Applications of Advanced Computational Modelling for Principal Underground Mining Hazards Management and Control

Underground coal mining is facing increased threats from the hazards of spontaneous combustion and heating of coal, abnormal mine gas emissions, and harmful dust concentrations in underground workings, due to increased production outputs and extraction depth of cover. To control and mitigate these engineering problems, there is a need to gain critical knowledge of spontaneous heating in the longwall (LW) goaf, gas migration patterns onto the LW face, and ventilation dynamics and dust dispersion in complex underground environments. Advanced Computational Fluid Dynamics (CFD) modelling can be used to simulate various scenarios portraying these hazards that may occur in underground LWs and provide much-needed knowledge and fundamental science that can be used to develop robust and effective control and mitigation strategies against these hazards. A comprehensive literature review has been conducted to understand these principal mining hazards (PMH), with a particular emphasis on the applications of CFD modelling in the prevention management and control of those PMH arising during coal extraction process. The insufficiencies and gaps in research on spontaneous combustion in active LW goaf, gas migration onto the LW face, and dust dispersion and transport in the development heading were identified. In addition, several field studies were carried out in underground coal mines in Australia to gain a better understanding of these mining issues and collate essential data for the CFD modelling studies. In recent years, goaf heating and spontaneous combustion incidents have been reported in several Australian underground coal mines during normal production cycles. The onset of these heating incidents was dictated by many operational and environmental parameters. Based on the site-specific conditions of an underground coal mine, where the coal seam gas is of approximately 80% carbon dioxide (CO2) and 20% methane (CH4) with a gas emission rate of 2000 l/s, CFD models were developed and validated with field gas monitoring data collected from the Tube Bundle System. The CFD models incorporated a user defined function (UDF) of gas emission and permeability variations in a three-dimensional (3D) space of computational domain representing the LW panels and goaf areas. Simulation results indicated that better goaf inertisation could be achieved when nitrogen (N2) was injected via cut-throughs (C/T) at about 250 m behind the LW face on the maingate (MG) side and surface boreholes at 100 m and 700 m on the tailgate (TG) side, with a total injection rate greater than 1750 l/s. The oxygen concentration on the MG and TG side dropped below 5% at distances of 120 m and 75 m behind the LW face, with a confined oxidation zone area of 35375 m2, which was approximately one-third of the oxidation zone area without inert gas injection. The impact of geological variations (i.e., coal seam orientations and goaf gas composition) on spontaneous combustion prevention and management was further studied using CFD models. The influence of ventilation design and operational parameters (e.g., tightness of the goaf seals) on spontaneous combustion control was also investigated by additional CFD models based on field data. During LW sealing-off, the ventilation flow dynamics change within the goaf, which considerably increases the risk of spontaneous combustion and gas explosion. To prevent these hazards, CFD models were developed and calibrated with field gas monitoring data to simulate a range of operational scenarios of different ventilation arrangements. The modelling studies indicated that at least six gas sensors should be employed and positioned appropriately to ensure effective goaf atmosphere monitoring for risk management during the LW sealing-off process. Extensive CFD-DPM (Discrete phase model) coupling modelling studies were conducted to investigate dust-related issues in LW gateroad development panels. Based on site-specific conditions, a CFD model incorporating a Continuous Miner (CM), Shuttle Car (SC) and exhausting ventilation tube was established and validated with onsite dust monitoring data. Three scenarios of CM cutting at the middle, floor and roof positions were considered and simulated. In all cases, the simulation results indicated that high levels of dust exposure would occur to left-hand-side (LHS) operators and consequently they should be equipped with high-quality personal protective equipment and stay behind the ventilation duct inlet during coal cutting process, while miners standing at the right-hands-side (RHS) of the CM for roof and/or rib bolting and machine operation should stay immediately behind the bolting rig where dust concentration was relatively low. The studies conducted in this thesis provided new insights into the current goaf inertisation practices to effectively manage and control spontaneous heating in LW goaf by considering geological variations and mining design. Furthermore, the CFD modelling study of gas flow dynamics during the panel sealing-off process provides new knowledge of ventilation and goaf gas dynamics, which is critical to the positioning of gas monitoring sensors to reliably measure goaf atmosphere changes, thus minimizing spontaneous heating and gas explosion risks with much-improved mine safety. The research work also shed light on the dust and ventilation behaviour in gateroad development panels, and provided several recommendations for operators’ locations and dust mitigation strategies to improve the health and safety of miners. The research outcomes from this study contribute to the improvement of current practices and guidance for PMH management and control in underground mines and tunnelling projects

Investigating blast fume propagation, concentration and clearance in underground mines using computational fluid dynamics (CFD)

Blasting activities using standard industry explosives is an essential component of underground hard rock mining operations. Blasting operations result in the release of noxious gases, presenting both safety and productivity threats. Overestimation of post-blast re-entry time results in production losses, while underestimation leads to injuries and fatalities. Research shows that most underground mines simply standardize post-blast re-entry times based on experiences and observations. Few underground mines use theoretical methods for calculating post-blast re-entry time. These theoretical methods, however, are unable to account for the variations in the blasting conditions. Literature review shows that: (i) there is currently no means of estimating safe blast distance (i.e., blast exclusion zone); and (ii) there is a lack of a comprehensive relationship for calculating optimal post-blast re-entry time and optimal air quantity in underground mines. An important factor associated with blast fume dilution and clearance, the fan duct discharge location, needs to be studied in details. To achieve the above goals, the computational fluid dynamics (CFD) method is used to simulate blast fume dispersion and clearance in the underground mine. An experiment has been successfully conducted at the Missouri S&T Experimental Mine to acquire blast data to validate the proposed CFD model. Computational fluid dynamics simulation results compare favorably with blast data from Missouri S&T Experimental Mine with a coefficient of determination (R2) of 0.97. Based on the verified CFD model, various blasting and ventilation conditions were studied. A linear relationship has been developed and validated for estimating safe blast distances. Four equations have been generated and validated to conservatively calculate optimal air quantity and post-blast re-entry time based on commonly used blasting and ventilation conditions --Abstract, page iii

Mining Safety and Sustainability I

Safety and sustainability are becoming ever bigger challenges for the mining industry with the increasing depth of mining. It is of great significance to reduce the disaster risk of mining accidents, enhance the safety of mining operations, and improve the efficiency and sustainability of development of mineral resource. This book provides a platform to present new research and recent advances in the safety and sustainability of mining. More specifically, Mining Safety and Sustainability presents recent theoretical and experimental studies with a focus on safety mining, green mining, intelligent mining and mines, sustainable development, risk management of mines, ecological restoration of mines, mining methods and technologies, and damage monitoring and prediction. It will be further helpful to provide theoretical support and technical support for guiding the normative, green, safe, and sustainable development of the mining industry

Multiple simulation experimental studies of gas emission, distribution and migration rules in mine ventilation system and goaf area

Gas problems have created severe difficulties for the mining industry around the world, leading to high expenditures and intensity research efforts, and determined attempts to enhance the various ventilation optimization and gas drainage techniques. Meanwhile, gas research is thriving in recent years, and gas drainage technology will continue to be a growing industry over the coming decades in many mining countries. Safety mining technologies including field investigation, numerical simulation and laboratorial experiments have been improved to develop a better understanding of the causes of mine gas-related disasters over the last two decades. In addition, new and multiple gas control strategies and technologies have been developed, including optimizing the ventilation system constantly, preventing goaf spontaneous combustion timely, enhancing gas risk management effectively, determining the gas emission zone exactly, and implementing a reasonable gas drainage plan correctly. The first part of the dissertation introduces a multiple gas disaster prevention, control and reduction strategy. Firstly, the basic theories of gas emission, distribution and migration are discussed. Then a numerical prediction model based on a specific coal mine is established to predict its gas emission. The second part of the dissertation offers the establishment of the numerical simulation model (CFD) and laboratorial experimental model for the purpose of discussing the gas distribution and migration rule and determining the most effective gas drainage zones in the working face and goaf. Both of the numerical simulation results and the laboratorial experimental results also demonstrate that the most effective gas drainage spot constantly varies with the area where mining activities are performed. In the case of numerical simulation experimental results, it is mainly located in the area of 40m-250m (between working face and deep goaf), 30m-40m from the working face floor (between the working face floor to the roof), and approximately 60m-170m (between air inlet and air outlet). In the case of laboratorial simulation experimental results, it mainly locates in coal seam and rock stratum separation area of 27cm-243cm (between working face and deep goaf), 28cm-42cm (between the working face floor to the roof) and 78cm-182cm (between air inlet and air outlet). The last part of this dissertation provides a field study in order to obtain the gas distribution and migration rule in the working face and goaf. The field measured results show the average gas drainage rate increased from 39.6 m3·min-1 (U-type ventilation system) to approximately 48.9 m3·min-1 (U+L-type ventilation system) while the gas concentration of the special drainage tunnel, upper corner and air outlet decreased from 1.88%, 0.85% and 0.61% (U-type ventilation system) to 1.69%, 0.75% and 0.55% (U+L-type ventilation system), respectively. These results indicate the layout of the gas drainage boreholes is rational and effective; the gas drainage volume is reliable. Therefore, it is feasible and reliable to arrange the layout of gas drainage tunnels based on the experimental results of numerical simulation and laboratorial test.Los problemas ocasionados por gas han creado graves dificultades para la industria minera en todo el mundo, por lo que ha implicado altos gastos y esfuerzos de investigación y intentos de mejorar en diversas técnicas de optimización de la ventilación y drenaje de gas. Mientras tanto, la investigación sobre gas ha aumentado considerable en los últimos años y la tecnología de drenaje de gas seguirá siendo una industria en crecimiento en las próximas décadas en muchos países mineros. Las tecnologías mineras de seguridad, incluyendo la investigación de campo, la simulación numérica y experimentos en laboratorio han mejorado para una mejor comprensión de las causas de los desastres relacionados con el gas de las minas en las últimas dos décadas. Además, se han desarrollado nuevos y múltiples estrategias y tecnologías de control de gas, incluyendo la optimización del sistema de ventilación, impidiendo excavaciones de combustión espontánea oportuna, mejorando así la gestión eficaz de riesgos causados por gases, determinando la zona de emisión de gases con exactitud, y la implementación de un plan de drenaje de gas correctamente. La primera parte de la tesis se presenta una estrategia múltiple de la prevención de desastres de gas, control y reducción. En primer lugar, se analizarán las teorías básicas de la emisión de gases, la distribución y la migración. Luego se establecerá un modelo de predicción numérica basada en una mina de carbón específica para predecir su emisión de gases. La segunda parte de la tesis ofrece el establecimiento del modelo numérico de simulación (CFD) y el modelo experimental de laboratorio con el fin de discutir la distribución de gas y norma de migración y la determinación de las zonas de drenaje de gas más eficaces en el frente de trabajo y terraplén. Tanto los resultados del simulación numéricos como los resultados experimentales de laboratorio demuestran que el punto de drenaje más eficaz de gas varía constantemente según el área donde se realizan las actividades mineras. En el caso de los resultados experimentales de simulación numérica, que se encuentra principalmente en el área de 40m-250m (entre la superficie del tierra y el zona excavada), 30m-40m desde la superficie de trabajo (desde la superficie del trabajo hasta el techo), y aproximadamente 60m-170m (entre el entrada y salida de aire). En el caso de los resultados experimentales de simulación en el laboratorio, se localiza principalmente en la veta de carbón y la zona de separación del estrato rocoso de 27cm-243cm (entre la superficie de la tierra y la zona excavada), 28cm-42cm (desde la superficie del trabajo hasta el techo) y 78cm-182cm (entre la entrada y salida de aire). La última parte de esta tesis concluye un estudio de campo con el fin de obtener la distribución de gas y el estado migratorio entre la superficie y la zona escavada. Los resultados de campo medidos muestran que la tasa de drenaje de gas en promedio aumentó 39,6 m3·min-1 (sistema de ventilación de tipo T) a aproximadamente 48,9 m3 · min-1 (sistema de ventilación de T + L-tipo), mientras que la concentración de gas del drenaje especial en túnel, esquina superior y salida de aire se redujo de 1,88%, 0,85% y 0,61% (sistema de ventilación de tipo U) a 1,69%, 0,75% y 0,55% (U + de tipo L sistema de ventilación), respectivamente. Estos resultados indican que la disposición de las perforaciones de drenaje de gas es racional y eficaz; el volumen de drenaje de gas es fiable. Por lo tanto, es factible y fiable para organizar la disposición de túneles de drenaje de gas sobre la base de los resultados experimentales de simulación numérica y la prueba de laboratorio

A Builder's Guide to Water and Energy

The work on which this report is based was supported in part by funds provided by the Office of Water Research and Technology (Project A-Q65-ALAS), US. Department of the interior, Washington, D.C., as authorized by the Water Research and Development Act of 1978

Advances in Unconventional Oil and Gas

This book focuses on the latest progress in unconventional oil and gas (such as coalbed methane, shale gas, tight gas, heavy oil, hydrate, etc.) exploration and development, including reservoir characterization, gas origin and storage, accumulation geology, hydrocarbon generation evolution, fracturing technology, enhanced oil recovery, etc. Some new methods are proposed to improve the gas extraction in coal seams, characterize the relative permeability of reservoirs, improve the heat control effect of hydrate-bearing sediment, improve the development efficiency of heavy oil, increase fracturing effectiveness in tight reservoirs, etc

Technology of high-level nuclear waste disposal. Advances in the science and engineering of the management of high-level nuclear wastes. Volume 2

The twenty papers in this volume are divided into three parts: site exploration and characterization; repository development and design; and waste package development and design. These papers represent the status of technology that existed in 1981 and 1982. Individual papers were processed for inclusion in the Energy Data Base

GEOPHYSICAL SURVEYS AIMED TO SAVE HUMAN LIVES BY FACILITATING SAFETY ASSESSMENT

Two research projects by the Water and Energy Team of the National Energy TechnologyLaboratory were carried out in collaboration between the US Department of Energy and theUniversity of Pittsburgh. Both projects are related to investigating current and potential impacts of abandoned coal mines on the adjacent populated regions.The first project was carried out in West Virginia over 14 active and abandoned coal slurryimpoundments (Appendix A) in order to remotely investigate their current condition and potential hazards related to the mine-waste pools. Three main scenarios of impoundment failure are overtopping of the impoundment, internal erosion (piping) and entry of unconsolidated material into adjacent mine voids due to subsidence. To characterize these potential hazards, helicopter-mounted electromagnetic (HEM) surveys were completed to identify fluid saturated zones within coal waste and to delineate the paths of filtrate fluid flow. Attempts were also madeto identify flooded mine workings underlying the impoundment areas. A total of 431 flight lineswere processed, each from 2 to over 4 km in length, in total more than 1300 line-kilometers ofHEM survey. Follow-up, ground-based resistivity surveys verified the results of the HEM investigations. The HEM and ground-based geophysical surveys proved to be effective indelineating the phreatic surface, determining seep locations, imaging areas of unconsolidatedslurry, locating areas where process water has invaded adjacent aquifers, potentially depictingthe possible location of flooded underground mine workings and locating infiltration zones.The second project took place in southwestern Pennsylvania. In order to image beneath the surface and identify zones of possible gas accumulation and migration routes, reflection seismic surveys were completed in this area. Seismic imaging was successful in identifying regions of subsurface gas accumulation. Because of the urban nature of the survey, it was very challenging to collect and process seismic reflection data

Green Low-Carbon Technology for Metalliferous Minerals

Metalliferous minerals play a central role in the global economy. They will continue to provide the raw materials we need for industrial processes. Significant challenges will likely emerge if the climate-driven green and low-carbon development transition of metalliferous mineral exploitation is not managed responsibly and sustainably. Green low-carbon technology is vital to promote the development of metalliferous mineral resources shifting from extensive and destructive mining to clean and energy-saving mining in future decades. Global mining scientists and engineers have conducted a lot of research in related fields, such as green mining, ecological mining, energy-saving mining, and mining solid waste recycling, and have achieved a great deal of innovative progress and achievements. This Special Issue intends to collect the latest developments in the green low-carbon mining field, written by well-known researchers who have contributed to the innovation of new technologies, process optimization methods, or energy-saving techniques in metalliferous minerals development