International Journal of Mining and Mineral Engineering (11 papers in press)
Required strength estimation of a cemented backfill with the front wall exposed and back wall pressured
by Guangsheng Liu, Li Li, Xiaocong Yang, Lijie Guo
Abstract: Open stoping with delayed backfill is increasingly utilized in underground mines worldwide. A critical task in application of this type of mining method is to estimate the minimum required strength of exposed cemented backfill. Several analytical solutions have been proposed to evaluate the required strength of cemented backfill with one open face, confined by three rock walls. In practice, a cemented backfill in contact with an uncemented backfill on one side may need to be exposed on the opposite side. The uncemented backfill can apply a pressure on the exposed cemented backfill and affects its stability. In this study, a lateral pressure equal to the isostatic overburden pressure is considered for the uncemented backfill. An analytical solution is proposed for evaluating the minimum required strength of the cemented backfill with the front wall exposed and back wall pressured. The ensued solution constitutes an upper bound solution for assessing the minimum required strength of the cemented backfill exposed on one side and confined by an uncemented backfill on the opposite side. The proposed analytical solution is validated by numerical modeling performed with FLAC3D.
Keywords: Cemented backfill; Required strength; Critical strength; Analytical solution; Numerical modeling; Mitchell; FLAC3D.
Review on Low-Cost Wireless Communication Systems for Slope Stability Monitoring in Opencast Mines
by Guntha Karthik, Singam Jayanthu
Abstract: Slope stability is one of the primary problems faced by opencast mines. The conventional geotechnical sensors are monitored by technicians in the field and the available wireless monitoring systems like Slope Stability Radar (SSR), Light Detection And Ranging (LiDAR) are more expensive. The purpose of this paper is to introduce the different cost-effective real-time slope monitoring systems. Critical observations on recent low cost wireless slope monitoring systems were presented. By deploying the Wireless Data Transmission System using advanced antennas at respective slope instruments in underground or opencast mines, we can collect data without any physical connections. Wireless sensor networks (WSNs) are well suited to monitor the movement, and it consist of sensor nodes which measure physical quantities and transmit the preprocessed measurement results to a base station wirelessly. Developments in information and communications technology (ICT) support the collection, connection and analysis of data through sensing and monitoring of slopes in mines. This paper gives the detailed review on available low-cost wireless slope monitoring systems for opencast mines.
Keywords: Slope Stability; Opencast mine; Wireless sensor networks; Time Domain Reflectometry.
Draw Rate Management System Using Mathematical Programming in Extraction Sequence Optimization of Block Cave Mining
by Farshad Nezhadshahmohammad, Hamid Aghababaei, Yashar Pourrahimian
Abstract: Planning of caving operations poses complexities in different areas such as safety, ground control, and production scheduling. Draw control is fundamental to the success of block-cave operation. Although some complex theories and mathematical draw control systems have been applied in block-cave mines, most of them did not have an exact production rate curve to manage draw rates of drawpoints and are too complex to provide a solution for real block-caving mines. This paper presents a mixed-integer linear programming (MILP) model to optimize the extraction sequence of drawpoints over multiple time horizons of block cave mines with respect to the draw control systems. Four draw rate strategies are formulated to guarantee practical solutions. Furthermore, dilution and caving are improved indirectly, because the method considers the draw rate strategy. Application and comparison of the four models for production scheduling based on draw control systems are presented using 298 drawpoints over 15 periods.
Keywords: Block cave mine; Production rate curve; Draw rate; Mathematical formulation; MILP.
Oil Sands Production Scheduling and Waste Management with Optimum Cut-off Grade Policy
by Navid Seyed Hosseini, Eugene Ben-Awuah
Abstract: Cut-off grade is the criterion that separates ore from waste and it determines the amount of ore and waste material in the final pit limit. In order to generate an optimum production schedule for the mine life, cut-off grade optimization is used to determine the cut-off grade, duration of mining of the grade and the amount of material mined. This research developed a heuristic optimization model that generates an optimum cut-off grade policy and a schedule for ore and waste material including overburden, interburden and tailings coarse sand dyke materials for dyke construction in oil sands mining. Scenarios investigated include: no stockpiling and stockpiling with limited reclamation duration. The scenario of reclaiming the stockpile after one year had the highest net present value (NPV) as well as the highest cut-off grade profile. Reclaiming the stockpile after two years had less NPV due to reduction in processing recovery resulting from oxidation.
Keywords: Integrated Cut-Off Grade Optimization model; oil sands mining; production scheduling; waste management; dyke construction; stockpiling.
Assessment of Blast Induced Vibrations Based on Regulatory Criteria (A Case Study of Limestone Mine, Nigeria).
by Victor Abioye Akinbinu
Abstract: The aim of this study is to assess the effect of blast-induced vibration of limestone quarries on the environment. This was attained through extensive plan of measurements. Six blasts were carried out covering all the working faces with number of blast hole per blast ranging from 30 to 56. Weight of charge per delay ranged from 240 to 448 kg. The distance between the locations of the vibrograph and the center of the blast ranged from 0.8 to 3 km. The vibrograph was used to measure the maximum magnitudes of three mutually perpendicular components of the peak particle velocities and air blast over pressure levels. Complete wave traces of the vibrations were also recorded. Blast induced vibrations can cause human annoyance, discomfort, and damage to nearby structures. Hence, measurements of ground vibrations and air blast levels and use of published damage criteria are necessary to judge the design of the blasting operations, if it complies with the safe regulated levels. Ground vibration induced by blasting at the Quarries was monitored from selected locations. All of the events recorded during this research obey the USBMRI8485 and Office of Surface Mining (OSM) regulation criteria. Maximum allowed peak particle velocity does not exceed 0.75inch/sec (168.75 mm/sec) for the measured distances from blast point It was observed that the structures at the monitored locations were safe.
Keywords: air blast; blast-induced vibration; limestone quarries; peak particle velocities; published damage criteria.
Attracting young people to the mining industry Six recommendations
by Jan Johansson, Bo Johansson, Joel Lööw, Magnus Nygren, Lena Abrahamsson
Abstract: The present workforce in the mining industry is ageing and mining companies have difficulties recruiting young people who are not particularly interested in working in the industry. Simultaneously, mining companies tend to rely on contractors that offer volume flexibility and expertise, often in a combination that is economically appealing. This makes recruitment and development of the whole of the mining workforce complex. To recruit the right workforce, mining companies and their contractors need to cooperate and improve their knowledge about both attractive and repelling work features so that they can make wiser strategic decisions based on facts.
Based on a Swedish context, we discuss different aspects of attractive workplaces and summarise our lessons learned in six recommendations dealing with general health and safety issues, work organisation, competence development, gender equality, social responsibility, and outsourcing. We hope that these recommendations will provide some guidance on how future attractive mining workplaces can be achieved.
The paper is based on experiences from the Swedish mining industry and two large European Union projects, Innovative Technologies and Concepts for the Intelligent Deep Mine of the Future (I2mine) and Sustainable Intelligent Mining Systems (SIMS).
Keywords: mining; attractive workplace; automation; health; safety; risk; work environment; corporate social responsibility.
Mine-to-mill multi-objective optimal blending with technical and economic constraints using a modified genetic algorithm
by Oscar Daniel Chuk, Carlos Gustavo Rodriguez Medina, Marina Romero, Luis Ventura Gutierrez, Juan Pedro Gil
Abstract: Optimisation techniques have been used effectively in the open pit mine planning. However, they are incorporated more slowly in the optimal solution of mine-to-mill blending. Specifically, no contributions are observed from the multi-objective approach. This work shows the application of a multi-objective genetic algorithm with additional non - natural genetic operations to the solution of this problem. The implementation of the algorithm in a particular case, but easily generalizable, is presented. The results show the efficiency of the procedure, with significant improvements in the Net Present Value.
Keywords: Blending; Mine-to-mill; Optimisation; Multi-objective; Genetic Algorithm; Net Present Value.
A New Method for Correcting Characteristic Curves for Centrifugal Compressors
by Chang Haijun, Wu Changchun
Abstract: In gas pipeline industry, a centrifugal compressors performance is often tested in the factory under specified condition and formulated as performance map before it is offered to its buyer. Concerned performances include head, efficiency and so on. A compressors original head or efficiency characteristic curve may deviate from its actual one because of various reasons after it runs in field for a period of time. So correction is needed before these characteristic curves are used for simulation, optimization or other applications. A compressors actual head and efficiency are extracted from its operating records and used for correction. The correction method is designed according to the idea to move a compressors characteristic curves to best fit its actual performance. Two different types of compressors operated on Central Asia China gas pipeline are utilized to test the proposed method and satisfactory results are got.
Keywords: gas pipeline; centrifugal compressor; head; efficiency; correction.
Theoretical equation of initial top-coal boundary in longwall top-coal caving mining
by Weijie Wei, Zhengyang Song, Jinwang Zhang
Abstract: The theoretical equation of initial top-coal boundary (ITCB) is one of the fundamental problems of top-coal drawing law in long wall top-caving (LTCC) mining. The granular mechanical model of ITCB is established based on loose medium flow field theory. By analyzing the stressed top-coal on ITCB along the section of coal seam thickness and face advancement directions, the theoretical equation of ITCB is deduced respectively in the two conditions of first gangue drawing out and excessive gangue drawing out. The theoretical equation is further modified by a large number of experimental data. The value ranges of correction coefficient k and lateral stress transfer coefficient m in modified equation are given. The modified equation can be used to fit the ITCB in different coal seams conditions more precisely, which is the foundation of the control of drawbody in LTCC. Meanwhile, it is found that the ITCB at excessive gangue drawing out condition is in the special shape that the top opening is elliptical and the bottom opening is rectangle. The theoretical equation of ITCB can provide meaningful guidance to the improvement of top-coal recovery ratio in LTCC.
Keywords: longwall top-coal caving (LTCC); initial top-coal boundary; granular mechanics; theoretical equation; top-coal drawing law; PFC simulation.
Evaluation of the steady-state coal permeability experiments: A numerical simulation study
by Jie Zang, Kai Wang
Abstract: By using the numerical simulator developed in our previous work, this paper conducted four simulation cases on the steady-state coal permeability experiments. One case is not backpressure-regulated and the other three are backpressure-regulated with different constant differential pressures between the upstream and the downstream end. The simulation results indicate that the backpressure-regulated steady-state method is superior to the non-backpressure-regulated in terms of the measurement accuracy. The results also indicate that a small differential pressure may be preferable to a higher value for the backpressure-regulated method in order to obtain more accurate permeability measurements. These conclusions may be meaningful for future coal permeability measurements with the steady-state method.
Keywords: Coal permeability experiment; Steady-state method; Numerical simulation; Backpressure regulator; Coalbed methane.
Storing energy in disused underground mine voids: comparing pumped water- and compressed air-based technologies
by Friederike Kaiser, Frank Winde, Ewald Erasmus
Abstract: Large scale energy storage is becoming ever more important for balancing loads due to increased intermittent electric energy supply from wind and solar power plants. This paper explores how abandoned mine voids can be utilized for this purpose comparing the technological and economical suitability of two different technologies: underground pumped hydro energy storage (UPHES) and compressed air energy storage (CAES). By integrating these technologies into post-closure development concepts mine voids can be prevented from becoming environmental liabilities thereby averting costs associated with the indefinite pumping and treating of polluted water emanating from flooded mines. Apart from differing in construction costs, profitability, energy storage capabilities and grid-related flexibility each technology also requires different geological conditions that are to be considered when selecting the best suited one for a specific mine.
Keywords: CAES; pumped hydro energy-storage; underground mine void; feasibility; energy storage efficiency; economic viability; post-mining development.