Optimization design for roadheader cutting head by orthogonal experiment and finite element analysis

U radu se istražuje optimizacija konstrukcije rezne glave stroja za bušenje. U tu su svrhu kao varijable optimizacije izabrani brzina rotacije, brzina oscilacije, rezni kutovi pijuka i kutovi nagiba pijuka, a kao ciljevi optimizacije izabrani su srednja vrijednost rezultirajuće sile i koeficijent varijacije reznog opterećenja. Učinci ovih parametara na indekse evaluacije analiziraju se ortogonalnim eksperimentom i analizom konačnih elemenata. Također je provedena analiza promjene trenda indeksa evaluacije s promjenama eksperimentalnih čimbenika. U usporedbi s originalnim projektom, dva indeksa evaluacije smanjila su se za 18,3 % i 5,5 % nakon optimizacije, čime je značajno poboljšana rezna performansa rezne glave stroja za bušenje.Optimization design for roadheader cutting head is investigated in this paper. For this purpose, the rotation velocity, the swing velocity, the cutting angles of picks, and the inclination angles of picks are chosen as the variable for the optimization, and the mean value of resultant force and variation coefficient of cutting load are chosen as optimization objective. The effects of these parameters on evaluation indexes are studied by orthogonal experiment and finite element analysis. The change trend of the evaluation indexes with the experimental factors is also carried out. Compared with the original design, the two evaluation indexes decreased by 18,3 % and 5,5 % after optimization design separately, which improves the cutting performance of roadheader cutting head efficiently

Modeling of ground excavation with the particle finite element method

The present work introduces a new application of the Particle Finite Element Method (PFEM) for the modeling of excavation problems. PFEM is presented as a very suitable tool for the treatment of excavation problem. The method gives solution for the analysis of all processes that derive from it. The method has a high versatility and a reasonable computational cost. The obtained results are really promising.Postprint (published version

Saturation effects on mechanical excavatability of Roubidoux sandstone under selected rock cutting tools

This study investigated the differences in the cutting performance of two rock cutting tools in dry and saturated rock. For this purpose, a permeable quartzose sandstone was subjected to a series of full scale linear rock cutting tests, in both dry and saturated conditions, using a constant cross-section (CCS) disc cutter and a radial drag pick at a constant cutting speed. In this rock, saturation with water reduced the forces acting on the disc cutter by 27-48% (significant at 90% confidence), but also reduced the chip yield by nearly as much. Even though the specific energy of fragmentation went down 8-10%, the difference was not statistically significant. Contrary to the behavior under the disc cutter, water saturation increased the drag pick cutting forces by 9-10%, which is suggestive but not enough to be statistically significant. It did not increase the chip yield by a concomitant amount, however, so the specific energy went up by 28% (significant at 90% confidence). The unexpected differences in the effect of water saturation on the rock fragmentation response to these cutters might be explained by the effects due to their different fragmentation mechanisms, such as the relative size of the crushed zone that forms beneath the cutters. The relationship between cutting speed and rock permeability was expected to be a major factor influencing the effective pressure beneath a cutter in saturated rock. However, load-indentation tests with pore pressure measurement at the same speed showed that the pore pressure within the tested sandstone remained too low to affect the rock fracture process. Other possible mechanisms are discussed --Abstract, page iii

The development of the Cracked-Chevron-Notched Brazilian Disc method for rock fracture toughness measurement and tunnelling machine performance prediction

PhD ThesisThis thesis consists of two parts: Part I The Development of Cracked-Chevron-Notched Brazilian Disc Method for Rock Fracture Toughness Measurement. Part II The Prediction of Tunnelling Machine Performance. In part I, a new novel method-Cracked-Chevron-Notched Brazilian disc (CCNBD) specimen is developed for rock fracture toughness measurement based on three-dimensional numerical analysis and experimental validation. A programme was undertaken to investigate the dependence of rock fracture toughness using CCNBD method on the dimensions of the specimen. A comparison with chevron-notched bending specimens and chevron-notched shod rod specimens were performed. Mixed-mode rock fracture investigations and mode II rock fracture toughness measurement has been studied. It is found that CCNBD method gives very comparable results with that of chevron-notched bending specimen and chevron-notched short-rod specimen recommended by the testing commission of the ISRM. The only requirements are that the diameter of specimen should be larger than 50 mm and a/R should be less than 0.85. It is found that mode II rock fracture toughness testing results using the CSTBD method depends on its dimensionless crack length. The short crack length CSTBD specimen is recommended for further testing. Mode I rock fracture toughness testing using the CSTBD method also shows its dependence on dimensionless crack length a/ Il, short crack length could generate comparable results with that by the CCNBD, SR and CB methods. The CCNBD method has the following advantages: (1) The loading and displacement measurement apparatus is very simple; (2) The magnitude of failure load is generally larger than 1 kN which is of considerable benefit to those loading machines with a preload of 1 kN; (3) can be used for mixed-mode rock fracture investigations and mode II rock fracture toughness measurements; (5) It needs only a small sample for testing; (6) It is convenient for measuring rock fracture toughness in different orientations; (7) Specimen preparation is very simple. Author proposed that this method could be used for the third chevron notched specimen for the measurement of mode I rock fracture toughness. On the part II, the prediction of tunnelling machine performance was analysed based on comprehensive analysis of existing methods for the prediction of tunnelling machine performance and curvilinear regression ,analysis of intact rock cuttability using a large database including rock physical, mechanical, energy, textural and fracture properties. A full review of existing models for the drag tool rock cutting mechanisms is presented. A drag tool rock cutting mechanism based on rock fracture properties is presented. A new model based on mixed mode rock fracture mechanism for drag tool rock cutting was recommended for future research. The following conclusions were drawn: (1) the toughness index, moduli ratio are very important rock properties for the prediction of rock cuttability. (2)new prediction equations analysed by new statistical analysis give more accurate prediction than results analysed by Me Feat Smith; (3) rock cuttability prediction has strong dependence on rock lithology determination; (4) the most important variables for the prediction of rock specific energy are: cone indenter, toughness index, moduli ratio. For the sandstone group, the most important prediction variables are: cone indenter, moduli ratio and toughness index; (5) the most important variables for the prediction of rock cutter wear are: grain roundness and lathe abrasivity index. For the sandstone group, the most important prediction variables are: cone indenter and lathe abrasivity index; (6) the most important prediction variables for coarseness index are: impact strength index, lathe abrasivity index and toughness index. For the sandstone group, the most important prediction variables are: toughness index and grain density; (7) rock fracture toughness has strong correlation with rock specific energy.The British Council: Chinese Government

Volume II: Mining Innovation

Contemporary exploitation of natural raw materials by borehole, opencast, underground, seabed, and anthropogenic deposits is closely related to, among others, geomechanics, automation, computer science, and numerical methods. More and more often, individual fields of science coexist and complement each other, contributing to lowering exploitation costs, increasing production, and reduction of the time needed to prepare and exploit the deposit. The continuous development of national economies is related to the increasing demand for energy, metal, rock, and chemical resources. Very often, exploitation is carried out in complex geological and mining conditions, which are accompanied by natural hazards such as rock bursts, methane, coal dust explosion, spontaneous combustion, water, gas, and temperature. In order to conduct a safe and economically justified operation, modern construction materials are being used more and more often in mining to support excavations, both under static and dynamic loads. The individual production stages are supported by specialized computer programs for cutting the deposit as well as for modeling the behavior of the rock mass after excavation in it. Currently, the automation and monitoring of the mining works play a very important role, which will significantly contribute to the improvement of safety conditions. In this Special Issue of Energies, we focus on innovative laboratory, numerical, and industrial research that has a positive impact on the development of safety and exploitation in mining

Commissioning adiabatic oven testing - an inter-laboratory comparison

Adiabatic oven testing for spontaneous combustion assessment has been a primary method used by the Australian and New Zealand coal industries for input to the development of Principal Hazard Management Plans for mining operations. Consistency of results is important to ensure that the ratings obtained are accurate and reliable for maintaining the integrity of the database used to compare between mines and for obtaining site specific relationships. This paper presents the results from commissioning tests of four new adiabatic ovens at two different laboratories, which show the high level of reproducibility and repeatability needed for confidence in planning of future mining operations. The results cover a range of coal self-heating rates to show the validity of the testing and the reliability of the adiabatic ovens

RISKGATE and Australian coal operations

The major Australian Coal Association Research Program (ACARP) project, RISKGATE has now completed three years of knowledge capture and system development. The body of knowledge for risk management of tyres, collisions, fires, isolation, strata underground, ground control open cut, explosions, explosives underground, explosives open cut, manual tasks and slips/trips/falls was launched in December 2012. Recently, the project added knowledge about outbursts, coal bumps and bursts, human-machine interface, tailings dams, occupational hygiene and inrush to the original 11 topics. In 2014, the project plans (pending ACARP funding approval) to focus on issues around Fitness for Work. RISKGATE provides an environment for knowledge capture and knowledge exchange to drive innovation and cross industry sharing of current practice in the identification, assessment and management of risk. By capturing operational knowledge from industry experts, RISKGATE provides a cumulative corporate memory at a time of high personnel turnover in the coal industry. RISKGATE is the largest single ACARP Occupational Health and Safety (OHS) initiative to date. This paper presents an overview of the first seventeen topics, topic structures, and contrasts and inter-relationships between topics. The second part of the paper discusses some early steps that companies are taking to integrate RISKGATE into their operations; and conclude with some thoughts on where RISKGATE can go in the future

Comparative analysis of coal fatalities in Australia, South Africa, India, China and USA, 2006-2010

Coal mining (especially underground) is considered one of the most hazardous industries, and as a result considerable focus is applied to eliminating or mitigating hazards through careful mine planning, equipment selection and certification, and development of management systems and procedures. Regulatory agencies have developed in-house methods for reporting, classification and tracking of fatalities and other incidents according to the type of event, often including consideration of different hazard types. Unfortunately, direct comparison of mining safety statistics between countries is confounded by considerable differences in the way that individual countries classify specific fatalities or incidents. This paper presents a comparative analysis of coal mining fatality data in Australia, South Africa, India, China and the United States from 2006 to 2010. Individual classification definitions are compared between the five countries, and methods presented to normalise each country’s hazard definitions and reporting regimes around the RISKGATE framework of seventeen different priority unwanted events (or topics). Fatality data from individual countries is then re-classified according to the different RISKGATE topics, thereby enabling a comparative analysis between all five countries. This paper demonstrates the utility and value of a standard classification approach, and submits the RISKGATE framework as a model for classification that could be applied globally in coal mining. RISKGATE is the largest health and safety project ever funded by the Australian coal industry (http://www.riskgate.org) to build an industry body of knowledge to assist in managing common industry hazards. A comprehensive knowledge base has been captured for risk management of tyres, collisions, fires, isolation, strata underground, ground control open cut, explosions, explosives, manual tasks and slips/trips/falls. This has been extended to outburst, coal burst and bumps, interface displays and controls, tailings dams and inrush

Optimisation of waste-dump lift heights for pre-strip operations

The optimisation of waste dump design parameters is a vital aspect that has the potential to significantly influence operational costs within mining operations. This research study investigates the effects waste dump lift height has on a truck-shovel coal mining operation. The analysis focusses upon simulating various dump lift heights in a truck-shovel operation in order to determine the optimal overall dump lift height. The dump lift height is the height to which each dump level or lift is constructed. The optimal height will therefore be determined by plotting the simulated cost results for each height and undergoing a comparative study. Additional factors incorporated within the simulation results include the cost of haulage, and ancillary equipment works (dozers, graders and water cartsto maintain the dump and construct haul roads to each new dump lift. Generating results from the research analysis to closely resemble real world applications, current mine data is incorporated within each simulation, including dig, dump and equipment data obtained from King 2 North pit of the Meandu mine located in Queensland