A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength.The suction of the soil samples was controlled usin...A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength.The suction of the soil samples was controlled using a vapour equilibrium technique,with four suction levels ranging from 3.29 MPa to 198.14 MPa,where water retention is dominated by adsorption.The experimental results show that the tested soil exhibits a brittle failure mode under high suction,significantly distinguishing the hydro-mechanical behaviour of the soil at high suction from that observed at low suction.This brittle failure mode significantly increases the contribution of suction to peak strength compared to residual strength,causes the soil to fail before reaching the critical state,a phenomenon not observed in soils under high suction,and results in dilatancy caused by damage to the soil particle aggregates rather than particle rearrangement.The dilatancy data obtained from the triaxial tests reveal that significant soil dilatancy occurs during shear after reaching peak strength,with the maximum dilatancy angle increasing with suction and decreasing with confining pressure.However,the initial dry density has a negligible impact on the soil's dilatancy under high suction levels.This observation further supports that,for unsaturated soils under high suction levels,dilatancy is attributed to damage to soil particle aggregates rather than the rearrangement of soil particles.展开更多
Scour has been widely accepted as a key reason for bridge failures.Bridges are susceptible and sensitive to the scour phenomenon,which describes the loss of riverbed sediments around the bridge supports because of flo...Scour has been widely accepted as a key reason for bridge failures.Bridges are susceptible and sensitive to the scour phenomenon,which describes the loss of riverbed sediments around the bridge supports because of flow.The carrying capacity of a deep-water foundation is influenced by the formation of a scour hole,which means that a severe scour can lead to a bridge failure without warning.Most of the current scour predictions are based on deterministic models,while other loads at bridges are usually provided as probabilistic values.To integrate scour factors with other loads in bridge design and research,a quantile regression model was utilized to estimate scour depth.Field data and experimental data from previous studies were collected to build the model.Moreover,scour estimations using the HEC-18 equation and the proposed method were compared.By using the“CCC(Calculate,Confirm,and Check)”procedure,the probabilistic concept could be used to calculate various scour depths with the targeted likelihood according to a specified chance of bridge failure.The study shows that with a sufficiently large and continuously updated database,the proposed model could present reasonable results and provide guidance for scour mitigation.展开更多
Underground infrastructure plays a kind of crucial role in modern production and living,especially in big cities where the ground space has been fully utilized.In the context of recent advancements in digital technolo...Underground infrastructure plays a kind of crucial role in modern production and living,especially in big cities where the ground space has been fully utilized.In the context of recent advancements in digital technology,the demand for the application of digital twin technology in underground infrastructure has become increasingly urgent as well.However,the interaction and co-integration between underground engineering entities and virtual models remain relatively limited,primarily due to the unique nature of underground engineering data and the constraints imposed by the development of information technology.This research focuses on underground engineering infrastructure and provides an overview of the application of novel information technologies.Furthermore,a comprehensive framework for digital twin implementation,which encompasses five dimensions and combines emerging technologies,has been proposed.It thereby expands the horizons of the intersection between underground engineering and digital twins.Additionally,a practical project in Wenzhou serves as a case study,where a comprehensive database covering the project’s entire life cycle has been established.The physical model is visualized,endowed with functional implications and data analysis capabilities,and integrated with the visualization platform to enable dynamic operation and maintenance management of the project.展开更多
The surcharge load at the ground surface inevitably breaks the original equilibrium state between the underneath tunnel and the surrounding soil,which will impact the service performance of a subway tunnel.This paper ...The surcharge load at the ground surface inevitably breaks the original equilibrium state between the underneath tunnel and the surrounding soil,which will impact the service performance of a subway tunnel.This paper presents a novel semi-analytical approach for assessing the time-dependent,longitudinal responses of a subway tunnel in soft soil strata induced by the surcharge load.The solution is developed based on the framework of the classical"two-stage method"but innovatively incorporates the effects of ground stratification,the consolidation process,and the longitudinal stiffness reduction of the lining.Biot’s poroelastic theory in conjunction with the Laplace-Fourier transform technique is selected to model the deformation of the stratified ground,while the Timoshenko beam on a Pasternak foundation is employed to model the mechanical responses of the tunnel.The proposed semi-analytical solution is validated not only by comparison with benchmark solutions and a finite element model,but also by predicting a well-documented field measurement.Parametric analyses are conducted to investigate the effects of the elastic modulus and the permeability coefficient of the stratified ground on the longitudinal responses of the tunnel.It is expected that the proposed solution can serve as a useful tool for evaluating the effects of the surcharge load on the longitudinal responses of a subway tunnel.展开更多
基金support from the China Scholarship Council(CSC)-University of Technology Sydney joint scholarship and the National Key R&D Program of China(Grant No.2016YFC0800200)is gratefully acknowledged.
文摘A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength.The suction of the soil samples was controlled using a vapour equilibrium technique,with four suction levels ranging from 3.29 MPa to 198.14 MPa,where water retention is dominated by adsorption.The experimental results show that the tested soil exhibits a brittle failure mode under high suction,significantly distinguishing the hydro-mechanical behaviour of the soil at high suction from that observed at low suction.This brittle failure mode significantly increases the contribution of suction to peak strength compared to residual strength,causes the soil to fail before reaching the critical state,a phenomenon not observed in soils under high suction,and results in dilatancy caused by damage to the soil particle aggregates rather than particle rearrangement.The dilatancy data obtained from the triaxial tests reveal that significant soil dilatancy occurs during shear after reaching peak strength,with the maximum dilatancy angle increasing with suction and decreasing with confining pressure.However,the initial dry density has a negligible impact on the soil's dilatancy under high suction levels.This observation further supports that,for unsaturated soils under high suction levels,dilatancy is attributed to damage to soil particle aggregates rather than the rearrangement of soil particles.
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51908421 and 41172246).
文摘Scour has been widely accepted as a key reason for bridge failures.Bridges are susceptible and sensitive to the scour phenomenon,which describes the loss of riverbed sediments around the bridge supports because of flow.The carrying capacity of a deep-water foundation is influenced by the formation of a scour hole,which means that a severe scour can lead to a bridge failure without warning.Most of the current scour predictions are based on deterministic models,while other loads at bridges are usually provided as probabilistic values.To integrate scour factors with other loads in bridge design and research,a quantile regression model was utilized to estimate scour depth.Field data and experimental data from previous studies were collected to build the model.Moreover,scour estimations using the HEC-18 equation and the proposed method were compared.By using the“CCC(Calculate,Confirm,and Check)”procedure,the probabilistic concept could be used to calculate various scour depths with the targeted likelihood according to a specified chance of bridge failure.The study shows that with a sufficiently large and continuously updated database,the proposed model could present reasonable results and provide guidance for scour mitigation.
基金support was received from the Top Discipline Plan of Shanghai Universities-Class I(Grant No.2022-3-YB-02)the Science and Technology Program of Shanghai,China(Scientific and Technological Innovation Action Plan,Grant No.22692195500).
文摘Underground infrastructure plays a kind of crucial role in modern production and living,especially in big cities where the ground space has been fully utilized.In the context of recent advancements in digital technology,the demand for the application of digital twin technology in underground infrastructure has become increasingly urgent as well.However,the interaction and co-integration between underground engineering entities and virtual models remain relatively limited,primarily due to the unique nature of underground engineering data and the constraints imposed by the development of information technology.This research focuses on underground engineering infrastructure and provides an overview of the application of novel information technologies.Furthermore,a comprehensive framework for digital twin implementation,which encompasses five dimensions and combines emerging technologies,has been proposed.It thereby expands the horizons of the intersection between underground engineering and digital twins.Additionally,a practical project in Wenzhou serves as a case study,where a comprehensive database covering the project’s entire life cycle has been established.The physical model is visualized,endowed with functional implications and data analysis capabilities,and integrated with the visualization platform to enable dynamic operation and maintenance management of the project.
基金supported by the Shanghai Municipal Science and Technology Project,China(Grant No.21XD1430900)the Fundamental Research Funds for the Central Universities,the Top Discipline Plan of Shanghai Universities-Class I(Grant No.2022-3-YB-02)Open Research Project from Key Laboratory of Geotechnical and Underground Engineering,Tongji University,China(Grant No.KLE-TJGE-B2101).
文摘The surcharge load at the ground surface inevitably breaks the original equilibrium state between the underneath tunnel and the surrounding soil,which will impact the service performance of a subway tunnel.This paper presents a novel semi-analytical approach for assessing the time-dependent,longitudinal responses of a subway tunnel in soft soil strata induced by the surcharge load.The solution is developed based on the framework of the classical"two-stage method"but innovatively incorporates the effects of ground stratification,the consolidation process,and the longitudinal stiffness reduction of the lining.Biot’s poroelastic theory in conjunction with the Laplace-Fourier transform technique is selected to model the deformation of the stratified ground,while the Timoshenko beam on a Pasternak foundation is employed to model the mechanical responses of the tunnel.The proposed semi-analytical solution is validated not only by comparison with benchmark solutions and a finite element model,but also by predicting a well-documented field measurement.Parametric analyses are conducted to investigate the effects of the elastic modulus and the permeability coefficient of the stratified ground on the longitudinal responses of the tunnel.It is expected that the proposed solution can serve as a useful tool for evaluating the effects of the surcharge load on the longitudinal responses of a subway tunnel.
