A Large Goaf Group Treatment by means of Mine Backfill Technology

There are few studies on the management methods of large-scale goaf groups per the specific surrounding rock mass conditions of each goaf. This paper evaluates comprehensively the stability of the multistage large-scale goaf group in a Pb-Zn mine in Inner Mongolia, China, via the modified Mathews stability diagram technique. The volume of each goaf to be backfilled was quantitatively analyzed in the combination of theoretical analysis and three-dimensional laser scanning technology. The corresponding mechanical characteristics of the filling were determined by laboratory testing while formulating the treatment scheme of the large goaf group using the backfill method. The applicability of the treatment scheme using the backfill was verified by the combination of the numerical results of the distribution of the surrounding rock failure zone and the monitored data of the surface subsidence. The research results and treatment scheme using the backfill can provide a reference for similar conditions of mines worldwide.

Characterization of Strength and Quality of Cemented Mine Backfill Made up of Lead-Zinc Processing Tailings

Predicting the reactions of the backfill materials exposed to the effects of air and groundwater will eventually ensure an efficient and accurate mine fill system for sustainable mining operations. This paper reveals the effect of the mobility of sulfur ions within lead-zinc processing tailings on strength and quality of cemented mine backfills. Some laboratory tests such as X-ray diffraction, ion chromatography, scanning electron microscopy, combustion tests, chemical analysis, pH and zeta potential measurements were performed to better characterize the backfill’s mechanical and microstructural properties. Moreover, CEM II/A-P Portland pozzolan and CEM IV/A pozzolanic cements as ready-to-use cement products were used for cemented mine backfill preparation. To ensure the carrier of the lead-zinc tailings and to prevent the mobility of the sulfurous components, a binder content ranging from 3 to 7 wt% were employed in mine backfills. The experimental findings demonstrate that the used cement type and proportions were insufficient and some fractures are occurred in the samples due to the sulfur ion mobility. Accordingly, one can state clearly that the elemental analysis through the combustion test method can provide fast and reliable results in the determination of sulfur within lead-zinc processing tailings.

The Potential Re-Use of Saudi Mine Tailings in Mine Backfill: A Path towards Sustainable Mining in Saudi Arabia

The Kingdom of Saudi Arabia covers an area of approximately 2 million km2 and is rich in natural resources that are necessary for industrial development. The estimated mineral wealth beneath the Kingdom’s soil is approximately USD 1.33 trillion, as reported by the Ministry of Industry and Mineral Resources. The Kingdom’s vision for 2030 is to develop the mining sector to become the third pillar of the domestic economy. Therefore, exploration and mining activities are expected to accelerate over the next decade, which will lead to increased waste production. New executive regulations issued in January 2021 contain several sustainable elements related to the environment, social responsibility, and occupational health and safety. Therefore, this study aims to promote an example of sustainable mining activities in the Kingdom that could be adapted to meet the regulatory requirements. Cemented paste backfill samples of varying composition were made with waste materials from a Saudi copper mine for re-injection into underground mining cavities to minimize waste exposure to the environment. The samples were tested for unconfined compressive strength (UCS) after 7, 14, 28, 56, and 90 days of curing. Results from a statistically designed experiment technique show that the samples developed sufficient strength to be used in mine backfilling applications. Strong negative relationships were detected between the UCS and the water-to-binder ratio. There is strong potential for mine backfill technology to be applied to a wide range of Saudi Arabian mines to enhance the sustainability of the mining sector.

New Definition of Ultrafine Particles in Mine Paste and Its Relationship with Rheological Properties

Mine backfill paste is generally composed of tailings and coarse aggregates. In engineering practice, the definitions in fill material classification are vague. In this paper, the size range of ultrafine particles is defined by the Stokes sedimentation test and hydraulic coarseness method. The size range of ultrafine particles is affected not only by the geometric size of the particles but also by the physical characteristics of the particles themselves. This definition has more comprehensive considerations and stricter physical and mathematical significance than the traditional definition of ultrafine particles based only on size. There is a strong correlation between ultrafine particles in fill materials and the rheological properties of the mine backfill paste. In this study, through experiments and correlation analysis, it was found that the content of ultrafine particles is positively correlated with the plastic viscosity of the mine backfill paste, and its growth range is exponential. The coarse aggregate content is positively correlated with the yield stress of the mine backfill paste. A regression analysis model was established for the rheological properties of mine backfill paste. The model has few factors and high correlation, so it can simply and efficiently predict the rheological properties of mine backfill paste and guide engineering practice.

Evaluation of Backfill Operation Models Using SBSC and IFAHP Approach

As the mine backfill is recognized as one promising technique for the sustainable development, it is crucial to explore the backfill operation mechanism for the mining industry. At present, the self-management and outsourcing model are generally selected to apply in backfill operation and management worldwide. The advantages are insufficient from the strategic and sustainable perspective. Therefore, the study proposes joint venture alliance and concerns the superiority on mine backfill management. In order to evaluate the models, this study puts forward the integrated method which involves combination of SBSC and IFAHP. A strategic and hierarchical framework of SBSC on the basis of sustainability is formulated, which includes 6 perspectives and 16 secondary indexes. Simultaneously, the IFAHP approach is used for determination of the weights of indexes and calculation of the final score, which enables to assess mine backfill operation activity more objectively. The results show that the self-management model provides little advantages whereas the outsourcing model is the better operation mechanism. By contrast, joint venture alliance is rated as the optimal backfill operation model of the mining industry. The research findings of this study would help the mining industry to evaluate objectively and make an appropriate decision on the backfill operation model in the mining industry.

The Potential to Replace Cement with Nano-Calcium Carbonate and Natural Pozzolans in Cemented Mine Backfill

The effectiveness of mine backfilling depends on the properties of its constituents. The high cost of cement, which is commonly used as a binder in mine backfill, has led researchers to seek alternatives to partially replace it with other binders. This study investigated the potential to use nano-calcium carbonate (NCC) and natural pozzolans (zeolite and pumice) along with Portland cement (PC) in mine backfill. Two types of experimental samples were prepared: (1) gold tailings and silica sand to investigate the effect of NCC and (2) nickel tailings to investigate the effect of natural pozzolans. The unconfined compressive strength (UCS) was measured for samples cured for up to 56 days. Moreover, selected samples were subject to mercury intrusion porosimetry to investigate microstructural properties. Results show that addition of NCC did not improve the UCS of backfill prepared with gold tailings and cured for 28 days, whereas a dosage of 1% NCC in backfill samples prepared with silica sand improved UCS by 20%, suggesting that the gold tailings negatively affected strength development. Natural pozzolans, in particular, 20% zeolite, had 24% higher UCS after 56 days of curing compared to samples prepared with PC and thus have the potential to partially replace cement in mine backfill.