This work presents a grounding protection system of the central solenoid model coil(CSMC)of the Comprehensive Research Facility for Fusion Technology(CRAFT).The scheme of neutral point voltage detections has been adop...This work presents a grounding protection system of the central solenoid model coil(CSMC)of the Comprehensive Research Facility for Fusion Technology(CRAFT).The scheme of neutral point voltage detections has been adopted in grounding protection system.Compared with the usual current acquisition,the measurement data is accurate,there is no redundant loop,and the economic benefit is high.In this study,the single-end and double-end grounding fault protections of superconducting magnet coil are analyzed,and the fault voltage and current under different fault conditions are calculated.The simulation model of CSMC magnet grounding fault is established,and the simulation results of the model are basically consistent with the theoretical calculation.Finally,a small capacity experiment platform is used to verify the function of the grounding protection system.The experimental results show that by comparing the neutral fault sampling voltage with the theoretical grounding protection threshold,the grounding protection system can effectively detect different types of grounding faults and transmit signals to the control system to protect the coils of superconducting magnets.展开更多
Under complex flight conditions,such as obstacle avoidance and extreme sea state,wing-in-ground(WIG)effect aircraft need to ascend to higher altitudes,resulting in the disappearance of the ground effect.A design of hi...Under complex flight conditions,such as obstacle avoidance and extreme sea state,wing-in-ground(WIG)effect aircraft need to ascend to higher altitudes,resulting in the disappearance of the ground effect.A design of high-speed WIG airfoil considering non-ground effect is carried out by a novel two-step inverse airfoil design method that combines conditional generative adversarial network(CGAN)and artificial neural network(ANN).The CGAN model is employed to generate a variety of airfoil designs that satisfy the desired lift-drag ratios in both ground effect and non-ground effect conditions.Subsequently,the ANN model is utilized to forecast aerodynamic parameters of the generated airfoils.The results indicate that the CGAN model contributes to a high accuracy rate for airfoil design and enables the creation of novel airfoil designs.Furthermore,it demonstrates high accuracy in predicting aerodynamic parameters of these airfoils due to the ANN model.This method eliminates the necessity for numerical simulations and experimental testing through the design procedure,showcasing notable efficiency.The analysis of airfoils generated by the CGAN model shows that airfoils exhibiting high lift-drag ratios under both flight conditions typically have cambers of among[0.08c,0.105c],with the positions of maximum camber occurring among[0.35c,0.5c]of the chord length,and the leading-edge radiuses of these airfoils primarily cluster among[0.008c,0.025c]展开更多
Backfill is often employed in mining operations for ground support,with its positive impact on ground stability acknowledged in many underground mines.However,existing studies have predominantly focused only on the st...Backfill is often employed in mining operations for ground support,with its positive impact on ground stability acknowledged in many underground mines.However,existing studies have predominantly focused only on the stress development within the backfill material,leaving the influence of stope backfilling on stress distribution in surrounding rock mass and ground stability largely unexplored.Therefore,this paper presents numerical models in FLAC3D to investigate,for the first time,the time-dependent stress redistribution around a vertical backfilled stope and its implications on ground stability,considering the creep of surrounding rock mass.Using the Soft Soil constitutive model,the compressibility of backfill under large pressure was captured.It is found that the creep deformation of rock mass exercises compression on backfill and results in a less void ratio and increased modulus for fill material.The compacted backfill conversely influenced the stress distribution and ground stability of rock mass which was a combined effect of wall creep and compressibility of backfill.With the increase of time or/and creep deformation,the minimum principal stress in the rocks surrounding the backfilled stope increased towards the pre-mining stress state,while the deviatoric stress reduces leading to an increased factor of safety and improved ground stability.This improvement effect of backfill on ground stability increased with the increase of mine depth and stope height,while it is also more pronounced for the narrow stope,the backfill with a smaller compression index,and the soft rocks with a smaller viscosity coefficient.Furthermore,the results emphasize the importance of minimizing empty time and backfilling extracted stope as soon as possible for ground control.Reduction of filling gap height enhances the local stability around the roof of stope.展开更多
The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield...The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.展开更多
Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,i...Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.展开更多
The level of ground shaking,as determined by the peak ground acceleration(PGA),can be used to analyze seismic hazard at a certain location and is crucial for constructing earthquake-resistant structures.Predicting the...The level of ground shaking,as determined by the peak ground acceleration(PGA),can be used to analyze seismic hazard at a certain location and is crucial for constructing earthquake-resistant structures.Predicting the PGA immediately after an earthquake occurs allows for the issuing of a warning by an earthquake early warning system.In this study,we propose a deep learning model,ConvMixer,to predict the PGA recorded by weak-motion velocity seismometers in Japan.We use 5-s threecomponent seismograms,from 2 s before until 3 s after the P-wave arrival time of the earthquake.Our dataset comprised more than 50,000 single-station waveforms recorded by 10 seismic stations in the K-NET,Kiki-NET,and Hi-Net networks between 2004 and 2023.The proposed ConvMixer is a patch-based model that extracts global features from input seismic data and predicts the PGA of an earthquake by combining depth and pointwise convolutions.The proposed ConvMixer network had a mean absolute error of 2.143 when applied to the test set and outperformed benchmark deep learning models.In addition,the proposed ConvMixer demonstrated the ability to predict the PGA at the corresponding station site based on 1-second waveforms obtained immediately after the arrival time of the P-wave.展开更多
This article studies a class of nonlinear Kirchhoff equations with exponential critical growth,trapping potential,and perturbation.Under appropriate assumptions about f and h,the article obtained the existence of norm...This article studies a class of nonlinear Kirchhoff equations with exponential critical growth,trapping potential,and perturbation.Under appropriate assumptions about f and h,the article obtained the existence of normalized positive solutions for this equation via the Trudinger-Moser inequality and variational methods.Moreover,these solutions are also ground state solutions.Additionally,the article also characterized the asymptotic behavior of solutions.The results of this article expand the research of relevant literature.展开更多
[Objective]Implementation of the Ten-Year Fishing Ban policy may alter fish diversity and niche characteristics of dominant species in spawning grounds within the National Nature Reserve for Rare and Endemic Fish in t...[Objective]Implementation of the Ten-Year Fishing Ban policy may alter fish diversity and niche characteristics of dominant species in spawning grounds within the National Nature Reserve for Rare and Endemic Fish in the Upper Yangtze River.This study initiated continuous monitoring of natural spawning habitats from February 2022 to assess these ecological changes.[Methods]Environmental DNA(eDNA)metabarcoding was employed to analyze fish species composition,biodiversity patterns,and niche parameters of dominant species.Water sampling followed the CEN/TS 19461 standard across five monitoring transects(ZT1-ZT5).[Results]The eDNA analysis detected 45 species of fish belonging to 38 genera,13 families,and 3 orders were detected through environmental DNA(eDNA)in this survey,including 10 species endemic to the upper reaches of the Yangtze River,such as Procypris rabaudi and Myxocyprinus asiaticus.The fish community was mainly composed of bottom-dwelling,settling ovum-producing,omnivorous fish.The variation ranges of the Chao1 index,ACE index,Shannon index,and Simpson index are 736~996,719~965,1.58~3.23,and 0.83~0.99,respectively,indicating that fish species in spawning sites are abundant and community distribution uniformity is high.All indexes are highest at ZT1 monitoring points.Cluster analysis showed that,at a certain similarity level,fish community types in spawning sites could be basically divided into two groups:ZT1,ZT3,and ZT5 clustered together,and ZT2 and ZT4 clustered together,indicating similar fish community habitats.There are 9 dominant fish species in typical deep pool habitats in the reserve,with niche widths(Bi)ranging from 1.13 to 3.87.The dominant fish species are broad and medium niche fish,such as Cyprinus carpio and Hemiculter tchangi,with the niche overlap index(Oik)of some dominant fish species reaching more than 0.95.This indicates fierce competition for resources among the fish in this spawning ground.[Conclusion]The Zhutuo spawning ground demonstrates high species richness with homogeneous community structure and intense resource competition.This study establishes an eDNA-based monitoring framework that enhances conventional survey method,providing critical baseline data for adaptive management under the fishing moratorium regime.展开更多
Objectives:This study aimed to generate a theoretical framework based on empirical data to explain the behavioral patterns closely related to young and middle-aged patients with lymphoma throughout the disease.Methods...Objectives:This study aimed to generate a theoretical framework based on empirical data to explain the behavioral patterns closely related to young and middle-aged patients with lymphoma throughout the disease.Methods:This study followed the classic grounded theory methodology,involving procedures such as theoretical sampling,substantive coding,theoretical coding,constant comparison,and memo writing and sorting.Multiple data types were used based on the principle of“all is data,”including 34 participants providing interview data along with observation notes and 40 relevant secondary texts from the“Lymphoma House”network platform and the“Lymphoma House 086”public account.Two autobiographical books written by lymphoma patients were also selected as data resources.Data collection and analysis were conducted in an iterative process until theoretical saturation was reached.The COREQ checklist was followed to report this study.Results:The main concern of middle-aged and young patients with lymphoma was identifiedas restoring normality,while managing uncertainty was the main behavioral pattern for restoring normality.Uncertainty consists of two interrelated types:inherent uncertainty of illness and perceived uncertainty of patients.Four strategies are used to manage uncertainty:reconstructing certainty,adaptive coping,defensive buffering,and compensatory changing.Managing uncertainty is influenced by disease characteristics and perceptions,social resources,and cultural concepts.The consequence of managing uncertainty is reaching a new normality.Conclusions:Pervasive uncertainty significantly affects the daily lives of young and middle-aged patients with lymphoma.Consequently,strategies for managing disease-related uncertainty to sustain normality are commonly observed in this population.This theoretical framework for addressing uncertainty can serve as a foundation for understanding and developing tailored interventions to manage uncertainty.Future research should focus on managing uncertainty to help patients restore normality.展开更多
With recent technological advancements,tunnel boring machines(TBM)have developed and exhibited high performance in large diameters and weak ground conditions.Tunnels are crucial structures that significantly influence...With recent technological advancements,tunnel boring machines(TBM)have developed and exhibited high performance in large diameters and weak ground conditions.Tunnels are crucial structures that significantly influence the timelines of highway and railway projects.Therefore,the construction of tunnels with TBMs becomes a preferred option.In this study,a comparative analysis between TBM and the New Austrian Tunneling Method(NATM)for tunnel construction is performed in the construction of the T1 tunnel with a diameter of 13 m,which is the longest tunnel in the E?me-Salihli section of Ankara-izmir High-Speed Railway Project(Türkiye).The selection of TBM type,measures taken in problematic sections,and application issues of TBM are discussed.The impact of correct description of geological and geotechnical conditions on both selection and performance of TBM is presented.An earth pressure balanced type TBM is chosen for the construction of the T1 tunnel.Because of the additional engineering measures taken before excavation in problematic areas,the tunnel was completed with great success within the initially planned timeframe.From this point of view,this study is an important case and may contribute to worldwide tunneling literature.展开更多
A three-dimensional coupled sea ice-ice shelf-ocean numerical model is developed for the Prydz Bay,Antarctica,using the Regional Ocean Modeling System with a grid resolution of approximately 2 km.The influence of the ...A three-dimensional coupled sea ice-ice shelf-ocean numerical model is developed for the Prydz Bay,Antarctica,using the Regional Ocean Modeling System with a grid resolution of approximately 2 km.The influence of the grounding giant iceberg D15 on the distribution of sea ice and polynyas in the Prydz Bay is analyzed through two numerical experiments.Iceberg D15,grounded off the western edge of the West Ice Shelf(WIS),obstructs the southwestward transport of sea ice along the east coast of Prydz Bay,causing sea ice to accumulate to the east of the iceberg and form multi-year fast ice.Grounding of Iceberg D15 also decreases sea ice coverage off its south edge and creates ice-free openings in spring near Davis Station and Zhongshan Station,facilitating the accessibility of vessels to the research stations.These simulated sea ice patterns closely match current satellite observations.When Iceberg D15 is removed,the previously blocked sea ice north of the iceberg,which moved westward,shifts southwesterly along the coastline,leading to a reduction in sea ice thickness during winter and spring,as well as lower sea ice concentrations in spring across large areas north and west of the iceberg.In contrast,the sea ice thickness increases considerably southwest of the WIS,extending to the front of the Amery Ice Shelf during seasons covered by sea ice.The increase in sea ice concentration can also extend to as far as 75°E in spring.Without Iceberg D15,which previously contributed to the ice barrier of Barrier Polynya(BP),the shape of BP changes,the area of BP and Davis Polynya(DP)decreases,and the polynya off the northwest edge of the WIS near 83°E expands.These polynya patterns are much similar to the satellite remote sensing observations before Iceberg D15 was grounded.From April to October,the total area of BP and DP decreases by 2.83×10^(4)km^(2)(60%)and 2.20×10^(3)km^(2)(20%),respectively,while the total sea ice production decreases by 4.11×10^(10)m^(3)(66%)and 1.52×10^(10)m^(3)(52%)compared to the experiment with iceberg.These results indicate the substantial effects of grounding giant icebergs on the spatio-temporal distribution of sea ice,the area of polynyas,and sea ice production.High-resolution Antarctic coastal numerical models,typically with grid scales of kilometers,are sufficient to represent large icebergs,and adding the grounding giant icebergs is crucial for producing realistic simulations of sea ice and polynyas.展开更多
A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state ...A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state of the medium and low speed maglev coupled system by the additional deformation of the maglev track.This study investigated the dynamic properties of the coupled vibration system affected by the subgrade settlement.First,a theoretical coupled vibration model of a maglev train-track-ground girder system with uneven subgrade settlement was proposed and verified.Then,the effect mechanism of the coupled system caused by the uneven subgrade settlement was explored.Finally,settlement types and subgrade support voiding were examined.The analysis showed that the uneven subgrade settlement considerably increased the dynamic responses of the levitation control system and maglev vehicle while having a minor influence on those of the track-ground girder.The influence of a single ground girder settling was the strongest,and adjacent sides’settling of two ground girders was the weakest for the vibration of a maglev train.An extremely large uneven settlement exceeding 6 mm led to active levitation control system instability.The subgrade support voiding enlarged the vehicle-induced vibration of the track ground girder.展开更多
Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissur...Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissure area was developed and validated by using experimental results.Numerical analyses were conducted to investigate the seismic response and failure mode of subway stations in a ground fissure area with different locations.Effects of ground fissure on deformations and internal forces of a station,soil pressures and soil plastic strains were discussed.The results showed that the seismic response of the station was significantly amplified by the ground fissure,and stations in the ground fissure area displayed obvious rocking deformation during earthquakes as compared to those in the area without fissures.It also was found that the soil yielding around the station,the dislocation occurring in the ground fissure area,and the dynamic amplification effect were more significant under vertical ground motion,which weakened the station’s ductility and accelerated its destruction process.展开更多
Pre-injection is a technique that involves injecting grout materials into the ground prior to excavation,with the aim of stabilizing the surrounding rock mass.This paper introduces an analytical closed-form model for ...Pre-injection is a technique that involves injecting grout materials into the ground prior to excavation,with the aim of stabilizing the surrounding rock mass.This paper introduces an analytical closed-form model for determining the ground reaction curve of tunnels in rock masses exhibiting elastic-brittleplastic behavior and adhering to the Mohr-Coulomb failure criterion.The model incorporates the reinforced region created by the pre-injection method.When the rock mass is reinforced through preinjection,plastic regions can form independently in both the natural and injected rock masses.This leads to six distinct modes of the problem.The analytical model presented in this paper considers three possible scenarios for the development of plastic regions.Each scenario comprises four stages,with each stage representing a different mode of the problem.While injecting the rock mass can enhance its strength and stiffness,it may also increase the brittleness of the injected rock mass and create stress concentrations within it,particularly when brittle grouts are used.As a result,this can elevate the risk of rockburst due to unstable failure.The results obtained from the model demonstrate that ductile grout performs exceptionally well in controlling tunnel convergence in rock masses,as it accommodates deformation without sudden failure,even in squeezing rock mass conditions.Conversely,the use of brittle grouts should be approached with caution,particularly in squeezing rock masses,due to their susceptibility to rockburst incidents.展开更多
This paper presents the design and ground verification for vision-based relative navigation systems of microsatellites,which offers a comprehensive hardware design solution and a robust experimental verification metho...This paper presents the design and ground verification for vision-based relative navigation systems of microsatellites,which offers a comprehensive hardware design solution and a robust experimental verification methodology for practical implementation of vision-based navigation technology on the microsatellite platform.Firstly,a low power consumption,light weight,and high performance vision-based relative navigation optical sensor is designed.Subsequently,a set of ground verification system is designed for the hardware-in-the-loop testing of the vision-based relative navigation systems.Finally,the designed vision-based relative navigation optical sensor and the proposed angles-only navigation algorithms are tested on the ground verification system.The results verify that the optical simulator after geometrical calibration can meet the requirements of the hardware-in-the-loop testing of vision-based relative navigation systems.Based on experimental results,the relative position accuracy of the angles-only navigation filter at terminal time is increased by 25.5%,and the relative speed accuracy is increased by 31.3% compared with those of optical simulator before geometrical calibration.展开更多
Solar energy is a pivotal clean energy source in the transition to carbon neutrality from fossil fuels.However,the intermittent and stochastic characteristics of solar radiation pose challenges for accurate simulation...Solar energy is a pivotal clean energy source in the transition to carbon neutrality from fossil fuels.However,the intermittent and stochastic characteristics of solar radiation pose challenges for accurate simulation and prediction.Accurately simulating and predicting solar radiation and its variability are crucial for optimizing solar energy utilization.This study conducted simulation experiments using the WRF-Solar model from 25 June to 25 July 2022,to evaluate the accuracy and performance of the simulated solar radiation across China.The simulations covered the whole country with a grid spacing of 27 km and were compared with ground observation network data from the Chinese Ecosystem Research Network.The results indicated that WRF-Solar can accurately capture the spatiotemporal patterns of global horizontal irradiance over China,but there is still an overestimation of solar radiation,and the model underestimates the total cloud cover.The root-mean-square error ranged from 92.83 to 188.13 W m^(-2) and the mean bias(MB)ranged from 21.05 to 56.22 W m^(-2).The simulation showed the smallest MB at Lhasa on the Qinghai–Tibet Plateau,while the largest MB was observed in Southeast China.To enhance the accuracy of solar radiation simulation,the authors compared the Fast All-sky Radiation Model for Solar with the Rapid Radiative Transfer Model for General Circulation Models and found that the former provides better simulation.展开更多
Blast-induced ground vibration,quantified by peak particle velocity(PPV),is a crucial factor in mitigating environmental and structural risks in mining and geotechnical engineering.Accurate PPV prediction facilitates ...Blast-induced ground vibration,quantified by peak particle velocity(PPV),is a crucial factor in mitigating environmental and structural risks in mining and geotechnical engineering.Accurate PPV prediction facilitates safer and more sustainable blasting operations by minimizing adverse impacts and ensuring regulatory compliance.This study presents an advanced predictive framework integrating Cat Boost(CB)with nature-inspired optimization algorithms,including the Bat Algorithm(BAT),Sparrow Search Algorithm(SSA),Butterfly Optimization Algorithm(BOA),and Grasshopper Optimization Algorithm(GOA).A comprehensive dataset from the Sarcheshmeh Copper Mine in Iran was utilized to develop and evaluate these models using key performance metrics such as the Index of Agreement(IoA),Nash-Sutcliffe Efficiency(NSE),and the coefficient of determination(R^(2)).The hybrid CB-BOA model outperformed other approaches,achieving the highest accuracy(R^(2)=0.989)and the lowest prediction errors.SHAP analysis identified Distance(Di)as the most influential variable affecting PPV,while uncertainty analysis confirmed CB-BOA as the most reliable model,featuring the narrowest prediction interval.These findings highlight the effectiveness of hybrid machine learning models in refining PPV predictions,contributing to improved blast design strategies,enhanced structural safety,and reduced environmental impacts in mining and geotechnical engineering.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
Ground reinforcement is crucial for tunnel construction, especially in soft rock tunnels. Existing analytical models are inadequate for predicting the ground reaction curves (GRCs) for reinforced tunnels in strain-sof...Ground reinforcement is crucial for tunnel construction, especially in soft rock tunnels. Existing analytical models are inadequate for predicting the ground reaction curves (GRCs) for reinforced tunnels in strain-softening (SS) rock masses. This study proposes a novel analytical model to determine the GRCs of SS rock masses, incorporating ground reinforcement and intermediate principal stress (IPS). The SS constitutive model captures the progressive post- peak failure, while the elastic-brittle model simulates reinforced rock masses. Nine combined states are innovatively investigated to analyze plastic zone development in natural and reinforced regions. Each region is analyzed separately, and coupled through boundary conditions at interface. Comparison with three types of existing models indicates that these models overestimate reinforcement effects. The deformation prediction errors of single geological material models may exceed 75%. Furthermore, neglecting softening and residual zones in natural regions could lead to errors over 50%. Considering the IPS can effectively utilize the rock strength to reduce tunnel deformation by at least 30%, thereby saving on reinforcement and support costs. The computational results show a satisfactory agreement with the monitoring data from a model test and two tunnel projects. The proposed model may offer valuable insights into the design and construction of reinforced tunnel engineering.展开更多
With the rapid urbanization process,ground collapses caused by anthropogenic activities occur frequently.Accurate susceptibility mapping is of great significance for disaster prevention and control.In this study,1198 ...With the rapid urbanization process,ground collapses caused by anthropogenic activities occur frequently.Accurate susceptibility mapping is of great significance for disaster prevention and control.In this study,1198 ground collapse cases in Shenzhen from 2017 to 2020 were collected.Eight effective factors(elevation,relief,clay proportion,average annual precipitation,distance from water,land use type,building density,and road density)were selected to construct the evaluation index system.Ground collapse susceptibility was analyzed and mapped using the normalized frequency ratio(NFR),logistic regression(LR),and NFR-LR coupling models.Finally,the result rationality and performance of the three models were compared through frequency ratio(FR)and ROC curve.The results indicate that all three models can effectively evaluate the ground collapse susceptibility(AUC>0.7),and the NFR-LR model result is more rational and has the best performance(AUC=0.791).The very high and high susceptibility zones cover a total area of 545.68 km^(2) and involve Nanshan,Luohu,and Futian District,as well as some areas of Baoan,Guangming,and Longgang District.The ground collapses in Shenzhen mainly occurred in the built-up areas,and the greater intensity of anthropogenic activities,the more susceptible to the disaster.展开更多
文摘This work presents a grounding protection system of the central solenoid model coil(CSMC)of the Comprehensive Research Facility for Fusion Technology(CRAFT).The scheme of neutral point voltage detections has been adopted in grounding protection system.Compared with the usual current acquisition,the measurement data is accurate,there is no redundant loop,and the economic benefit is high.In this study,the single-end and double-end grounding fault protections of superconducting magnet coil are analyzed,and the fault voltage and current under different fault conditions are calculated.The simulation model of CSMC magnet grounding fault is established,and the simulation results of the model are basically consistent with the theoretical calculation.Finally,a small capacity experiment platform is used to verify the function of the grounding protection system.The experimental results show that by comparing the neutral fault sampling voltage with the theoretical grounding protection threshold,the grounding protection system can effectively detect different types of grounding faults and transmit signals to the control system to protect the coils of superconducting magnets.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,the Fundamental Research Funds for the Central Universities(No.ILA220101A23)CARDC Fundamental and Frontier Technology Research Fund(No.PJD20200210)the Aeronautical Science Foundation of China(No.20200023052002).
文摘Under complex flight conditions,such as obstacle avoidance and extreme sea state,wing-in-ground(WIG)effect aircraft need to ascend to higher altitudes,resulting in the disappearance of the ground effect.A design of high-speed WIG airfoil considering non-ground effect is carried out by a novel two-step inverse airfoil design method that combines conditional generative adversarial network(CGAN)and artificial neural network(ANN).The CGAN model is employed to generate a variety of airfoil designs that satisfy the desired lift-drag ratios in both ground effect and non-ground effect conditions.Subsequently,the ANN model is utilized to forecast aerodynamic parameters of the generated airfoils.The results indicate that the CGAN model contributes to a high accuracy rate for airfoil design and enables the creation of novel airfoil designs.Furthermore,it demonstrates high accuracy in predicting aerodynamic parameters of these airfoils due to the ANN model.This method eliminates the necessity for numerical simulations and experimental testing through the design procedure,showcasing notable efficiency.The analysis of airfoils generated by the CGAN model shows that airfoils exhibiting high lift-drag ratios under both flight conditions typically have cambers of among[0.08c,0.105c],with the positions of maximum camber occurring among[0.35c,0.5c]of the chord length,and the leading-edge radiuses of these airfoils primarily cluster among[0.008c,0.025c]
基金the funding support from the National Natural Science Foundation of China(Grant Nos.52304101 and 52004206)the China Postdoctoral Science Foundation(Grant No.2023MD734215)。
文摘Backfill is often employed in mining operations for ground support,with its positive impact on ground stability acknowledged in many underground mines.However,existing studies have predominantly focused only on the stress development within the backfill material,leaving the influence of stope backfilling on stress distribution in surrounding rock mass and ground stability largely unexplored.Therefore,this paper presents numerical models in FLAC3D to investigate,for the first time,the time-dependent stress redistribution around a vertical backfilled stope and its implications on ground stability,considering the creep of surrounding rock mass.Using the Soft Soil constitutive model,the compressibility of backfill under large pressure was captured.It is found that the creep deformation of rock mass exercises compression on backfill and results in a less void ratio and increased modulus for fill material.The compacted backfill conversely influenced the stress distribution and ground stability of rock mass which was a combined effect of wall creep and compressibility of backfill.With the increase of time or/and creep deformation,the minimum principal stress in the rocks surrounding the backfilled stope increased towards the pre-mining stress state,while the deviatoric stress reduces leading to an increased factor of safety and improved ground stability.This improvement effect of backfill on ground stability increased with the increase of mine depth and stope height,while it is also more pronounced for the narrow stope,the backfill with a smaller compression index,and the soft rocks with a smaller viscosity coefficient.Furthermore,the results emphasize the importance of minimizing empty time and backfilling extracted stope as soon as possible for ground control.Reduction of filling gap height enhances the local stability around the roof of stope.
基金financially supported by the National Natural Science Foundation of China(Grant No.52078334)the National Key Research and Development Program of China(Grant No.2017YFC0805402)the Tianjin Research Innovation Project for Postgraduate Students(Grant No.2021YJSB141).
文摘The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.
基金supported by 2024 Central Guidance Local Science and Technology Development Fund Project"Study on the mechanism and evaluation method of thermal pollution in water bodies,as well as research on thermal carrying capacity".(Grant 246Z4506G)Key Research and Development Project in Hebei Province:"Key Technologies and Equipment Research and Demonstration of Multiple Energy Complementary(Electricity,Heat,Cold System)for Solar Energy,Geothermal Energy,Phase Change Energy"(Grant 236Z4310G)the Hebei Academy of Sciences Key Research and Development Program"Research on Heat Transfer Mechanisms and Efficient Applications of Intermediate and Deep Geothermal Energy"(22702)。
文摘Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.
基金the National Research Institute of Astronomy and Geophysics (NRIAG) for supporting this work
文摘The level of ground shaking,as determined by the peak ground acceleration(PGA),can be used to analyze seismic hazard at a certain location and is crucial for constructing earthquake-resistant structures.Predicting the PGA immediately after an earthquake occurs allows for the issuing of a warning by an earthquake early warning system.In this study,we propose a deep learning model,ConvMixer,to predict the PGA recorded by weak-motion velocity seismometers in Japan.We use 5-s threecomponent seismograms,from 2 s before until 3 s after the P-wave arrival time of the earthquake.Our dataset comprised more than 50,000 single-station waveforms recorded by 10 seismic stations in the K-NET,Kiki-NET,and Hi-Net networks between 2004 and 2023.The proposed ConvMixer is a patch-based model that extracts global features from input seismic data and predicts the PGA of an earthquake by combining depth and pointwise convolutions.The proposed ConvMixer network had a mean absolute error of 2.143 when applied to the test set and outperformed benchmark deep learning models.In addition,the proposed ConvMixer demonstrated the ability to predict the PGA at the corresponding station site based on 1-second waveforms obtained immediately after the arrival time of the P-wave.
基金Supported by National Natural Science Foundation of China(11671403,11671236)Henan Provincial General Natural Science Foundation Project(232300420113)。
文摘This article studies a class of nonlinear Kirchhoff equations with exponential critical growth,trapping potential,and perturbation.Under appropriate assumptions about f and h,the article obtained the existence of normalized positive solutions for this equation via the Trudinger-Moser inequality and variational methods.Moreover,these solutions are also ground state solutions.Additionally,the article also characterized the asymptotic behavior of solutions.The results of this article expand the research of relevant literature.
文摘[Objective]Implementation of the Ten-Year Fishing Ban policy may alter fish diversity and niche characteristics of dominant species in spawning grounds within the National Nature Reserve for Rare and Endemic Fish in the Upper Yangtze River.This study initiated continuous monitoring of natural spawning habitats from February 2022 to assess these ecological changes.[Methods]Environmental DNA(eDNA)metabarcoding was employed to analyze fish species composition,biodiversity patterns,and niche parameters of dominant species.Water sampling followed the CEN/TS 19461 standard across five monitoring transects(ZT1-ZT5).[Results]The eDNA analysis detected 45 species of fish belonging to 38 genera,13 families,and 3 orders were detected through environmental DNA(eDNA)in this survey,including 10 species endemic to the upper reaches of the Yangtze River,such as Procypris rabaudi and Myxocyprinus asiaticus.The fish community was mainly composed of bottom-dwelling,settling ovum-producing,omnivorous fish.The variation ranges of the Chao1 index,ACE index,Shannon index,and Simpson index are 736~996,719~965,1.58~3.23,and 0.83~0.99,respectively,indicating that fish species in spawning sites are abundant and community distribution uniformity is high.All indexes are highest at ZT1 monitoring points.Cluster analysis showed that,at a certain similarity level,fish community types in spawning sites could be basically divided into two groups:ZT1,ZT3,and ZT5 clustered together,and ZT2 and ZT4 clustered together,indicating similar fish community habitats.There are 9 dominant fish species in typical deep pool habitats in the reserve,with niche widths(Bi)ranging from 1.13 to 3.87.The dominant fish species are broad and medium niche fish,such as Cyprinus carpio and Hemiculter tchangi,with the niche overlap index(Oik)of some dominant fish species reaching more than 0.95.This indicates fierce competition for resources among the fish in this spawning ground.[Conclusion]The Zhutuo spawning ground demonstrates high species richness with homogeneous community structure and intense resource competition.This study establishes an eDNA-based monitoring framework that enhances conventional survey method,providing critical baseline data for adaptive management under the fishing moratorium regime.
基金supported by the Postgraduate Supervision Fund within the School of Nursing at Fujian Medical University(No.110013)。
文摘Objectives:This study aimed to generate a theoretical framework based on empirical data to explain the behavioral patterns closely related to young and middle-aged patients with lymphoma throughout the disease.Methods:This study followed the classic grounded theory methodology,involving procedures such as theoretical sampling,substantive coding,theoretical coding,constant comparison,and memo writing and sorting.Multiple data types were used based on the principle of“all is data,”including 34 participants providing interview data along with observation notes and 40 relevant secondary texts from the“Lymphoma House”network platform and the“Lymphoma House 086”public account.Two autobiographical books written by lymphoma patients were also selected as data resources.Data collection and analysis were conducted in an iterative process until theoretical saturation was reached.The COREQ checklist was followed to report this study.Results:The main concern of middle-aged and young patients with lymphoma was identifiedas restoring normality,while managing uncertainty was the main behavioral pattern for restoring normality.Uncertainty consists of two interrelated types:inherent uncertainty of illness and perceived uncertainty of patients.Four strategies are used to manage uncertainty:reconstructing certainty,adaptive coping,defensive buffering,and compensatory changing.Managing uncertainty is influenced by disease characteristics and perceptions,social resources,and cultural concepts.The consequence of managing uncertainty is reaching a new normality.Conclusions:Pervasive uncertainty significantly affects the daily lives of young and middle-aged patients with lymphoma.Consequently,strategies for managing disease-related uncertainty to sustain normality are commonly observed in this population.This theoretical framework for addressing uncertainty can serve as a foundation for understanding and developing tailored interventions to manage uncertainty.Future research should focus on managing uncertainty to help patients restore normality.
文摘With recent technological advancements,tunnel boring machines(TBM)have developed and exhibited high performance in large diameters and weak ground conditions.Tunnels are crucial structures that significantly influence the timelines of highway and railway projects.Therefore,the construction of tunnels with TBMs becomes a preferred option.In this study,a comparative analysis between TBM and the New Austrian Tunneling Method(NATM)for tunnel construction is performed in the construction of the T1 tunnel with a diameter of 13 m,which is the longest tunnel in the E?me-Salihli section of Ankara-izmir High-Speed Railway Project(Türkiye).The selection of TBM type,measures taken in problematic sections,and application issues of TBM are discussed.The impact of correct description of geological and geotechnical conditions on both selection and performance of TBM is presented.An earth pressure balanced type TBM is chosen for the construction of the T1 tunnel.Because of the additional engineering measures taken before excavation in problematic areas,the tunnel was completed with great success within the initially planned timeframe.From this point of view,this study is an important case and may contribute to worldwide tunneling literature.
基金The National Natural Science Foundation of China under contract Nos 41976217 and 42306249the National Key Research and Development Program of China under contract No.2018YFA0605701.
文摘A three-dimensional coupled sea ice-ice shelf-ocean numerical model is developed for the Prydz Bay,Antarctica,using the Regional Ocean Modeling System with a grid resolution of approximately 2 km.The influence of the grounding giant iceberg D15 on the distribution of sea ice and polynyas in the Prydz Bay is analyzed through two numerical experiments.Iceberg D15,grounded off the western edge of the West Ice Shelf(WIS),obstructs the southwestward transport of sea ice along the east coast of Prydz Bay,causing sea ice to accumulate to the east of the iceberg and form multi-year fast ice.Grounding of Iceberg D15 also decreases sea ice coverage off its south edge and creates ice-free openings in spring near Davis Station and Zhongshan Station,facilitating the accessibility of vessels to the research stations.These simulated sea ice patterns closely match current satellite observations.When Iceberg D15 is removed,the previously blocked sea ice north of the iceberg,which moved westward,shifts southwesterly along the coastline,leading to a reduction in sea ice thickness during winter and spring,as well as lower sea ice concentrations in spring across large areas north and west of the iceberg.In contrast,the sea ice thickness increases considerably southwest of the WIS,extending to the front of the Amery Ice Shelf during seasons covered by sea ice.The increase in sea ice concentration can also extend to as far as 75°E in spring.Without Iceberg D15,which previously contributed to the ice barrier of Barrier Polynya(BP),the shape of BP changes,the area of BP and Davis Polynya(DP)decreases,and the polynya off the northwest edge of the WIS near 83°E expands.These polynya patterns are much similar to the satellite remote sensing observations before Iceberg D15 was grounded.From April to October,the total area of BP and DP decreases by 2.83×10^(4)km^(2)(60%)and 2.20×10^(3)km^(2)(20%),respectively,while the total sea ice production decreases by 4.11×10^(10)m^(3)(66%)and 1.52×10^(10)m^(3)(52%)compared to the experiment with iceberg.These results indicate the substantial effects of grounding giant icebergs on the spatio-temporal distribution of sea ice,the area of polynyas,and sea ice production.High-resolution Antarctic coastal numerical models,typically with grid scales of kilometers,are sufficient to represent large icebergs,and adding the grounding giant icebergs is crucial for producing realistic simulations of sea ice and polynyas.
基金National Natural Science Foundation of China under Grant Nos.52478467and 52108417Guangdong Basic and Applied Basic Research Foundation under Grant No.2024A1515012569the Natural Science Basic Research Program of Shaanxi under Grant No.2021JQ-101。
文摘A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state of the medium and low speed maglev coupled system by the additional deformation of the maglev track.This study investigated the dynamic properties of the coupled vibration system affected by the subgrade settlement.First,a theoretical coupled vibration model of a maglev train-track-ground girder system with uneven subgrade settlement was proposed and verified.Then,the effect mechanism of the coupled system caused by the uneven subgrade settlement was explored.Finally,settlement types and subgrade support voiding were examined.The analysis showed that the uneven subgrade settlement considerably increased the dynamic responses of the levitation control system and maglev vehicle while having a minor influence on those of the track-ground girder.The influence of a single ground girder settling was the strongest,and adjacent sides’settling of two ground girders was the weakest for the vibration of a maglev train.An extremely large uneven settlement exceeding 6 mm led to active levitation control system instability.The subgrade support voiding enlarged the vehicle-induced vibration of the track ground girder.
基金National Natural Science Foundation of China under Grant No.52108473Project of Shaanxi Engineering Technology Research Center for Urban Geology and Underground Space under Grant No.2025KT-03Key Project of Education Department of Shaanxi Province under Grant No.23JY042。
文摘Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissure area was developed and validated by using experimental results.Numerical analyses were conducted to investigate the seismic response and failure mode of subway stations in a ground fissure area with different locations.Effects of ground fissure on deformations and internal forces of a station,soil pressures and soil plastic strains were discussed.The results showed that the seismic response of the station was significantly amplified by the ground fissure,and stations in the ground fissure area displayed obvious rocking deformation during earthquakes as compared to those in the area without fissures.It also was found that the soil yielding around the station,the dislocation occurring in the ground fissure area,and the dynamic amplification effect were more significant under vertical ground motion,which weakened the station’s ductility and accelerated its destruction process.
文摘Pre-injection is a technique that involves injecting grout materials into the ground prior to excavation,with the aim of stabilizing the surrounding rock mass.This paper introduces an analytical closed-form model for determining the ground reaction curve of tunnels in rock masses exhibiting elastic-brittleplastic behavior and adhering to the Mohr-Coulomb failure criterion.The model incorporates the reinforced region created by the pre-injection method.When the rock mass is reinforced through preinjection,plastic regions can form independently in both the natural and injected rock masses.This leads to six distinct modes of the problem.The analytical model presented in this paper considers three possible scenarios for the development of plastic regions.Each scenario comprises four stages,with each stage representing a different mode of the problem.While injecting the rock mass can enhance its strength and stiffness,it may also increase the brittleness of the injected rock mass and create stress concentrations within it,particularly when brittle grouts are used.As a result,this can elevate the risk of rockburst due to unstable failure.The results obtained from the model demonstrate that ductile grout performs exceptionally well in controlling tunnel convergence in rock masses,as it accommodates deformation without sudden failure,even in squeezing rock mass conditions.Conversely,the use of brittle grouts should be approached with caution,particularly in squeezing rock masses,due to their susceptibility to rockburst incidents.
基金supported in part by the Doctoral Initiation Fund of Nanchang Hangkong University(No.EA202403107)Jiangxi Province Early Career Youth Science and Technology Talent Training Project(No.CK202403509).
文摘This paper presents the design and ground verification for vision-based relative navigation systems of microsatellites,which offers a comprehensive hardware design solution and a robust experimental verification methodology for practical implementation of vision-based navigation technology on the microsatellite platform.Firstly,a low power consumption,light weight,and high performance vision-based relative navigation optical sensor is designed.Subsequently,a set of ground verification system is designed for the hardware-in-the-loop testing of the vision-based relative navigation systems.Finally,the designed vision-based relative navigation optical sensor and the proposed angles-only navigation algorithms are tested on the ground verification system.The results verify that the optical simulator after geometrical calibration can meet the requirements of the hardware-in-the-loop testing of vision-based relative navigation systems.Based on experimental results,the relative position accuracy of the angles-only navigation filter at terminal time is increased by 25.5%,and the relative speed accuracy is increased by 31.3% compared with those of optical simulator before geometrical calibration.
基金supported by the National Natural Science Foundation of China[grant number 42175132]the National Key R&D Program[grant number 2020YFA0607802]the CAS Information Technology Program[grant number CAS-WX2021SF-0107-02]。
文摘Solar energy is a pivotal clean energy source in the transition to carbon neutrality from fossil fuels.However,the intermittent and stochastic characteristics of solar radiation pose challenges for accurate simulation and prediction.Accurately simulating and predicting solar radiation and its variability are crucial for optimizing solar energy utilization.This study conducted simulation experiments using the WRF-Solar model from 25 June to 25 July 2022,to evaluate the accuracy and performance of the simulated solar radiation across China.The simulations covered the whole country with a grid spacing of 27 km and were compared with ground observation network data from the Chinese Ecosystem Research Network.The results indicated that WRF-Solar can accurately capture the spatiotemporal patterns of global horizontal irradiance over China,but there is still an overestimation of solar radiation,and the model underestimates the total cloud cover.The root-mean-square error ranged from 92.83 to 188.13 W m^(-2) and the mean bias(MB)ranged from 21.05 to 56.22 W m^(-2).The simulation showed the smallest MB at Lhasa on the Qinghai–Tibet Plateau,while the largest MB was observed in Southeast China.To enhance the accuracy of solar radiation simulation,the authors compared the Fast All-sky Radiation Model for Solar with the Rapid Radiative Transfer Model for General Circulation Models and found that the former provides better simulation.
基金the Deanship of Scientific Research at Northern Border University,Arar,KSA for funding this research work through the project number"NBUFFMRA-2025-2461-09"。
文摘Blast-induced ground vibration,quantified by peak particle velocity(PPV),is a crucial factor in mitigating environmental and structural risks in mining and geotechnical engineering.Accurate PPV prediction facilitates safer and more sustainable blasting operations by minimizing adverse impacts and ensuring regulatory compliance.This study presents an advanced predictive framework integrating Cat Boost(CB)with nature-inspired optimization algorithms,including the Bat Algorithm(BAT),Sparrow Search Algorithm(SSA),Butterfly Optimization Algorithm(BOA),and Grasshopper Optimization Algorithm(GOA).A comprehensive dataset from the Sarcheshmeh Copper Mine in Iran was utilized to develop and evaluate these models using key performance metrics such as the Index of Agreement(IoA),Nash-Sutcliffe Efficiency(NSE),and the coefficient of determination(R^(2)).The hybrid CB-BOA model outperformed other approaches,achieving the highest accuracy(R^(2)=0.989)and the lowest prediction errors.SHAP analysis identified Distance(Di)as the most influential variable affecting PPV,while uncertainty analysis confirmed CB-BOA as the most reliable model,featuring the narrowest prediction interval.These findings highlight the effectiveness of hybrid machine learning models in refining PPV predictions,contributing to improved blast design strategies,enhanced structural safety,and reduced environmental impacts in mining and geotechnical engineering.
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Projects(52208382, 52278387, 51738002) supported by the National Natural Science Foundation of ChinaProject(2022YJS072) supported by the Fundamental Research Funds for the Central Universities,China。
文摘Ground reinforcement is crucial for tunnel construction, especially in soft rock tunnels. Existing analytical models are inadequate for predicting the ground reaction curves (GRCs) for reinforced tunnels in strain-softening (SS) rock masses. This study proposes a novel analytical model to determine the GRCs of SS rock masses, incorporating ground reinforcement and intermediate principal stress (IPS). The SS constitutive model captures the progressive post- peak failure, while the elastic-brittle model simulates reinforced rock masses. Nine combined states are innovatively investigated to analyze plastic zone development in natural and reinforced regions. Each region is analyzed separately, and coupled through boundary conditions at interface. Comparison with three types of existing models indicates that these models overestimate reinforcement effects. The deformation prediction errors of single geological material models may exceed 75%. Furthermore, neglecting softening and residual zones in natural regions could lead to errors over 50%. Considering the IPS can effectively utilize the rock strength to reduce tunnel deformation by at least 30%, thereby saving on reinforcement and support costs. The computational results show a satisfactory agreement with the monitoring data from a model test and two tunnel projects. The proposed model may offer valuable insights into the design and construction of reinforced tunnel engineering.
基金jointed supported by the National Natural Science Foundation of China(Nos.41920104007,41731284)。
文摘With the rapid urbanization process,ground collapses caused by anthropogenic activities occur frequently.Accurate susceptibility mapping is of great significance for disaster prevention and control.In this study,1198 ground collapse cases in Shenzhen from 2017 to 2020 were collected.Eight effective factors(elevation,relief,clay proportion,average annual precipitation,distance from water,land use type,building density,and road density)were selected to construct the evaluation index system.Ground collapse susceptibility was analyzed and mapped using the normalized frequency ratio(NFR),logistic regression(LR),and NFR-LR coupling models.Finally,the result rationality and performance of the three models were compared through frequency ratio(FR)and ROC curve.The results indicate that all three models can effectively evaluate the ground collapse susceptibility(AUC>0.7),and the NFR-LR model result is more rational and has the best performance(AUC=0.791).The very high and high susceptibility zones cover a total area of 545.68 km^(2) and involve Nanshan,Luohu,and Futian District,as well as some areas of Baoan,Guangming,and Longgang District.The ground collapses in Shenzhen mainly occurred in the built-up areas,and the greater intensity of anthropogenic activities,the more susceptible to the disaster.
