Since 2005, the ACG has published conference papers across the geotechnical mining spectrum, including: underground and open pit mining, paste and thickened tailings and mine closure. The repository aims to provide the mining geomechanics fraternity with open access, peer-reviewed conference proceedings that may assist readers to maintain and develop their skills, knowledge and capabilities.
?Hindustan Zincs Rampura Agucha Mine is a world class orebody that has successfully transitioned from an open pit operation to an underground sublevel open stoping with paste backfill operation. The mine currently has two identical paste plants that each can produce between 160-185 m3/hr of cemented paste backfill. Plant #1 was commissioned in 2014 and plant #2 was commissioned in 2019. The two plants are equipped with Putzmeister piston pumps that pump from the plant to the edge of the pit, down a borehole to the North and South main ramps and then down the ramps to the top of the underground orebody approximately 500 m below surface. Each plant was designed with an operating and standby paste pump. Most of the orebody can be reached from these main lines, however, at the extreme north end of the pit, there is portion of the underground orebody that is above the uppermost underground delivery level and at a significant horizontal distance from the main paste trunk lines. Because of the location of these northern stopes, an overland pipeline to the north of the pit is required before entering a borehole down to the stoping levels. This lateral distance on surface and underground would have resulted in very high pressure on the paste pumps, and a decision was made to temporarily install the standby pump from plant 2 at a booster station that would allow the northern stopes to be reached with a 2 stage pumping system instead of a single stage pumping system. The booster station was installed and commissioned in 2019 and this paper discusses the design principles regarding booster stations in general as well as the specific design, commissioning, and operational experiences with the booster station at Rampura Agucha Mine.
In the early 1960s, a series of field instrumentations were initiated by the US Bureau of Mines on hydraulic fill. These studies were conducted in order to better understand the characteristics of hydraulic backfill. Cemented paste backfill (CPB) has gained wider acceptance in the mining industry and the number of operations utilising CPB has expanded significantly. One of the earliest attempts at field measurement in CPB occurred over 20 years ago. Since then, extensive scientific research has been conducted on CPB material in order to provide mines with a rational design process; however, there has been limited published instrumentation programs. The authors affiliated company has been involved with in-stope backfill instrumentation programs at numerous operations. Because of the data collection and field experience, the authors have a better understanding of how in situ backfill behaves, and how operations can use this information to safely improve the efficiency of their backfilling operation. In order to improve the safety and efficiencies of backfilling for other mines and other practitioners, a collection of published data along with additional case studies are provided. This paper summarises both hydraulic and CPB instrumentation results focusing on the important mechanical properties of backfill: time to onset of effective stresses and hydrostatic loading (i.e. fluid backfill to soil?like material), influences of flushes, thermal expansion and contraction, and influences of seismic and blast events.
?Inspired by the success of cemented paste backfill in the west orebody of Chambishi Copper Mine, integrated disposal of paste backfill and surface high-concentration tailings stacking was applied in the southeast orebody. This paper presents the integrated disposal system, including two deep cone thickeners, double-shaft horizontal mixer, two plunger pumps for underground backfill and three diaphragm pumps for surface stacking. The challenges of the integrated disposal system were deep backfilling (0.98 km) and long-distance discharging (15 km), so a combination of gravity flow and pumping was used in paste backfill and three diaphragm pumps with a preset pressure of 7 MPa were applied for surface stacking. The annual ore production in the southeast orebody is 3.3 Mt, which is 3.3 times larger than that of the west orebody. Therefore, the capacity of the integrated disposal system also needs to be expanded. The capacity of the paste backfill system and surface stacking system were 160 m3/h with paste concentration of 75 wt.% and 265 m3/h with slurry concentration of 55 wt.%, respectively. In the first phase, the cement to tailings ratios for primary and second stopes are 1/8 and 1/24 respectively. To meet the backfill strength and reduce the cost, waste rock will be added in paste backfill in the second phase, the waste rock to tailings ratio is 1/3, the cement to tailings and waste rock ratio for primary stopes are 1:12, and 1:30 for secondary stopes. As a result, the UCS after 28 days for primary and second stopes were 1.2 MPa and 0.5 MPa, respectively.
Cemented paste backfill (CPB) has been utilised globally in mines based on its benefits of non-segregation, non-bleeding and homogeneity. Due to a lack of research around the mechanism(s) driving anti-segregation properties, nowadays only some engineering empirical parameters including the slump or the fine particle content of backfill slurries can be used as the descriptive criterion for CPB. To better understand the antisegregation mechanism of CPB, so a quantitative criterion for its identification can be determined, the segregation-induced inhomogeneous properties of cemented tailings backfill have been experimentally investigated. Samples (diameter 75 mm and height 150 mm) with different solid contents were poured, cured and cut into sections of equal height. Thereafter, titration measures of EDTA-2Na and helium porosimeter have been used respectively to test the cement content and porosity of each section. Results show that the cement contents decreased from top to bottom along the curing height of samples, while the porosities increased along the settling direction. The inhomogeneity of cemented samples is affected obviously by the solids content of the paste, and it is notable that there is a turning point for the slurry concentration value over which the homogeneity will be improved dramatically. The turning point could be used as a new criterion for CPB definition from the perspective of inhomogeneity inhibition.
The objective during TSF beach development is to still maintain a slurry that is pumpable and self-distributing at the tailings storage facility (TSF), rather than having to rely on trucks or on conveyors and stacking systems to manage a cake, but one that will deposit at a steeper beach slope than can be achieved by thickening alone. The use of ultra paste has the potential to broaden the range of topographic conditions that will suit thickened tailings discharge. This paper presents a case study for a large copper mine in which underflow from a series of paste thickeners with a nominal tonnage of 3,660 tph at 59% solids concentration would be mixed with 1,363 tph of filter cake at 80% solids concentration. The combined tailings (ultra paste) would be discharged equally into two open channels (flumes) at the combined solids concentration of 63.5%. The ultimate goal of adopting an ultra paste scheme is to produce homogenous consistency tailings, hence proper mixing of the paste and filter cake has to occur. In this study based on a series of tests, the mixing requirement has been assessed. The study also covers a conceptual investigation of natural turbulent mixing (NTM) of the filtered tailings with paste thickened tailings and issues associated with the deposition of the combined tailings, the ultra paste, into the existing TSF. In the conclusion, the study indicates that NTM can possibly occur only for the case in which the total tailings are discharged into one channel, which is not practical due to limitations with regards to tailings management. Hence, mechanical mixing has been recommended in this case.
The Chinalco Toromocho copper mine uses four (4) 43-m diameter paste-type tailings thickener, each is designed to process over 1,300 dry metric tons per hour, mtph and 3,600 cubic meters per hour, m3/h of slurry. The target non-Newtonian underflow was designed to be pumped to the tailings storage facility, TSF to be surface stacked. Difficulty has been experienced achieving the target underflow causing water balance, pumping capacity and other issues. Chinalco contracted WesTech to perform an optimization study to evaluate the benefit of retrofitting their feed system and mechanism of their thickeners with the latest advances in the market. Plant trend data was analyzed over the past 1.5 years, establishing the current operation of the site. The tailings stream variation range in dry mtph, particle size distribution, PSD, and flocculant consumption, are shown. The underflow weight percent and overflow clarity operating ranges were tracked. The analysis gives the effect these critical parameters have on thickener performance. A comparison is provided of the predicted modernization performance in response to the established operating variability. This paper provides a review of the Toromocho thickeners trend data based performance, optimization study results, and the mines way forward to optimize their tailings thickeners.
?Chile produces large amounts of tailings daily which must be safely disposed on the earths surface. There are a series of strategies that have been successfully used in our country to store tailings, among them are thickened and paste tailings. Paste tailings are an advantageous technique that allows for greater recovery of water while improving physical stability of the structure. Although challenges are faced worldwide when large production rates are tried to be thickened, the technique seems promising for countries like Chile where there is an ongoing water crisis. The stability of paste tailings facilities is highly influenced by water content or saturation. As consolidation occurs the tailings loses water. However, as the evaporation front takes place, the material goes from a saturated to a non-saturated state. Unsaturated paste has shown improved resistance, e.g. liquefaction resistance almost double when saturation drops below 90%. A well planned facility operation should consider the monitoring of the water content of the paste. However, this is sometimes difficult, due to the large areas that must be controlled and the danger associated with manual moisture measurements in the field. In this context, we proposed the use of hyperspectral cameras to obtain a relationship between the paste moisture content and light reflectance. This would allow to generate moisture surface map and to the use of this data to monitor for instance evaporation rates or water balance in tailings storage facilities. This article summarizes laboratory main findings and proposes a series of procedures to implement the technique in the field.
Paste thickening represents a proven and effective method for the safe disposal of tailings and maximises water recovery. The optimum density for disposal is often at the limits of that achievable in commercially available thickeners. This paper looks at the options available to increase paste density to meet the disposal requirements and to stabilise paste properties through blending filtered tailings with thickened tailings, supported by experimental data and case studies.
?Tailings transport is an integrated element in any wet tailings storage facility (TSF). Tailings from the process plant are often thickened to a moderate or relatively high (but still pumpable) solids concentration, depending on several parameters mainly the TSF deposition requirements and strategies, process plant water security status and the dewatering technology utilised. This paper overviews the transportation of paste and thickened tailings and discusses various aspects and considerations in the hydraulic design of the system. Material characteristics, flow behaviour assessment (rheological behaviour measurement and interpretation) and the basis of design definition are discussed. The recent developments in environmental authorities regulations associated with the tailings pipeline burst and leakage management are also reviewed in this paper. The tailings leakage and spillage to the environment is one the main concerns for any tailings hydraulic transportation system, therefore as part of the tailings pipeline design, the pipeline integrity failure (due to pipe wear, overpressure bursting etc.) should be thoroughly analysed to propose proper mitigation measures. The paper discusses a methodology to assess the potential tailings volume release to the environment in an event of the pipeline integrity failure which would be of interest to the operators and designers.