The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill...The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill mining workface should also be considered. In this study, we established a main roof strata model with loads in accordance with the theory of key strata to investigate the stability of the overburden in solid dense filling mining. We analyzed the stress distribution law of the main roof strata based on elastic thin plate theory. The results show that the position of the long side midpoint of the main roof strata failed more easily because of tensile yield, indicating that this position is the area where failure is likely to occur more easily. We also deduced the stability mechanics criterion of the main roof strata based on tensile yield criterion. The factors affecting the stability of the overburden in solid dense filling mining were also analyzed, including the thickness and elasticity modulus of the main roof strata, overlying strata loads, advanced distance and length of workface, and elastic foundation coefficient of backfill body. The research achievements can provide an important theoretical basis for determining the designed size of the solid dense filling mining workface.展开更多
The nuclear spin relaxation rate （l/T1） is measured for GaAs two-dimensional （2D） electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A ＂tilte...The nuclear spin relaxation rate （l/T1） is measured for GaAs two-dimensional （2D） electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A ＂tilted plateau＂ feature is observed near the Landau level filling factor v = 1 in 1/T1 versus v. Both the width and magnitude of the plateau increase with decreasing electron density. At low temperatures, lIT1 exhibits an Arrhenius temperature dependence within the tilted plateau regime. The extracted energy gaps are up to two orders of magnitude smaller than the corresponding charge transport gaps. These results point to a nontrivial mechanism for the disorder-enhanced nuclear spin relaxation, in which microscopic inhomogeneities play a key role for the low energy spin excitations related to skyrmions.展开更多
There are many water-filling factors in Xiaotun Coal Mine, such as effective precipitation, goaf water, mining-induced fissure zone, surface water system, aquifers and tectonics. For different mining levels, the relat...There are many water-filling factors in Xiaotun Coal Mine, such as effective precipitation, goaf water, mining-induced fissure zone, surface water system, aquifers and tectonics. For different mining levels, the relative importance of these factors is different, and the water-filling condition is changed accordingly. So it is urgent to make it clear for mining. To ensure the safety of mining, we build a system of preventing mine water-filling using detailed AHP (analytical hierarchy process) calculation. This system is based on the analysis of mine water-filling factors in order to define the relative importance of the factors. Decision-makers use it as a strong scientific basis for Xiaotun Coal Mine.The method offered in this paper has been proved to be very applicable.展开更多
During the later period of construction of Tianshengqiao concrete faced rockfill dam(CFRD), cracks appeared in the upstream fill slope. The main reason was the nonuniform deformation. The treatment methods were: for c...During the later period of construction of Tianshengqiao concrete faced rockfill dam(CFRD), cracks appeared in the upstream fill slope. The main reason was the nonuniform deformation. The treatment methods were: for cracks with opening less than 1 cm, the cracked slope was compacted with added effort to eliminate cracks; for cracks with opening greater than 1 cm , crack grouting was carried out . The practice demonstrated the treatment was successful. Careful analysis of the relation between sectionalized filling and crack emergence is of significance in guiding the construction design and drawing out filling plan for a high CFRD.展开更多
In this study, nine simplified short composite columns consisting of core CFST (concrete filled steel tube) of different diameters and outer reinforced concrete were constructed to study their compressive performance ...In this study, nine simplified short composite columns consisting of core CFST (concrete filled steel tube) of different diameters and outer reinforced concrete were constructed to study their compressive performance under axial or eccentric compression. The failure mode is characterized by the crush of the outer concrete. The bearing capacity increases at first and then decreases with further increase of the position coefficient. It can be concluded that position coefficient is an important structural parameter that has considerable influences on the ultimate bearing capacity of the composite columns. The outer concrete, steel tubes and longitudinal reinforcement are found to work in a cooperative manner under axial or eccentric compression when the position coefficient is about 0.5. An improved bearing capacity algorithm that takes the position coefficient into account has been proposed based on the experimental and simulation results and current technical specification in China. It has been proven to be precise and safe.展开更多
Nonlinear response history analyses and use of strong ground motion data including near-field effects has become a common practice in both performance based design of tall buildings and design of base-isolated buildin...Nonlinear response history analyses and use of strong ground motion data including near-field effects has become a common practice in both performance based design of tall buildings and design of base-isolated buildings. On the other hand, ordinary buildings are commonly analysed via response spectrum analysis following the rules of conventional seismic codes, most of which do not take near-field effects into account. This study evaluates the necessity and the adequacy of near-source factors for ordinary fixed-base buildings that are not specifically classified as tall, by comparing dynamic responses of 3, 8, and 15-story benchmark buildings obtained via （1） linear time history analyses using 220 record components from 13 historical earthquakes and 45 synthetic earthquake records of different magnitudes and fault distances and （2） response spectrum analyses in accordance with the Turkish Earthquake Code 2007 -representing seismic codes not taking near-field effects into account- and the Uniform Building Code 1997 which takes near-field effects into account via near-source factors that amplify design response spectrum. It is shown that near-source factors are crucial for the safe design of not-so-tall ordinary fixed-base buildings but those defined in UBC97 may still not be adequate for those located in the vicinity of the fault.展开更多
This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was use...This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was used to assess the material loading system performance which is one of the key components of the total cycle time for material transportation in an open-pit mine. Loading is among the components of cycle time during which material is being handled. The data analyzed?was?collected from a computerized dispatch system at GGM from which 62,000 loading dispatches per month involving several shifts, 14 excavators and 49 trucks were loaded. About 4465 dispatches per excavator and 1276 dispatches per truck were assessed using loading cycle time data for each dispatch for a period of four months (between August and December). Under fixed tonnage loaded and waste type (33 t of non-acid forming waste rock),?it was observed that loading cycle time depends on excavator model, location and truck being loaded. Average cycle times, PDFS?and CDFS of loading cycle time series were used to identify differences in performance under different situations. It was concluded that shift availability for excavators, loading location, excavator model and truck-shovel combinations strongly affect the productivity during loading process in an open-pit mine.展开更多
基金Financial support for this work, provided by the National Natural Science Foundation of China (No.51404013)the Natural Science Foundation of Anhui Province (Nos.1508085ME77 and 1508085QE89)the Open Projects of State Key Laboratory for Geomechanics & Deep Underground Engineering at the China University of Mining and Technology (No.SKLGDUEK1212)
文摘The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill mining workface should also be considered. In this study, we established a main roof strata model with loads in accordance with the theory of key strata to investigate the stability of the overburden in solid dense filling mining. We analyzed the stress distribution law of the main roof strata based on elastic thin plate theory. The results show that the position of the long side midpoint of the main roof strata failed more easily because of tensile yield, indicating that this position is the area where failure is likely to occur more easily. We also deduced the stability mechanics criterion of the main roof strata based on tensile yield criterion. The factors affecting the stability of the overburden in solid dense filling mining were also analyzed, including the thickness and elasticity modulus of the main roof strata, overlying strata loads, advanced distance and length of workface, and elastic foundation coefficient of backfill body. The research achievements can provide an important theoretical basis for determining the designed size of the solid dense filling mining workface.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB921703 and 2015CB921102)the National Natural Science Foundation of China(Grant Nos.91121003,11374337,and 61425015)the Chinese Academy of Sciences,the BMBF,and the German–Israel Foundation
文摘The nuclear spin relaxation rate （l/T1） is measured for GaAs two-dimensional （2D） electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A ＂tilted plateau＂ feature is observed near the Landau level filling factor v = 1 in 1/T1 versus v. Both the width and magnitude of the plateau increase with decreasing electron density. At low temperatures, lIT1 exhibits an Arrhenius temperature dependence within the tilted plateau regime. The extracted energy gaps are up to two orders of magnitude smaller than the corresponding charge transport gaps. These results point to a nontrivial mechanism for the disorder-enhanced nuclear spin relaxation, in which microscopic inhomogeneities play a key role for the low energy spin excitations related to skyrmions.
文摘There are many water-filling factors in Xiaotun Coal Mine, such as effective precipitation, goaf water, mining-induced fissure zone, surface water system, aquifers and tectonics. For different mining levels, the relative importance of these factors is different, and the water-filling condition is changed accordingly. So it is urgent to make it clear for mining. To ensure the safety of mining, we build a system of preventing mine water-filling using detailed AHP (analytical hierarchy process) calculation. This system is based on the analysis of mine water-filling factors in order to define the relative importance of the factors. Decision-makers use it as a strong scientific basis for Xiaotun Coal Mine.The method offered in this paper has been proved to be very applicable.
文摘During the later period of construction of Tianshengqiao concrete faced rockfill dam(CFRD), cracks appeared in the upstream fill slope. The main reason was the nonuniform deformation. The treatment methods were: for cracks with opening less than 1 cm, the cracked slope was compacted with added effort to eliminate cracks; for cracks with opening greater than 1 cm , crack grouting was carried out . The practice demonstrated the treatment was successful. Careful analysis of the relation between sectionalized filling and crack emergence is of significance in guiding the construction design and drawing out filling plan for a high CFRD.
基金Funded by the National Natural Science Foundation of China(Grant No. 51178119)
文摘In this study, nine simplified short composite columns consisting of core CFST (concrete filled steel tube) of different diameters and outer reinforced concrete were constructed to study their compressive performance under axial or eccentric compression. The failure mode is characterized by the crush of the outer concrete. The bearing capacity increases at first and then decreases with further increase of the position coefficient. It can be concluded that position coefficient is an important structural parameter that has considerable influences on the ultimate bearing capacity of the composite columns. The outer concrete, steel tubes and longitudinal reinforcement are found to work in a cooperative manner under axial or eccentric compression when the position coefficient is about 0.5. An improved bearing capacity algorithm that takes the position coefficient into account has been proposed based on the experimental and simulation results and current technical specification in China. It has been proven to be precise and safe.
文摘Nonlinear response history analyses and use of strong ground motion data including near-field effects has become a common practice in both performance based design of tall buildings and design of base-isolated buildings. On the other hand, ordinary buildings are commonly analysed via response spectrum analysis following the rules of conventional seismic codes, most of which do not take near-field effects into account. This study evaluates the necessity and the adequacy of near-source factors for ordinary fixed-base buildings that are not specifically classified as tall, by comparing dynamic responses of 3, 8, and 15-story benchmark buildings obtained via （1） linear time history analyses using 220 record components from 13 historical earthquakes and 45 synthetic earthquake records of different magnitudes and fault distances and （2） response spectrum analyses in accordance with the Turkish Earthquake Code 2007 -representing seismic codes not taking near-field effects into account- and the Uniform Building Code 1997 which takes near-field effects into account via near-source factors that amplify design response spectrum. It is shown that near-source factors are crucial for the safe design of not-so-tall ordinary fixed-base buildings but those defined in UBC97 may still not be adequate for those located in the vicinity of the fault.
文摘This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was used to assess the material loading system performance which is one of the key components of the total cycle time for material transportation in an open-pit mine. Loading is among the components of cycle time during which material is being handled. The data analyzed?was?collected from a computerized dispatch system at GGM from which 62,000 loading dispatches per month involving several shifts, 14 excavators and 49 trucks were loaded. About 4465 dispatches per excavator and 1276 dispatches per truck were assessed using loading cycle time data for each dispatch for a period of four months (between August and December). Under fixed tonnage loaded and waste type (33 t of non-acid forming waste rock),?it was observed that loading cycle time depends on excavator model, location and truck being loaded. Average cycle times, PDFS?and CDFS of loading cycle time series were used to identify differences in performance under different situations. It was concluded that shift availability for excavators, loading location, excavator model and truck-shovel combinations strongly affect the productivity during loading process in an open-pit mine.
