The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and ce...The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.展开更多
The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compressio...The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.展开更多
Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potentia...Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potential hazard of“hard metal disease”under the exposure to cobalt dust.The changes in microstructure,corrosion rate and volumetric loss rate of the two materials were compared under electrochemical corrosion and erosion-corrosion in alkaline environment.The results demonstrates that Ti(C,N)-Mo_(2)C-Ni cermet undergoes passivation when exposed to electrochemical corrosion of NaOH solution,resulting in a significant increase in oxygen content on the corroded surface.The corrosion rate of cermet is approximately one order of magnitude lower than that of the cemented carbide.Under the erosion-corrosion of an alkaline sand-water mixture,both the cermet and cemented carbide experience a gradual increase in volumetric loss rate with prolonging the erosion time.During erosion,the rim phase in cermet is fragile,so cracks easily penetrate it while the core phase remains intact.The medium-grained cemented carbide commonly demonstrates transgranular fracture mode,while in the fine-grained cemented carbide,cracks tend to propagate along phase boundaries.The erosive wear and damage caused by sand particles play a predominant role in the erosion-corrosion process of alkaline sand-water mixtures.This process represents an accelerated destructive phenomenon influenced and intensified by the combined effects of corrosion and erosion.It is confirmed that using cermet as an alternative anti-wear material to cemented carbides is feasible under alkaline conditions,and even better.展开更多
The influence of graphene platelets(GPLs)on the WC grain size of WC-Co-GPLs cemented carbide prepared by low-pressure sintering was investigated.The role of GPLs in refining WC grains was explored by characterizing gr...The influence of graphene platelets(GPLs)on the WC grain size of WC-Co-GPLs cemented carbide prepared by low-pressure sintering was investigated.The role of GPLs in refining WC grains was explored by characterizing grain size and phase distribution.Results show that the addition of GPLs leads to significant grain refinement of WC and the more uniform distribution of WC grain size.When the content of GPLs is 0.10wt%,the average WC grain size in the cemented carbide is 0.39μm,which is 32%lower than that in WC-Co.However,the shape of WC grains is almost unaffected,while the mean free path of Co decreases.The grain refinement of WC is attributed to the homogeneous distribution of GPLs between WC/WC and WC/Co grain boundaries,which hinders the solution and precipitation process of WC in liquid phase Co,as well as the migration and growth of WC grains.Additionally,GPLs can serve as heat transfer plates in materials to improve cooling efficiency,thus inhibiting the growth of WC grain.展开更多
Utilizing mine solid waste as a partial cement substitute(CS)to develop new cementitious materials is a significant technological innovation that will decrease the expenses associated with filling mining.To realize th...Utilizing mine solid waste as a partial cement substitute(CS)to develop new cementitious materials is a significant technological innovation that will decrease the expenses associated with filling mining.To realize the resource utilization of magnesium slag(MS)and blast furnace slag(BFS),the effects of different contents of MS and BFS as partial CSs on the deformation and energy characteristics of cemented tailings backfill on different curing ages(3,7,and 28 d)were discussed.Meanwhile,the destabilization failure energy criterion of the backfill was established from the direction of energy change.The results show that the strength of all backfills increased with increasing curing age,and the strengths of the backfills exceeded 1.342 MPa on day 28.The backfill with 50%BFS+50%cement has the best performance in mechanical properties(the maximum strength can reach 6.129 MPa)and is the best choice among these CS combinations.The trend in peak strain and elastic modulus of the backfill with increasing curing age may vary depending on the CS combination.The energy index at peak stress of the backfill with BFS as a partial CS was significantly higher than that of the backfill under other CS combinations.In contrast,the enhancement of the energy index when MS was used as a partial CS was not as significant as BFS.Sharp changes in the energy consumption ratio after continuous smooth changes can be used as a criterion for destabilization and failure of the backfill.The research results can provide guidance for the application of MS and BFS as partial CSs in mine filling.展开更多
Tungsten carbide-based(WC-based)cemented carbides are widely recognized as high-performance tool materials.Traditionally,single metals such as cobalt(Co)or nickel(Ni)serve as the binder phase,providing toughness and s...Tungsten carbide-based(WC-based)cemented carbides are widely recognized as high-performance tool materials.Traditionally,single metals such as cobalt(Co)or nickel(Ni)serve as the binder phase,providing toughness and structural integrity.Replacing this phase with high-entropy alloys(HEAs)offers a promising approach to enhancing mechanical properties and addressing sustainability challenges.However,the complex multi-element composition of HEAs complicates conventional experimental design,making it difficult to explore the vast compositional space efficiently.Traditional trial-and-error methods are time-consuming,resource-intensive,and often ineffective in identifying optimal compositions.In contrast,artificial intelligence(AI)-driven approaches enable rapid screening and optimization of alloy compositions,significantly improving predictive accuracy and interpretability.Feature selection techniques were employed to identify key alloying elements influencing hardness,toughness,and wear resistance.To enhance model interpretability,explainable artificial intelligence(XAI)techniques—SHapley Additive exPlanations(SHAP)and Local Interpretable Model-agnostic Explanations(LIME)—were applied to quantify the contributions of individual elements and uncover complex elemental interactions.Furthermore,a high-throughput machine learning(ML)–driven screening approach was implemented to optimize the binder phase composition,facilitating the discovery of HEAs with superiormechanical properties.Experimental validation demonstrated strong agreement between model predictions and measured performance,confirming the reliability of the ML framework.This study underscores the potential of integrating ML and XAI for data-driven materials design,providing a novel strategy for optimizing high-entropy cemented carbides.展开更多
With the growing demand for sustainable development in the mining industry,cemented paste backfill(CPB)materials,primarily composed of tailings,play a crucial role in mine backfilling and underground support systems.T...With the growing demand for sustainable development in the mining industry,cemented paste backfill(CPB)materials,primarily composed of tailings,play a crucial role in mine backfilling and underground support systems.To enhance the mechanical properties of CPB materials,fiber reinforcement technology has gradually gained attention,though challenges remain in predicting its performance.This study develops a hybrid model based on the adaptive equilibrium optimizer(adap-EO)-enhanced XGBoost method for accurately predicting the uniaxial compressive strength of fiber-reinforced CPB.Through systematic comparison with various other machine learning methods,results demonstrate that the proposed hybridmodel exhibits excellent predictive performance on the test set,achieving a coefficient of determination(R^(2))of 0.9675,root mean square error(RMSE)of 0.6084,and mean absolute error(MAE)of 0.4620.Input importance analysis reveals that cement-tailings ratio,curing time,and concentration are the three most critical factors affectingmaterial strength,with cement-tailings ratio showing a positive correlation with strength,concentrations above 70% significantly improvingmaterial strength,and curing periods beyond 28 days being essential for strength development.Fiber parameters contribute secondarily but notably to material strength,with fiber length exhibiting an optimal range of approximately 12 mm.This study not only provides a high-precision strength prediction model but also reveals the inherent correlations between various parameters and material performance,offering scientific basis for mixture optimization and engineering applications of fiber-reinforced CPB materials.展开更多
Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rat...Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rates,and adequate strength remains a significant challenge for cemented rockfill.This study used a composite alkali activator to activate gangue cemented rockfill.The compressive strength,scanning electron microscopy,energy dispersive spectrometer,mercury intrusion porosimetry,X-ray diffraction,and thermogra-vimetric tests were carried out to investigate the effect of the composite alkali activator proportion on the compressive strength,micro-structure,and composition of the cemented rockfill.The calcium silicate hydrate(C–S–H)molecular model of cemented rockfill was con-structed to explore the fracture evolution of the nucleated molecular structure under tension.The results show that compressive strength initially increased and then decreased with the activator proportion,the optimal activator proportion of 1:2 resulted in a 31.25%increase in strength at 3 d.This reasonable activator proportion strengthens the pozzolanic effect of gangue,and consumes more calcium hydroxide to inhibit its agglomeration,ultimately achieving the densification of microstructure.The activator proportion inevitably substitutes calcium ions with sodium ions in the C–S–H molecular model.The 12%substitution of calcium ions increases the adhesion between silicon chain layers,which is beneficial to the interlayer stress transfer.This work proposes a method for preparing low-cost cemented rockfill from al-kali-activated gangue,which can be used for solid waste recycling and reducing cement consumption to achieve low-carbon goals.展开更多
This research examines the impact of sulphate on pore water pressure(PWP)development in cement paste backfill(CPB)containing polycarboxylate ether(PES)superplasticizers under thermal-hydraulic-mechanical-chemical(THMC...This research examines the impact of sulphate on pore water pressure(PWP)development in cement paste backfill(CPB)containing polycarboxylate ether(PES)superplasticizers under thermal-hydraulic-mechanical-chemical(THMC)conditions that imitate actual field curing scenarios.PWP in CPB-PES,with and without sulphate,was assessed under non-isothermal field curing temperatures,varied drainage conditions,and curing stresses using a specially experimental setup.Key findings indicate that PWP behavior in CPB with PES under field conditions diverges markedly from standard laboratory conditions due to the significant effects of field curing temperatures,drainage conditions,and backfill self-weight.The study establishes that high sulphate ion concentrations notably increase initial PWP and slow its dissipation by interfering with the cement hydration process.This interference delays hydration,reduces pore water consumption,and lowers capillary pressure.Moreover,the results show that THMC conditions,especially non-isothermal field temperatures and varied drainage scenarios,considerably accelerate cement hydration compared to standard laboratory conditions,resulting in a more rapid decrease in PWP.Furthermore,improved drainage under THMC conditions mitigates the adverse effects of sulphates by facilitating sulphate ion removal,thus supporting more efficient cement hydration and CPB self-desiccation.The insights gained from this research are essential for understanding PWP behavior in sulphate-bearing CPB-PES in the field,developing predictive THMC models for backfill performance assessment,and enhancing the safety and effectiveness of mining backfills.展开更多
The multi-objective optimization of backfill effect based on response surface methodology and desirability function(RSM-DF)was conducted.Firstly,the test results show that the uniaxial compressive strength(UCS)increas...The multi-objective optimization of backfill effect based on response surface methodology and desirability function(RSM-DF)was conducted.Firstly,the test results show that the uniaxial compressive strength(UCS)increases with cement sand ratio(CSR),slurry concentration(SC),and curing age(CA),while flow resistance(FR)increases with SC and backfill flow rate(BFR),and decreases with CSR.Then the regression models of UCS and FR as response values were established through RSM.Multi-factor interaction found that CSR-CA impacted UCS most,while SC-BFR impacted FR most.By introducing the desirability function,the optimal backfill parameters were obtained based on RSM-DF(CSR is 1:6.25,SC is 69%,CA is 11.5 d,and BFR is 90 m^(3)/h),showing close results of Design Expert and high reliability for optimization.For a copper mine in China,RSM-DF optimization will reduce cement consumption by 4758 t per year,increase tailings consumption by about 6700 t,and reduce CO_(2)emission by about 4758 t.Thus,RSM-DF provides a new approach for backfill parameters optimization,which has important theoretical and practical values.展开更多
To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,t...To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,thereby improving both microstructure uniformity and mechanical properties of sintered bodies.The results indicate that WIP reduces defects in MEX greens,thus decreasing the dimensions and numbers of defects,modifying shapes of pores within sintered bodies,while preserving surface quality and shape characteristics.Compared with WC-9Co prepared via MEX followed by debinding and sintering(DS),the hardness of WC-9Co prepared using MEX-WIP-DS does not change significantly,ranging HV_(30)1494-1508,the transverse rupture strength increases by up to 49.3%,reaching 2998-3514 MPa,and the fracture toughness remains high,ranging 14.8-17.0 MPa·m^(1/2).The mechanical properties surpass comparable cemented carbides fabricated through other AM methods and are comparable to those produced by powder metallurgy.The integration of green WIP into MEX-DS broadens the MEX processing window,and improves the overall mechanical properties of MEX AM WC-Co cemented carbides.展开更多
Investigation techniques,such as uniaxial compression tests,acoustic emission,digital image correlation monitoring,and scanning electron microscopy,were used from macroscopic and microscopic perspectives to investigat...Investigation techniques,such as uniaxial compression tests,acoustic emission,digital image correlation monitoring,and scanning electron microscopy,were used from macroscopic and microscopic perspectives to investigate the effects of gangue particle-size gradation on the damage characteristics of cemented backfill.The peak strength,acoustic emission characteristics,and failure modes of cemented backfills with different gangue size gradations were examined.Test results indicated that with an increase in the gradation coefficient,the compressive strength of the gangue-cemented backfill first increased and then decreased.When the gradation coefficient is 0.5,the maximum compressive strength of the backfill is 4.28 MPa.The acoustic emission counts during the loading of gangue-cemented fills with different gradation coefficients passed through three phases:rising,active,and significantly active.The number of internal pores and cracks,as well as the uneven distribution of their locations,cause differences in acoustic emission characteristics at the same stage and variations in the strength of the backfill due to the different gangue particle-size gradations in the filler sample.展开更多
In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 21...In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.展开更多
Utilizing coarse aggregates containing mining waste rock for backfilling addresses the strength requirements and reduces the expenses associated with binder and solid waste treatment.However,this type of material is p...Utilizing coarse aggregates containing mining waste rock for backfilling addresses the strength requirements and reduces the expenses associated with binder and solid waste treatment.However,this type of material is prone to aggregate segregation,which can lead to uneven deformation and damage to the backfill.We employed an image-segmentation method that incorporated machine learning to analyze the distribution information of the aggregates on the splitting surface of the test blocks.The results revealed a nonlinear rela-tionship between aggregate segregation and variations in solid concentration(SC)and cement/aggregate ratio(C/A).The SC of 81wt%-82wt%and C/A of 10.00wt%-12.50wt%reflect surges in fluid dynamics,friction effects,and shifts in their dominance.A uniaxial compression experiment,supplemented with additional strain gauges and digital image correlation technology,enabled us to analyze the mechanical properties and failure mechanism under the influence of aggregate segregation.It was found that the uniaxial compressive strength,ranging from 1.75 MPa to 12.65 MPa,is linearly related to both the SC and C/A,and exhibits no significant relation-ship with the degree of segregation in numerical terms.However,the degree of segregation affects the development trend of the elastic modulus to a certain extent,and a standard deviation of the aggregate area ratio of less than 1.63 clearly indicates a higher elastic modu-lus.In the pouring direction,the top area of the test block tended to form a macroscopic fracture surface earlier.By contrast,the compressibility of the bottom area was greater than that of the top area.The intensification of aggregate segregation widened the differences in the deformation and failure characteristics between the different areas.For samples with different uniformities,significant differences in local deformation ranging from 515.00μεto 1693.70μεwere observed during the stable deformation stage.The extreme unevenness of the aggregate leads to rapid crack penetration in the sample,causing macroscopic tensile failure and resulting in premature structural failure.展开更多
The backfill should keep stable in the primary stope when mining an adjacent secondary stope in subsequent open stoping mining methods,and the large-size mined-out area is usually backfilled by multiple backfilling be...The backfill should keep stable in the primary stope when mining an adjacent secondary stope in subsequent open stoping mining methods,and the large-size mined-out area is usually backfilled by multiple backfilling before the recovery of a secondary stope,resulting in a layered structure of backfill in stope.Therefore,it is significant to investigate the deformation responses and mechanical properties of stratified cemented tailings backfill(SCTB)with different layer structures to remain self-standing as an artificial pillar in the primary stope.The current work examined the effects of enhance layer position(1/3,1/2,and 2/3)and thickness ratio(0,0.1,0.2,and 0.3)on the mechanical properties,deformation,energy evolution,microstructures,and failure modes of SCTB.The results demonstrate that the incorporation of an enhance layer significantly strengthens the deformation and strength of SCTB.Under a confining pressure of 50 kPa,the peak deviatoric stress rises from 525.6 to 560.3,597.1,and 790.5 kPa as the thickness ratio of enhance layer is increased from 0 to 0.1,0.2,and 0.3,representing a significant increase of 6.6%,13.6%,and 50.4%.As the confining pressure increases,the slopes of the curves in the elastic stage become steep,and the plastic phase is extended accordingly.Additionally,the incorporation of the enhance layer significantly improves the energy storage linit of SCTB specimen.As the thickness ratio of the enhance layer increases from 0 to 0.1,0.2,and 0.3,the elastic energy rises from 0.54 to 0.67,0.84,and 1.00 MJ·m^(-3),representing a significant increase of 24.1%,55.6%,and 85.2%.The internal friction angles and cohesions of the SCTB specimens are higher than those of the CTB specimens,however,the cohesion is more susceptible to enhance layer position and thickness ratio than the internal friction angle.The failure style of the SCTB specimen changes from shear failure to splitting bulging failure and shear bulging failure with the presence of an enhance layer.The crack propagation path is significantly blocked by the enhance layer.The findings are of great significance to the application and stability of the SCTB in subsequent stoping backfilling mines.展开更多
The binder phase performs critically on the comprehensive properties of cemented carbides,especially the hardness(HV)and fracture toughness(K_(IC))relationship.There are strong motivations in both research community a...The binder phase performs critically on the comprehensive properties of cemented carbides,especially the hardness(HV)and fracture toughness(K_(IC))relationship.There are strong motivations in both research community and industry for developing alternative binders to Co in cemented carbide system,due to the reasons such as price instability,property degeneration,and toxicity.Herein,six kinds of high entropy alloys(HEA)including CoCrFeNiMn,CoCrFeMnAl,CoCrFeNiAl,CoCrNiMnAl,CoFeNiMnAl,and CrFeNiMnAl were employed as the alternative binder for the preparation of WC-HEA cemented carbides through mechanical alloying and two-step spark plasma sintering.The impacts of HEA on the microstructures,mechanical properties,and thermal conductivity of WC-HEA hardmetals were determined and discussed.WC-HEA hardmetals exhibited both superior HV and K_(IC)to WC-metal or WC-intermetallic cemented carbides,indicating that HEA alloys were not only harder but also tougher in comparison with traditional metal or intermetallic binders.The HEA bonded hardmetals yielded thermal conductivities much lower than that of traditional WC-Co cemented carbide.The excellent HV-K_(IC)relationship of WC-HEA facilitated the potential engineering structural application of cemented carbides.展开更多
TiC steel-bound cemented carbide body was prepared by direct writing printing.The effects of powder content(89.28,89.49,89.69,89.88,and 90.07 wt%)and dispersant content(0.017,0.034,0.051,and 0.068 wt%)on the slurry an...TiC steel-bound cemented carbide body was prepared by direct writing printing.The effects of powder content(89.28,89.49,89.69,89.88,and 90.07 wt%)and dispersant content(0.017,0.034,0.051,and 0.068 wt%)on the slurry and printing body were studied.The experimental results show that with the increase of powder content,the viscosity of the slurry gradually increases,the settlement rate gradually decreases,and the size and linewidth of the blank body gradually decreases.When the powder content is 89.69 wt%,the sedimentation stability and extrusion stability of the slurry are the best,and the density of the blank body is the highest,which is 3.8275 g/cm^(3),which is suitable for direct writing printing.The addition of dispersant reduced the viscosity of the slurry;With the increase of dispersant content,the surface line width and size of the printed body gradually increased.When the dispersant content is 0.034 wt%,the extrusion stability of the slurry is the best,and the density of the body is the highest,which is 3.8901 g/cm^(3).展开更多
Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the s...Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(i.e.cohesion and internal friction angle)when they are supported by cemented backfilling.In this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure criterion.Our analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be determined.The value of s3max predicted using the proposed method is generally less than 3 MPa.Within this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb theory.The proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,i.e.the situation in which the cohesion value is too large and the friction angle is too small can effectively be avoided.The proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB method.The shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical simulations.The numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.展开更多
Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already w...Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already widespread worldwide and requires careful stewardship.In this study,we review the presence of potentially toxic elements(PTEs)in PG and describe their associations with soil properties,anthropogenic activities,and surrounding organisms.Then,we review different ex-/in-situ solutions for promoting the sustainable management of PG,with an emphasis on in-situ cemented paste backfill,which offers a cost-effective and highly scalable opportunity to advance the value-added recovery of PG.However,concerns related to the PTEs'retention capacity and long-term effectiveness limit the implementation of this strategy.Furthermore,given that the large-scale demand for ordinary Portland cement from this conventional option has resulted in significant CO_(2) emissions,the technology has recently undergone additional scrutiny to meet the climate mitigation ambition of the Paris Agreement and China's Carbon Neutrality Economy.Therefore,we discuss the ways by which we can integrate innovative strategies,including supplementary cementitious materials,alternative binder solutions,CO_(2) mineralization,CO_(2) curing,and optimization of the supply chain for the profitability and sustainability of PG remediation.However,to maximize the co-benefits in environmental,social,and economic,future research must bridge the gap between the feasibility of expanding these advanced pathways and the multidisciplinary needs.展开更多
During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution ...During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.展开更多
基金funded by the National Natural Science Foundation of China(52474131)the National Natural Science Foundation of China(42467022)+1 种基金the Yunnan Major Scientific and Technological Projects(Grant No.202202AG050014)the Yunnan Fundamental Research Projects(NO.202101BE070001-038,202201AT070146).
文摘The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.
基金financially supported by the National Natural Science Foundation of China(Nos.52174092,51904290,and 52374147)the Natural Science Foundation of Jiangsu Province,China(No.BK20220157)+2 种基金the Fundamental Research Funds for the Central Universities,China(No.2022YCPY0202)the National Key Research and Development Program of China(No.2023YFC3804204)the Major Program of Xinjiang Uygur Autonomous Region S cience and Technology(No.2023A01002)。
文摘The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.
基金Chongqing Light Alloy Materials and Processing Engineering Technology Research Center Open Fund Project(GCZX201903)Yunnan Province Major Science and Technology Special Project Plan(202302AA310038)Sichuan University-Suining Municipal-University Cooperation Project(2023CDSN-12)。
文摘Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potential hazard of“hard metal disease”under the exposure to cobalt dust.The changes in microstructure,corrosion rate and volumetric loss rate of the two materials were compared under electrochemical corrosion and erosion-corrosion in alkaline environment.The results demonstrates that Ti(C,N)-Mo_(2)C-Ni cermet undergoes passivation when exposed to electrochemical corrosion of NaOH solution,resulting in a significant increase in oxygen content on the corroded surface.The corrosion rate of cermet is approximately one order of magnitude lower than that of the cemented carbide.Under the erosion-corrosion of an alkaline sand-water mixture,both the cermet and cemented carbide experience a gradual increase in volumetric loss rate with prolonging the erosion time.During erosion,the rim phase in cermet is fragile,so cracks easily penetrate it while the core phase remains intact.The medium-grained cemented carbide commonly demonstrates transgranular fracture mode,while in the fine-grained cemented carbide,cracks tend to propagate along phase boundaries.The erosive wear and damage caused by sand particles play a predominant role in the erosion-corrosion process of alkaline sand-water mixtures.This process represents an accelerated destructive phenomenon influenced and intensified by the combined effects of corrosion and erosion.It is confirmed that using cermet as an alternative anti-wear material to cemented carbides is feasible under alkaline conditions,and even better.
基金National Natural Science Foundation of China(51572224)Guangdong Young Creative Talents(2023KQNCX039)+2 种基金Guangdong Basic and Applied Basic Research Foundation(2023A1515110551)Innovative Team in Higher Educational Institutions of Guangdong Province(2020KCXTD039)2023 Lingnan Normal College Students Innovation and Entrepreneurship Training Program(1742)。
文摘The influence of graphene platelets(GPLs)on the WC grain size of WC-Co-GPLs cemented carbide prepared by low-pressure sintering was investigated.The role of GPLs in refining WC grains was explored by characterizing grain size and phase distribution.Results show that the addition of GPLs leads to significant grain refinement of WC and the more uniform distribution of WC grain size.When the content of GPLs is 0.10wt%,the average WC grain size in the cemented carbide is 0.39μm,which is 32%lower than that in WC-Co.However,the shape of WC grains is almost unaffected,while the mean free path of Co decreases.The grain refinement of WC is attributed to the homogeneous distribution of GPLs between WC/WC and WC/Co grain boundaries,which hinders the solution and precipitation process of WC in liquid phase Co,as well as the migration and growth of WC grains.Additionally,GPLs can serve as heat transfer plates in materials to improve cooling efficiency,thus inhibiting the growth of WC grain.
基金Projects(52274108,U2341265)supported by the National Natural Science Foundation of ChinaProject(2022YFC2904103)supported by the National Key Research and Development Program of China。
文摘Utilizing mine solid waste as a partial cement substitute(CS)to develop new cementitious materials is a significant technological innovation that will decrease the expenses associated with filling mining.To realize the resource utilization of magnesium slag(MS)and blast furnace slag(BFS),the effects of different contents of MS and BFS as partial CSs on the deformation and energy characteristics of cemented tailings backfill on different curing ages(3,7,and 28 d)were discussed.Meanwhile,the destabilization failure energy criterion of the backfill was established from the direction of energy change.The results show that the strength of all backfills increased with increasing curing age,and the strengths of the backfills exceeded 1.342 MPa on day 28.The backfill with 50%BFS+50%cement has the best performance in mechanical properties(the maximum strength can reach 6.129 MPa)and is the best choice among these CS combinations.The trend in peak strain and elastic modulus of the backfill with increasing curing age may vary depending on the CS combination.The energy index at peak stress of the backfill with BFS as a partial CS was significantly higher than that of the backfill under other CS combinations.In contrast,the enhancement of the energy index when MS was used as a partial CS was not as significant as BFS.Sharp changes in the energy consumption ratio after continuous smooth changes can be used as a criterion for destabilization and failure of the backfill.The research results can provide guidance for the application of MS and BFS as partial CSs in mine filling.
文摘Tungsten carbide-based(WC-based)cemented carbides are widely recognized as high-performance tool materials.Traditionally,single metals such as cobalt(Co)or nickel(Ni)serve as the binder phase,providing toughness and structural integrity.Replacing this phase with high-entropy alloys(HEAs)offers a promising approach to enhancing mechanical properties and addressing sustainability challenges.However,the complex multi-element composition of HEAs complicates conventional experimental design,making it difficult to explore the vast compositional space efficiently.Traditional trial-and-error methods are time-consuming,resource-intensive,and often ineffective in identifying optimal compositions.In contrast,artificial intelligence(AI)-driven approaches enable rapid screening and optimization of alloy compositions,significantly improving predictive accuracy and interpretability.Feature selection techniques were employed to identify key alloying elements influencing hardness,toughness,and wear resistance.To enhance model interpretability,explainable artificial intelligence(XAI)techniques—SHapley Additive exPlanations(SHAP)and Local Interpretable Model-agnostic Explanations(LIME)—were applied to quantify the contributions of individual elements and uncover complex elemental interactions.Furthermore,a high-throughput machine learning(ML)–driven screening approach was implemented to optimize the binder phase composition,facilitating the discovery of HEAs with superiormechanical properties.Experimental validation demonstrated strong agreement between model predictions and measured performance,confirming the reliability of the ML framework.This study underscores the potential of integrating ML and XAI for data-driven materials design,providing a novel strategy for optimizing high-entropy cemented carbides.
基金funded by the National Natural Science Foundation of China(Grant 42177164)the Distinguished Youth Science Foundation of Hunan Province of China(2022JJ10073)supported by China Scholarship Council with the grant number of 202006370006.
文摘With the growing demand for sustainable development in the mining industry,cemented paste backfill(CPB)materials,primarily composed of tailings,play a crucial role in mine backfilling and underground support systems.To enhance the mechanical properties of CPB materials,fiber reinforcement technology has gradually gained attention,though challenges remain in predicting its performance.This study develops a hybrid model based on the adaptive equilibrium optimizer(adap-EO)-enhanced XGBoost method for accurately predicting the uniaxial compressive strength of fiber-reinforced CPB.Through systematic comparison with various other machine learning methods,results demonstrate that the proposed hybridmodel exhibits excellent predictive performance on the test set,achieving a coefficient of determination(R^(2))of 0.9675,root mean square error(RMSE)of 0.6084,and mean absolute error(MAE)of 0.4620.Input importance analysis reveals that cement-tailings ratio,curing time,and concentration are the three most critical factors affectingmaterial strength,with cement-tailings ratio showing a positive correlation with strength,concentrations above 70% significantly improvingmaterial strength,and curing periods beyond 28 days being essential for strength development.Fiber parameters contribute secondarily but notably to material strength,with fiber length exhibiting an optimal range of approximately 12 mm.This study not only provides a high-precision strength prediction model but also reveals the inherent correlations between various parameters and material performance,offering scientific basis for mixture optimization and engineering applications of fiber-reinforced CPB materials.
基金supported by the Key Research and Development Special Tasks of Xinjiang,China (No.2022B01051-2)the National Natural Science Foundation of China (Nos.U23B2091,42372328,and 52478253)+1 种基金the Natural Science Foundation of Jiangsu Province,China (No.BK20240209)the Science and Technology Program Special Fund of Jiangsu Province (Frontier Leading Technology Basic Research) Major projects,China (No.BK 20222004)
文摘Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rates,and adequate strength remains a significant challenge for cemented rockfill.This study used a composite alkali activator to activate gangue cemented rockfill.The compressive strength,scanning electron microscopy,energy dispersive spectrometer,mercury intrusion porosimetry,X-ray diffraction,and thermogra-vimetric tests were carried out to investigate the effect of the composite alkali activator proportion on the compressive strength,micro-structure,and composition of the cemented rockfill.The calcium silicate hydrate(C–S–H)molecular model of cemented rockfill was con-structed to explore the fracture evolution of the nucleated molecular structure under tension.The results show that compressive strength initially increased and then decreased with the activator proportion,the optimal activator proportion of 1:2 resulted in a 31.25%increase in strength at 3 d.This reasonable activator proportion strengthens the pozzolanic effect of gangue,and consumes more calcium hydroxide to inhibit its agglomeration,ultimately achieving the densification of microstructure.The activator proportion inevitably substitutes calcium ions with sodium ions in the C–S–H molecular model.The 12%substitution of calcium ions increases the adhesion between silicon chain layers,which is beneficial to the interlayer stress transfer.This work proposes a method for preparing low-cost cemented rockfill from al-kali-activated gangue,which can be used for solid waste recycling and reducing cement consumption to achieve low-carbon goals.
文摘This research examines the impact of sulphate on pore water pressure(PWP)development in cement paste backfill(CPB)containing polycarboxylate ether(PES)superplasticizers under thermal-hydraulic-mechanical-chemical(THMC)conditions that imitate actual field curing scenarios.PWP in CPB-PES,with and without sulphate,was assessed under non-isothermal field curing temperatures,varied drainage conditions,and curing stresses using a specially experimental setup.Key findings indicate that PWP behavior in CPB with PES under field conditions diverges markedly from standard laboratory conditions due to the significant effects of field curing temperatures,drainage conditions,and backfill self-weight.The study establishes that high sulphate ion concentrations notably increase initial PWP and slow its dissipation by interfering with the cement hydration process.This interference delays hydration,reduces pore water consumption,and lowers capillary pressure.Moreover,the results show that THMC conditions,especially non-isothermal field temperatures and varied drainage scenarios,considerably accelerate cement hydration compared to standard laboratory conditions,resulting in a more rapid decrease in PWP.Furthermore,improved drainage under THMC conditions mitigates the adverse effects of sulphates by facilitating sulphate ion removal,thus supporting more efficient cement hydration and CPB self-desiccation.The insights gained from this research are essential for understanding PWP behavior in sulphate-bearing CPB-PES in the field,developing predictive THMC models for backfill performance assessment,and enhancing the safety and effectiveness of mining backfills.
基金Funded by the Deep Underground National Science&Technology Major Project gram of China(No.2024ZD1003704)the National Natural Science Foundation of China(Nos.51834001 and 52374111)。
文摘The multi-objective optimization of backfill effect based on response surface methodology and desirability function(RSM-DF)was conducted.Firstly,the test results show that the uniaxial compressive strength(UCS)increases with cement sand ratio(CSR),slurry concentration(SC),and curing age(CA),while flow resistance(FR)increases with SC and backfill flow rate(BFR),and decreases with CSR.Then the regression models of UCS and FR as response values were established through RSM.Multi-factor interaction found that CSR-CA impacted UCS most,while SC-BFR impacted FR most.By introducing the desirability function,the optimal backfill parameters were obtained based on RSM-DF(CSR is 1:6.25,SC is 69%,CA is 11.5 d,and BFR is 90 m^(3)/h),showing close results of Design Expert and high reliability for optimization.For a copper mine in China,RSM-DF optimization will reduce cement consumption by 4758 t per year,increase tailings consumption by about 6700 t,and reduce CO_(2)emission by about 4758 t.Thus,RSM-DF provides a new approach for backfill parameters optimization,which has important theoretical and practical values.
基金supported by the Key Project of Chinese Academy of Engineering(No.2019-XZ-11)the General Project of Chinese Academy of Engineering(No.2023-XY-18)+1 种基金the Open Fund of National Joint Engineering Research Center for Abrasion Control and Molding of Metal Materials of China(No.HKDNM201907)the Independent Project of State Key Laboratory of Powder Metallurgy,China。
文摘To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,thereby improving both microstructure uniformity and mechanical properties of sintered bodies.The results indicate that WIP reduces defects in MEX greens,thus decreasing the dimensions and numbers of defects,modifying shapes of pores within sintered bodies,while preserving surface quality and shape characteristics.Compared with WC-9Co prepared via MEX followed by debinding and sintering(DS),the hardness of WC-9Co prepared using MEX-WIP-DS does not change significantly,ranging HV_(30)1494-1508,the transverse rupture strength increases by up to 49.3%,reaching 2998-3514 MPa,and the fracture toughness remains high,ranging 14.8-17.0 MPa·m^(1/2).The mechanical properties surpass comparable cemented carbides fabricated through other AM methods and are comparable to those produced by powder metallurgy.The integration of green WIP into MEX-DS broadens the MEX processing window,and improves the overall mechanical properties of MEX AM WC-Co cemented carbides.
基金financially supported by the National Natural Science Foundation of China(Nos.52174095 and51804310)。
文摘Investigation techniques,such as uniaxial compression tests,acoustic emission,digital image correlation monitoring,and scanning electron microscopy,were used from macroscopic and microscopic perspectives to investigate the effects of gangue particle-size gradation on the damage characteristics of cemented backfill.The peak strength,acoustic emission characteristics,and failure modes of cemented backfills with different gangue size gradations were examined.Test results indicated that with an increase in the gradation coefficient,the compressive strength of the gangue-cemented backfill first increased and then decreased.When the gradation coefficient is 0.5,the maximum compressive strength of the backfill is 4.28 MPa.The acoustic emission counts during the loading of gangue-cemented fills with different gradation coefficients passed through three phases:rising,active,and significantly active.The number of internal pores and cracks,as well as the uneven distribution of their locations,cause differences in acoustic emission characteristics at the same stage and variations in the strength of the backfill due to the different gangue particle-size gradations in the filler sample.
基金supported by the National Natural Science Foundation of China(Nos.U21A20399 and 52274407)Liaoning Province Applied Basic Research Program(No.2022JH2/101300212).
文摘In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.
基金funded by the National Natural Science Foundation of China(Nos.52130404 and 52304121)the Fundamental Research Funds for the Central Universities,China(No.FRF-TP-22-112A1).
文摘Utilizing coarse aggregates containing mining waste rock for backfilling addresses the strength requirements and reduces the expenses associated with binder and solid waste treatment.However,this type of material is prone to aggregate segregation,which can lead to uneven deformation and damage to the backfill.We employed an image-segmentation method that incorporated machine learning to analyze the distribution information of the aggregates on the splitting surface of the test blocks.The results revealed a nonlinear rela-tionship between aggregate segregation and variations in solid concentration(SC)and cement/aggregate ratio(C/A).The SC of 81wt%-82wt%and C/A of 10.00wt%-12.50wt%reflect surges in fluid dynamics,friction effects,and shifts in their dominance.A uniaxial compression experiment,supplemented with additional strain gauges and digital image correlation technology,enabled us to analyze the mechanical properties and failure mechanism under the influence of aggregate segregation.It was found that the uniaxial compressive strength,ranging from 1.75 MPa to 12.65 MPa,is linearly related to both the SC and C/A,and exhibits no significant relation-ship with the degree of segregation in numerical terms.However,the degree of segregation affects the development trend of the elastic modulus to a certain extent,and a standard deviation of the aggregate area ratio of less than 1.63 clearly indicates a higher elastic modu-lus.In the pouring direction,the top area of the test block tended to form a macroscopic fracture surface earlier.By contrast,the compressibility of the bottom area was greater than that of the top area.The intensification of aggregate segregation widened the differences in the deformation and failure characteristics between the different areas.For samples with different uniformities,significant differences in local deformation ranging from 515.00μεto 1693.70μεwere observed during the stable deformation stage.The extreme unevenness of the aggregate leads to rapid crack penetration in the sample,causing macroscopic tensile failure and resulting in premature structural failure.
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.2023JCCXNY01)Guangxi Key Technologies R&D Program,China(No.2022AB31022).
文摘The backfill should keep stable in the primary stope when mining an adjacent secondary stope in subsequent open stoping mining methods,and the large-size mined-out area is usually backfilled by multiple backfilling before the recovery of a secondary stope,resulting in a layered structure of backfill in stope.Therefore,it is significant to investigate the deformation responses and mechanical properties of stratified cemented tailings backfill(SCTB)with different layer structures to remain self-standing as an artificial pillar in the primary stope.The current work examined the effects of enhance layer position(1/3,1/2,and 2/3)and thickness ratio(0,0.1,0.2,and 0.3)on the mechanical properties,deformation,energy evolution,microstructures,and failure modes of SCTB.The results demonstrate that the incorporation of an enhance layer significantly strengthens the deformation and strength of SCTB.Under a confining pressure of 50 kPa,the peak deviatoric stress rises from 525.6 to 560.3,597.1,and 790.5 kPa as the thickness ratio of enhance layer is increased from 0 to 0.1,0.2,and 0.3,representing a significant increase of 6.6%,13.6%,and 50.4%.As the confining pressure increases,the slopes of the curves in the elastic stage become steep,and the plastic phase is extended accordingly.Additionally,the incorporation of the enhance layer significantly improves the energy storage linit of SCTB specimen.As the thickness ratio of the enhance layer increases from 0 to 0.1,0.2,and 0.3,the elastic energy rises from 0.54 to 0.67,0.84,and 1.00 MJ·m^(-3),representing a significant increase of 24.1%,55.6%,and 85.2%.The internal friction angles and cohesions of the SCTB specimens are higher than those of the CTB specimens,however,the cohesion is more susceptible to enhance layer position and thickness ratio than the internal friction angle.The failure style of the SCTB specimen changes from shear failure to splitting bulging failure and shear bulging failure with the presence of an enhance layer.The crack propagation path is significantly blocked by the enhance layer.The findings are of great significance to the application and stability of the SCTB in subsequent stoping backfilling mines.
基金supported by the National Natural Science Foundation of China(No.52375451)the Shandong Provincial Natural Science Foundation,China(Nos.ZR2023YQ052 and ZR2023ME087)+5 种基金the Shandong Provincial Technological SME Innovation Capability Promotion Project,China(No.2023TSGC0375)the Young Taishan Scholars Program of Shandong Province,China(No.tsqn202306041)the Guangdong Basic and Applied Basic Research Foundation,China(No.2023A1515010044)the Shandong Provincial Youth Innovation Team,China(No.2022KJ038)the Open project of State Key Laboratory of Solid Lubrication,China(No.LSL-22-11)Qilu Youth Scholar Project Funding of Shandong University,China.
文摘The binder phase performs critically on the comprehensive properties of cemented carbides,especially the hardness(HV)and fracture toughness(K_(IC))relationship.There are strong motivations in both research community and industry for developing alternative binders to Co in cemented carbide system,due to the reasons such as price instability,property degeneration,and toxicity.Herein,six kinds of high entropy alloys(HEA)including CoCrFeNiMn,CoCrFeMnAl,CoCrFeNiAl,CoCrNiMnAl,CoFeNiMnAl,and CrFeNiMnAl were employed as the alternative binder for the preparation of WC-HEA cemented carbides through mechanical alloying and two-step spark plasma sintering.The impacts of HEA on the microstructures,mechanical properties,and thermal conductivity of WC-HEA hardmetals were determined and discussed.WC-HEA hardmetals exhibited both superior HV and K_(IC)to WC-metal or WC-intermetallic cemented carbides,indicating that HEA alloys were not only harder but also tougher in comparison with traditional metal or intermetallic binders.The HEA bonded hardmetals yielded thermal conductivities much lower than that of traditional WC-Co cemented carbide.The excellent HV-K_(IC)relationship of WC-HEA facilitated the potential engineering structural application of cemented carbides.
基金“TiC Steel Composite 3D Gel Printing Molding and its Densification Mechanism”Hebei Province Natural Science Foundation funded project-Youth Science Fund Project(E2021210094)“TiC Steel-bonded Cemented Carbide 3D Gel Printing Forming and Densification Mechanism”Sichuan Powder Metallurgy Engineering-Technology Research Center open project(SC-FMYJ2020-07)“Design Preparation of MAC Composite Powder and Research on the Mechanism of Strengthening Steel-bonded Cemented Carbide”Hebei Provincial Department of Education Natural Science-Youth Fund project(QN2024021)。
文摘TiC steel-bound cemented carbide body was prepared by direct writing printing.The effects of powder content(89.28,89.49,89.69,89.88,and 90.07 wt%)and dispersant content(0.017,0.034,0.051,and 0.068 wt%)on the slurry and printing body were studied.The experimental results show that with the increase of powder content,the viscosity of the slurry gradually increases,the settlement rate gradually decreases,and the size and linewidth of the blank body gradually decreases.When the powder content is 89.69 wt%,the sedimentation stability and extrusion stability of the slurry are the best,and the density of the blank body is the highest,which is 3.8275 g/cm^(3),which is suitable for direct writing printing.The addition of dispersant reduced the viscosity of the slurry;With the increase of dispersant content,the surface line width and size of the printed body gradually increased.When the dispersant content is 0.034 wt%,the extrusion stability of the slurry is the best,and the density of the body is the highest,which is 3.8901 g/cm^(3).
基金Financial support for this work was provided by the General Program and Youth Fund Program of the National Natural Science Foundation of China(Grant Nos.42377175 and 42002292).
文摘Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(i.e.cohesion and internal friction angle)when they are supported by cemented backfilling.In this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure criterion.Our analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be determined.The value of s3max predicted using the proposed method is generally less than 3 MPa.Within this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb theory.The proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,i.e.the situation in which the cohesion value is too large and the friction angle is too small can effectively be avoided.The proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB method.The shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical simulations.The numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.
基金the National Natural Science Foundation of China(Nos.552104156,52074351,and 52004330)the National Natural Science Foundation of Hunan Province,China(No.2022JJ30714)the Science and Technology Innovation Program of Hunan Province,China(No.2021RC3125)。
文摘Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already widespread worldwide and requires careful stewardship.In this study,we review the presence of potentially toxic elements(PTEs)in PG and describe their associations with soil properties,anthropogenic activities,and surrounding organisms.Then,we review different ex-/in-situ solutions for promoting the sustainable management of PG,with an emphasis on in-situ cemented paste backfill,which offers a cost-effective and highly scalable opportunity to advance the value-added recovery of PG.However,concerns related to the PTEs'retention capacity and long-term effectiveness limit the implementation of this strategy.Furthermore,given that the large-scale demand for ordinary Portland cement from this conventional option has resulted in significant CO_(2) emissions,the technology has recently undergone additional scrutiny to meet the climate mitigation ambition of the Paris Agreement and China's Carbon Neutrality Economy.Therefore,we discuss the ways by which we can integrate innovative strategies,including supplementary cementitious materials,alternative binder solutions,CO_(2) mineralization,CO_(2) curing,and optimization of the supply chain for the profitability and sustainability of PG remediation.However,to maximize the co-benefits in environmental,social,and economic,future research must bridge the gap between the feasibility of expanding these advanced pathways and the multidisciplinary needs.
基金financially supported by the National Natural Science Foundation of China(Nos.52274143 and 51874284).
文摘During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.
