Deep Mining Operations Research Articles

Felsic magma-water interaction in shallow intrusive environments: Timing between fluidal peperites and intrusive hyaloclastites in a jurassic cryptodome from the eastern Deseado Massif (patagonia, Argentina)

This work describes the facies architecture, morphology and textures of a Jurassic rhyodacitic cryptodome outcropping in the Don Nicolás Mine, an important Au–Ag producing mine located in the Deseado Massif, Argentinean Patagonia. The access to 70 m deep surface mining operation and to a large number of diamond drill cores offer a unique chance to explore the volcanic rock assemblage of this body, allowing to study intrusion and growth mechanisms of a shallow subvolcanic body, and also providing insights into the timing between different brecciation processes occurring during magma intrusion into a poorly consolidated and water saturated pyroclastic sequence. Facies analysis allowed to infer this body as the result of a rhyodacitic magma intruding in a single and steady endogenous inflation pulse, resulting in the development of a flow banded core and a fluidal peperite envelope due to the combination of relatively low magma viscosities (for a rhyodacitic melt), the development of stable vapor films insulating the flowing magma and also allowing the ductile deformation of the rhyodacite clasts, and the fluidization of the unconsolidated and water saturated host rocks. After the main inflation stage stopped, the collapse of the vapor films resulted in quench fragmentation modifying the originally fluidal shape of many clast at the peperites, specially at the outer portion of the breccia envelope where fluidal clast shapes were almost completely erased due to this process. At the same time water invaded the inner portions of the intrusion, causing widespread quenching and the development of intrusive hyaloclastites at the edges of the coherent facies.

In situ monitoring and 3D geomechanical numerical modelling to evaluate seismic and aseismic rock deformation in response to deep mining

In this work we investigated seismic and aseismic rock mass behaviors in response to deep underground mining. For this purpose, an area under production of the metal mine of Garpenberg (Sweden) was instrumented with a geophysical and geotechnical monitoring network. In situ monitoring data were analyzed and interpreted considering mining operations and the local geological setting. In addition, a 3D elasto-plastic numerical model was built to better understand the interactions between quasi-static stress changes due to mining and the generation of the induced seismicity. Results of this multiparameter approach show a complex rock mass response. We observed two main types of seismic behaviors: one local and temporally short, directly induced by production, the other long-lasting over time and remote from excavations being mainly controlled by geological heterogeneities. In addition to seismicity, we also observed creep-like phenomena induced by mining. In turn, these time-dependent strains appear to be a third mechanism driving seismicity. All these findings underline the importance of considering both seismic and aseismic deformations when one wants to characterize the rock mass response to mining. This significantly enhances our understanding of the phenomena involved, as well as their interactions, for an improved hazard assessment in deep mining operations.

Approbation of the technology of efficient application of excavator-automobile com-plexes in the deep open mines

Approbation of the technology of efficient application of excavator-automobile com-plexes in the deep open mines

Automation technology to increase productivity and reduce energy consumption in deep underground mining operations

Automation technology to increase productivity and reduce energy consumption in deep underground mining operations

Evaluation of Heat Transfer Performance between Rock and Air in Seasonal Thermal Energy Storage Unit

Ventilation is one of the most energy demanding parts of deep underground mining operations due to the extensive amounts of energy needed to cool (or heat) the substantial amount of air flow in underground workings. This considerable amount of energy demand can be partially satisfied by extracting renewable energies or using alternative energy solutions available at mine sites. In Canada, some mining operations have the opportunity to create a Seasonal Thermal Energy Storage (STES) unit by blowing mine intake air through large volumes of rock mass dumped in a decommissioned pit. This technique allows for creation of the so-called “Natural Heat Exchanger (NHE)” which moderates seasonal air temperature oscillations. This paper signifies a novel heat transfer model for performance assessment of a NHE system. It investigates the potential for energy savings by implementation of variable number and position of ventilation trenches in underground mines. In this regard, a 3-D heat transfer model is developed to evaluate the thermal storage and the heat transfer between broken rock mass and ventilated air flow and also to specify how design parameters such as position and number of ventilation trenches will affect the heat transfer performance as well as the total energy savings. The results of this study show that NHE can be applied in thermal management of underground mines with the aim of decreasing energy consumption for heating, cooling and ventilation purposes.

Shear Strength of a Cemented Paste Backfill Submitted to High Confining Pressure

Deep mining operations require special measures in order to keep safe and economic aspects. After mine ore is extracted, voids are created and need to be filled with high-strength, low-cost materials. Cemented Paste Backfill (CPB) has recently become one of the main alternatives in filling stopes. Although numerous papers have mentioned the magnitudes of the strength of this material, its behavior under high confining pressures is still not well understood. Therefore, the purpose of this study is to increase the knowledge regarding the CPB behavior. Triaxial compression tests were performed using a Hoek Cell and Load Frame System under high confining pressures. Samples with two different binder contents were used in order to obtain the CPB strength improvement. Besides the self-weight consolidation curing method, samples were subjected to a different curing method that simulated a zero gravity condition (rotating wheel) in the first curing day to compare their mixture properties. The results suggested that both curing method and binder content have influenced the geomechanical properties of Cemented Paste Backfill. By increasing the curing time, the CPB shear strength has increased slightly, whereas specimens with higher binder content presented a significant increase in shear strength values.

Seismic exploration of the world’s deepest gold and platinum orebodies in South Africa - Overview of the past, present and a look into the future Minerals keynote paper

Without doubt, the geologically complex Witwatersrand Basin in South Africa is by far the most important known gold-producing province. It has produced about one-third of the gold ever mined, worldwide. Gold mining in the goldfields takes place at depths ranging from 500 to 4200 m below surface. Many call the underground workings the 'devil's workplace'. This means that there are an increasing number of technical challenges in exploration and optimizing new resources, with rising costs and reduced effective mine designs. There are about 20 or more gold ore bodies (quartz pebble conglomerates) that have been mined, or are currently in production. Furthermore, the Bushveld Complex of South Africa is estimated to contain about 70% of the world's reserves of platinum group elements. The most important platinum ore bodies are the Merensky Reef and the UG2. This paper presents the past and current research activities on the use and implementations of seismic methods for gold and platinum exploration and deep mine planning and designs. It, particularly, presents a state-of-the-art in seismic design and acquisition, processing, interpretation of the seismic data as well as modelling of strato-structural complexies of the basin using advance techniques. The current challenges and possible future solutions are further discussed with special emphasis on the reflection seismic imaging limitations. For example, reflection seismic data acquired on the surface in the Witwatersrand Basin and Bushveld Complex have wavelengths of approximately 60-100 m, providing vertical seismic resolution of approx. 20 m. Consequently, it is difficult to resolve the top and bottom of thin reefs (~ 1m in thickness) due to seismic wave interference as well as to detect faults with throws less than 20 m. However, gold reefs as thin as 20 cm to 1m are currently the main targets for deep mining and faults that crosscut these reefs with throws as small two meters may present difficulties to deep future mining operations. Recent research work has further demonstrated that some of these minor faults may act as conduits for ingress of water and flammable gas into underground workings. There has been more of hard-rock reflection seismics undertaken in South Africa than anywhere else in the world. Therefore, this paper attempts to answer the following trickier question: Will seismic application in the mining industry in South Africa accelerate or decline in the coming years?

Geomechanical safety assessment for transversely isotropic rock mass subjected to deep mining operations

The largest risk for mining operations conducted within the Legnica–Głogów Copper Basin is created mostly by high-energy tremors, the hypocenters of which are located within the main roof strata composed of sedimentary-type rocks — mainly dolomite and anhydrite — about 40–200 m above the excavated copper ore body. These categories of rock clearly exhibit anisotropic strength–deformation characteristics that may significantly affect the safety level value represented by the appropriate safety margin (or safety factor) based on an adequate strength hypothesis. As the focal mechanism most often encountered in such tremors is a slipping-type mechanism with a rupture plane, typically the Mohr–Coulomb theory of strength is applied for a safety level assessment in Polish copper mines. It has been assumed, however, that strength theories based on anisotropic failure criteria should serve as better indicators of correlation between observed and well-characterized sedimentary rock strata failure mechanisms and the location of concentrated areas of the negative values of margin of safety within the rock mass. As changing levels of stress in the rock mass during the mining process may be tracked effectively using solutions offered by appropriate three-dimensional geomechanical models (e.g., finite element method), the assessment of these changes due to mining-face progress is also possible in the location where the seismic tremor occurred. This assessment is characterized by its focal mechanism using the appropriate geophysical methods that permit finding such geomechanical conditions, engaging also the rock mass’ strain–stress states and the material anisotropic characteristics. On the basis of the long-term path of rock mass loading — due to mining predicted by numerical modeling — this could indicate the necessary conditions that should be fulfilled if the anticipated methods of the geophysics failure mechanism could be developed. This is particularly important for anisotropic rock structures. The proposed approach is illustrated using an example of a strong seismic energy event of 0.22 GJ that occurred in 2005 in an area of the Rudna mine.

NUMERICAL MODELLING OF MINE DEWATERING AND FLOODING IN THE EVANDER GOLD BASIN, SOUTH AFRICA

The assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in South Africa. The cessation of mine dewatering has led to large volumes of contaminated discharges in the western parts of the Witwatersrand Basin. Towards the eastern extremity of the Basin, the detached Evander Goldfield has been mined since the early 1950s at depths of between 400 m and 2 000 m below ground level, while overlain by shallower coal mining operations. The hydrogeology of the Evander Basin can be categorised by a shallow weathered-fractured rock aquifer comprising of the glacial and deltaic sediments of the Karoo Supergroup, while the deeper historically confined fractured bedrock aquifer consists predominantly of quartzite with subordinate lava, shale and conglomerate of the Witwatersrand Supergroup. The deep Witwatersrand aquifer has been actively dewatered for the past 60 years at a peak rate of 60 ML/d in the mid-to-late 1960s. Modelling the impacts of mine dewatering and flooding on a regional scale as for the Evander Goldfield presents many challenges including the appropriate discretisation of mine voids and the accurate modelling of layered aquifer systems. To predict the environmental impacts of both the historic and future deep-mining operations at Shaft 6, a detailed conceptual model of the aquifer systems and a 3-dimensional model of the mine voids were incorporated into a numerical groundwater model. This model was used to simulate the dewatering and post-closure rebound of the water tables in the vicinity of the mine. This model could serve as an example for the successful modelling of mine dewatering and flooding scenarios for other parts of the Witwatersrand Basin.

Influence of pre-existing discontinuities and bedding planes on hydraulic fracturing initiation

Pressure-driven fracturing, also known as hydraulic fracturing, is a process widely used for developing geothermal resources, extracting hydrocarbons from unconventional reservoirs such as tight sandstone and shale formations, as well as for preconditioning the rock-mass during deep mining operations. While the overall process of pressure-driven fracturing is well understood, a quantitative description of the process is difficult due to both geologic and mechanistic uncertainties. Among them, the simulation of fractures growing in a complex heterogeneous medium is associated with computational difficulties. Experimental evidence based on micro-seismic monitoring clearly demonstrates the important influence of rock mass fabric on hydraulic fracture development, and the interaction between fluid-driven fractures and pre-existing discontinuities. However, these components are not well accounted for by standard numerical approaches. Thus, the design of hydraulic fracturing operations continues to be based on simplified models whereby the rock mass is treated as a homogeneous continuum. The purpose of this paper is to present the preliminary results obtained using the combined finite-discrete element technology to study the interaction between fluid driven fractures and natural rock mass discontinuities.

Sustainable canadian mining

Mining is a major industrial activity in Canada and will increase in importance as world demand continues to grow. Demand for mining resources is such that we have little choice but to conduct operations at greater and greater depths. This paper will outline the challenges faced by modern and deep mining operations for establishing safe and sustainable working conditions. The consideration of occupational health and safety in mining vehicle design remains cursory. Current personal protective devices are rudimentary. Risks will increase as mining operations reach greater depths. Organizational and generational changes, continued expansion of mining operations, and economic pressures will complicate the situation. One possible solution would be to design new intelligent personal protective equipment, taking into consideration multiple major human factors concerns by utilizing interdisciplinary industrial/academic research partnerships.

An integrated dynamic model of ocean mining system and fast simulation of its longitudinal reciprocating motion

An integrated dynamic model of China’s deep ocean mining system is developed and the fast simulation analysis of its longitudinal reciprocating motion operation processes is achieved. The seafloor tracked miner is built as a three-dimensional single-body model with six-degree-of-freedom. The track-terrain interaction is modeled by partitioning the track-terrain interface into a certain number of mesh elements with three mutually perpendicular forces, including the normal force, the longitudinal shear force and the lateral shear force, acting on the center point of each mesh element. The hydrodynamic force of the miner is considered and applied. By considering the operational safety and collection efficiency, two new mining paths for the miner on the seafloor are proposed, which can be simulated with the established single-body dynamic model of the miner. The pipeline subsystem is built as a three-dimensional multi-body discrete element model, which is divided into rigid elements linked by flexible connectors. The flexible connector without mass is represented by six spring-damper elements. The external hydrodynamic forces of the ocean current from the longitudinal and lateral directions are both considered and modeled based on the Morison formula and applied to the mass center of each corresponding discrete rigid element. The mining ship is simplified and represented by a general kinematic point, whose heave motion induced by the ocean waves and the longitudinal and lateral towing motions are considered and applied. By integrating the single-body dynamic model of the miner and the multi-body discrete element dynamic model of the pipeline, and defining the kinematic equations of the mining ship, the integrated dynamic model of the total deep ocean mining system is formed. The longitudinal reciprocating motion operation modes of the total mining system, which combine the active straight-line and turning motions of the miner and the ship, and the passive towed motions of the pipeline, are proposed and simulated with the developed 3D dynamic model. Some critical simulation results are obtained and analyzed, such as the motion trajectories of key subsystems, the velocities of the buoyancy modules and the interaction forces between subsystems, which in a way can provide important theoretical basis and useful technical reference for the practical deep ocean mining system analysis, operation and control.

The Issue of Income from Operating Ukraine Coal Deep Mines/ Problematika Hospodářského Výsledku Hlubinných Uhelných Dolů Ukrajiny

Abstract This paper focuses on looking for factors that influence the income of deep coal mining operations in Ukraine. The method of discriminate analysis was employed for assessing economic success of the operations. It could be concluded that mining-geological conditions are the most significant cause of influence; the human factor is of lesser importance.

Case study: Energy savings for a deep-mine water reticulation system

In deep level mining, water reticulation systems are one of the major consumers of electricity. The refrigeration plants, together with the underground water supply and dewatering systems are integrated to form one complete water reticulation system. This integrated water reticulation system extracts hot water from the mine, cools it down and returns the cold water to the various underground mining levels. As much as 42% of the total energy consumption on a typical deep level gold mine can be ascribed to the water reticulation system. Reducing the overall water demand and therefore electricity costs will depend on climatic conditions, operating strategy, water reservoir capacity, and electricity tariff rates. In this paper, a method is presented to determine the optimum water reticulation strategy for different electricity tariffs. This model minimises the total operating cost of the water reticulation system by a trade-off between the cost involved in providing effective pump control and the savings achieved under a specified electricity tariff. A case study of a typical deep mining operation shows that a reduction of 65% during peak demand and 2% overall electricity reduction is possible by adopting this new control strategy. The corresponding savings in operating cost is 13%. Techniques were developed to integrate, simulate, optimise and control all components of the water reticulation system. This will allow for a quick assessment of the effect of individual components on the complete system. By integrating all these components into a single system, the operation of each component can be assessed and optimally controlled without adversely affecting other operations of the system.

Failures in a load–haul–dump vehicle axle used in deep mining operations

Following the significantly shorter life for overhauled drive axles from load–haul–dump vehicles than had been experienced with original equipment units which already showed a reduced life over that normally expected, an investigation was launched when an axle failed at even lower operating hours than previously experienced. The investigation showed no defect or deficiency in the components used in rebuilding or in assembly, but highlighted the use of a lubricant unsuited to the application. The use of a more appropriate lubricant resulted in much extended service life of both re-manufactured and original equipment units.

Crustal structure of the Kaapvaal craton and its significance for early crustal evolution

High-quality seismic data obtained from a dense broadband array near Kimberley, South Africa, exhibit crustal reverberations of remarkable clarity that provide well-resolved constraints on the structure of the lowermost crust and Moho. Receiver function analysis of Moho conversions and crustal multiples beneath the Kimberley array shows that the crust is 35 km thick with an average Poisson's ratio of 0.25. The density contrast across the Moho is ∼15%, indicating a crustal density about 2.86 gm/cc just above the Moho, appropriate for felsic to intermediate rock compositions. Analysis of waveform broadening of the crustal reverberation phases suggests that the Moho transition can be no more than 0.5 km thick and the total variation in crustal thickness over the 2400 km 2 footprint of the array no more than 1 km. Waveform and travel time analysis of a large earthquake triggered by deep gold mining operations (the Welkom mine event) some 200 km away from the array yield an average crustal thickness of 35 km along the propagation path between the Kimberley array and the event. P- and S-wave velocities for the lowermost crust are modeled to be 6.75 and 3.90 km/s, respectively, with uppermost mantle velocities of 8.2 and 4.79 km/s, respectively. Seismograms from the Welkom event exhibit theoretically predicted but rarely observed crustal reverberation phases that involve reflection or conversion at the Moho. Correlation between observed and synthetic waveforms and phase amplitudes of the Moho reverberations suggests that the crust along the propagation path between source and receiver is highly uniform in both thickness and average seismic velocity and that the Moho transition zone is everywhere less than about 2 km thick. While the extremely flat Moho, sharp transition zone and low crustal densities beneath the region of study may date from the time of crustal formation, a more geologically plausible interpretation involves extensive crustal melting and ductile flow during the major craton-wide Ventersdorp tectonomagmatic event near the end of Archean time.

The future of the dolomitic springs after mine closure on the Far West Rand, Gauteng, RSA

Approximately 1.2 km of dolomitic limestone overlies the Far West Rand gold reefs southwest of Johannesburg, South Africa. This karst aquifer is partitioned into several groundwater compartments by predominantly north–south trending syenite dykes. Prior to mining, the primary water flow was westwards, decanting over dyke boundaries as a succession of springs along the Lower Wonderfontein Spruit. Dewatering of the overlying dolomitic aquifer for safety and economic reasons by deep gold mining operations, caused the water levels of four compartments to drop and their respective springs to dry up. By perforating dykes, formerly separated aquifers were hydraulically interconnected by mining. Using historical and recent data of water flow—surface and groundwater—and pumping rates, a geohydrological model is presented. The results suggest that the water tables will rise to their pre-mining levels within 30 years after mining ceases and that the dry springs will flow again, despite the compartments being connected by the extensive mining operations.

REVIEW OF CURRENT HIGH DENSITY PASTE FILL AND ITS TECHNOLOGY

Backfilling techniques are widely used in large-scale underground mines. Massive pillars, which have been left in place for stability, limit mining activity. Backfilling allows for safe recovery of the ore remaining in pillars and assures long-term stability. The high rock stresses which result from deep mining operations can be relieved by backfilling. Initially, waste rock was used to fill the openings left by mining operations, though with mixed results. The need to improve safety and reduce costs has prompted the mining industry to investigate alternative backfill methods. Hydraulic filling with Portland cement has shown considerable promise, but little has been done to define the parameters for an effective design. The objective of this paper is to enhance the understanding of current paste backfill practice. Sixty to seventy weight-percent solids-cemented backfill slurries are currently being used in the mining industry (as a matter of practicality). However, deficiencies in this particular ratio need to be examined. Physical properties of mine tailings are unique based on their geology and the milling process. Flaws in the cemented backfill slurries are usually a result of poor hydration and slime build-up to levels that cause additional dewatering, high equipment/operating costs, and work delays. Furthermore, the required strength and quality of the fill may be affected by high water-cement ratios, as well as by its consolidation time, permeability, and volume changes.

Permit Required Discharge to Pollutants

In conjunction with deep mining operations, Valley Camp Coal Company owned a refuse pile (“gob pile”) and built a sedimentary pond at its base. Water in the pond collected drainage from the pile before it entered Storch's Run, a body of water. Valley Camp had obtained a non‐transferable pollution control permit from the state allowing treated effluent from the gob pile to be discharged into a creek into which Storch's Run flowed. Subsequently Rayle Coal Company acquired the property from Valley Camp that included the gob pile. Immediately after acquiring the property, Rayle altered the method of collecting and treating the drainage. It utilized a series of settling ponds and ditches in the stream bed of Storch's Run. Rayle did not apply for a discharge permit although ordered to do so by the state. The state concluded that although Rayle's method reduced the amount of acid mine drainage, it did not eliminate such drainage into Storch's Run and the creek. In time, the state upheld the requirement that Rayle apply for the permit.

Emergency Medical Care in the Underground Environment

Underground medical care is required in certain instances where patients sustain life or limb threatening injuries or illness while in the underground environment. This most often occurs during deep mining operations, both coal and non-coal, and during recreational caving activities. Additional situations such as industrial tunneling, underground repositories and storage areas and building collapses, such as might occur in a natural disaster or in terroristic activities might also occasion the need for such care. The U.S. mining industry suffered 102 fatal accidents with 250 total permanent disabilities during 1980. In 1983 there were 70 fatalities and in 1984, 124 miners died because of mining accidents. Analysis of accident reports indicate that 25–50% of these injuries may have been ameliorated by timely delivery of physician and paramedic based care in the underground environment. From 1967–1975, 187 recorded caving accidents resulted in 33 deaths among 311 victims. It is unclear how many of these fatalities or injuries could have been prevented or ameliorated by rapid delivery of physician and paramedic based underground medical care.