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There is little process control employed at aggregate crushing plants and essentially no optimization at the primary or jaw crushing stage. Jaw crusher selection is very dependent on the subjective judgment/experience of individuals, the characterization of rock material using inadequate and unrepresentative tests, and the desire to limit secondary breakage, resulting in the conservative selection and operation of jaw crushers. A method for predicting the power consumption, product size, and volumetric capacity of jaw crushers based on fracture toughness has been proposed in this study. A new fracture toughness test, the Edge Notched Disk Wedge Splitting test, has been developed and verified in order to rapidly assess the fracture toughness of six quarry rocks. A High Energy Crushing Test system has been used to simulate the operational settings of a jaw crusher so that comparison of fracture toughness, specific comminution energy, and breakage distribution could be performed. The results indicate that the specific comminution energy required to reduce a rock particle to a given size increases with fracture toughness. The breakage distribution has also been shown to be dependent upon fracture toughness as long as the elastic modulus is taken into account. Laboratory jaw crushing experiments show that the capacity of a jaw crusher is dependent upon fracture toughness and the elastic modulus. Models for the prediction of power consumption, breakage function/product size, and volumetric capacity have been developed based on these results. At the experimental level, the models were able to predict the specific comminution energy to within 1% and t10 (characteristic crushing parameter) to within 10%. Prediction of the product size distribution produced by a lab-scale jaw crusher, for four different rocks, was within ± 5% (in terms of percent passing). The models allow for the selection of a jaw crusher based on the nature of the rock being broken and the average amount of size reduction done on the feed material. The models can also be used to optimize feed and operational settings, as well to determine the product size produced for a given rock and reduction ratio. / Ph. D.

Seismicity at a deep hard rock mine can be a precursor to ground failure events. Seismicity data can be used in double-difference tomography, which produce tomograms showing velocity distributions in the rock mass that can be used to infer relative stress of the rock mass. The data set used for the double-difference tomography inversion was from Creighton Mine in Sudbury, Ontario, Canada, and consisted of two months of data averaging 150 microseismic events per day. Three separate studies were conducted to evaluate the applications of double-difference tomography on a deep hard rock mine. These studies produced mine scale tomograms, stope scale tomograms of two active stopes, and stope scale tomograms for a cluster of events. TomoDD was used for the tomographic inversion, with other commercial programs used to view the results. All three studies produced results consistent with prior mine knowledge and basic concepts of rock mass stress redistribution. Mine scale tomograms accurately displayed a low velocity where the mined ore body is known to be with adjacent high velocity, stope scale tomograms of the two stopes both correctly demonstrated a low velocity relaxed zone near the stope following a production blast, and stope scale tomograms of an event cluster displayed consistency in results for two clusters in periods before, during, and after each cluster. The three studies show that double-difference tomography is a promising tool for observing rock mass stress redistribution that provides a baseline evaluation for the potential uses of the technology in a deep hard rock mine. / Master of Science

Submitted by admin tede (tede@pucgoias.edu.br) on 2017-06-01T14:03:52Z No. of bitstreams: 1 EMERSON MAGALHÃES.pdf: 4503685 bytes, checksum: f660dc448e46fbaa62e032dbcea91699 (MD5) / Made available in DSpace on 2017-06-01T14:03:52Z (GMT). No. of bitstreams: 1 EMERSON MAGALHÃES.pdf: 4503685 bytes, checksum: f660dc448e46fbaa62e032dbcea91699 (MD5) Previous issue date: 2017-03-10 / The present work has the objective of analyzing the construction of the cultural and musical scene of alternative rock from Goiás. From the notion of field, abstracted from the work of Pierre Bourdieu (2012), presents the rock from its roots and its emergence in the United States as well as its main agents and musicians. There is also the Brazilian rock of the 80's, influenced by the majors, followed by the opposition of the punk movement, in parallel with the São Paulo working-class movement, as a periphery movement and groups forgotten by the great musical media. Through the motto of it yourself, punks countered this idea of dominance by major record companies, provoking a conflict between the dominant, represented by the majors, and the dominated, represented by the underground punk movement. This movement reverberates in Goiás and the youth of Goiás promote, through festivals and fanzines, a local rock forgotten of the call Axis Rio-São Paulo and against the attempt to create a sertaneja musical identity for the goianos. In this process, it creates a musical and cultural scene with its own identity. The work heard entrepreneurs, participants of bands in interviews and had as theoretical contributions of Napolitano (2005), Benevides (2010), (2013), Bourdieu (1996), (2007), (2012), Alexandre (2002), Dapieve (1996), O‟Hara (2005), Friedlander (2002), Dias(2000), Brandini (2004), Kossa (2005). / O presente trabalho tem como objetivo a análise da construção da cena cultural e musical do rock alternativo goiano. A partir da noção de campo, abstraída da obra de Pierre Bourdieu (2012), apresenta-se o rock desde suas raízes e o seu o seu surgimento nos Estados Unidos assim como seus principais agentes e músicos. Apresenta-se também o rock brasileiro dos anos 80, influenciado pelas grandes gravadoras (majors), seguido da contraposição do movimento punk, paralelamente ao movimento operário de São Paulo, como um movimento de periferia e de grupos esquecidos pela grande mídia musical. Através do lema do it yourself (faça você mesmo) os punks se contrapuseram a essa ideia de domínio das grandes gravadoras, provocando um conflito entre os dominantes, representado pelas majors, e os dominados, representados pelo movimento underground punk. Esse movimento reverbera em Goiás e a juventude goiana promove, através de festivais e fanzines, um rock local esquecido do chamado Eixo Rio-São Paulo e contra a tentativa de se criar uma identidade musical sertaneja para os goianos. Nesse processo, cria uma cena musical e cultural com identidade própria. O trabalho ouviu empresários, participantes de bandas em entrevistas e teve como aportes teóricos Napolitano (2005), Benevides (2010), (2013), Bourdieu (1996), (2007), (2012), Alexandre (2002), Dapieve (1996), O‟Hara (2005), Friedlander (2002), Dias(2000), Brandini (2004), Kossa (2005).

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Rock falls are the cause of the majority of mining-related injuries and fatalities in deep tabular South African mines. The standard process of entry examination is performed before working shifts and after blasting to detect structurally loose rocks. This process is performed by a miner using a pinch bar to ‘sound’ a rock by striking it and making a judgement based on the frequency response of the resultant sound. The Electronic Sounding Device (ESD) developed by the CSIR aims to assist in this process by performing a concurrent prediction of the structural state of the rock based on the acoustic waveform generated in the sounding process. This project aimed to identify, develop and deploy an effective classification model to be used on the ESD to perform this assessment. The project was undertaken in three main stages: the collection of labelled acoustic samples from working areas; the extraction of descriptive features from the waveforms; and the competitive evaluation of suitable classification models. Acoustic samples of the sounding process were recorded at the Driefontein mine operation by teams of Gold Fields employees. The samples were recorded in working areas on each of the four reefs that were covered by the shafts of the mine complex. Samples were labelled as ‘safe’ or ‘unsafe’ to indicate an expert’s judgement of the rock’s structural state. A laboratory-controlled environment was also created to provide a platform from which to collect acoustic samples with objective labelling. Three sets of features were extracted from the acoustic waveforms to form a descriptive feature dataset: four statistical moments of the frequency distribution of the waveform formed; the average energy contained in 16 discrete frequency bands in the data; and 12 Mel Frequency Cepstral Coefficients (MFCCs). Classification models from four model families were competitively evaluated for best accuracy in predicting structural states. The models evaluated were k-nearest neighbours, self-organising maps, decision trees, random forests, logistic regression, neural networks, and support vector machines with radial basis function and polynomial kernels. The sensitivity of the models, i.e. their ability to avoid predicting a ‘safe’ status when the rock mass was actually loose, was used as the critical performance measure. A single-hidden-layer feed-forward neural network with 15 nodes in the hidden layer and a sigmoid activation function was found to best suited for acoustic classification on the ESD. Additional feature selection was performed to identify the optimised form of the model. The final model was successfully implemented on the ESD platform. / AFRIKAANSE OPSOMMING: Rotsstortings is die oorsaak van die meerderheid van mynbouverwante ongelukke en ongevalle in diep tabulêre Suid-Afrikaanse myne. Die standaard proses van pretoegang ondersoeke om strukturele los rotse te erken, word uitgevoer voor enige werkskof en na skietwerk. Dit word gedoen deur ‘n myner wat ‘n breekyster teen die rots kap en ‘n oordeel vel op die frekwensie weergawe van die gevolglike klank. Die ‘Elektroniese Klinking Toestel’ (Electronic Sounding Device, ESD) is ontwikkel deur die WNNR met die doel om die proses te ondersteun. Dit word gedoen deur ‘n gelyktydige voorspelling van die strukturele toestand gebaseer op die akoestiese golfvorm gegenereer in die proses van klinking. Die projek stel ten doel om ’n effektiewe klassifikasie-model te identifiseer, te ontwikkel en toe te pas in die ESD om hierdie assessering uit te voer. Die projek vind in drie stadiums plaas: die insameling van geëtiketteerde akoestiese monsters van die werkareas; die ekstraksie van beskrywende kenmerke van die golfvorms en die mededingende evaluering van geskikte klassifiseringsmodelle. Klinking akoestiese monsters is opgeneem by Driefontein mynbouoperasie deur spanne van Gold Fields se werknemers. Die akoestiese monsters is opgeneem in werkareas van elk van die vier goudriwwe wat deur die skagte van die mynkompleks gedek word. Monsters is as ‘veilig’ of ‘onveilig’ geëtiketteer as aanduiding van die ekspert se oordeel van die rots se strukturele toestand. ‘n Laboratorium gekontroleerde omgewing is ook geskep om ’n platform te skep vanwaar akoestiese monsters met objektiewe etikettering waargeneem word. Drie stelle van kenmerke is onttrek van die akoestiese golfvorms om ‘n beskrywende datastel van kenmerke te vorm: vier statistiese momente van die frekwensie verspreiding van die gevormde golfvorm; gemiddelde energie ingesluit in sestien diskrete frekwensiebande in die data; en twaalf ‘Mel Frequency Cepstrum Coefficients’ (MFCCs). Klassifikasie modelle van die vier modelsamestellings was kompeterend geëvalueer vir die beste akkuraatheid in voorspellings van strukturele toestande. Klassifikasie modelle het k-naaste bure, selforganiserende kaarte, besluitnemingsbome, lukrake woude, logistieke regressie, neurale netwerke en steun-vektor masjiene met radiale basisfunksie en polinominale kerne. Die meting van die sensitiwiteit van die modelle, met betrekking tot die vermoë van die modelle om veilige voorspellings te beperk wanneer die rotsmassa los is, was gebruik as ’n kritiese werksverrigtingsmeting. ‘n Enkel-verskuilde-laag neurale netwerk met 15 nodes in die verskuilde laag en ’n sigmoïde aktiveringsfunksie is gevind as die mees geskikte vir die ESD. Addisionele keuse van kenmerke is uitgevoer deur die geoptimiseerde vorm van die model te identifiseer. Die model was suksesvol geïmplementeer op die ESD platform.

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published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Applied Geosciences / Master / Master of Science

The relationship between lithology and slope morphology is investigated at eight sites on granitic, andesitic, and sedimentary rock slopes in the Tucson Mountains. Several methods are used in the study. Topographic profiles are constructed. Skewness indices of the slope shapes, maximum and minimum slope angles, and slope lengths of the different slope profiles are computed and compared with each other. Debris size analysis is done to better determine hillfront/piedmont junctions. Slope surface regularities of the three lithological slopes are analysed and compared. The results show that the granitic piedmont slopes are found to be slightly concave to almost rectilinear, indicating their high resistance to erosive processes. In contrast, the concavity of the andesitic and sedimentary piedmont slopes demonstrate their inability to resist the erosive attack on them. However, in the case of the hillfront slopes, slope forms do not reflect lithological variations.