As underground mining advances to greater depths,cemented paste backfill(CPB)is increasingly subjected to complex thermo-mechanical loading conditions,including multiaxial stress states and elevated temperatures.This ...As underground mining advances to greater depths,cemented paste backfill(CPB)is increasingly subjected to complex thermo-mechanical loading conditions,including multiaxial stress states and elevated temperatures.This study investigates the coupled effects of field-representative vertical self-weight and horizontal rockwall closure stresses,along with in-situ temperatures,on the mechanical behavior and pore water pressure(PWP)evolution of CPB.Experiments were conducted using a novel apparatus capable of controlling multiaxial stress and temperature during curing,replicating in-situ stress paths and thermal profiles typical of deep mine environments.Results show that multiaxial stress enhances CPB strength and stiffness by promoting denser particle packing,reducing porosity,and increasing frictional resistance.Elevated temperatures independently accelerate early-age cement hydration,further improving bond strength and stiffness.When combined,multiaxial stress and elevated temperature produce a synergistic enhancement in unconfined compressive strength(UCS)and elastic modulus,as confirmed by two-way ANOVA and synergy index analysis.PWP responses were also highly sensitive to thermo-mechanical conditions.The evolution of positive and negative PWP was governed by the interplay of thermal expansion,hydration-induced desaturation,and mechanical compaction.Multiaxial stress amplified early positive PWP and delayed its dissipation,whereas elevated temperature accelerated hydration and reduced pore pressure,leading to enhanced suction at later ages.A transient“stress-induced resaturation”effect was observed under late-stage excessive horizontal stress but was mitigated by elevated temperatures.These findings provide critical insights into the coupled mechanical and hydraulic behavior of CPB under realistic field conditions and offer guidance for optimizing backfill design,binder content,and barricade stability in deep mining applications.展开更多
Targeting Chang'E-8 mission'in-situ resource utilization(ISRU)for sustainable lunar habitats,laser powder bed fusion(LPBF)provides a viable pathway for in-situ additive manufacturing of lunar regolith.To eluci...Targeting Chang'E-8 mission'in-situ resource utilization(ISRU)for sustainable lunar habitats,laser powder bed fusion(LPBF)provides a viable pathway for in-situ additive manufacturing of lunar regolith.To elucidate mission relevant mechanical behavior and failure mechanisms of LPBF fabricated lunar regolith simulants,mare type and highland type simulant specimens were produced.Microstructural characterization,mechanical test coupled with three-dimensional digital image correlation(3D-DIC),and an energy-dissipation framework were employed for comprehensive analysis.The pristine highland specimens achieved 5.79 MPa and a peak strain of 0.13(50 mm×50 mm×30 mm),significantly outperforming their mare counterparts.Wire-cutting to 20 mm×20 mm×20 mm lowered strength by~20%and peak strain to 0.04,indicating cutting-induced defects reduce ductility.All specimens displayed multipeaked stress–strain curves.3D-DIC revealed band-type strain localization in pristine highland samples,diffuse strain patterns in cut highland samples,and highly tortuous,network-type bands in mare samples;the anisotropy index was also quantified.Fragmented particles exhibited fractal dimensions ranging from 1.6 to 2.0(size 1.25–9 mm).Energy evolution progressed through three distinct stages:elastic energy storage,progressive energy dissipation delaying crack propagation,and final unstable collapse.An energy-based damage model was established and validated.The data and methods developed support Chang'E-8 missions'ISRU demonstrations and establish a transferable framework toward sustainable lunar habitats.展开更多
Coal serves not only as a crucial energy resource but also as a significant reservoir of critical metal elements,including Lithium(Li),Gallium(Ga),Germanium(Ge),and rare earth elements(REE).This paper provides a syste...Coal serves not only as a crucial energy resource but also as a significant reservoir of critical metal elements,including Lithium(Li),Gallium(Ga),Germanium(Ge),and rare earth elements(REE).This paper provides a systematic review of the enrichment characteristics,occurrence modes,and comprehensive utilization potential of these critical metals in coal.Globally,the distribution of these metal resources exhibits significant regional heterogeneity.While the concentration in most coals falls below industrial cut-off grades,anomalous enrichment in specific coal basins results in Li,Ga,Ge,and REE concentrations far exceeding global averages,highlighting their considerable potential as unconventional metal deposits.The occurrence modes of these metals are diverse:Li is primarily hosted in mineral phases;Ga exists in inorganic,organic,and complex forms;Ge shows a strong association with organic matter;and REE are mainly present in adsorbed/isomorphic forms within clay minerals,while also displaying organic affinity.Direct extraction of metals from raw coal is often cost-prohibitive;effective recovery is therefore more feasible when integrated with coal processing.Metals are further enriched in solid wastes such as coal gangue,fly ash,and bottom ash,from which recovery is more economically and technically viable.Current comprehensive utilization primarily employs integrated mineral processing-hydrometallurgy approaches.Future research should focus on elucidating the precise occurrence forms of metals in coal and solid wastes,optimizing pre-treatment methods,and selecting effective activators and leachants.Advancing the synergistic extraction and green recovery of multiple associated resources from coal and its by-products is essential for achieving high-value,comprehensive utilization of coal-based resources.展开更多
基金the University of Ottawa, the China Scholarship Council and the Natural Sciences and Engineering Research Council of Canada (NSERC) for their financial support.
文摘As underground mining advances to greater depths,cemented paste backfill(CPB)is increasingly subjected to complex thermo-mechanical loading conditions,including multiaxial stress states and elevated temperatures.This study investigates the coupled effects of field-representative vertical self-weight and horizontal rockwall closure stresses,along with in-situ temperatures,on the mechanical behavior and pore water pressure(PWP)evolution of CPB.Experiments were conducted using a novel apparatus capable of controlling multiaxial stress and temperature during curing,replicating in-situ stress paths and thermal profiles typical of deep mine environments.Results show that multiaxial stress enhances CPB strength and stiffness by promoting denser particle packing,reducing porosity,and increasing frictional resistance.Elevated temperatures independently accelerate early-age cement hydration,further improving bond strength and stiffness.When combined,multiaxial stress and elevated temperature produce a synergistic enhancement in unconfined compressive strength(UCS)and elastic modulus,as confirmed by two-way ANOVA and synergy index analysis.PWP responses were also highly sensitive to thermo-mechanical conditions.The evolution of positive and negative PWP was governed by the interplay of thermal expansion,hydration-induced desaturation,and mechanical compaction.Multiaxial stress amplified early positive PWP and delayed its dissipation,whereas elevated temperature accelerated hydration and reduced pore pressure,leading to enhanced suction at later ages.A transient“stress-induced resaturation”effect was observed under late-stage excessive horizontal stress but was mitigated by elevated temperatures.These findings provide critical insights into the coupled mechanical and hydraulic behavior of CPB under realistic field conditions and offer guidance for optimizing backfill design,binder content,and barricade stability in deep mining applications.
基金supported by the Young Student Project of National Natural Science Foundation of China(No.525B2139)the National Key Research and Development Program of China(Nos.2023YFB3711300 and 2021YFF0500301)the Space Application System of China Manned Space Program(No.KJZ-YYWCL404)。
文摘Targeting Chang'E-8 mission'in-situ resource utilization(ISRU)for sustainable lunar habitats,laser powder bed fusion(LPBF)provides a viable pathway for in-situ additive manufacturing of lunar regolith.To elucidate mission relevant mechanical behavior and failure mechanisms of LPBF fabricated lunar regolith simulants,mare type and highland type simulant specimens were produced.Microstructural characterization,mechanical test coupled with three-dimensional digital image correlation(3D-DIC),and an energy-dissipation framework were employed for comprehensive analysis.The pristine highland specimens achieved 5.79 MPa and a peak strain of 0.13(50 mm×50 mm×30 mm),significantly outperforming their mare counterparts.Wire-cutting to 20 mm×20 mm×20 mm lowered strength by~20%and peak strain to 0.04,indicating cutting-induced defects reduce ductility.All specimens displayed multipeaked stress–strain curves.3D-DIC revealed band-type strain localization in pristine highland samples,diffuse strain patterns in cut highland samples,and highly tortuous,network-type bands in mare samples;the anisotropy index was also quantified.Fragmented particles exhibited fractal dimensions ranging from 1.6 to 2.0(size 1.25–9 mm).Energy evolution progressed through three distinct stages:elastic energy storage,progressive energy dissipation delaying crack propagation,and final unstable collapse.An energy-based damage model was established and validated.The data and methods developed support Chang'E-8 missions'ISRU demonstrations and establish a transferable framework toward sustainable lunar habitats.
基金supported by the Key Support Project of Regional Innovation and Development Joint Fund of the National Natural Science Foundation of China(No.U24A2095).
文摘Coal serves not only as a crucial energy resource but also as a significant reservoir of critical metal elements,including Lithium(Li),Gallium(Ga),Germanium(Ge),and rare earth elements(REE).This paper provides a systematic review of the enrichment characteristics,occurrence modes,and comprehensive utilization potential of these critical metals in coal.Globally,the distribution of these metal resources exhibits significant regional heterogeneity.While the concentration in most coals falls below industrial cut-off grades,anomalous enrichment in specific coal basins results in Li,Ga,Ge,and REE concentrations far exceeding global averages,highlighting their considerable potential as unconventional metal deposits.The occurrence modes of these metals are diverse:Li is primarily hosted in mineral phases;Ga exists in inorganic,organic,and complex forms;Ge shows a strong association with organic matter;and REE are mainly present in adsorbed/isomorphic forms within clay minerals,while also displaying organic affinity.Direct extraction of metals from raw coal is often cost-prohibitive;effective recovery is therefore more feasible when integrated with coal processing.Metals are further enriched in solid wastes such as coal gangue,fly ash,and bottom ash,from which recovery is more economically and technically viable.Current comprehensive utilization primarily employs integrated mineral processing-hydrometallurgy approaches.Future research should focus on elucidating the precise occurrence forms of metals in coal and solid wastes,optimizing pre-treatment methods,and selecting effective activators and leachants.Advancing the synergistic extraction and green recovery of multiple associated resources from coal and its by-products is essential for achieving high-value,comprehensive utilization of coal-based resources.
