Cemented Rockfill Research Articles

Improvement of cemented rockfill by premixing low-alkalinity activator and fly ash for recycling gangue and partially replacing cement

Recycling mining wastes such as gangue for cemented rockfill is a key approach for sustainable development while ensuring the safety of underground structures in the mining industry. However, achieving sufficient strength for this low-cost material remains a fundamental challenge. This study explores an approach to strengthen cemented rockfill by using well-graded gangue, and by partially replacing Portland cement with fly ash and a premixed low-alkalinity activator. The effects of activator dosage and curing time on mechanical properties, composition and microstructure of cemented rockfill were investigated through uniaxial compression, XRD, FTIR, TG/DTG, MIP and SEM-EDS analyses. Results show overall improvements in the performance of cemented rockfill despite its low cement content, and the use of a low-cost low-alkaline activator. The 28-d compressive strength improved by over 30 % to reach 8 MPa with only 7.7 % wt. Portland cement and incorporating more than 60 % wt. of waste gangue in its mix composition. The main source of strength is calcium silicate hydrate and calcium aluminate silicate hydrate, the latter playing an increasing contribution with longer curing due to fly ash activation. Addition of premixed activator to fly ash enhanced the formation of Ca6Si6O17(OH)2, and CaO∙Al2O3∙xSiO2∙yH2O. Activator causes densification of the microstructure and this occurs predominantly on pores smaller than 1 μm. The optimum mix having the highest performance-cost ratio contains between 10 % and 15 % activator. This work reveals an effective and low-cost method of premixing fly ash with a low-alkalinity activator for recycling mining wastes and reducing cement.

Use of microgrid fibre as a new reinforcement additive to improve compressive and tensile strength values of cemented rock fill mixes

ABSTRACT In this study, use of microgrid fibre (MGF) was tested as a new polypropylene fibre additive for cemented rock fill (CRF) mixes and compared with the conventional polypropylene fibre type geosynthetics. Changes in the uniaxial compressive strength and indirect tensile (splitting) strength values of CRF specimens were investigated for the use of different fibre types. In this experimental study, cemented basalt aggregate type rock fill materials were tested in case of using different amounts of fibre additives and cement contents. According to the results obtained from this experimental study, it was determined that MGF type new fibre additives can supply better increases in strength values in comparison with the conventional polypropylene fibre products. It was assessed that MGF type novel additives can be used to make better adherence in the CRF mixes and reinforcement performances under both compression and tension cases than those of the conventional fibre additive products.

Technical Assessment and Implementation of Cemented Rock Fill at the Cerro Lindo Mining Unit in Peru

Technical Assessment and Implementation of Cemented Rock Fill at the Cerro Lindo Mining Unit in Peru

Effect of CNT-FA hybrid on the mechanical, permeability and microstructure properties of gangue cemented rockfill

Solid waste resource reuse, such as fabricating cemented rockfill material, plays a central role in underground reinforcement projects and construction waste recycling. However, the cement applied in the cemented rockfill material still brings massive CO2 emissions and energy consumption. Hence, we take the 0.009 wt% carbon nanotubes (CNTs) combining fly ash(FA) to replace 20% cement to explore a more sustainable improvement for cemented rockfill material. The results demonstrated that CNTs modified specimens exhibited a 17.6% reinforcement in elastic modulus, while the compressive strength remains almost unchanged. The modified specimen also shows fewer and sparser acoustic emission activities, indicating lower destruction intensity. Furthermore, with the help of CNTs filling the pores, water sorptivity and gas permeability tests showed that the impermeability improved by 8.4%-19.7%. By calculating the fractal dimension of the fracture surface SEM images, the CNTs reinforced specimens show better integrity and less structural damage. Metal intrusion measurements indicated that CNTs minify the ITZ width, split micropores in ITZ to reduce porosity under all equalized diameters significantly, especially at 65–70 μm, and form a network skeleton in the pores at the edge of the ITZ to prevent pores from connecting with microscopic defects in the cement matrix. The findings of this work can enhance the understanding of CNTs in composites fabrication and guide the application of CNTs in construction, transportation and mineral engineering in the future.

Effects of aggregate strength and mass fraction on mesoscopic fracture characteristics of cemented rockfill from gangue as recycled aggregate

The discrete element model considering media properties and interface differences was constructed for revealing the mesoscopic fracture characteristic of cemented rockfill in this study. The effects of aggregate strength and mass fraction on strength, deformation, energy and cracking of cemented rockfill were investigated. The results showed that the generally concerned two-element intergranular fracture between aggregates and cement matrix ITZ only plays a leading role in one fracture characteristic, but the failure induced by damaged aggregates is more severe than this fracture characteristic. The fracture characteristic transformation induced deterioration of cemented rockfill is catastrophic. The compressive strength of the specimen produced from 12.88 MPa gangue is nearly 30% worse than that of 32.77 MPa. And this fracture characteristic transformation is related to the aggregate mass fraction. The aggregate strength corresponding to the turning aggregate to cemented matrix strength ratio decreases from 52 MPa to 32 MPa with increasing the aggregate mass fraction from 42.7% to 57.7%. Therefore, the development of cemented rockfill requires more attention to the compatibility as characterized by the aggregates to cement matrix strength ratio and aggregate mass fraction. As the strength ratio increases, the recycled aggregates transform from defect clusters to load bearing phases in cemented rockfill.

Influence of industrial graphene oxide on tensile behavior of cemented waste rock backfill

Cemented waste rock backfill (CWRB) is an important supporting technology for underground engineering safety and waste recycling. However, the brittle nature of cementitious materials, particularly weak tensile behavior, always compromises the performance of the CWRB. In this study, the industrial graphene oxide (IGO) was adopted to reinforce the tensile behavior of the CWRB specimens and be mixed with fly ash to fabricate environmentally friendly, cost-effective, high-performance backfilling materials. The results showed that the tensile strength of the CWRB specimens was significantly improved up to approximately 230%, by only mixing 0.007 wt% IGO. The low water-to-cement (W/C) ratio benefited from the enhancing effects of the IGO on CWRB’s tensile performance. Molecular dynamics simulations further revealed the underlying nanoscale reinforcing mechanisms of IGO, indicating that the tensile strength enhancement is mainly due to GO nanosheets effectively improving the ductility of the nanocomposites and delaying the failure of cementitious materials. The microstructure characterization proved that IGO could generate nucleation effects and pore infilling effects to optimize the microstructure in the interfacial transition zone (ITZ) of CWRB. Acoustic emission monitoring and digital photography characterization technologies implied that incorporating IGO could effectively reduce the micro-damage degree of the CWRB specimens during the failure process. This phenomenon ensures the integrity of the specimen during the destabilization failure process and reinforces resistance to the compressive load. This research not only broadens our understanding of GO in enhancing cementitious composites but also inspires the potential application of the IGO for strengthening the performance of cemented rockfill and the sustainability of waste rock recycling.

Effects of carbon nanotube dosage and aggregate size distribution on mechanical property and microstructure of cemented rockfill

The mechanical and structural properties of cemented rockfill produced by mineral wastes as recycled aggregates limit its application. In this paper, the macroscopic mechanical and microscopic scanning tests were carried out to study the mechanical property and microstructure of cemented rockfill reinforced by carbon nanotubes (CNTs) and fractal aggregates. The strengthening and deterioration mechanisms of CNT dosage on cemented rockfill were revealed for systematically evaluating its engineering availability. The influencing mechanism of aggregate size distribution on cemented rockfill was clarified to analyze the contribution of optimizing aggregate size distribution. The results show that the strengthening of cemented rockfill by appropriate CNTs includes bridging microcracks, compacting micropores and reinforcing cemented matrix, while the deterioration by excessive CNTs is attributed to form the agglomerative clusters and hollow cemented matrices. The cemented rockfill with superior aggregate size distribution has uniform and dense microstructure with relatively few defects, which is conducive to CNT reinforcement.

Large-scale characterisation of cemented rock fill performance for exposure stability analysis

A novel large-scale geomechanical laboratory testing program is developed to provide full characterization of the strength and deformational response of cemented rockfill (CRF) material for use in exposure stability analyses. Uniaxial compressive strength (UCS), direct shear, and three-point bending tensile tests are performed on large-scale samples that require the use of novel processes and laboratory equipment. For the first time, the shear properties of large-scale CRF samples have been investigated using direct shear tests under constant normal stiffness (CNS) boundary conditions. Large-scale three-point bending tests are also conducted to obtain true tensile strengths without having to infer them from UCS test results. For up to 28 days curing time, the effects of particle size distribution and binder quantity are experimentally examined for each compression, tension, and shear failure mode through a study of the full stress–strain response. In order to obtain accurate laboratory results, findings are compared against published large-scale tests from various mine sites. The results show that the large-scale samples completed herein provide a reliable UCS estimate with standard deviations of less than one. It is also found that the direct shear responses are substantially larger for simulated CRF: Sidewall contacts than CRF: CRF contacts, and tensile strength responses are higher than previously estimated at 10% of the UCS strength. The effect of particle size distribution on the geomechanical response of the CRF material is highlighted through the large-scale sample testing. The findings of this research study provide increased technical understanding for the development of CRF structures in underground mines that are cost-effective, safe, and durable. Additionally, this research study establishes a practical testing methodology that overcomes the challenges that occur in collecting quantitative geomechanical data from large-scale CRF samples for design purposes.

Strength prediction based on ultrasonic property of fractal gangue cemented rockfill reinforced by carbon nanotubes

Producing cemented rockfill for supplying building material and underground filling material is currently the most effective approach to recycle solid mineral waste. Investigating its ultrasonic property and constructing a model for predicting its strength are of great significance to its on-site assessment and engineering stability. Ultrasonic detection test was carried out on the fractal gangue cemented rockfill reinforced by carbon nanotubes (CNTs) to study the effects of the curing time, CNT dosage and aggregate size distribution on its ultrasonic property. The relation between ultrasonic pulse velocity (UPV) and uniaxial compressive strength (UCS) was established through uniaxial compression test, and the model I for predicting the strength of cemented rockfill was built based on this relationship. The coupling relationship between the curing time, CNT dosage, particle size distribution (PSD) fractal dimension of aggregates, UPV and the UCS of cemented rockfill was established by genetic algorithm (GA), and the strength prediction model II was constructed based on this coupling relationship. The difference between both prediction models and the matching degree between predictive strength and experimental data were discussed, a more accurate method for predicting the strength of cemented backfill was proposed. The results show that the relationship between CNT dosage and UPV can be described by the quadratic function, it believes that the optimal CNT dosage is between 0.05% and 0.10% for cemented rockfill. The relationship between PSD fractal dimension and UPV can be characterized by the quadratic function, it considers that the optimal PSD fractal dimension is in the range of 2.4150 and 2.6084 for the aggregates in cemented rockfill, and this optimal aggregate size distribution is easily affected by other conditions. The exponential function σ1c=ξ10eξ11v-ξ10 can be used to describe the relationship between UPV and UCS, the prediction model I based on this relationship for predicting the strength of cemented rockfill has the determination coefficient of 0.9164 matching with the experimental data. The prediction model II based on the coupling relationship combining material parameters with UPV correction by using GA performs the reliable prediction accuracy with 4.5223% of mean absolute percentage error (MAPE) and 0.9513 of determination coefficient better than model I.

Investigation of Backfilling Step Effects on Stope Stability

Cemented rock fill (CRF) is commonly used in cut-and-fill stoping operations in underground mining. This allows for the maximum recovery of ore. Backfilling can improve stope stability in underground workings and then improve ground stability of the whole mine site. However, backfilling step scenarios vary from site to site. This paper presents the investigation of five different backfilling step scenarios and their impacts on the stability of stopes at four different mining levels. A comprehensive comparison of displacements, major principal stress, and Stress Concentration Factor (SCF) was conducted. The results show that different backfilling step scenarios have little influence on the final displacement for displacement in the stopes. Among the five backfilling scenarios, the major principal stress and stress concentration factor (SCF) have almost the same final results. The backfilling scenario SCN-1 is the optimum option among these five backfilling scenarios. It can immediately prevent the increase of the displacement and reduce the sidewall stress concentration, thereby preventing possible failures. Using the same strength of CRF can achieve the same effects among the four mining levels. Applying backfilling CRF of the same strength at different mining depths is acceptable and feasible to improve the stability of the stopes.

STUDY OF THE INFLUENCE OF BACKFILLING ON STABILITY AND LOCATION OF REMAINING STOPES IN SILL PILLAR RECOVERY

To extract steeply dipping orebodies, many mines in Canada have adopted the sublevel stoping method, such as blasthole stoping (BHS) and sublevel longhole retreat (SLR). In such methods, sill pillars are initially kept in place to support the weight of the overburden in underground mining. After the stope mining is complete, the stope voids will be backfilled with cemented rockfill (CRF). The strength of the CRF affects the stability of the adjacent stopes in the sill pillar recovery excavation scheme. Sill pillar recovery may cause prolonged failure, fatality, and equipment loss. Choosing a rational location of the last mined stope in sill pillar recovery can effectively eliminate the possible instability caused by the sill pillar recovery process. This paper uses the Finite Element Method (FEM) to present a comparison of sidewall swellings, floor heaves, and the roof subsidence of the crossing cuts in each stope among different last mined stope location scenarios. At all the 21 location scenarios, most of the roof corner displacements in undercuts are less than 10 cm, while in the overcuts, all the displacements in roof corners are over 10 cm. The values of the floor heave in the overcuts are more than 7 times that in the undercuts. Roofs in both undercuts and overcuts are prone to failures. Floors in the undercuts are more stable than the floors in the overcuts. For the optimum location of the last mined stope in sill pillar recovery, the last mined stope should be at least four-stope-width away from the two sill pillar edges

Sustainable Underground Iron Ore Mining in Ukraine with Backfilling Worked-Out Area

The present paper considers aspects of underground iron ore mining in Ukraine, in particular the level of mine production and reserves of basic ore fields. It analyzes and generalizes the practice of using cemented rockfill under difficult mining and hydrogeological conditions of the Pivdenno-Bilozerske high-grade iron ore field. The Belozersky iron ore district is the only one in Ukraine that, without any technological cycle of beneficiation, can provide both domestic and foreign consumers with high-quality raw iron ore as required by world markets. The PJSC Zaporizhzhia iron ore plant extracts iron ore from the Pivdenno-Bilozerske field with an iron content of more than 60% using the low-waste, environmentally friendly technology of backfilling the mined-out area with a hardening mixture. The peculiarities of the technology for steep deposit mining and the main processes of backfilling operations in terms of preparation, transportation, and construction of the backfill mass with its stability assessment are explained in detail in this paper. As a result of using cemented rockfill, rock mass stability is provided, a considerable part of industrial waste is disposed of in the mined-out area, and the earth’s surface subsidence within the area is prevented (in comparison with mining enterprises in other fields).

A Gaussian process machine learning model for cemented rockfill strength prediction at a diamond mine

As a main strategy of backfilling in mining operations, cemented rockfill (CRF) is extensively used because of its high strength and mine waste disposal convenience. The CRF strength has a direct bearing on ground support performance in backfill mining, which necessitates investigating CRF strength determination. This study employed a Gaussian process (GP) machine learning model to reflect the relationship between CRF compressive strength and material components as well as curing age. More than one thousand data from a public database were used to train the GP model with an automatic hyperparameter optimization. A series of laboratory tests prepared eight test samples for our predicting as well as the true values for model validation. The GP model achieved a predicting accuracy with the r2 value 0.90 and the MSE value 7.78 based on CRF true values we obtained in the laboratory. In addition, seven test samples’ true values resided inside the 95% confidence interval of the GP prediction. We also constructed three other machine learning models to conduct the same work as the GP model did. The results showed that the GP model performed the best of four models, which demonstrated that the GP model was effective and robust in dealing with time series predicting task.

Long-Term Stability of a 13.7 × 30.5-m (45 × 100-ft) Undercut Span Beneath Cemented Rockfill at the Turquoise Ridge Mine, Nevada.

In 2001, researchers from the National Institute for Occupational Safety and Health (NIOSH) installed instruments at the Turquoise Ridge Mine in cooperation with Placer Dome, Inc. to monitor the geomechanical behavior and stability of a cemented rockfill (CRF) sill and the surrounding host rock during test mining of a large undercut span beneath backfill. Six parallel, adjacent drifts were mined and backfilled to construct a CRF sill, approximately 22.9 m (75 ft) wide by 30.5 m (100 ft) long. The sill was then partially undercut, successfully creating a 13.7-m (45-ft) wide by 30.5-m (100-ft) long span beneath the CRF. Only small vertical displacements were measured in the overlying host rock during mining, with most of the movement occurring at shallow depths in the mine roof. Because the back above the CRF sill remained stable, the majority of the mining-induced stress was transferred to the host rock abutments rather than to the backfilled drifts. During retreat mining of the undercut span, the CRF sill and the mine roof remained stable. Most of the measured vertical displacement was caused by separation of the backfill from the overlying host rock, or deflection of the CRF sill, which was comparable to the deflection of a monolithic, elastic plate having similar dimensions, material properties, and undercut spans. The CRF sill moved in mass as a single unit rather than as individual drift segments, and the vertical cold joints between adjacent backfill drifts did not adversely affect their stability. Additional measurements collected from the instruments have shown that the backfill span is still intact and in stable condition more than 16 years after the completion of undercut mining. Displacements in the mine roof and abutments have stabilized, and vertical stress and deformation within the CRF have generally leveled off or decreased. Although only slight mining-induced loads were transferred to the backfilled drifts, the CRF has confined the abutment ribs and mine roof, thereby improving their long-term stability. Results of compressive and tensile strength tests conducted with CRF samples from the test site indicate that the long-term compressive strength gain for CRF is similar to that of concrete, and that the tensile-to-compressive strength ratio for CRF is about 1/6 rather than 1/10. Assuming the in-place CRF gained strength at the same rate as the lab samples, an analytical analysis of the flexural stability of the CRF undercut span shows that the Factor of Safety for the span should have logically increased over time. By providing a better understanding of the long-term strength properties and geomechanical behavior of CRF, these research findings help improve the methods that are used for designing stable, long-term undercut entries beneath cemented backfill.

An experimental study on compressive behaviour of cemented rockfill

• Technical information and data for better optimization and design of cemented rockfill (CRF) are presented. • Strength and stress-strain behaviour of CRF are a function of the packing density of the aggregates. • CRF with coarser particles and the best grain size distribution has the highest strength. • Addition of sand can increase the strength of CRF. • A partial replacement of ordinary Portland cement with fly ash improves the strength of the CRF. Cemented rockfill (CRF) has more superior mechanical properties (e.g., compressive strength, stiffness, cohesion and friction angle) over other types of backfill material, such as cemented paste backfill (CPB) and hydraulic fill, with the same amount of binder. A comprehensive understanding of the mechanical performance of CRF is critical for effectively applying CRF technology to underground mines. In this paper, the effects of aggregate gradation, the addition of sand, and binder content and type on the uniaxial compressive strength (UCS) and stress-strain behaviour of CRF are experimentally investigated for up to 90 days of curing. The results show that CRF with coarser particles and the best grain size distribution has the highest strength over that with uniform-sized rock aggregate, and the strength of the CRF increases with increased maximum particle size of the rock aggregate. The strength of the CRF increases in proportion with the amount of ordinary Portland cement (OPC). The addition of sand enhances the strength of the CRF samples; the extent of the increase in strength depends on the sand/aggregate replacement ratio. A partial replacement (20–50%) of OPC with fly ash (FA) appears to improve the strength of the CRF samples due to the micro-filler effect, whereas a negative effect is observed when blast furnace slag (Slag) with relatively low strength activity index is used instead. Moreover, the stress-strain response of CRF is strongly influenced by the curing age, aggregate gradation, addition of sand, and binder content and type. The results of this investigation provide technical information for designing cost-effective, safe and durable CRF structures in underground mines.

Assessment of digital image correlation method in determining large scale cemented rockfill strains

A conventional contact method (using linear transducers) and a non-contact method are deployed to measure the axial and lateral deformations of large scale cylindrical cemented rockfill specimens. Experimental works incorporating two pinhole cameras to create one stereovision by digital image correlation shows that the non-contact method is as reliable for testing large cylindrical specimens as measurements done by using linear variable displacement transformer and string potentiometer. Considering this particular large specimen, the experiment resulted in the acceptable mean difference between lateral strain using both methods is 5.1 percent, and 14.5 percent for the axial strain. This occurrence is inevitable due to the heterogeneity of the concrete system and the placement of the monitoring point in digital image correlation method, although the comparison of stress-strain relationship in both methods still indicates a conformity. Based on the results of the present experiments, the authors recommend the non-contact method for a detailed investigation of the material behavior during the uniaxial compressive strength tests. Full field strain measurement enables this digital method to examine local strains near cracks at any point, a very useful tool for studying material deformation behavior.

Particle size distribution of aggregate effects on mechanical and structural properties of cemented rockfill: Experiments and modeling

This study presents the particle size distribution of aggregate effects on the mechanical and structural properties of cemented rockfill. The uniaxial compression tests with acoustic emission (AE) monitoring, ultrasonic tests and scanning electron microscope (SEM) tests were carried out on the cemented rockfill, for which the aggregate particles satisfied the Talbot gradation theory. The particle flow model was constructed in the numerical software of PFC3D to reproduce the crack evolution and particle failure of cemented rockfill specimen. The AE characteristics, microstructures, numbers and distributions of initiated cracks and particle failure models of cemented rockfill under different particle size distributions of aggregates were discussed. The influence mechanism of the particle size distribution of aggregate on the strength, dilatancy and ultrasonic properties of cemented rockfill was analyzed. The results showed that the cemented rockfill with the overly fine or coarse particle size distribution of aggregate not only presented the more deteriorative microstructures, but also had the more early damaged areas with active AE signals and more initiated cracks during loading. However, the strength of cemented rockfill related to the crack distribution in the structure in addition to the number of initiated cracks. The concentration of cracks in the structure also caused the particle failure mode to present a certain dilatancy to further affect the loading capacity of the cemented rockfill. Among all the specimens, the cemented rockfill with Talbot index of 0.6 performed the relatively dense microstructures, superior structural properties and symmetric and uniform distribution of initiated cracks leading to optimize its strength, deformation and ultrasonic properties.

Aggregate gradation effects on dilatancy behavior and acoustic characteristic of cemented rockfill

Investigating the effect of the aggregate gradation on the material properties of cemented rockfill is significant for the green mining, economic benefit and engineering safety. Consequently, the ultrasonic test, uniaxial compression experiment and acoustic emission (AE) monitor on cemented rockfill were carried out, for which the aggregate satisfied Talbot gradation. The dilatancy behavior and AE characteristic of cemented rockfill under load were investigated. The damage in the internal structure under compression was revealed by the deformation and AE signals of cemented rockfill. The effect of the Talbot index on the ultrasonic pulse velocity (UPV) and the strength parameters such as stress of dilatancy onset and uniaxial compressive strength (UCS) of cemented rockfill was analyzed. The mechanical properties of cemented rockfill materials were evaluated by the establishment of the relation between the UPV and the strength parameter. The results show that The difference between the stress of dilatancy onset and the UCS, the deformation performance and the activity of AE signals during dilatancy are positive correlated with the Talbot index of aggregate in cemented rockfill. The relation between the UPV and the strength parameters (stress of dilatancy onset and UCS) of cemented rockfill can be characterized by the positive linearity, and the UPV is also suitable for characterizing the stress of dilatancy onset of cemented rockfill material. The cubic polynomial is more suitable for describing the relations between the parameters of strength and UPV and the Talbot index of aggregate than the quadratic polynomial, and the Talbot index with optimal aggregate gradation reflected the maximum strength of cemented rockfill material should be around 0.45–0.47.

Particle Size Distribution of Cemented Rockfill Effects on Strata Stability in Filling Mining

It is of great significance for engineering safety, economic benefits, environmental protection, and sustainable development to investigate the strata stability in filling mining with cemented rockfill. Consequently, this paper is based on a specific coal mine where we applied the fully-mechanized longwall mining and filling and designed a cemented rockfill material for which the particles satisfied the Talbot gradation. Uniaxial and triaxial compression experiments were carried out on the cemented rockfill specimen, which obtained the relations between the mechanical parameters (Poisson ratio, elastic modulus, compressive strength, cohesive force, internal friction angle, and tensile strength) and the particle size distribution of the aggregate. The excavation and filling processes in the coal seam were simulated based on the numerical software FLAC3D. The characteristics of the displacement and stress fields of the strata when the goaf was filled by cemented rockfill with different granule gradations were discussed. The influences of the particle size distribution and mining distance on the maximum subsidence displacement of the coal seam roof, internal stress of the backfill, and the stress of the rock mass in the coalface were analyzed. The feasibility and effectiveness of the filling mining with cemented rockfill to protect the integrity of the overlying strata were discussed. The results showed that optimizing the particle size distribution of the aggregate in cemented rockfill could increase the loading capacity of the backfill to improve the filling effect, effectively control the strata movement, and decrease the stress of rock mass in the coalface to reduce the potential danger.

Dynamic model validation using blast vibration monitoring in mine backfill

Sublevel stoping mining methods with delayed backfill are employed for mining steeply dipping ore deposits at deeper horizons. Cemented rockfill (CRF) is used as a backfilling material for open stopes formed during mining. In primary-secondary mining sequence, blast vibrations are induced in CRF during the extraction of adjacent stopes. Higher magnitude of blast vibrations may destabilize CRF causing failure and dilution of precious ore. This paper presents a methodology for calibrating a FLAC3D numerical model, encompassing mine backfill with blast-induced vibration data recorded from field instrumentation. Two FLAC3D models are prepared, one for simulating the blasting process and the other is prepared for backfill stability analysis. The first model resulted in load vectors to be applied to backfill and rock interface. The second model showed that the backfill fails under the blast vibrations induced by the adjacent production stope. The results of the back analysis of fill failure are presented and discussed. The methodology may serve as numerical model calibration procedure for mine backfill.