Artificially cemented soils have been widely used as filling materials in highway and railway construction.The shear strength evolution of filling materials upon moist variation can determine the stability of subgrade...Artificially cemented soils have been widely used as filling materials in highway and railway construction.The shear strength evolution of filling materials upon moist variation can determine the stability of subgrade and embankments.This study conducted water retention tests,MIP tests,and multi-stage triaxial shear tests on cement-treated granite residual soil(GRS)to determine its water retention curve(WRC)upon free drying,pore structure,and peak shear strength qf,respectively.The water retention behavior and shear strength evolution upon free drying were modeled based on the dual-porosity structure of cement-treated GRS and the effective stress principle,respectively.Results show that the drying-WRC is bimodal and higher cement dosage yields a more severe decrease in the water retention capacity within a specific suction range.For a given confining pressure,the peak shear strength qf increased with increasing cement dosage or suction value s.The peak shear strength qf also solely depends on the suction value in the peak stress state.In addition,the cement-treated GRS has a bimodal pore size distribution curve,and its macro-and micro-void ratios remain almost unchanged after free drying.The bimodal drying-WRC of the cement-treated GRS can be modeled by differentiating the water retention mechanisms in macro-and micro-pores.Moreover,using the macro-pore degree of saturation as the effective stress parameterχ=S_(rM),the q_(f)–p′_(f)relationship(where p′_(f)is the effective mean pressure at failure)under various suction and stress conditions can be unified,and the q_(f)–s relationships at various net confining pressuresσ_(3),net can be well reproduced.These findings can help design subgrade and embankments constructed by artificially cemented GRS and assess their safe operation upon climate change.展开更多
The specialized equipment utilized in long-line tunnel engineering is evolving towards large-scale,multifunctional,and complex orientations.The vibration caused by the high-frequency units during regular operation is ...The specialized equipment utilized in long-line tunnel engineering is evolving towards large-scale,multifunctional,and complex orientations.The vibration caused by the high-frequency units during regular operation is supported by the foundation of the units,and the magnitude of vibration and the operating frequency fluctuate in different engineering contexts,leading to variations in the dynamic response of the foundation.The high-frequency units yield significantly diverse outcomes under different startup conditions and times,resulting in failure to meet operational requirements,influencing the normal function of the tunnel,and causing harm to the foundation structure,personnel,and property in severe cases.This article formulates a finite element numerical computation model for solid elements using three-dimensional elastic body theory and integrates field measurements to substantiate and ascertain the crucial parameter configurations of the finite element model.By proposing a comprehensive startup timing function for high-frequency dynamic machines under different startup conditions,simulating the frequency andmagnitude variations during the startup process,and suggesting functions for changes in frequency and magnitude,a simulated startup schedule function for high-frequency machines is created through coupling.Taking into account the selection of the transient dynamic analysis step length,the dynamic response results for the lower dynamic foundation during its fundamental frequency crossing process are obtained.The validation checks if the structural magnitude surpasses the safety threshold during the critical phase of unit startup traversing the structural resonance region.The design recommendations for high-frequency units’dynamic foundations are provided,taking into account the startup process of the machine and ensuring the safe operation of the tunnel.展开更多
Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,...Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,and solar energy harvesting for glazed facades.In this study,we addressed these conflicts by introducing a new dynamic and vertical photovoltaic integrated building envelope(dvPVBE)that offers extraordinary flexibility with weather-responsive slat angles and blind positions,superior architectural aesthetics,and notable energy-saving potential.Three hierarchical control strategies were proposed for different scenarios of the dvPVBE:power generation priority(PGP),natural daylight priority(NDP),and energy-saving priority(ESP).Moreover,the PGP and ESP strategies were further analyzed in the simulation of a dvPVBE.An office room integrated with a dvPVBE was modeled using EnergyPlus.The influence of the dvPVBE in improving the building energy efficiency and corresponding optimal slat angles was investigated under the PGP and ESP control strategies.The results indicate that the application of dvPVBEs in Beijing can provide up to 131%of the annual energy demand of office rooms and significantly increase the annual net energy output by at least 226%compared with static photovoltaic(PV)blinds.The concept of this novel dvPVBE offers a viable approach by which the thermal load,daylight penetration,and energy generation can be effectively regulated.展开更多
The relationship between environmental quality and economic growth has been a hot topic for decades.After years of rapid industrialization and urbanization,China’s environmental challenges are approaching a turning p...The relationship between environmental quality and economic growth has been a hot topic for decades.After years of rapid industrialization and urbanization,China’s environmental challenges are approaching a turning point.Following the principles of ecological civilization construction,China is on its way to maintaining high-quality and green economic development.On 10 June 2020,the Chinese Government reported the key findings of the Second National General Survey of Pollution Sources(fiscal year 2017),which provides strong quantitative evidence of progress toward ecological civilization.In terms of our comparison between the two National General Surveys in 2007 and 2017,it was found that environmental pollution,measured in terms of many wastewater and air emission pollutant discharges,is decreasing despite the steady growth in economic activities—and at a noticeably fast pace.Other national and local governments can adopt some of China’s ecological civilization practices,within their own individual contexts.展开更多
Sandstorm,which injects generous newly emerging microbes into the atmosphere covering cities,adversely affects the air quality in built environments.However,few studies have examined the change of airborne bacteria du...Sandstorm,which injects generous newly emerging microbes into the atmosphere covering cities,adversely affects the air quality in built environments.However,few studies have examined the change of airborne bacteria during severe sandstorm events.In this work,we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia onMarch 15th,2021,which affected large areas of China and Mongolia.The characteristics of the sandstorm were compared with those of the subsequent clean and haze days.The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction(qPCR)and high-throughput sequencing technology.During the sandstorm,the particulate matter(PM)concentration and bacterial richnesswere extremely high(PM_(2.5):207μg/m^(3);PM_(10):1630μg/m^(3);5700 amplicon sequence variants/m^(3)).In addition,the sandstorm brought 10 pathogenic bacterial genera to the atmosphere,posing a grave hazard to human health.As the sandstorm subsided,small bioaerosols(0.65–1.1μm)with a similar bacterial community remained suspended in the atmosphere,bringing possible long-lasting health risks.展开更多
Flexural performance of joints is critical for prefabricated structures.This study presents a novel channel steel-bolt(CB)joint for prefabricated subway stations.Full-scale tests are carried out to investigate the fle...Flexural performance of joints is critical for prefabricated structures.This study presents a novel channel steel-bolt(CB)joint for prefabricated subway stations.Full-scale tests are carried out to investigate the flexural behavior of the CB joint under the design loads of the test-case station.In addition,a three dimensional(3D)finite element(FE)model of the CB joint is established,incorporating viscous contact to simulate the bonding and detachment behaviors of the interface between channel steel and concrete.Based on the 3D FE model,the study examines the flexural bearing mechanism and influencing factors for the flexural performance of the CB joint.The results indicate that the flexural behavior of the CB joint exhibits significant nonlinear characteristics,which can be divided into four stages.To illustrate the piecewise linearity of the bending moment-rotational angle curve,a four-stage simplified model is proposed,which is easily applicable in engineering practice.The study reveals that axial force can enhance the flexural capacity of the CB joint,while the preload of the bolt has a negligible effect.The flexural capacity of the CB joint is approximate twice the value of the designed bending moment,demonstrating that the joint is suitable for the test-case station.展开更多
Considering that people spend more than 80%of their time indoors,ambient particulate matter(PM)in the built environment could pose severe environmental health risks to public health.PM sampling,a technique for the enr...Considering that people spend more than 80%of their time indoors,ambient particulate matter(PM)in the built environment could pose severe environmental health risks to public health.PM sampling,a technique for the enrichment of PM in the air,is essential for ambient PM composition analysis to understand its environmental and health effect.The filtering method that is widely used features a complex post-processing and carries the risk of pore clogging.It is a great challenge to sample airborne PM efficiently for subsequent analysis.Here,we proposed a novel miniaturized electrostatic sampler based on corona discharge and a modified vertically focused electric field for efficient PM sampling.Four intercoupling physical fields in the developed sampler were analyzed,including corona discharge,airflow,particle charging and particle deposition.The collection efficiencies for particles with various sizes(0.01–10μm)were conducted by simulation and the lowest efficiency occurs at about 0.3–0.5μm.With an increase in discharging voltage from−6 kV to−9 kV,the lowest efficiency rises from 88.2%to 96.6%.An electrostatic sampler entity was manufactured to test the collection efficiency of PM and the results are in good agreement with the simulation.The induced ring plate can significantly improve the total collection efficiency from 35%to 90%under−6 kV discharging voltage in the experiment.The novel electrostatic sampler exhibits potential and enlightenment for efficient and convenient PM sampling.展开更多
This paper presents a case study of the clogging of a slurry-shield tunnel-boring machine(TBM)experienced during tunnel operations in clay-rich argillaceous siltstones under the Ganjiang River,China.The clogging exper...This paper presents a case study of the clogging of a slurry-shield tunnel-boring machine(TBM)experienced during tunnel operations in clay-rich argillaceous siltstones under the Ganjiang River,China.The clogging experienced during tunneling was due to special geological conditions,which had a considerably negative impact on the slurry-shield TBM tunneling performance.In this case study,the effect of clogging on the slurry-shield TBM tunneling performance(e.g.,advance speed,thrust,torque,and penetration per revolution)was fully investigated.The potential for clogging during tunnel operations in argillaceous siltstone was estimated using an existing empirical classification chart.Many improvement measures have been proposed to mitigate the clogging potential of two slurry-shield TBMs during tunneling,such as the use of an optimum cutting wheel,a replacement cutting tool,improvements to the circulation flushing system and slurry properties,mixed support integrating slurry,and compressed air to support the excavation face.The mechanisms and potential causes of clogging are explained in detail,and the contributions of these mitigation measures to tunneling performance are discussed.By investigating the actual operational parameters of the slurry-shield TBMs,these mitigation measures were proven to be effective in mitigating the clogging potential of slurry-shield TBMs.This case study provides valuable information for slurry-shield TBMs involving tunneling in clay-rich sedimentary rocks.展开更多
In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first vali...In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first validated by the results from a full-scale model test.Then,based on the load-structure method,this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening.The influence of loosening position,loosening range,and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses.The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions,thus changing the deformation pattern and force state.After the loosening occurs,the bending moment of the ring in the loosening range increases and the axial force decreases.The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range a is 90°.The vertical convergence of the ring increases with increasing of the loosening extent,and the equivalent stiffness decreases linearly with increasing of the loosening extent.The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening,and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.展开更多
Ground movements caused by the construction of tunnels and excavation are inevitable.Estimation of such movements is a very important for risk management in tunnel design.This paper presents a case study of ground set...Ground movements caused by the construction of tunnels and excavation are inevitable.Estimation of such movements is a very important for risk management in tunnel design.This paper presents a case study of ground settlements induced by twin shield tunnelling in Copenhagen using analytical and numerical methods and their predictions.The predictions are compared with the monitored settlements.The comparison shows that the predictions are sufficiently conservative.展开更多
The presented research introduces a novel hybrid deep learning approach for the dynamic prediction of the attitude and position of super-large diameter shields-a critical consideration for construction safety and tunn...The presented research introduces a novel hybrid deep learning approach for the dynamic prediction of the attitude and position of super-large diameter shields-a critical consideration for construction safety and tunnel lining quality.This study proposes a hybrid deep learning approach for predicting dynamic attitude and position prediction of super-large diameter shield.The approach consists of principal component analysis(PCA)and temporal convolutional network(TCN).The former is used for employing feature level fusion based on features of the shield data to reduce uncertainty,improve accuracy and the data effect,and 9 sets of required principal component characteristic data are obtained.The latter is adopted to process sequence data in predicting the dynamic attitude and position for the advantages and potential of convolution network.The approach’s effectiveness is exemplified using data from a tunnel construction project in China.The obtained results show remarkable accuracy in predicting the global attitude and position,with an average error ratio of less than 2 mm on four shield outputs in 97.30%of cases.Moreover,the approach displays strong performance in accurately predicting sudden fluctuations in shield attitude and position,with an average prediction accuracy of 89.68%.The proposed hybrid model demonstrates superiority over TCN,long short-term memory(LSTM),and recurrent neural network(RNN)in multiple indexes.Shapley additive exPlanations(SHAP)analysis is also performed to investigate the significance of different data features in the prediction process.This study provides a real-time warning for the shield driver to adjust the attitude and position of super-large diameter shields.展开更多
In this paper,a continuum model with dynamic earth pressure coefficient is established to describe the granular slump process by introducingμ(I)rheology.This rheology is adopted to quantify the normal stresses in our...In this paper,a continuum model with dynamic earth pressure coefficient is established to describe the granular slump process by introducingμ(I)rheology.This rheology is adopted to quantify the normal stresses in our proposed model rather than shear stresses in classical models.The constitutive laws of different depth-averaged continuum approaches including the hydrodynamic,Savage–Hutter and proposed models are comparatively investigated in terms of the rheological effects on the spread of a granular column.The simulation results indicate that the proposed dynamic model captures some significant features during granular slump on inclined planes with different inclination angles(for example,the runout distance,runout time,and final profile).The proposed model can also reproduce the inner static sided axisymmetric region observed in tests when the granular column's initial aspect ratio(ratio of height to radii)is small.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.52379104,42202298)Joint fund of National Natural Science Foundation of China-Railway Corporation for basic research of high-speed railway (Grant No.U1934208).
文摘Artificially cemented soils have been widely used as filling materials in highway and railway construction.The shear strength evolution of filling materials upon moist variation can determine the stability of subgrade and embankments.This study conducted water retention tests,MIP tests,and multi-stage triaxial shear tests on cement-treated granite residual soil(GRS)to determine its water retention curve(WRC)upon free drying,pore structure,and peak shear strength qf,respectively.The water retention behavior and shear strength evolution upon free drying were modeled based on the dual-porosity structure of cement-treated GRS and the effective stress principle,respectively.Results show that the drying-WRC is bimodal and higher cement dosage yields a more severe decrease in the water retention capacity within a specific suction range.For a given confining pressure,the peak shear strength qf increased with increasing cement dosage or suction value s.The peak shear strength qf also solely depends on the suction value in the peak stress state.In addition,the cement-treated GRS has a bimodal pore size distribution curve,and its macro-and micro-void ratios remain almost unchanged after free drying.The bimodal drying-WRC of the cement-treated GRS can be modeled by differentiating the water retention mechanisms in macro-and micro-pores.Moreover,using the macro-pore degree of saturation as the effective stress parameterχ=S_(rM),the q_(f)–p′_(f)relationship(where p′_(f)is the effective mean pressure at failure)under various suction and stress conditions can be unified,and the q_(f)–s relationships at various net confining pressuresσ_(3),net can be well reproduced.These findings can help design subgrade and embankments constructed by artificially cemented GRS and assess their safe operation upon climate change.
基金Smart Integration Key Technologies and Application Demonstrations of Large Scale Underground Space Disaster Prevention and Reduction in Guangzhou International Financial City([2021]–KJ058).
文摘The specialized equipment utilized in long-line tunnel engineering is evolving towards large-scale,multifunctional,and complex orientations.The vibration caused by the high-frequency units during regular operation is supported by the foundation of the units,and the magnitude of vibration and the operating frequency fluctuate in different engineering contexts,leading to variations in the dynamic response of the foundation.The high-frequency units yield significantly diverse outcomes under different startup conditions and times,resulting in failure to meet operational requirements,influencing the normal function of the tunnel,and causing harm to the foundation structure,personnel,and property in severe cases.This article formulates a finite element numerical computation model for solid elements using three-dimensional elastic body theory and integrates field measurements to substantiate and ascertain the crucial parameter configurations of the finite element model.By proposing a comprehensive startup timing function for high-frequency dynamic machines under different startup conditions,simulating the frequency andmagnitude variations during the startup process,and suggesting functions for changes in frequency and magnitude,a simulated startup schedule function for high-frequency machines is created through coupling.Taking into account the selection of the transient dynamic analysis step length,the dynamic response results for the lower dynamic foundation during its fundamental frequency crossing process are obtained.The validation checks if the structural magnitude surpasses the safety threshold during the critical phase of unit startup traversing the structural resonance region.The design recommendations for high-frequency units’dynamic foundations are provided,taking into account the startup process of the machine and ensuring the safe operation of the tunnel.
基金supported by the National Natural Science Foundation of China(52078269 and 52325801).
文摘Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,and solar energy harvesting for glazed facades.In this study,we addressed these conflicts by introducing a new dynamic and vertical photovoltaic integrated building envelope(dvPVBE)that offers extraordinary flexibility with weather-responsive slat angles and blind positions,superior architectural aesthetics,and notable energy-saving potential.Three hierarchical control strategies were proposed for different scenarios of the dvPVBE:power generation priority(PGP),natural daylight priority(NDP),and energy-saving priority(ESP).Moreover,the PGP and ESP strategies were further analyzed in the simulation of a dvPVBE.An office room integrated with a dvPVBE was modeled using EnergyPlus.The influence of the dvPVBE in improving the building energy efficiency and corresponding optimal slat angles was investigated under the PGP and ESP control strategies.The results indicate that the application of dvPVBEs in Beijing can provide up to 131%of the annual energy demand of office rooms and significantly increase the annual net energy output by at least 226%compared with static photovoltaic(PV)blinds.The concept of this novel dvPVBE offers a viable approach by which the thermal load,daylight penetration,and energy generation can be effectively regulated.
基金Huabo Duan acknowledges financial support from the China National Key Research and Development(R&D)Plan(2018YFB1502804)the Scientific Research Fund of Introduced High Talent of Shenzhen University(827-000044),China.
文摘The relationship between environmental quality and economic growth has been a hot topic for decades.After years of rapid industrialization and urbanization,China’s environmental challenges are approaching a turning point.Following the principles of ecological civilization construction,China is on its way to maintaining high-quality and green economic development.On 10 June 2020,the Chinese Government reported the key findings of the Second National General Survey of Pollution Sources(fiscal year 2017),which provides strong quantitative evidence of progress toward ecological civilization.In terms of our comparison between the two National General Surveys in 2007 and 2017,it was found that environmental pollution,measured in terms of many wastewater and air emission pollutant discharges,is decreasing despite the steady growth in economic activities—and at a noticeably fast pace.Other national and local governments can adopt some of China’s ecological civilization practices,within their own individual contexts.
基金This work was supported by the National Natural Science Foundation of China(No.52078269).
文摘Sandstorm,which injects generous newly emerging microbes into the atmosphere covering cities,adversely affects the air quality in built environments.However,few studies have examined the change of airborne bacteria during severe sandstorm events.In this work,we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia onMarch 15th,2021,which affected large areas of China and Mongolia.The characteristics of the sandstorm were compared with those of the subsequent clean and haze days.The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction(qPCR)and high-throughput sequencing technology.During the sandstorm,the particulate matter(PM)concentration and bacterial richnesswere extremely high(PM_(2.5):207μg/m^(3);PM_(10):1630μg/m^(3);5700 amplicon sequence variants/m^(3)).In addition,the sandstorm brought 10 pathogenic bacterial genera to the atmosphere,posing a grave hazard to human health.As the sandstorm subsided,small bioaerosols(0.65–1.1μm)with a similar bacterial community remained suspended in the atmosphere,bringing possible long-lasting health risks.
基金This work was financially supported by the Key Research and Development Program of Guangdong Province(No.2019B111105001)the National Natural Science Foundation of China(Grant No.51938008)the Natural Science Foundation of Shenzhen(No.JCYJ20210324094607020).
文摘Flexural performance of joints is critical for prefabricated structures.This study presents a novel channel steel-bolt(CB)joint for prefabricated subway stations.Full-scale tests are carried out to investigate the flexural behavior of the CB joint under the design loads of the test-case station.In addition,a three dimensional(3D)finite element(FE)model of the CB joint is established,incorporating viscous contact to simulate the bonding and detachment behaviors of the interface between channel steel and concrete.Based on the 3D FE model,the study examines the flexural bearing mechanism and influencing factors for the flexural performance of the CB joint.The results indicate that the flexural behavior of the CB joint exhibits significant nonlinear characteristics,which can be divided into four stages.To illustrate the piecewise linearity of the bending moment-rotational angle curve,a four-stage simplified model is proposed,which is easily applicable in engineering practice.The study reveals that axial force can enhance the flexural capacity of the CB joint,while the preload of the bolt has a negligible effect.The flexural capacity of the CB joint is approximate twice the value of the designed bending moment,demonstrating that the joint is suitable for the test-case station.
基金financially supported by the National Natural Science Foundation of China (No.52078269,No.52178068).
文摘Considering that people spend more than 80%of their time indoors,ambient particulate matter(PM)in the built environment could pose severe environmental health risks to public health.PM sampling,a technique for the enrichment of PM in the air,is essential for ambient PM composition analysis to understand its environmental and health effect.The filtering method that is widely used features a complex post-processing and carries the risk of pore clogging.It is a great challenge to sample airborne PM efficiently for subsequent analysis.Here,we proposed a novel miniaturized electrostatic sampler based on corona discharge and a modified vertically focused electric field for efficient PM sampling.Four intercoupling physical fields in the developed sampler were analyzed,including corona discharge,airflow,particle charging and particle deposition.The collection efficiencies for particles with various sizes(0.01–10μm)were conducted by simulation and the lowest efficiency occurs at about 0.3–0.5μm.With an increase in discharging voltage from−6 kV to−9 kV,the lowest efficiency rises from 88.2%to 96.6%.An electrostatic sampler entity was manufactured to test the collection efficiency of PM and the results are in good agreement with the simulation.The induced ring plate can significantly improve the total collection efficiency from 35%to 90%under−6 kV discharging voltage in the experiment.The novel electrostatic sampler exhibits potential and enlightenment for efficient and convenient PM sampling.
基金gratefully acknowledge the support of funds from the National Natural Science Foundation of China(Grant Nos.52090084,52208400).
文摘This paper presents a case study of the clogging of a slurry-shield tunnel-boring machine(TBM)experienced during tunnel operations in clay-rich argillaceous siltstones under the Ganjiang River,China.The clogging experienced during tunneling was due to special geological conditions,which had a considerably negative impact on the slurry-shield TBM tunneling performance.In this case study,the effect of clogging on the slurry-shield TBM tunneling performance(e.g.,advance speed,thrust,torque,and penetration per revolution)was fully investigated.The potential for clogging during tunnel operations in argillaceous siltstone was estimated using an existing empirical classification chart.Many improvement measures have been proposed to mitigate the clogging potential of two slurry-shield TBMs during tunneling,such as the use of an optimum cutting wheel,a replacement cutting tool,improvements to the circulation flushing system and slurry properties,mixed support integrating slurry,and compressed air to support the excavation face.The mechanisms and potential causes of clogging are explained in detail,and the contributions of these mitigation measures to tunneling performance are discussed.By investigating the actual operational parameters of the slurry-shield TBMs,these mitigation measures were proven to be effective in mitigating the clogging potential of slurry-shield TBMs.This case study provides valuable information for slurry-shield TBMs involving tunneling in clay-rich sedimentary rocks.
基金the financial support provided by National Key R&D Program of China under Grant No.2018YFB2100901the National Natural Science Foundation of China under Grant Nos.51938008,52090081and China Academy of Railway Sciences Fund Project under Grand No.2019YJ181.
文摘In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first validated by the results from a full-scale model test.Then,based on the load-structure method,this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening.The influence of loosening position,loosening range,and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses.The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions,thus changing the deformation pattern and force state.After the loosening occurs,the bending moment of the ring in the loosening range increases and the axial force decreases.The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range a is 90°.The vertical convergence of the ring increases with increasing of the loosening extent,and the equivalent stiffness decreases linearly with increasing of the loosening extent.The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening,and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.
基金funded by the National Natural Science Foundation of China(Grant Nos.51938008,52090084)China Postdoctoral Science Foundation(Grant No.2021T140475).
文摘Ground movements caused by the construction of tunnels and excavation are inevitable.Estimation of such movements is a very important for risk management in tunnel design.This paper presents a case study of ground settlements induced by twin shield tunnelling in Copenhagen using analytical and numerical methods and their predictions.The predictions are compared with the monitored settlements.The comparison shows that the predictions are sufficiently conservative.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52078304,51938008,52090084,and 52208354)Guangdong Province Key Field R&D Program Project(Grant Nos.2019B111108001 and 2022B0101070001)+1 种基金Shenzhen Fundamental Research(Grant No.20220525163716003)the Pearl River Delta Water Resources Allocation Project(CD88-GC022020-0038).
文摘The presented research introduces a novel hybrid deep learning approach for the dynamic prediction of the attitude and position of super-large diameter shields-a critical consideration for construction safety and tunnel lining quality.This study proposes a hybrid deep learning approach for predicting dynamic attitude and position prediction of super-large diameter shield.The approach consists of principal component analysis(PCA)and temporal convolutional network(TCN).The former is used for employing feature level fusion based on features of the shield data to reduce uncertainty,improve accuracy and the data effect,and 9 sets of required principal component characteristic data are obtained.The latter is adopted to process sequence data in predicting the dynamic attitude and position for the advantages and potential of convolution network.The approach’s effectiveness is exemplified using data from a tunnel construction project in China.The obtained results show remarkable accuracy in predicting the global attitude and position,with an average error ratio of less than 2 mm on four shield outputs in 97.30%of cases.Moreover,the approach displays strong performance in accurately predicting sudden fluctuations in shield attitude and position,with an average prediction accuracy of 89.68%.The proposed hybrid model demonstrates superiority over TCN,long short-term memory(LSTM),and recurrent neural network(RNN)in multiple indexes.Shapley additive exPlanations(SHAP)analysis is also performed to investigate the significance of different data features in the prediction process.This study provides a real-time warning for the shield driver to adjust the attitude and position of super-large diameter shields.
基金funded by the National Natural Science Foundation of China(Grant Nos.52008261 and 52090081)the Key Research and Development Program of China Railway(Grant No.K2019G033).
文摘In this paper,a continuum model with dynamic earth pressure coefficient is established to describe the granular slump process by introducingμ(I)rheology.This rheology is adopted to quantify the normal stresses in our proposed model rather than shear stresses in classical models.The constitutive laws of different depth-averaged continuum approaches including the hydrodynamic,Savage–Hutter and proposed models are comparatively investigated in terms of the rheological effects on the spread of a granular column.The simulation results indicate that the proposed dynamic model captures some significant features during granular slump on inclined planes with different inclination angles(for example,the runout distance,runout time,and final profile).The proposed model can also reproduce the inner static sided axisymmetric region observed in tests when the granular column's initial aspect ratio(ratio of height to radii)is small.
