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
A loss of ground directional stability can trigger a high-speed Unmanned Aerial Vehicle(UAV)to veer off the runway.In order to investigate the combined effects of the key structural and operational parameters on the U...A loss of ground directional stability can trigger a high-speed Unmanned Aerial Vehicle(UAV)to veer off the runway.In order to investigate the combined effects of the key structural and operational parameters on the UAV ground directional stability from a global perspective,a fully parameterized mathematical high-speed UAV ground nonlinear dynamic model is developed considering several nonlinear factors.The bifurcation analysis procedure of a UAV ground steering system is introduced,following which the simulation efficiency is greatly improved comparing with the time-domain simulation method.Then the numerical continuation method is employed to investigate the influence of the nose wheel steering angle and the global stability region is obtained.The bifurcation parameter plane is divided into several parts with different stability properties by the saddle nodes and the Hopf bifurcation points.We find that the UAV motion states will never cross the bifurcation curve in the nonlinear system.Also,the dual-parameter bifurcation analyses are presented to give a complete description of the possible steering performance.It is also found that BT bifurcation appears when the UAV initial rectilinear velocity and the tire frictional coefficient vary.In addition,results indicate that the influence of tire frictional coefficient has an opposite trend to the influence of initial rectilinear velocity.Overall,using bifurcation analysis method to identify the parameter regions of a UAV nonlinear ground dynamic system helps to improve the development efficiency and quality during UAV designing phase.展开更多
The capabilities of GIS in modeling fault patterns are explored for Irkutsk city in East Siberia with implications for ground stability. The neotectonic structure of the area is visualized in three dimension （3D） ta...The capabilities of GIS in modeling fault patterns are explored for Irkutsk city in East Siberia with implications for ground stability. The neotectonic structure of the area is visualized in three dimension （3D） taking into account fault dips, using the ArcGIS, GlobalMapper and Paradigm Geophysical packages. The study area is divided into blocks of different size classes according to the length-based ranks of the bounding faults, which are of five classes distinguished with the equal interval method. The blocks show different deformation patterns, with different densities and strikes of crossing and bounding faults. The data are statistically processed using GIS to estimate the deformation degrees of blocks in arbitrary units per square kilometer using the attributes of rank and crossing/bounding position of faults and the size of blocks. The deformation degrees are then compared with available estimates of ground stability measured as a score of points corresponding to destabilizing factors. Although the comparison generally confirms some linkage between the deformation degree of blocks and their ground stability, the correlation is intricate and ambiguous. In order to enhance the advantages of GIS in building and analyzing 3D models of fault patterns for estimating ground stability and mitigating geological hazards, it is expected in the future to proceed from the reported initial step of visualization to more advanced analysis.展开更多
Over the past few decades, many optical fiber sensing techniques have been developed. Among these available sensing methods, optical fiber Bragg grating（FBG） is probably the most popular one. With its unique capabil...Over the past few decades, many optical fiber sensing techniques have been developed. Among these available sensing methods, optical fiber Bragg grating（FBG） is probably the most popular one. With its unique capabilities, FBG-based geotechnical sensors can be used as a sensor array for distributive（profile） measurements, deployed under water（submersible）, for localized high resolution and/or differential measurements. The authors have developed a series of FBG-based transducers that include inclination, linear displacement and gauge/differential pore pressure sensors. Techniques that involve the field deployment of FBG inclination, extension and pore-pressure sensor arrays for automated slope stability and ground subsidence monitoring have been developed. The paper provides a background of FBG and the design concepts behind the FBG-based field monitoring sensors. Cases of field monitoring using the FBG sensor arrays are presented, and their practical implications are discussed.展开更多
Man-made strata occur throughout the world.Also locally called“fill”or“reclaimed land,”most man-made strata were formed by industrial activity.Some strata are inert,well consolidated and properly“engineered”for ...Man-made strata occur throughout the world.Also locally called“fill”or“reclaimed land,”most man-made strata were formed by industrial activity.Some strata are inert,well consolidated and properly“engineered”for their intended future use.Many other,however,are polluted,contaminated and potentially unstable owing to poor environmental management and monitoring.Such deposits are often stratigraphically complex and thus require site-specific geologic and geotechnical investigation to ensure ground stability and to avoid release of surface,subsurface and airborne pollutants.展开更多
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supported by the National Natural Science Foundation of China(Nos.51905264 and 12002157)the China Postdoctoral Science Foundation Funded Project,China(Nos.2019M650115,2019M661818 and 2020T130298)+3 种基金the Science&Technology Innovation Project for Overseas Scholars in Nanjing,China(No.YQR20046)the National Defense Outstanding Youth Science Foundation,China(No.2018-JCJQ-ZQ-053)the Fundamental Research Funds for the Central Universities,China(No.NF2018001)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘A loss of ground directional stability can trigger a high-speed Unmanned Aerial Vehicle(UAV)to veer off the runway.In order to investigate the combined effects of the key structural and operational parameters on the UAV ground directional stability from a global perspective,a fully parameterized mathematical high-speed UAV ground nonlinear dynamic model is developed considering several nonlinear factors.The bifurcation analysis procedure of a UAV ground steering system is introduced,following which the simulation efficiency is greatly improved comparing with the time-domain simulation method.Then the numerical continuation method is employed to investigate the influence of the nose wheel steering angle and the global stability region is obtained.The bifurcation parameter plane is divided into several parts with different stability properties by the saddle nodes and the Hopf bifurcation points.We find that the UAV motion states will never cross the bifurcation curve in the nonlinear system.Also,the dual-parameter bifurcation analyses are presented to give a complete description of the possible steering performance.It is also found that BT bifurcation appears when the UAV initial rectilinear velocity and the tire frictional coefficient vary.In addition,results indicate that the influence of tire frictional coefficient has an opposite trend to the influence of initial rectilinear velocity.Overall,using bifurcation analysis method to identify the parameter regions of a UAV nonlinear ground dynamic system helps to improve the development efficiency and quality during UAV designing phase.
文摘The capabilities of GIS in modeling fault patterns are explored for Irkutsk city in East Siberia with implications for ground stability. The neotectonic structure of the area is visualized in three dimension （3D） taking into account fault dips, using the ArcGIS, GlobalMapper and Paradigm Geophysical packages. The study area is divided into blocks of different size classes according to the length-based ranks of the bounding faults, which are of five classes distinguished with the equal interval method. The blocks show different deformation patterns, with different densities and strikes of crossing and bounding faults. The data are statistically processed using GIS to estimate the deformation degrees of blocks in arbitrary units per square kilometer using the attributes of rank and crossing/bounding position of faults and the size of blocks. The deformation degrees are then compared with available estimates of ground stability measured as a score of points corresponding to destabilizing factors. Although the comparison generally confirms some linkage between the deformation degree of blocks and their ground stability, the correlation is intricate and ambiguous. In order to enhance the advantages of GIS in building and analyzing 3D models of fault patterns for estimating ground stability and mitigating geological hazards, it is expected in the future to proceed from the reported initial step of visualization to more advanced analysis.
文摘Over the past few decades, many optical fiber sensing techniques have been developed. Among these available sensing methods, optical fiber Bragg grating（FBG） is probably the most popular one. With its unique capabilities, FBG-based geotechnical sensors can be used as a sensor array for distributive（profile） measurements, deployed under water（submersible）, for localized high resolution and/or differential measurements. The authors have developed a series of FBG-based transducers that include inclination, linear displacement and gauge/differential pore pressure sensors. Techniques that involve the field deployment of FBG inclination, extension and pore-pressure sensor arrays for automated slope stability and ground subsidence monitoring have been developed. The paper provides a background of FBG and the design concepts behind the FBG-based field monitoring sensors. Cases of field monitoring using the FBG sensor arrays are presented, and their practical implications are discussed.
文摘Man-made strata occur throughout the world.Also locally called“fill”or“reclaimed land,”most man-made strata were formed by industrial activity.Some strata are inert,well consolidated and properly“engineered”for their intended future use.Many other,however,are polluted,contaminated and potentially unstable owing to poor environmental management and monitoring.Such deposits are often stratigraphically complex and thus require site-specific geologic and geotechnical investigation to ensure ground stability and to avoid release of surface,subsurface and airborne pollutants.
