Paste backfill technology is one of the key supporting technologies to ensure national mineral resource security and implement the Two Mountains Theory.Nevertheless,the traditional extensive,experiencedependent,and mine-wide homogenized paste backfill design fails to satisfy the engineering requirements of goafs in terms of spatial difference,functional difference,and environmental constraint difference under complex mining conditions.To solve the above problems,the concept of personalized paste backfill was proposed.Taking differentiated paste performance requirements and precise customization of paste materials as the core,it achieved multi-objective directional regulation of paste backfill materials by identifying performance indexes of different mining areas and working conditions and combining mineral fingerprint characteristics of solid wastes.This paper elaborated the differentiated performance requirements of paste and precise customization of paste materials.The differentiated performance requirements of paste mainly cover mechanical properties,pipeline transport performance,consolidation forming performance,environmental safety,low carbon and emission reduction,and other aspects.The precise customization of paste materials involves raw material system identification,material structure optimization,cementitious system construction,functional component addition,and whole-process quality control.It is indicated that future research should be strengthened in goaf demand identification,solid waste mineral fingerprint analysis,intelligent decision-making of material proportioning,and system dynamic regulation methods,so as to promote the high-quality development of paste backfill towards refinement,intelligence,and customization.

In response to the technical challenges faced by gold mines employing cyanidation gold extraction processes,such as the scarcity of backfill aggregates,the instability of traditional backfill performance,and high costs,this study conducted experimental research on lightweight energy-absorbing paste backfill.The basic physicochemical properties and energy absorption characteristics of the lightweight energy-absorbing backfill were systematically evaluated using XRD,slump and bleeding rate tests,uniaxial compressive strength tests,and triaxial compression mechanical behavior studies.The results indicate that when the dry density of the lightweight energyabsorbing backfill is between 500 kg/m³ and 650 kg/m³,the slurry bleeding rate ranges from 1.20%to 1.45%,achieving stable structural flow paste backfill.After 3 d of curing,the uniaxial compressive strength reaches 0.6–1.0 MPa.Furthermore,under triaxial confining pressure conditions,the material’s strength exhibits a positive correlation with increasing pressure,demonstrating excellent energy absorption characteristics.This research provides technical support for the subsequent promotion and application of lightweight energy-absorbing paste backfill in gold mines.

As open-pit mining in the west mining area of the Songshunangou Gold Mine gradually approaches its final boundary,the transition to underground mining has become an important approach for deep resource development.During the open-pit to underground transition,the boundary crown pillar acts as a key isolation structure connecting the pit bottom and the underground stopes,and its thickness directly affects slope stability,underground mining safety,and surface subsidence control.To determine a reasonable crown pillar thickness,this study systematically analyzed the engineering geological and hydrogeological conditions of the mining area and applied several theoretical methods,including the thickness-span ratio method,load transfer intersection line method,Protodyakonov arch theory,and the K.B.Rubenietha empirical formula,to calculate the safety thickness of the crown pillar under different stope span conditions.The calculated safe thickness obtained from these theoretical approaches mainly ranged from 14 m to 20 m.By considering unfavorable factors such as fractured rock mass structures,freeze-thaw cycles in cold regions,and groundwater effects,an engineering safety allowance was introduced based on the theoretical results,and the minimum safe thickness of the boundary crown pillar was finally determined to be 25 m.Furthermore,a three-dimensional numerical model coupling the open pit and underground stopes was established using Flac^3D to simulate the stress and displacement evolution during staged underground mining and backfilling.The simulation results show that under a crown pillar thickness of 25 m,the maximum compressive stress of the pillar is about 15 MPa,and the maximum displacement is 7.905 cm,both of which are within the rock mass strength and engineering stability limits,indicating that the crown pillar remains stable overall.The research results provide a scientific basis for the design of open-pit to underground mining at the mine.

To address the massive waste rock and tailings generated during ore mining processes,this study conducted Brazilian splitting tests on waste rock-tailings backfill specimens to achieve efficient utilization of general solid waste in mines and gain insights into the influence mechanisms of tensile strength and energy dissipation characteristics in waste rock−tailings backfill.Response surface methodology was employed to analyze experimental results regarding tensile strength and energy dissipation.The research systematically investigated the effects of varying waste rock addition rates,ash-sand ratios,slurry concentrations,and curing ages on the backfill’s tensile strength and energy dissipation.Results demonstrate that stress–strain curves of waste rock-tailings backfill exhibit distinct four-phase features including compaction,elastic deformation,yielding,and fracture.Under identical slurry concentrations,tensile strength increases with rising ash-sand ratios,waste rock addition rates,and prolonged curing ages,with the ash-sand ratio at 1∶4 showing the most significant impact under controlled conditions.The response surface-based tensile strength prediction model of the backfill achieves a multiple correlation coefficient of 0.9687,revealing the influence hierarchy:curing age>ash-sand ratio>waste rock addition rate.Elastic strain energy density accounts for over 98%of total energy during backfill fracture,indicating that abrupt release of internal elastic strain energy constitutes the primary failure mechanism in Brazilian splitting tests.The research results can provide a theoretical basis for the optimization of waste rock−tailings backfill ratio in underground mines and for maintaining the stability of underground goafs and stopes.

Cement production is a major contributor to global CO₂emissions,motivating the research and development process of low-carbon cementitious materials using industrial solid waste as raw materials.This study investigated a metallurgical slag−gypsum composite cementitious material as a partial substitute for ordinary Portland cement,with emphasis on the hydration mechanisms,hydration products,and strength development rules of the metallurgical slag−gypsum composite cementitious material.A response surface methodology mixture design was used to optimize the proportions of steel slag,ground granulated blast furnace slag,and desulfurized gypsum.Ten mixtures were prepared and tested for uniaxial compressive strength at 7 d and 28 d,and selected typical mixtures were characterized using X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy.The response surface model exhibited excellent fitting performance,with the coefficients of determination(R2)for the models at curing ages of 7 d and 28 d being 0.987 and 0.837,respectively.The early strength of the material was primarily governed by the interaction between DG and slag,whereas the later strength was dominated by the regulating effect of the overall proportioning components.The hydration process exhibited distinct stage characteristics:The early stage was centered on the formation of ettringite,while the later stage relied on the growth of calcium-aluminosilicate gel to achieve matrix densification.The optimized proportioning group(33.5%SS,55%slag,and 11.5%DG)exhibited the best mechanical properties at 7 d and 28 d.The research results indicate that the metallurgical slag−gypsum composite cementitious material can provide the mechanical properties required for mine backfilling and other low-strength construction applications,while effectively reducing environmental impact.

In response to the lack of synergy between structural parameters and backfill strength in downward drift filling mining methods applied to complex ore bodies,a collaborative optimization study was conducted based on the Maoping lead-zinc mine to provide a foundation for safe mine expansion.A three-dimensional numerical model was built by employing Flac3D software to simulate the mining processes of three drift sizes,including 3.5 m×3.0 m,4.5 m×4.0 m,and 5.5 m×5.0 m.By adopting a bisection-based strength search method,the critical strength requirements of the bottom-layer backfill for each drift size were determined.Results indicate that under the drift size of 3.5 m×3.0 m,the critical cohesion is 350 kPa,corresponding to the uniaxial compressive strength of 0.96 MPa.When the drift size increases to 4.5 m×4.0 m,the critical cohesion rises to 410 kPa,with the strength requirement of 1.13 MPa.When the drift size grows to 5.5 m×5.0 m,the critical cohesion reaches 620 kPa,with the strength requirement of 1.71 MPa.By integrating the measured average backfill strength of 4.41 MPa and safety factor of 3.6,the actual required strength for the three drift sizes was calculated as 3.46 MPa,4.07 MPa,and 6.16 MPa,respectively.Analysis reveals that in the current backfill strength conditions,expanding the drift size from 3.5 m×3.0 m to 4.5 m×4.0 m is feasible,whereas further expansion to 5.5 m×5.0 m results in insufficient strength.This study elucidates the quantitative relationship between drift size expansion and backfill strength,thus providing concrete guidance for optimizing drift parameters and backfill mixture design in similar conditions,and holding guiding significance for safe and efficient mining.

Mix proportion experiments were conducted on early-strength composite filling materials by employing full tailings as the main raw material to enhance the early strength of mine backfill and reduce filling costs.The physical and chemical properties of the full tailings were analyzed,and the compatibility of four types of early-strength agents with full tailings paste was evaluated,with the mix proportions of composite cementitious materials optimized by orthogonal experiments.The results show that the HY-3 early-strength agent performs best in improving early strength,increasing the 3-day strength by approximately 50%at a dosage of 1%.Without activators,the synergistic effect of clinker and mineral powder significantly enhances later-stage strength.In the system containing activators,the c4 formulation(45%clinker+40%mineral powder+10%quicklime+5%anhydrous sodium sulfate)achieves the 3-day,7-day,and 28-day compressive strength of 2.06 MPa,4.70 MPa,and 7.70 MPa respectively under the cement-sand ratio of 1∶6 and slurry concentration of 76%.This meets the mine’s false bottom strength requirement and enables low-cost replacement of traditional cement-based filling materials.The results can provide reliable technical support for low-cost,high-strength,and high-efficiency mine filling.

To investigate the deformation characteristics and support optimization methods of roadways excavated in backfill under complex stress conditions,the stress distribution and roadway deformation failure characteristics of a copper mine in Serbia were surveyed.The stability of the backfill was evaluated based on a modified coal mine roof rating(mCMRR)system,and the support parameters for roadways excavated in the backfill were optimized by combining the analysis of roof bolt systems(ARBS)with numerical simulation.The results show that a high horizontal stress difference coefficient,fractured rock strata,and non-uniform stress transfer induced by intensive multi-level mining are the main causes of the complex stress regime in the mine,with roadway deformation characterized by roof crushing,apex failure,and shear staggering.The mCMRR value of the backfill in the bottom structure of the preliminary stope is 60.5,rated as"moderate"with a safety factor of 2.14.For the combined boltmesh-shotcrete support system in roadways excavated in the backfill,the existing bolt pattern can be optimized from 0.8 m×1.0 m to 1.0 m×1.2 m.Numerical simulation and industrial tests indicate that a support scheme consisting of roof bolts spaced at 1.0 m×1.2 m,ϕ6 mm@100 mm×100 mm steel mesh on the roof and sidewalls,and a 50 mm shotcrete layer,can effectively form a cooperative load-bearing structure of roadway and surrounding rock.The stress,displacement,and plastic zone distributions in the roof and sidewalls meet safety requirements,and the support cost is reduced by 8.3%.

As oxidized gold ores that are easier to process gradually deplete,the proportion of refractory arsenic-containing gold ores in global gold resources continues to rise.The simultaneous realization of"efficient dearsenication"and"gold liberation"has become one of the key challenges in the field of green metallurgy.Pressurized oxidation(POX)technology,relying on high-temperature and high-pressure wet environments,combines advantages such as fast reaction rates,effective arsenic solidification,and high gold recovery.It has demonstrated engineering potential in the pretreatment of some high-arsenic gold concentrates,achieving stable gold recovery rates of over 90%and dearsenication efficiency exceeding 95%.Based on the review of the mineralogical characteristics and arsenic occurrence states of arsenic-containing gold ores,this paper systematically summarized and compared experimental studies and industrial cases reported in recent years from four aspects:reaction mechanisms,thermodynamics and kinetics,process enhancement strategies,and arsenic fixation and environmental safety control.The results show that arsenopyrite and arsenical pyrite can be rapidly oxidized under conditions of 190℃–230℃,certain oxygen partial pressure,and acidity,where arsenic is converted from As(Ⅲ)to As(Ⅴ).Under suitable pH and n(Fe)(As)ranges,stable iron arsenate phases such as scorodite are preferentially formed,and the arsenic concentration in neutralization solutions can be reduced to milligram-per-liter levels.Segmented pressure strategies,increased slurry solid content,and optimized oxygen supply strategies help achieve nearautothermal operation,significantly reducing the consumption of external steam and fuel.The addition of solid arsenic carriers such as CaO and Fe2O3,along with the use of corrosion-resistant materials and structural optimization,can further improve arsenic residue leaching stability and extend the service life of equipment.Based on these findings,this paper discusses the applicability boundaries and advantages and limitations of POX in the clean pretreatment of arsenic-containing gold ores by considering energy consumption constraints and environmental emission requirements.Research demands related to digital twin simulation,intelligent process control,and arsenic residue resource utilization are proposed.The insights provided can offer theoretical support and technical references for process route selection,engineering scale-up design,and subsequent green transformation of high-arsenic refractory gold ores.

As metal mines progressively enter the stage of deep mining,the demands for mine safety as well as green and efficient production have become increasingly prominent.The backfilling mining method has emerged as a vital mining technique for deep ore bodies due to its effectiveness in ground pressure control,improvement of ore recovery rates,and enhancement of underground working conditions.Traditional backfilling mining methods,however,suffer from shortcomings such as high backfilling costs and significant labor intensity.Enhancing backfilling system efficiency,reducing mining backfilling costs,and decreasing workers’labor intensity have become key challenges in promoting backfilling in mines.As a novel solution to these challenges,intelligent backfilling technology has achieved positive results in many mining applications.This paper briefly introduced the basic concepts and principles of intelligent backfilling technology,analyzed the reasons for its rapid development,and provided a detailed overview of the current state of artificial intelligence algorithms in backfilling experiments as well as the construction of intelligent backfilling systems in China.Finally,the difficulties in research on intelligent backfilling technology were discussed,and some ideas for the future development direction of intelligent backfilling technology were provided.