The deep tunnels are prone to mud and water inrush disasters when crossing water-rich weak zones.A good understanding the hydromechanical behavior of the water-rich weak zone in deep tunnels is the prerequisite for de...The deep tunnels are prone to mud and water inrush disasters when crossing water-rich weak zones.A good understanding the hydromechanical behavior of the water-rich weak zone in deep tunnels is the prerequisite for determining the limit support pressure on the tunnel face.However,the seepage forces within the water-rich weak zone are not well estimated in existing models.To overcome this,an analytical model is proposed in this study to determine the limit support pressure of a deep tunnel crossing the water-rich weak zone.The seepage force in the water-rich weak zone is obtained by solving a group of Laplace equations about the hydraulic head,avoiding complex physical and mathematical approximation in existing models.Besides,the seepage boundary conditions in the water-rich weak zone are considered at the nodes on the Neumann boundary and the Dirichlet boundary.The effectiveness of the proposed model is then validated by numerical simulations and engineering practice.It shows that the proposed model has higher accuracy and wider applicability in estimating the hydraulic head.The proposed model can be used for stability analysis of tunnel faces.展开更多
The uplift resistance of the soil overlying shield tunnels significantly impacts their anti-floating stability.However,research on uplift resistance concerning special-shaped shield tunnels is limited.This study combi...The uplift resistance of the soil overlying shield tunnels significantly impacts their anti-floating stability.However,research on uplift resistance concerning special-shaped shield tunnels is limited.This study combines numerical simulation with machine learning techniques to explore this issue.It presents a summary of special-shaped tunnel geometries and introduces a shape coefficient.Through the finite element software,Plaxis3D,the study simulates six key parameters—shape coefficient,burial depth ratio,tunnel’s longest horizontal length,internal friction angle,cohesion,and soil submerged bulk density—that impact uplift resistance across different conditions.Employing XGBoost and ANN methods,the feature importance of each parameter was analyzed based on the numerical simulation results.The findings demonstrate that a tunnel shape more closely resembling a circle leads to reduced uplift resistance in the overlying soil,whereas other parameters exhibit the contrary effects.Furthermore,the study reveals a diminishing trend in the feature importance of buried depth ratio,internal friction angle,tunnel longest horizontal length,cohesion,soil submerged bulk density,and shape coefficient in influencing uplift resistance.展开更多
Tire-derived aggregate(TDA)is an engineered construction material produced from recycled scrap tires and is often used as a compressible layer overlying buried structures to reduce overburden loads.The potential ampli...Tire-derived aggregate(TDA)is an engineered construction material produced from recycled scrap tires and is often used as a compressible layer overlying buried structures to reduce overburden loads.The potential amplification of ground motion in a tunnel site is well understood,but the effect of the tunnel-TDA layer system on ground surface acceleration remains unclear.In this study,both linear and nonlinear dynamic analyses were performed to evaluate the contributions of a TDA layer to the acceleration amplification at the ground surface.The numerical model was calibrated using recorded data from a shaking table test and validated against the literature results,followed by extensive parametric studies.The mechanical and geometrical parameters investigated for the TDA layer included damping ratio,density,Young’s modulus,width,thickness,and depth.The predominant frequency and intensity level of input motions were also investigated.This study showed that the presence of the TDA layer provided an additional acceleration amplification effect.The amplification was more pronounced in areas above the tunnel,particularly for the wider and shallower TDA layer subjected to high frequency and low intensity input motions.展开更多
To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the ...To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the initial disturbance of the wave field induced by geological heterogeneity.The method transforms equivalent twodimensional free-field responses into equivalent nodal forces applied at the boundaries of a 3D numerical model.A longitudinally heterogeneous“hard-soft-hard”site and tunnel system is established,in which the surrounding rock is modeled using the Mohr-Coulomb constitutive law,while the concrete lining is described by the concrete damaged plasticity model.The deformation patterns and failure mechanisms of the site-tunnel system under SV-wave excitation are systematically investigated.The results indicate that seismic damage under SV-wave loading is mainly concentrated in the soft-rock region.Failure of the soft surrounding rock induces pronounced sliding of the overlying hard rock,and the tunnel suffers severe damage due to the combined effects of soft-rock failure and strong ground shaking.Parametric analyses further show that smaller impedance ratios,larger soft-rock widths,and larger incidence angles significantly intensify the seismic response of the tunnel.The findings of this study provide valuable insights for the seismic design of tunnels crossing longitudinally heterogeneous geological formations.展开更多
Shock tunnels are indispensable facilities for hypersonic aerodynamic experimentation.Within these systems,the diaphragm plays a pivotal role,as its rupture process critically influences shock wave generation quality,...Shock tunnels are indispensable facilities for hypersonic aerodynamic experimentation.Within these systems,the diaphragm plays a pivotal role,as its rupture process critically influences shock wave generation quality,experimental repeatability,and facility reliability.A thorough understanding of diaphragm rupture dynamics is therefore essential for optimizing shock tunnel design,improving experimental accuracy,and ensuring operational safety.To address the complex challenge of fully coupled multiphysics analysis in high-pressure-ratio shock tunnels,this study introduces a high-fidelity,three-dimensional,fully coupled Fluid-Structure Interaction(FSI)simulation framework.This framework seamlessly integrates the Dual Conservation Element and Solution Element(Dual-CESE)method,the Immersed Boundary Method(IBM),and the JohnsonCook(J-C)material constitutive and failure model.The combined approach enables synchronized simulation and analysis of the entire diaphragm rupture sequence—including pre-deformation,crack initiation and propagation,and fully developed petaling deformation—alongside the formation and evolution of the associated supersonic flow field.The simulation results show strong agreement with experimental observations,with the post-rupture geometric morphology accurately replicated and a shock wave velocity deviation of only 2.55%from experimental measurements.The study uncovers the dynamic failure mechanisms,revealing that nonlinear pressure loading initiates cracking within the diaphragm.It further elucidates how the nonlinearly coupled interactions between petaling dynamics and fracture morphology directly impact shock wave formation and evolution.This computational framework provides a novel and robust methodology for advancing shock tunnel design and conducting comprehensive reliability assessments.展开更多
Strong seismic excitation and fault dislocation are likely to occur simultaneously in high-intensity seismic zones,causing severe damage to tunnels crossing active fault zones.This paper aims to develop a novel analyt...Strong seismic excitation and fault dislocation are likely to occur simultaneously in high-intensity seismic zones,causing severe damage to tunnels crossing active fault zones.This paper aims to develop a novel analytical solution to determine the longitudinal mechanical responses of tunnels subjected to the combined effects of seismic waves and strike-slip faulting.Adopting the elastic springbeam model,the seismic waves are modelled as shear horizontal(SH)waves and the fault dislocation follows an S-shaped pattern;the superposition principle for free-fielddisplacements caused by both effects is assumed.In addition,the transmission and reflectionof seismic waves at the fault-rock geological interface and the tangential contact conditions at the tunnel-rock interface are considered.The analytical model is validated against numerical simulations,confirmingits accuracy in calculating tunnel responses.Moreover,a parametric study is conducted to evaluate the impact of key factors,including fault displacement,fault zone width,fault dip angle,earthquake frequency,rock conditions,tunnel lining stiffness,and tangential contact conditions,on tunnel responses.Compared with each effect alone,the combined effects of seismic waves and strike-slip faulting significantlychange the tunnel deformation and internal forces,leading to increased tunnel responses,especially within the fault zone and near the fault-rock interfaces.Depending on specificparameters,tunnel responses can be classifiedinto seismic-dominated,faulting-dominated,and seismic-faulting coupled responses on the basis of the relative contributions of each effect.The proposed analytical solution can be applied to quickly predict the longitudinal mechanical behaviour of tunnels under such combined effects in engineering applications.展开更多
An innovative real-time monitoring method for surrounding rock damage based on microseismic time-lapse double-difference tomography is proposed for delayed dynamic damage identification and insufficient detection of a...An innovative real-time monitoring method for surrounding rock damage based on microseismic time-lapse double-difference tomography is proposed for delayed dynamic damage identification and insufficient detection of adverse geological conditions in deep-buried tunnel construction.The installation techniques for microseismic sensors were optimized by mounting sensors at bolt ends which significantly improves signal-to-noise ratio(SNR)and anti-interference capability compared to conventional borehole placement.Subsequently,a 3D wave velocity evolution model that incorporates construction-induced disturbances was established,enabling the first visualization of spatiotemporal variations in surrounding rock wave velocity.It finds significant wave velocity reduction near the tunnel face,with roof and floor damage zones extending 40–50 m;wave velocities approaching undisturbed levels at 15 m ahead of the working face and on the laterally undisturbed side;pronounced spatial asymmetry in wave velocity distribution—values on the left side exceed those on the right,with a clear stress concentration or transition zone located 10–15 m;and systematically lower velocities behind the face than in front,indicating asymmetric rock damage development.These results provide essential theoretical support and practical guidance for optimizing dynamic construction strategies,enabling real-time adjustment of support parameters,and establishing safety early warning systems in deep-buried tunnel engineering.展开更多
Considering the expansion of mining operations into increasingly deeper areas,it is imperative to assess the influence of dynamic disturbance loads on the security of deep tunnels.Here,via AUTODYN finite difference so...Considering the expansion of mining operations into increasingly deeper areas,it is imperative to assess the influence of dynamic disturbance loads on the security of deep tunnels.Here,via AUTODYN finite difference software,a numerical analysis of the fracture characteristics of a fractured tunnel was employed under the coupled action of in-situ stress and dynamic disturbance loads.The experimental setup comprised a tunnel model with“I-shaped”cracks,and a drop impact device(DID)was employed to generate dynamic wave loads.A crack fracture test(CFT)was utilized to gather information on the fracture process,including initiation time and average propagation rate.A series of combined scenarios were subsequently simulated to replicate various in situ stress levels(ranging from 0.5 to 2.5 MPa)and dynamic loads.The results indicate that with increasing in situ stress,the crack propagation rate,crack propagation length,and crack break time(CBT)decrease;moreover,the circumferential tensile stress concentration factor in the tunnel also decreases,enhancing tunnel stability.Finally,changes in ground stress influence the propagation path of cracks.展开更多
In recent years,train-tail swaying of 160 km/h electric multiple units(EMUs)inside single-line tunnels has been heavily researched,because the issue needs to be solved urgently.In this paper,a co-simulation model of v...In recent years,train-tail swaying of 160 km/h electric multiple units(EMUs)inside single-line tunnels has been heavily researched,because the issue needs to be solved urgently.In this paper,a co-simulation model of vortex-induced vibration(VIV)of the tail car body is established,and the aerodynamics of train-tail swaying is studied.The simulation results were confirmed through a field test of operating EMUs.Furthermore,the influence mechanism of train-tail swaying on the wake flow field is studied in detail through a wind-tunnel experiment and a simulation of a reduced-scaled train model.The results demonstrate that the aerodynamic force frequency(i.e.,vortex-induced frequency)of the train tail increases linearly with train speed.When the train runs at 130 km/h,with a small amplitude of train-tail swaying(within 10 mm),the vortex-induced frequency is 1.7 Hz,which primarily depends on the nose shape of the train tail.After the tail car body nose is extended,the vortex-induced frequency is decreased.As the swaying amplitude of the train tail increases(exceeding 25 mm),the separation point of the high-intensity vortex in the train wake shifts downstream to the nose tip,and the vortex-induced frequency shifts from 1.7 Hz to the nearby car body hunting(i.e.,the primary hunting)frequency of 1.3 Hz,which leads to the frequency-locking phenomenon of VIV,and the resonance intensifies train-tail swaying.For the motor vehicle of the train tail,optimization of the yaw damper to improve its primary hunting stability can effectively alleviate train-tail swaying inside single-line tunnels.Optimization of the tail car body nose shape reduces the amplitude of the vortex-induced force,thereby weakening the aerodynamic effect and solving the problem of train-tail swaying inside the single-line tunnels.展开更多
Geological analysis,despite being a long-term method for identifying adverse geology in tunnels,has significant limitations due to its reliance on empirical analysis.The quantitative aspects of geochemical anomalies a...Geological analysis,despite being a long-term method for identifying adverse geology in tunnels,has significant limitations due to its reliance on empirical analysis.The quantitative aspects of geochemical anomalies associated with adverse geology provide a novel strategy for addressing these limitations.However,statistical methods for identifying geochemical anomalies are insufficient for tunnel engineering.In contrast,data mining techniques such as machine learning have demonstrated greater efficacy when applied to geological data.Herein,a method for identifying adverse geology using machine learning of geochemical anomalies is proposed.The method was identified geochemical anomalies in tunnel that were not identified by statistical methods.We by employing robust factor analysis and self-organizing maps to reduce the dimensionality of geochemical data and extract the anomaly elements combination(AEC).Using the AEC sample data,we trained an isolation forest model to identify the multi-element anomalies,successfully.We analyzed the adverse geological features based the multi-element anomalies.This study,therefore,extends the traditional approach of geological analysis in tunnels and demonstrates that machine learning is an effective tool for intelligent geological analysis.Correspondingly,the research offers new insights regarding the adverse geology and the prevention of hazards during the construction of tunnels and underground engineering projects.展开更多
With the implementation of significant national strategies and rapid socioeconomic development,many ultra-long deep tunnels are being constructed in the Qinghai–Xizang Plateau region.However,the extreme complexity an...With the implementation of significant national strategies and rapid socioeconomic development,many ultra-long deep tunnels are being constructed in the Qinghai–Xizang Plateau region.However,the extreme complexity and variability of the environment in this region pose significant challenges to the safe construction and long-term operation of the planned or under-construction ultra-long deep tunnels.To address these complex technical challenges,this paper provides a detailed analysis of the complex climate and geology features of the Qinghai–Xizang Plateau during tunnel construction.The climate characteristics of the Qinghai–Xizang Plateau include severe coldness,low oxygen,and unpredictable weather changes.The geological characteristics include complex stress distributions caused by the intense internal and external dynamic coupling of tectonic plates,widespread active tectonic structures,frequent high-intensity earthquakes,fractured rock masses,and numerous active fault zones.Based on the analysis,this paper elaborates on potential sources of major disasters resulting from the characteristics of ultra-long deep tunnel projects in the Qinghai–Xizang Plateau region.These potential disaster sources include the crossing of active fault zones,high geostress rockbursts,large deformation disasters,high-pressure water surges,geothermal hazards,inadequate long-distance ventilation and oxygen supply,and multi-hazard couplings.In response to these challenges,this paper systematically summarizes the latest research progress and technological achievements in the domestic and international literature,and proposes innovative ideas and future development prospects for disaster monitoring and early warning,mechanized intelligent construction,long-term safety services,and emergency security and rescue.These innovative measures are intended to address the challenges of tunnel disaster prevention and control in the complex environment of the Qinghai–Xizang Plateau,contributing to the safe construction and long-term operation of ultra-long deep tunnels in this region.展开更多
This study focuses on addressing ventilation and dust removal challenges during the construction of small-section tunnels using drilling and blasting techniques.Specifically,the research examines the shale gas gatheri...This study focuses on addressing ventilation and dust removal challenges during the construction of small-section tunnels using drilling and blasting techniques.Specifically,the research examines the shale gas gathering and transmission trunk line project in the Weiyuan and Luzhou blocks.To gain deeper insights into dust migration patterns,numerical simulations were conducted.The study further analyzed dust migration behavior in small-section tunnels and large steep-sloped shafts,taking into account various factors such as ventilation distance,tunnel slope,and section size.The results indicate that optimal ventilation occurs at distances of 15 and 13 m.Additionally,dust concentration was notably lower when the tunnel slope was 0°,suggesting that a flat slope is more advantageous for construction projects where the outlet wind speed remains constant.Moreover,as the tunnel’s cross-sectional size increases,dust concentration decreases significantly,further underscoring the benefits of larger tunnel sections in mitigating dust accumulation.展开更多
Dynamic stress adjustment in deep-buried high geostress hard rock tunnels frequently triggers catastrophic failures such as rockbursts and collapses.While a comprehensive understanding of this process is critical for ...Dynamic stress adjustment in deep-buried high geostress hard rock tunnels frequently triggers catastrophic failures such as rockbursts and collapses.While a comprehensive understanding of this process is critical for evaluating surrounding rock stability,its dynamic evolution are often overlooked in engineering practice.This study systematically summarizes a novel classification framework for stress adjustment types—stabilizing(two-zoned),shallow failure(three-zoned),and deep failure(four-zoned)—characterized by distinct stress adjustment stages.A dynamic interpretation technology system is developed based on microseismic monitoring,integrating key microseismic parameters(energy index EI,apparent stressσa,microseismic activity S),seismic source parameter space clustering,and microseismic paths.This approach enables precise identification of evolutionary stages,stress adjustment types,and failure precursors,thereby elucidating the intrinsic linkage between geomechanical processes(stress redistribution)and failure risks.The study establishes criteria and procedures for identifying stress adjustment types and their associated failure risks,which were successfully applied in the Grand Canyon Tunnel of the E-han Highway to detect 50 instances of disaster risks.The findings offer invaluable insights into understanding the evolution process of stress adjustment and pinpointing the disaster risks linked to hard rock in comparable high geostress tunnels.展开更多
Uneven terrain significantly increases the seismic risk of tunnels in loess deposits.To investigate the variations in optimal intensity measures(IMs)for shallowly buried loess tunnels considering biased terrain,nonlin...Uneven terrain significantly increases the seismic risk of tunnels in loess deposits.To investigate the variations in optimal intensity measures(IMs)for shallowly buried loess tunnels considering biased terrain,nonlinear dynamic analyses were conducted to obtain seismic responses validated by the actual damage pattern.Then IMs were evaluated based on the automatic calculation of the time history damage index fulfilled by a compiled Python program.Results showed that the plastic strain zone progressively developed and extended from the vault to the central slope surface with increasing seismic intensities,ultimately causing shear failure to the tunnel.For IMs at the slope top,peak ground velocity(PGV)(ζ=0.15),velocity spectrum intensity(VSI)(ζ=0.20),and peak spectrum velocity(PSv)(ζ=0.22)were all suitable for seismic fragility assessment.The VSI(ζ=0.17)was optimal,followed by PGV(ζ=0.19)and PSv(ζ=0.2)for those at the slope foot.Acceleration-related IMs were more sensitive to terrain variation.Comparative analyses demonstrated smaller damage probabilities for the IMs at the slope top than those at the slope foot under the same intensity level.The impact of unfavorable terrain on tunnels was accentuated as those located in uneven mountainous regions became more vulnerable to ground shaking.展开更多
Layered rock mass is a typical complex rock mass.Owing to its layered structure,its deformation and strength properties exhibit distinct anisotropic characteristics.Taking a deep-excavated railway tunnel as the engine...Layered rock mass is a typical complex rock mass.Owing to its layered structure,its deformation and strength properties exhibit distinct anisotropic characteristics.Taking a deep-excavated railway tunnel as the engineering context,this study investigates the asymmetric deformation laws of layered soft rock tunnels from two perspectives:laboratory tests and numerical simulations.Uniaxial saturated compression tests were conducted to analyze the anisotropic mechanical characteristics of rock bedding planes.This study established a model of layered rock mass tunnel excavation and support.From the perspectives of tunnel peripheral displacement,plastic zone,and maximum principal stress,it reveals the asymmetric deformation characteristics of the surrounding rock under different dip angles of bedding planes.These findings provide valuable insights for the construction of high-stress layered soft rock tunnels.展开更多
Accurate determination of rock mass parameters is essential for ensuring the accuracy of numericalsimulations. Displacement back-analysis is the most widely used method;however, the reliability of thecurrent approache...Accurate determination of rock mass parameters is essential for ensuring the accuracy of numericalsimulations. Displacement back-analysis is the most widely used method;however, the reliability of thecurrent approaches remains unsatisfactory. Therefore, in this paper, a multistage rock mass parameterback-analysis method, that considers the construction process and displacement losses is proposed andimplemented through the coupling of numerical simulation, auto-machine learning (AutoML), andmulti-objective optimization algorithms (MOOAs). First, a parametric modeling platform for mechanizedtwin tunnels is developed, generating a dataset through extensive numerical simulations. Next, theAutoML method is utilized to establish a surrogate model linking rock parameters and displacements.The tunnel construction process is divided into multiple stages, transforming the rock mass parameterback-analysis into a multi-objective optimization problem, for which multi-objective optimization algorithmsare introduced to obtain the rock mass parameters. The newly proposed rock mass parameterback-analysis method is validated in a mechanized twin tunnel project, and its accuracy and effectivenessare demonstrated. Compared with traditional single-stage back-analysis methods, the proposedmodel decreases the average absolute percentage error from 12.73% to 4.34%, significantly improving theaccuracy of the back-analysis. Moreover, although the accuracy of back analysis significantly increaseswith the number of construction stages considered, the back analysis time is acceptable. This studyprovides a new method for displacement back analysis that is efficient and accurate, thereby paving theway for precise parameter determination in numerical simulations.展开更多
To investigate groundwater influence on stability and rockburst mechanism of deep hard-rock rectangular tunnels,water-immersed treatment and uniaxial compressive acoustic emission(AE)experiments were conducted on rect...To investigate groundwater influence on stability and rockburst mechanism of deep hard-rock rectangular tunnels,water-immersed treatment and uniaxial compressive acoustic emission(AE)experiments were conducted on rectangular tunnel specimens.Energy dissipation characteristics,AE evolution characteristics and damage evolution characteristics of rectangular tunnels were analysed under waterimmersed condition.Under water-immersed condition,tunnel specimens were quite sensitive to water.Average peak stress and average peak strain energy exhibited negative exponential decay with waterimmersed time.Among them,after 12 d of water immersion,average peak stress of specimens decreased by 28%.Average total strain energy decreased by 70%.Average elastic strain energy decreased by 71%and average dissipated strain energy decreased by 68%.After 62 d of water immersion,average peak stress of specimens decreased by 34%.Average total strain energy decreased by 78%.Average elastic strain energy decreased by 79%and average dissipated strain energy decreased by 75%.Water weakened bonding among mineral particles.Moreover,it undermined load-bearing capacity and diminished energystorage properties.Under high stress,massive releasable elastic strain energy stored in natural specimens within pre-peak stage may abruptly release after peak stress.This caused rapid crack development and connection in specimens.During accumulation and release of elastic strain energy,initial failure typically occurred at sidewalls.This failure location was not affected by water.Compared with natural specimens,Specimens immersed in water for 62 d had the lowest peak values of cumulative amplitude,cumulative AE energy and cumulative AE count.After 62 d of water immersion,peak values of cumulative amplitude,cumulative AE energy and cumulative AE count of specimens decreased by 84%,97%and 99%.Compared with AE damage model,fitting degree of energy damage model was higher.For natural specimens,fitting degree of energy damage model was 0.96.For specimens immersed in water for 12 d,fitting degree of energy damage model was 0.96.For specimens immersed in water for 62 d,fitting degree of energy damage model was 0.72.Therefore,an energy damage model had more remarkable applicability and reliability.By establishing dynamic mapping relationship between energy and damage in the model,accuracy of rockburst early warning has been significantly improved.This provided scientific basis for support structure design of rectangular tunnels and regulation of high strain energy.展开更多
Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads ...Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.展开更多
The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,...The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,in combination with numerical simulation,was conducted to investigate the influence of ground fissures on a metro shield tunnel.The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall,resulting in a two-dimensional stress state of vertical shear and axial tension-compression,and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure.In addition,the damage to curved bolts includes tensile yield,flexural yield,and shear twist,leading to obvious concrete lining damage,particularly at the vault,arch bottom,and hance,indicating that the joints in these positions are weak areas.The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure,suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm,and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced.This study could provide a reference for metro design in ground fissure sites.展开更多
Polyurethane foam,when used as a compressible layer in deep soft rock tunnels,offers a feasible solution to reduce the support pressure on the secondary lining.The foam spraying method using sprayed polyurethane mater...Polyurethane foam,when used as a compressible layer in deep soft rock tunnels,offers a feasible solution to reduce the support pressure on the secondary lining.The foam spraying method using sprayed polyurethane material is convenient for engineering applications;however,the compressive behaviour and feasibility of sprayed polyurethane material as a compressible layer remain unclear.To address this gap,this study conducts uniaxial compression tests and scanning electron microscope(SEM)tests to investigate the compressive behaviour of the rigid foams fabricated from a self-developed polyurethane spray material.A peridynamics model for the composite lining with a polyurethane compressible layer is then established.After validating the proposed method by comparison with two tests,a parametric study is carried out to investigate the damage evolution of the composite lining with a polyurethane compressible layer under various combinations of large deformations and compressible layer parameters.The results indicate that the polyurethane compressible layer effectively reduces the radial deformation and damage index of the secondary lining while increasing the damage susceptibility of the primary lining.The thickness of the polyurethane compressible layer significantly influences the prevention effect of large deformation-induced damage to the secondary lining within the density range of 50e100 kg/m^(3).In accordance with the experimental and simulation results,a simple,yet reasonable and convenient approach for determining the key parameters of the polyurethane compressible layer is proposed,along with a classification scheme for the parameters of the polyurethane compressible layer.展开更多
基金support from the National Natural Science Foun-dation of China(Grant Nos.U24A20599 and 42277173)the National Science and Technology Major Project of China(Grant No.2024ZD1004300)is gratefully acknowledged.
文摘The deep tunnels are prone to mud and water inrush disasters when crossing water-rich weak zones.A good understanding the hydromechanical behavior of the water-rich weak zone in deep tunnels is the prerequisite for determining the limit support pressure on the tunnel face.However,the seepage forces within the water-rich weak zone are not well estimated in existing models.To overcome this,an analytical model is proposed in this study to determine the limit support pressure of a deep tunnel crossing the water-rich weak zone.The seepage force in the water-rich weak zone is obtained by solving a group of Laplace equations about the hydraulic head,avoiding complex physical and mathematical approximation in existing models.Besides,the seepage boundary conditions in the water-rich weak zone are considered at the nodes on the Neumann boundary and the Dirichlet boundary.The effectiveness of the proposed model is then validated by numerical simulations and engineering practice.It shows that the proposed model has higher accuracy and wider applicability in estimating the hydraulic head.The proposed model can be used for stability analysis of tunnel faces.
基金Guangzhou Metro Scientific Research Project(No.JT204-100111-23001)Chongqing Municipal Special Project for Technological Innovation and Application Development(No.CSTB2022TIAD-KPX0101)Science and Technology Research and Development Program of China State Railway Group Co.,Ltd.(No.N2023G045)。
文摘The uplift resistance of the soil overlying shield tunnels significantly impacts their anti-floating stability.However,research on uplift resistance concerning special-shaped shield tunnels is limited.This study combines numerical simulation with machine learning techniques to explore this issue.It presents a summary of special-shaped tunnel geometries and introduces a shape coefficient.Through the finite element software,Plaxis3D,the study simulates six key parameters—shape coefficient,burial depth ratio,tunnel’s longest horizontal length,internal friction angle,cohesion,and soil submerged bulk density—that impact uplift resistance across different conditions.Employing XGBoost and ANN methods,the feature importance of each parameter was analyzed based on the numerical simulation results.The findings demonstrate that a tunnel shape more closely resembling a circle leads to reduced uplift resistance in the overlying soil,whereas other parameters exhibit the contrary effects.Furthermore,the study reveals a diminishing trend in the feature importance of buried depth ratio,internal friction angle,tunnel longest horizontal length,cohesion,soil submerged bulk density,and shape coefficient in influencing uplift resistance.
基金Natural Science Foundation of Hebei Province under Grant No.E2025201025,the Science Research Project of Hebei Education Department under Grant No.BJK2024121the Open Fund of Hebei Cangzhou Groundwater and Land Subsidence National Observation and Research Station under Grant No.CGLOS-2025-04+1 种基金the HBU Innovation Team for Multi-Disaster Prevention in Transportation Geotechnics under Grant No.IT2023C04the Research Fund for Talented Scholars of HBU under Grant No.521100221063。
文摘Tire-derived aggregate(TDA)is an engineered construction material produced from recycled scrap tires and is often used as a compressible layer overlying buried structures to reduce overburden loads.The potential amplification of ground motion in a tunnel site is well understood,but the effect of the tunnel-TDA layer system on ground surface acceleration remains unclear.In this study,both linear and nonlinear dynamic analyses were performed to evaluate the contributions of a TDA layer to the acceleration amplification at the ground surface.The numerical model was calibrated using recorded data from a shaking table test and validated against the literature results,followed by extensive parametric studies.The mechanical and geometrical parameters investigated for the TDA layer included damping ratio,density,Young’s modulus,width,thickness,and depth.The predominant frequency and intensity level of input motions were also investigated.This study showed that the presence of the TDA layer provided an additional acceleration amplification effect.The amplification was more pronounced in areas above the tunnel,particularly for the wider and shallower TDA layer subjected to high frequency and low intensity input motions.
基金supported by the National Key Research and Development Program(Grant No.2024YFF0508203)the National Natural Science Foundation of China(Grant No.52378475)the Science and Technology Innovation Special Project of Xiongan New Area,National Key R&D Program(Grant No.2025XAGG0056)。
文摘To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the initial disturbance of the wave field induced by geological heterogeneity.The method transforms equivalent twodimensional free-field responses into equivalent nodal forces applied at the boundaries of a 3D numerical model.A longitudinally heterogeneous“hard-soft-hard”site and tunnel system is established,in which the surrounding rock is modeled using the Mohr-Coulomb constitutive law,while the concrete lining is described by the concrete damaged plasticity model.The deformation patterns and failure mechanisms of the site-tunnel system under SV-wave excitation are systematically investigated.The results indicate that seismic damage under SV-wave loading is mainly concentrated in the soft-rock region.Failure of the soft surrounding rock induces pronounced sliding of the overlying hard rock,and the tunnel suffers severe damage due to the combined effects of soft-rock failure and strong ground shaking.Parametric analyses further show that smaller impedance ratios,larger soft-rock widths,and larger incidence angles significantly intensify the seismic response of the tunnel.The findings of this study provide valuable insights for the seismic design of tunnels crossing longitudinally heterogeneous geological formations.
基金supported by the National Key R&D Program of China(No.2021YFC3100700)。
文摘Shock tunnels are indispensable facilities for hypersonic aerodynamic experimentation.Within these systems,the diaphragm plays a pivotal role,as its rupture process critically influences shock wave generation quality,experimental repeatability,and facility reliability.A thorough understanding of diaphragm rupture dynamics is therefore essential for optimizing shock tunnel design,improving experimental accuracy,and ensuring operational safety.To address the complex challenge of fully coupled multiphysics analysis in high-pressure-ratio shock tunnels,this study introduces a high-fidelity,three-dimensional,fully coupled Fluid-Structure Interaction(FSI)simulation framework.This framework seamlessly integrates the Dual Conservation Element and Solution Element(Dual-CESE)method,the Immersed Boundary Method(IBM),and the JohnsonCook(J-C)material constitutive and failure model.The combined approach enables synchronized simulation and analysis of the entire diaphragm rupture sequence—including pre-deformation,crack initiation and propagation,and fully developed petaling deformation—alongside the formation and evolution of the associated supersonic flow field.The simulation results show strong agreement with experimental observations,with the post-rupture geometric morphology accurately replicated and a shock wave velocity deviation of only 2.55%from experimental measurements.The study uncovers the dynamic failure mechanisms,revealing that nonlinear pressure loading initiates cracking within the diaphragm.It further elucidates how the nonlinearly coupled interactions between petaling dynamics and fracture morphology directly impact shock wave formation and evolution.This computational framework provides a novel and robust methodology for advancing shock tunnel design and conducting comprehensive reliability assessments.
基金supported by the National Natural Science Foundation of China(No.41941018)Shanghai Gaofeng Discipline Construction Funding.
文摘Strong seismic excitation and fault dislocation are likely to occur simultaneously in high-intensity seismic zones,causing severe damage to tunnels crossing active fault zones.This paper aims to develop a novel analytical solution to determine the longitudinal mechanical responses of tunnels subjected to the combined effects of seismic waves and strike-slip faulting.Adopting the elastic springbeam model,the seismic waves are modelled as shear horizontal(SH)waves and the fault dislocation follows an S-shaped pattern;the superposition principle for free-fielddisplacements caused by both effects is assumed.In addition,the transmission and reflectionof seismic waves at the fault-rock geological interface and the tangential contact conditions at the tunnel-rock interface are considered.The analytical model is validated against numerical simulations,confirmingits accuracy in calculating tunnel responses.Moreover,a parametric study is conducted to evaluate the impact of key factors,including fault displacement,fault zone width,fault dip angle,earthquake frequency,rock conditions,tunnel lining stiffness,and tangential contact conditions,on tunnel responses.Compared with each effect alone,the combined effects of seismic waves and strike-slip faulting significantlychange the tunnel deformation and internal forces,leading to increased tunnel responses,especially within the fault zone and near the fault-rock interfaces.Depending on specificparameters,tunnel responses can be classifiedinto seismic-dominated,faulting-dominated,and seismic-faulting coupled responses on the basis of the relative contributions of each effect.The proposed analytical solution can be applied to quickly predict the longitudinal mechanical behaviour of tunnels under such combined effects in engineering applications.
基金support of the National Natural Science Foundation of China(No.52274176)the Guangdong Province Key Areas R&D Program(No.2022B0101070001)+5 种基金Chongqing Elite Innovation and Entrepreneurship Leading talent Project(No.CQYC20220302517)the Chongqing Natural Science Foundation Innovation and Development Joint Fund(No.CSTB2022NSCQ-LZX0079)the National Key Research and Development Program Young Scientists Project(No.2022YFC2905700)the Chongqing Municipal Education Commission“Shuangcheng Economic Circle Construction in Chengdu-Chongqing Area”Science and Technology Innovation Project(No.KJCX2020031)the Fundamental Research Funds for the Central Universities(No.2024CDJGF-009)the Key Project for Technological Innovation and Application Development in Chongqing(No.CSTB2025TIAD-KPX0029).
文摘An innovative real-time monitoring method for surrounding rock damage based on microseismic time-lapse double-difference tomography is proposed for delayed dynamic damage identification and insufficient detection of adverse geological conditions in deep-buried tunnel construction.The installation techniques for microseismic sensors were optimized by mounting sensors at bolt ends which significantly improves signal-to-noise ratio(SNR)and anti-interference capability compared to conventional borehole placement.Subsequently,a 3D wave velocity evolution model that incorporates construction-induced disturbances was established,enabling the first visualization of spatiotemporal variations in surrounding rock wave velocity.It finds significant wave velocity reduction near the tunnel face,with roof and floor damage zones extending 40–50 m;wave velocities approaching undisturbed levels at 15 m ahead of the working face and on the laterally undisturbed side;pronounced spatial asymmetry in wave velocity distribution—values on the left side exceed those on the right,with a clear stress concentration or transition zone located 10–15 m;and systematically lower velocities behind the face than in front,indicating asymmetric rock damage development.These results provide essential theoretical support and practical guidance for optimizing dynamic construction strategies,enabling real-time adjustment of support parameters,and establishing safety early warning systems in deep-buried tunnel engineering.
基金Research Development Fund of Zhejiang A&F University,Grant/Award Number:2023LFR026National Natural Science Foundation of China,Grant/Award Numbers:12272247,52078467,52204104,52478371+1 种基金Sichuan Science and Technology Program,Grant/Award Numbers:2023NSFSC0908,2024YFHZ0033National Science Foundation of Zhejiang Province,Grant/Award Number:LHZ21E09001。
文摘Considering the expansion of mining operations into increasingly deeper areas,it is imperative to assess the influence of dynamic disturbance loads on the security of deep tunnels.Here,via AUTODYN finite difference software,a numerical analysis of the fracture characteristics of a fractured tunnel was employed under the coupled action of in-situ stress and dynamic disturbance loads.The experimental setup comprised a tunnel model with“I-shaped”cracks,and a drop impact device(DID)was employed to generate dynamic wave loads.A crack fracture test(CFT)was utilized to gather information on the fracture process,including initiation time and average propagation rate.A series of combined scenarios were subsequently simulated to replicate various in situ stress levels(ranging from 0.5 to 2.5 MPa)and dynamic loads.The results indicate that with increasing in situ stress,the crack propagation rate,crack propagation length,and crack break time(CBT)decrease;moreover,the circumferential tensile stress concentration factor in the tunnel also decreases,enhancing tunnel stability.Finally,changes in ground stress influence the propagation path of cracks.
基金supported by the National Natural Science Foundation of China(Nos.52372403 and U2268211)the Natural Science Foundation of Sichuan Province(No.2022NSFSC0034),China+1 种基金the National Railway Group Science and Technology Program(No.2023J071)the Traction Power State Key Laboratory of the Independent Research and Development Projects(No.2022TPL-T02),China.
文摘In recent years,train-tail swaying of 160 km/h electric multiple units(EMUs)inside single-line tunnels has been heavily researched,because the issue needs to be solved urgently.In this paper,a co-simulation model of vortex-induced vibration(VIV)of the tail car body is established,and the aerodynamics of train-tail swaying is studied.The simulation results were confirmed through a field test of operating EMUs.Furthermore,the influence mechanism of train-tail swaying on the wake flow field is studied in detail through a wind-tunnel experiment and a simulation of a reduced-scaled train model.The results demonstrate that the aerodynamic force frequency(i.e.,vortex-induced frequency)of the train tail increases linearly with train speed.When the train runs at 130 km/h,with a small amplitude of train-tail swaying(within 10 mm),the vortex-induced frequency is 1.7 Hz,which primarily depends on the nose shape of the train tail.After the tail car body nose is extended,the vortex-induced frequency is decreased.As the swaying amplitude of the train tail increases(exceeding 25 mm),the separation point of the high-intensity vortex in the train wake shifts downstream to the nose tip,and the vortex-induced frequency shifts from 1.7 Hz to the nearby car body hunting(i.e.,the primary hunting)frequency of 1.3 Hz,which leads to the frequency-locking phenomenon of VIV,and the resonance intensifies train-tail swaying.For the motor vehicle of the train tail,optimization of the yaw damper to improve its primary hunting stability can effectively alleviate train-tail swaying inside single-line tunnels.Optimization of the tail car body nose shape reduces the amplitude of the vortex-induced force,thereby weakening the aerodynamic effect and solving the problem of train-tail swaying inside the single-line tunnels.
基金the support from the National Natural Science Foundation of China(Nos.52279103,52379103)the Natural Science Foundation of Shandong Province(No.ZR2023YQ049)。
文摘Geological analysis,despite being a long-term method for identifying adverse geology in tunnels,has significant limitations due to its reliance on empirical analysis.The quantitative aspects of geochemical anomalies associated with adverse geology provide a novel strategy for addressing these limitations.However,statistical methods for identifying geochemical anomalies are insufficient for tunnel engineering.In contrast,data mining techniques such as machine learning have demonstrated greater efficacy when applied to geological data.Herein,a method for identifying adverse geology using machine learning of geochemical anomalies is proposed.The method was identified geochemical anomalies in tunnel that were not identified by statistical methods.We by employing robust factor analysis and self-organizing maps to reduce the dimensionality of geochemical data and extract the anomaly elements combination(AEC).Using the AEC sample data,we trained an isolation forest model to identify the multi-element anomalies,successfully.We analyzed the adverse geological features based the multi-element anomalies.This study,therefore,extends the traditional approach of geological analysis in tunnels and demonstrates that machine learning is an effective tool for intelligent geological analysis.Correspondingly,the research offers new insights regarding the adverse geology and the prevention of hazards during the construction of tunnels and underground engineering projects.
文摘With the implementation of significant national strategies and rapid socioeconomic development,many ultra-long deep tunnels are being constructed in the Qinghai–Xizang Plateau region.However,the extreme complexity and variability of the environment in this region pose significant challenges to the safe construction and long-term operation of the planned or under-construction ultra-long deep tunnels.To address these complex technical challenges,this paper provides a detailed analysis of the complex climate and geology features of the Qinghai–Xizang Plateau during tunnel construction.The climate characteristics of the Qinghai–Xizang Plateau include severe coldness,low oxygen,and unpredictable weather changes.The geological characteristics include complex stress distributions caused by the intense internal and external dynamic coupling of tectonic plates,widespread active tectonic structures,frequent high-intensity earthquakes,fractured rock masses,and numerous active fault zones.Based on the analysis,this paper elaborates on potential sources of major disasters resulting from the characteristics of ultra-long deep tunnel projects in the Qinghai–Xizang Plateau region.These potential disaster sources include the crossing of active fault zones,high geostress rockbursts,large deformation disasters,high-pressure water surges,geothermal hazards,inadequate long-distance ventilation and oxygen supply,and multi-hazard couplings.In response to these challenges,this paper systematically summarizes the latest research progress and technological achievements in the domestic and international literature,and proposes innovative ideas and future development prospects for disaster monitoring and early warning,mechanized intelligent construction,long-term safety services,and emergency security and rescue.These innovative measures are intended to address the challenges of tunnel disaster prevention and control in the complex environment of the Qinghai–Xizang Plateau,contributing to the safe construction and long-term operation of ultra-long deep tunnels in this region.
基金supported by the National Natural Science Foundation of China under the Youth Project(Grant No.52204087)Additional support was provided by the Science and Technology Research Program of the Chongqing Municipal Education Commission(Grant No.KJQN202200746).
文摘This study focuses on addressing ventilation and dust removal challenges during the construction of small-section tunnels using drilling and blasting techniques.Specifically,the research examines the shale gas gathering and transmission trunk line project in the Weiyuan and Luzhou blocks.To gain deeper insights into dust migration patterns,numerical simulations were conducted.The study further analyzed dust migration behavior in small-section tunnels and large steep-sloped shafts,taking into account various factors such as ventilation distance,tunnel slope,and section size.The results indicate that optimal ventilation occurs at distances of 15 and 13 m.Additionally,dust concentration was notably lower when the tunnel slope was 0°,suggesting that a flat slope is more advantageous for construction projects where the outlet wind speed remains constant.Moreover,as the tunnel’s cross-sectional size increases,dust concentration decreases significantly,further underscoring the benefits of larger tunnel sections in mitigating dust accumulation.
基金supported by the National Natural Science Foundation of China(Nos.42177173,U23A20651 and 42130719)and the Outstanding Youth Science Fund Project of Sichuan Provincial Natural Science Foundation(No.2025NSFJQ0003)。
文摘Dynamic stress adjustment in deep-buried high geostress hard rock tunnels frequently triggers catastrophic failures such as rockbursts and collapses.While a comprehensive understanding of this process is critical for evaluating surrounding rock stability,its dynamic evolution are often overlooked in engineering practice.This study systematically summarizes a novel classification framework for stress adjustment types—stabilizing(two-zoned),shallow failure(three-zoned),and deep failure(four-zoned)—characterized by distinct stress adjustment stages.A dynamic interpretation technology system is developed based on microseismic monitoring,integrating key microseismic parameters(energy index EI,apparent stressσa,microseismic activity S),seismic source parameter space clustering,and microseismic paths.This approach enables precise identification of evolutionary stages,stress adjustment types,and failure precursors,thereby elucidating the intrinsic linkage between geomechanical processes(stress redistribution)and failure risks.The study establishes criteria and procedures for identifying stress adjustment types and their associated failure risks,which were successfully applied in the Grand Canyon Tunnel of the E-han Highway to detect 50 instances of disaster risks.The findings offer invaluable insights into understanding the evolution process of stress adjustment and pinpointing the disaster risks linked to hard rock in comparable high geostress tunnels.
基金supported by the National Natural Science Foundation of China(Grant numbers 52208392,52068044,and 52168058)China Post-doctoral Science Foundation(Grant number 2021M693843)+1 种基金Tianyou Youth Talent Lift Program of Lanzhou Jiaotong University(Grant number 1520260306)Key Laboratory of Road and Bridge and Underground Engineering of Gansu Province(Grant number GSDQ-KF2020-5).
文摘Uneven terrain significantly increases the seismic risk of tunnels in loess deposits.To investigate the variations in optimal intensity measures(IMs)for shallowly buried loess tunnels considering biased terrain,nonlinear dynamic analyses were conducted to obtain seismic responses validated by the actual damage pattern.Then IMs were evaluated based on the automatic calculation of the time history damage index fulfilled by a compiled Python program.Results showed that the plastic strain zone progressively developed and extended from the vault to the central slope surface with increasing seismic intensities,ultimately causing shear failure to the tunnel.For IMs at the slope top,peak ground velocity(PGV)(ζ=0.15),velocity spectrum intensity(VSI)(ζ=0.20),and peak spectrum velocity(PSv)(ζ=0.22)were all suitable for seismic fragility assessment.The VSI(ζ=0.17)was optimal,followed by PGV(ζ=0.19)and PSv(ζ=0.2)for those at the slope foot.Acceleration-related IMs were more sensitive to terrain variation.Comparative analyses demonstrated smaller damage probabilities for the IMs at the slope top than those at the slope foot under the same intensity level.The impact of unfavorable terrain on tunnels was accentuated as those located in uneven mountainous regions became more vulnerable to ground shaking.
基金School-level Research Project of Xingxin Vocational and Technical College(YJYBKT202501)。
文摘Layered rock mass is a typical complex rock mass.Owing to its layered structure,its deformation and strength properties exhibit distinct anisotropic characteristics.Taking a deep-excavated railway tunnel as the engineering context,this study investigates the asymmetric deformation laws of layered soft rock tunnels from two perspectives:laboratory tests and numerical simulations.Uniaxial saturated compression tests were conducted to analyze the anisotropic mechanical characteristics of rock bedding planes.This study established a model of layered rock mass tunnel excavation and support.From the perspectives of tunnel peripheral displacement,plastic zone,and maximum principal stress,it reveals the asymmetric deformation characteristics of the surrounding rock under different dip angles of bedding planes.These findings provide valuable insights for the construction of high-stress layered soft rock tunnels.
基金supported by the National Natural Science Foundation of China(Grant Nos.52090081,52079068)the State Key Laboratory of Hydroscience and Hydraulic Engineering(Grant No.2021-KY-04).
文摘Accurate determination of rock mass parameters is essential for ensuring the accuracy of numericalsimulations. Displacement back-analysis is the most widely used method;however, the reliability of thecurrent approaches remains unsatisfactory. Therefore, in this paper, a multistage rock mass parameterback-analysis method, that considers the construction process and displacement losses is proposed andimplemented through the coupling of numerical simulation, auto-machine learning (AutoML), andmulti-objective optimization algorithms (MOOAs). First, a parametric modeling platform for mechanizedtwin tunnels is developed, generating a dataset through extensive numerical simulations. Next, theAutoML method is utilized to establish a surrogate model linking rock parameters and displacements.The tunnel construction process is divided into multiple stages, transforming the rock mass parameterback-analysis into a multi-objective optimization problem, for which multi-objective optimization algorithmsare introduced to obtain the rock mass parameters. The newly proposed rock mass parameterback-analysis method is validated in a mechanized twin tunnel project, and its accuracy and effectivenessare demonstrated. Compared with traditional single-stage back-analysis methods, the proposedmodel decreases the average absolute percentage error from 12.73% to 4.34%, significantly improving theaccuracy of the back-analysis. Moreover, although the accuracy of back analysis significantly increaseswith the number of construction stages considered, the back analysis time is acceptable. This studyprovides a new method for displacement back analysis that is efficient and accurate, thereby paving theway for precise parameter determination in numerical simulations.
基金funded by the National Science and Technology Major Project(No.2025ZD1700904)the National Natural Science Foundation of China(Nos.52174093 and 52034009)+1 种基金Fundamental Research Funds for the Central Universities(No.2023ZKPYNY03)Fundamental Research Funds for the Central Universities(Ph.D.Top Innovative Talents Fund of CUMTB)(No.BBJ2025002)。
文摘To investigate groundwater influence on stability and rockburst mechanism of deep hard-rock rectangular tunnels,water-immersed treatment and uniaxial compressive acoustic emission(AE)experiments were conducted on rectangular tunnel specimens.Energy dissipation characteristics,AE evolution characteristics and damage evolution characteristics of rectangular tunnels were analysed under waterimmersed condition.Under water-immersed condition,tunnel specimens were quite sensitive to water.Average peak stress and average peak strain energy exhibited negative exponential decay with waterimmersed time.Among them,after 12 d of water immersion,average peak stress of specimens decreased by 28%.Average total strain energy decreased by 70%.Average elastic strain energy decreased by 71%and average dissipated strain energy decreased by 68%.After 62 d of water immersion,average peak stress of specimens decreased by 34%.Average total strain energy decreased by 78%.Average elastic strain energy decreased by 79%and average dissipated strain energy decreased by 75%.Water weakened bonding among mineral particles.Moreover,it undermined load-bearing capacity and diminished energystorage properties.Under high stress,massive releasable elastic strain energy stored in natural specimens within pre-peak stage may abruptly release after peak stress.This caused rapid crack development and connection in specimens.During accumulation and release of elastic strain energy,initial failure typically occurred at sidewalls.This failure location was not affected by water.Compared with natural specimens,Specimens immersed in water for 62 d had the lowest peak values of cumulative amplitude,cumulative AE energy and cumulative AE count.After 62 d of water immersion,peak values of cumulative amplitude,cumulative AE energy and cumulative AE count of specimens decreased by 84%,97%and 99%.Compared with AE damage model,fitting degree of energy damage model was higher.For natural specimens,fitting degree of energy damage model was 0.96.For specimens immersed in water for 12 d,fitting degree of energy damage model was 0.96.For specimens immersed in water for 62 d,fitting degree of energy damage model was 0.72.Therefore,an energy damage model had more remarkable applicability and reliability.By establishing dynamic mapping relationship between energy and damage in the model,accuracy of rockburst early warning has been significantly improved.This provided scientific basis for support structure design of rectangular tunnels and regulation of high strain energy.
基金financially supported by National Natural Science Foundation of China(Grant Nos.52378401,52278504)the Fundamental Research Funds for the Central Universities(Grant No.30922010918)。
文摘Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.
基金supported by the National Key Research&Development Program of China(Grant No.2023YFC3008404)the Key Laboratory of Earth Fissures Geological Disaster,Ministry of Natural Resources,China(Grant Nos.EFGD20240609 and EFGD20240610).
文摘The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,in combination with numerical simulation,was conducted to investigate the influence of ground fissures on a metro shield tunnel.The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall,resulting in a two-dimensional stress state of vertical shear and axial tension-compression,and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure.In addition,the damage to curved bolts includes tensile yield,flexural yield,and shear twist,leading to obvious concrete lining damage,particularly at the vault,arch bottom,and hance,indicating that the joints in these positions are weak areas.The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure,suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm,and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced.This study could provide a reference for metro design in ground fissure sites.
基金financially supported by the National Key Research and Development Program of China(Grant Nos.2023YFB2604005)the National Key Research and Development 451 Program of China(Grant No.2021YFC3100803)the Yangtze River Water Science Research Joint Fund Key Project of National Natural Science Foundation of China(Grant No.U2340231).
文摘Polyurethane foam,when used as a compressible layer in deep soft rock tunnels,offers a feasible solution to reduce the support pressure on the secondary lining.The foam spraying method using sprayed polyurethane material is convenient for engineering applications;however,the compressive behaviour and feasibility of sprayed polyurethane material as a compressible layer remain unclear.To address this gap,this study conducts uniaxial compression tests and scanning electron microscope(SEM)tests to investigate the compressive behaviour of the rigid foams fabricated from a self-developed polyurethane spray material.A peridynamics model for the composite lining with a polyurethane compressible layer is then established.After validating the proposed method by comparison with two tests,a parametric study is carried out to investigate the damage evolution of the composite lining with a polyurethane compressible layer under various combinations of large deformations and compressible layer parameters.The results indicate that the polyurethane compressible layer effectively reduces the radial deformation and damage index of the secondary lining while increasing the damage susceptibility of the primary lining.The thickness of the polyurethane compressible layer significantly influences the prevention effect of large deformation-induced damage to the secondary lining within the density range of 50e100 kg/m^(3).In accordance with the experimental and simulation results,a simple,yet reasonable and convenient approach for determining the key parameters of the polyurethane compressible layer is proposed,along with a classification scheme for the parameters of the polyurethane compressible layer.
