural Science Foundation of Tianjin Municipality under Grant 12JCZDJC29000
文摘The dynamic soil-tunnel interaction is studied by indirect boundary element method （IBEM）, using the model of a rigid tunnel in layered half-space, which is simplified to a single soil layer on elastic bedrock, subjected to incident plane SH waves. The accuracy of the results is verified through comparison with the analytical solution. It is shown that soil-tunnel interaction in layered half-space is larger than that in homogeneous half-space and this interaction mechanism is essentially different from that of soil-foundation-superstructure interaction.
基金Supported by the National Natural Science Foundation of China (51078371,51021001)the Natural Science Foundation Project of CQ CSTC (2009BA4046,2009AB6194)
文摘Rock masses without pre-existing macrocracks can usually be considered as granular materials with only microcracks.During the excavation of the tunnels,microcracks may nucleate,grow and propagate through the rock matrix;secondary microcracks may appear,and discontinuous and incompatible deformation of rock masses may occur.The classical continuum elastoplastic theory is not suitable for analyzing discontinuous and incompatible deformation of rock masses.Based on non-Euclidean model of the discontinuous and incompatible deformation of rock masses,the distribution of stresses in the surrounding rock masses in deep tunnels is fluctuant or wave-like.The stress concentration at the tips of microcracks located in vicinity of stress wave crest is comparatively large,which may lead to the unstable growth and coalescence of secondary microcracks,and consequently the occurrence of fractured zones.On the other hand,the stress concentration at the tips of microcracks located around stress wave trough is relatively small,which may lead to the arrest of microcracks,and thus the non-fractured zones.The alternate appearance of stress wave crest and trough thus may induce the alternate occurrence of fractured and non-fractured zones in deep rock masses.For brittle rocks,the dissipated energy of microcrack growth is small,but the elastic strain energy stored in rock masses may be larger than the dissipated energy growths of pre-existing microcracks and secondary microcracks.The sudden release of the residual elastic strain energy may lead to rockburst.Based on this understanding,the criteria of rockburst are established.Furthermore,the relationship between rockbursts and zonal disintegration in the surrounding rock masses around deep tunnels is studied.The influences of the in-situ stresses and the physico-mechanical parameters on the distribution of rockburst zones and the ejection velocity of rock fragments are investigated in detail.
文摘The problem on the dynamic response of a rigid embedded foundation in the presence of an underground rigid tunnel and subjected to excitation of incident anti-plane SH waves is analyzed.By using the exact analytical solution for the two-dimensional SH-wave propagation in and around both the surface rigid foundation and subsurface rigid tunnel,those aspects of the resulting ground motions that are of special interest and importance for seismic resistant design in earthquake analyses have been examined.The computed amplitudes of the resulting periodic ground motions display a very complicated wave-interference between the surface foundation and underground tunnel that lead to observed standing wave patterns, together with abrupt changes in the wave amplitudes and large amplification of the incident motions.
基金supported by the National Natural Science Foundation of China(No.51378384)the Key Project of Natural Science Foundation of Tianjin Municipality(No. 12JCZDJC29000)
文摘The dynamic soil-tunnel interaction is studied by the model of a rigid tunnel embedded in layered half-space, which is simplified as a single soil layer on elastic bedrock to the excitation of P- and SV-waves. The indirect boundary element method is used, combined with the Green＇ s function of distributed loads acting on inclined lines. It is shown that the dynamic characteristics of soil-tunnel interaction in layered half-space are different much from that in homoge- neous half-space, and that the mechanism of soil-tunnel interaction is also different much from that of soil-founda- tion-superstructure interaction. For oblique incidence, the tunnel response for in-plane incident SV-waves is com- pletely different from that for incident SH-waves, while the tunnel response for vertically incident SV-wave is very similar to that of vertically incident SH-wave.
基金National Natural Science Foundation of China under Grant No.51478247。
文摘For the longitudinal seismic response analysis of a tunnel structure under asynchronous earthquake excitations,a longitudinal integral response deformation method classified as a practical approach is proposed in this paper.The determinations of the structural critical moments when maximal deformations and internal forces in the longitudinal direction occur are deduced as well.When applying the proposed method,the static analysis of the free-field computation model subjected to the least favorable free-field deformation at the tunnel buried depth is performed first to calculate the equivalent input seismic loads.Then,the equivalent input seismic loads are imposed on the integral tunnel-foundation computation model to conduct the static calculation.Afterwards,the critical longitudinal seismic responses of the tunnel are obtained.The applicability of the new method is verified by comparing the seismic responses of a shield tunnel structure in Beijing,determined by the proposed procedure and by a dynamic time-history analysis under a series of obliquely incident out-of-plane and in-plane waves.The results show that the proposed method has a clear concept with high accuracy and simple progress.Meanwhile,this method provides a feasible way to determine the critical moments of the longitudinal seismic responses of a tunnel structure.Therefore,the proposed method can be effectively applied to analyze the seismic response of a long-line underground structure subjected to non-uniform excitations.
