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Estimation of Rock Comminution Characteristics by Using Drill Penetration RatesPark, Junhyeok, Park, Junhyeok January 2016 (has links)
The characterization of rock properties is a vital task in the challenge for hard rock mining operation. A simplified and straightforward characterization of rock properties provides information about the safety of ground structure (e.g. slope, tunnel, etc.), and the strategy to improve productivity in terms of rock breakage process. The penetration-rate of drilling has been proposed to quantify the comminution characteristics of rock by virtue of real-time logging of drilling performance otherwise the data is obtained from a time- and cost-consuming laboratory test; this is called measurement while drilling. In the mining industry, this technique can be a useful tool that has allowed for the meticulous and routine data collection of geological information from blasthole drilling operations. In this study, the mechanical performance of drill and its interaction with the rock properties is investigated in laboratory scale. The rock properties include tensile strength, hardness, and grindability, which is considered as the influential parameters of the required energy consumption for the comminution processes. For sandstone samples, the penetration-rate data shows a good correlation with tensile strength, hardness, and Bond work index; this implies that penetration-rate data can be a good indicator to estimate comminution characteristics. Additionally we carried out the same test with limestone samples. Second, field study is conducted to investigate the interaction between current blast design and rock fragmentation. Fabricating the blast design and fragmentation through the blast operation might enable to construct proper strategy to reduce the energy cost of downstream processes including crushing and grinding by using the rock characteristics measured from the blasthole drilling. The concept of this process is a part of Mine-to-Mill optimization. The thesis proposed the blueprint of Mine-to-Mill optimization, providing a guideline for further in-situ research.
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Environmental Performance of Steel Grit and Specialty Sand as AbrasivesSilvadasan, Xavier 17 December 2004 (has links)
Dry abrasive blasting is a surface preparation process used in shipyards for cleaning the surfaces of the metal plates to be used in various components of the ship. Commonly used abrasives include sand, steel grit, mineral abrasives, metallic abrasives, and synthetic abrasives. The basic objective of this study was to understand the environmental performance of two abrasives, Steel Grit and Specialty Sand. The project was funded by the Gulf Coast Region Maritime technology Center (GCRMTC) and USEPA. It simulated actual blasting operations conducted at shipyards under enclosed, controlled conditions on plates similar to steel plates commonly blasted at shipyards. The emissions were measured using EPA Source Test Method to quantify particulate emissions. Steel Grit was observed to be more productive, less consuming, and more environmentally friendly compared to Specialty Sand. The findings obtained in this study will be valuable in reducing costs, improving productivity, and protecting the environment.
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Performance and Total PM Emission Factor Evaluation of Expendable AbrasivesKambham, Kalpalatha 22 May 2006 (has links)
Dry abrasive blasting is one of the most widely used methods of surface preparation. Air emissions from this process include particulate matter (PM) and metals. Spent abrasive generated from this process may be hazardous in nature. With increasing concern on health effects due to silica emissions from sand, use of alternative materials is suggested by health and regulatory agencies. The objective of this research was to evaluate performance of expendable abrasives and determine PM emission factors. Dry abrasive blasting was performed in an enclosed chamber and total PM samples were collected. Three commonly used expendable abrasives, coal slag, copper slag and specialty sand, were used to evaluate cleaner alternatives. Blast pressure and abrasive feed rate, two important process conditions were varied to study their effect on performance of an abrasive. Productivity, consumption and emission factors (performance parameters) were calculated and their variation with pressure and feed rate was evaluated. Two dimensional and three dimensional predicted models were developed to estimate the performance at intermediate blast pressure and feed rate conditions. Performance of the three abrasives was compared with respect to emission potential, productivity and consumption. Emission factors developed in this research will help in accurate estimation of total PM emissions and to select cleaner abrasives and optimum process conditions that will results in minimum emissions and reduced health risk. The productivity and consumption models will help is estimating life cycle costs including material cost, equipment cost, energy cost, labor costs, waste disposal cost, and compliance costs. Consumption models will also help in determining the quantity of spent abrasive generated, identify abrasives with lower material consumption, and identify process conditions that generate minimum spent abrasives. In addition, these models will help industries in making environmentally preferable purchasing (EPP), which results in pollution prevention and cost reduction.
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Evaluation of Productivity, Consumption, and Uncontrolled Total Particulate Matter Emission Factors of Recyclable AbrasivesSangameswaran, Sivaramakrishnan 22 May 2006 (has links)
Dry abrasive blasting is a commonly used surface preparation operation by many process industries to clean up metallic surfaces and achieve surface finishes suitable for future adhesion. Abrasives used in this process can be recyclable or expendable. This study was undertaken to evaluate the performance of three recyclable abrasives: garnet, barshot and steel grit/shot in terms of productivity (area cleaned per unit time), consumption (amount of abrasive used per unit area cleaned) and uncontrolled total particulate matter (TPM) emission factors (in terms of mass of pollutant emitted per unit area cleaned and mass of pollutant emitted per unit mass of abrasive consumed). Though there have been various attempts in the past to evaluate the performance of these abrasives, there has not been a streamlined approach to evaluate these parameters in the commonly used range of process conditions, or to identify and model the influences of key process variables on these performance parameters. The first step in this study was to evaluate the performance of these three abrasives in blasting painted steel panels under enclosed blasting conditions and using USEPA recommended protocols. The second step was to model the influences of blast pressure and abrasive feed rate, two most critical parameters on productivity, consumption and emission factors. Two and three dimensional models were obtained using multiple linear regression techniques to express productivity, consumption and TPM emission factors in terms of blast pressure and abrasive feed rate. Barshot was found to have high productivities over all and steel grit/shot demonstrated the least emission potential at almost all of the tested pressure and feed rate conditions. The data will help fill the gaps in literature currently available for dry abrasive blasting performance. The models obtained will help industries, the research community and the regulatory agencies to make accurate estimates of the performance parameters. Estimating productivity and consumption will help industries identify best management practices by optimizing the process conditions to achieve high productivity and low consumption rates. Emission factor determination will help in reducing the emissions to the atmosphere by choosing process conditions corresponding to minimum emissions. The performance parameters once optimized can result in reduction in material, labor, energy, emission and disposal costs, lower resource utilization and hence reduction in overall life cycle costs of dry abrasive process. The developed models will help industries in making environmentally preferable purchases thereby promoting source reduction options. PM emissions estimated using the models presented here will aid studies on health risk associated with inhalation of atmospheric PM.
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Improvement of blast-induced fragmentation and crusher efficiency by means of optimized drilling and blasting in AitikH. Beyglou, Ali January 2012 (has links)
Rock blasting is one of the most dominating operations in open pit mining efficiency. As many downstream processes depend on the blast-induced fragmentation, an optimized blasting strategy can influence the total revenue of a mine to a large extent.Boliden Aitik mine in northern Sweden is one of the largest copper mines in Europe. The annual production of the mine is expected to reach 36 million tonnes of ore in 2014; so continuous efforts are being made to boost the production. Highly automated equipment and new processing plant, in addition to new crushers, have sufficient capacity to reach the production goals; the current obstacle in the process of production increase is a bottleneck in crushers caused by oversize boulders. Boulders require extra efforts for secondary blasting or hammer breakage and if entered the crushers, they cause downtimes. Therefore a more evenly distributed fragmentation with less oversize material can be advantageous. Furthermore, a better fragmentation can cause a reduction in energy costs by demanding less amounts of crushing energy.In order to achieve a more favorable fragmentation, two alternative blast designs in addition to a reference design were tested and the results were evaluated and compared to the current design in Aitik. A comparatively large bench was divided to three sections with three different drill plans, which led to different specific charges in each section. The sections were drilled in patterns of 6x9 m, 7x9 m and 7x10 m of burden and spacing; planned specific charges of the sections were 1.17 kg/m3, 1.02 kg/m3, and 0.91 kg/m3 respectively. Similar to the current drill plan in Aitik, the section with 7x9 m (1.02 kg/m3 specific charge) was used as the reference for results comparison. The drilling and charging processes were monitored carefully and the post-blast parameters were measured accordingly. Laser scanning was used to measure the swelling of the sections and two different methods of image analysis were utilized to evaluate the fragmentation of the rock for each section. Drilling log data (MWD) were analyzed to evaluate the hardness of the rock; energy consumption log of the crusher was also analyzed and all the data was collected in a single database. VBA (Visual Basic for Applications) programming language was embedded within data spreadsheets to correlate the mentioned data to the coordinates of the rock by means of Minestar logs, which include both timestamps and coordinates of all machinery e.g. shovels and trucks.The results of the test show significant improvements in fragmentation and oversize material percentage in the section with 6x9 m drill plan (1.17 kg/m3). The advantage of 6x9 m plan was confirmed by 52% higher swelling, 66% lower oversize material and 26% lower crushing energy compared to the reference section. The section with 7x10 m drill plan (0.91 kg/m3) also showed theoretically acceptable results; however, the deviations from reference were not as large as formerly mentioned section. The swelling had a decrease of 8% compared to the reference section and the percentage of oversize material and crushing energy were increased by 16% and 2% respectively.Presented results are based only on technical aspects and do not include the costs of drilling and charging. Thus, in order to evaluate the drill plans in practice an economical evaluation of the sections should be conducted. Also a confirmation test with more accurate geology explorations is recommended.Finally, upon the request of Boliden Mines, a short report on the usage of Air-decking technique in Aitik is enclosed as an appendix. The report includes a brief introduction to air-decking and discusses practical solutions to apply this technique in Aitik. / Validerat; 20121001 (anonymous)
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Efeito do jateamento de óxido de alumínio e uso de selante industrial, na superfície de pilares protéticos Cone Morse, de restaurações implanto suportadas sobre a resistência ao contratorque / Effect of aluminum oxide blasting and use of industrial sealant on the outer abutment surface of the prosthetic morse taper system connection on the untightening torqueTunes, Fábio Sanches Magalhães 18 June 2012 (has links)
Problemas com desenho de conexões protéticas sobre implantes, microfendas, afrouxamento e, consequentemente, perdas das estruturas protéticas reabilitadoras são tópicos frequentes do estudo odontológico. Conexões do tipo Cone Morse, devido às suas características, diminuíram o índice desses problemas, abrindo uma nova perspectiva para o sucesso da prótese sobre implante. Contudo, ainda é frequente encontrar componentes que falham no desempenho, levando à falência da restauração, especialmente quando esses componentes não são bem ajustados, bem fixados ou, ainda, não possuem, na sua geometria, características suficientes para suportar as forças laterais e oclusais de um ciclo mastigatório. O objetivo deste estudo é avaliar a influência do jateamento com óxido de alumínio sobre a superfície externa dos componentes protéticos, separadamente e em conjunto, com um adesivo industrial, em uma tentativa de aumentar os valores de torque de abertura de componentes apertados em seu torque recomendado, pelo fabricante ou menor. Neste ensaio, foram utilizados 36 implantes da marca Straumann®, de 10mm de comprimento com diâmetro de 4,8 mm, os quais foram divididos em 6 grupos: Grupo 1 = controle, torque de 35 N.cm; Grupo 2 = superfície jateada com óxido de alumínio (# 320) e torque de 35 N.cm; Grupo 3 = superfície jateada com óxido de alumínio (# 320) e torque de 25 N.cm; Grupo 4 = superfície jateada com óxido de alumínio (# 100) e torque de 25 N.cm; Grupo 5 = superfície jateada com óxido de alumínio (# 320), aplicação de adesivo e torque de 25 N.cm; Grupo 6 = superfície jateada com óxido de alumínio (# 100), aplicação de adesivo e torque de 25 N.cm, que receberam componentes protéticos sólidos de 5,5 mm de altura, regulares e alterados. As modificações incluídas foram o jateamento com partículas de óxido de alumínio (100 e 320 micra) e o uso de Loctite® 277 como adesivo industrial. Os conjuntos implante-componente foram levados até uma máquina de controle de tração, Instron®, e, após a sua calibração, as amostras dos grupos foram apertadas em 35 e 25 N.cm, com um conjunto catraca-torquímetro, com checagem visual e registro no software acoplado à máquina de ensaio. Após trinta dias, os grupos foram levados à máquina novamente e o conjunto abutment-implante foi desapertado, agora somente com registro no software da máquina de ensaio. Os valores e porcentagens da diferença entre torque de aperto e desaperto foram avaliados estatisticamente, e comparados entre os grupos. Para todas as associações, o valor de p deveria ser menor ou igual 0,05, para relevância. O grupo Jateado 35 N.cm, 320 micra, não apresentou valores mais altos do que o grupo Controle no momento do torque de desaperto, assim como os grupos Jateados 25 N.cm 100 e 320 micra. Os grupos Jateados 25 N.cm, 100 e 320 micra, com adesivo, mostraram uma resistência por volta de uma vez e meia maior, no torque de desaperto do que o grupo Controle 35 N.cm. / Problems with design of prosthetic implant connections, microleakage,! loosening which leads to loss of rehabilitative prosthetic structures are frequent topics of dental study. Morse taper connections, due to its characteristics, decreased the rate of these problems opening a new perspective to the success of the prosthesis supported over implant. However, it is still frequent to find components that fail in performance leading to failure of restoration especially when these components are not well adjusted, tightened or do not have in its geometry enough characteristics to support the occlusal and lateral forces in a masticatory cycle. The aim of this study is to evaluate the influence of blasting with aluminum oxide on the outer surface of the prosthetic components separately and in conjunction with an industrial adhesive in an attempt to increase the opening torque values of components tightened on their recommended torque by the manufacturer or less, therefore allowing the dentist an early intervention in the prosthetic rehabilitation. In this test, 36 Straumann® implants of 10mm high and 4,8mm wide were used. They were divided into six groups: Group 1 Solid abutments control group - 35 N.cm tightened; Group 2 - Solid sandblasted abutments, 35 N.cm aluminum oxide 320 microns size particles; Group 3 - Solid sandblasted abutments, 25 N.cm aluminum oxide 320 microns size particles; Group 4 - Solid sandblasted abutments, 25 N.cm aluminum oxide 100 microns size particles; Group 5 - Solid sandblasted abutments, 25 N.cm aluminum oxide 320 microns size particles with glue application; Group 6 - Solid sandblasted abutments, 25 N.cm aluminum oxide 100 microns size particles with glue application, which received 5,5 mm high regular and modified solid abutments. The included modifications were sandblasting with aluminum oxide particles (100 and 320 microns) and the use of Loctite® 277 as an industrial adhesive. The samples were taken to a traction control test machine, Instron ®, and after calibration the group samples were tightened on 35 and 25 N.cm with a ratchet-wrench set with visual check. The data was recorded in a software coupled to the test machine. After thirty days the groups were brought again to the test machine and the samples were untightened. At this point the resulting data was recorded only in the testing machine software. The values and percentages of the changes between the tightening and loosening torques were recorded and compared among the study groups. For all associations a p-value < 0.05 was considered significant. The group blasted 35 N.cm, 320 microns did not show higher values than the control group at the time of loosening torque as well as groups blasted 25 N.cm 100 and 320 microns. The groups blasted 25 N.cm, 100 and 320 microns with adhesive showed a resistance around one and a half times greater in the loosening torque than the control group 35 N.cm.
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Escavação de rochas com furos de grande diâmetro na mineração a céu aberto. / Rock blasting with large diameter blastholes in the open pit mining.Collantes Candia, Renan 17 July 2006 (has links)
Esta dissertação apresenta uma revisão bibliográfica dos principais aspectos envolvidos nas operações de escavação de rochas com furos de grande diâmetro na mineração a céu aberto. O trabalho expõe o método de perfuração rotativa por ser o mais utilizado na execução desta operação unitária de lavra. Faz-se também um estudo dos principais agentes de desmonte que contribuem no emprego de furos de grande diâmetro na indústria da mineração, especialmente na explotação de minérios metálicos. São analisadas as propriedades do maciço rochoso, na determinação da carga específica e sua influência nos resultados da escavação de rochas por explosivos. É realizada ainda uma análise da metodologia utilizada para o dimensionamento do plano de fogo, baseando-se na inter-relação existente entre seus diversos elementos geométricos. Apresenta-se também a teoria de crateras como uma metodologia alternativa para dimensionamento de plano de fogo. Finalmente mostram-se os principais impactos ambientais decorrentes da detonação de explosivos na escavação de rochas. / This dissertation presents a bibliographical review of the main aspects involved in the open pit blasting operation using large diameter blastholes. The work displays the method of rotary drilling, being the most frequent used in the execution of this mining unitary operation. Here is presented a study of the main blasting agents that contribute to the increasing application of large diameter blastholes in the mining industry, especially in the field of metallic ores. The properties of the rock mass are analysed, in the determination of the powder factor and its influence on the results of rock excavation by explosives. An analysis of the methodology used for the determination a shot plan is carried out based on the existing interrelation between diverse geometric elements involved. The crater theory is also presented as an alternative methodology for the same purpose. Finally, the main environmental impacts caused by blasting in the rock excavation are discussed.
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Desenvolvimento e construção de um sismógrafo para monitoramento de vibrações e pressão acústica / not availableVarella Neto, Celso Bairros 03 April 2017 (has links)
Esta pesquisa apresenta o projeto, construção e testes, tanto de laboratório como de campo de um sismógrafo de engenharia para o monitoramento dos níveis de vibração e pressão acústica, resultantes do processo de desmonte de rocha utilizando explosivos. Desenvolveram-se filtros e amplificadores com características que atendam às especificações impostas pelo guia intitulado \"ISEE Performance Specifications for Blasting Seismographs\" (ISEE, 2011), bem como, foram utilizados sensores (geofones e microfone) desenvolvidos e fabricados por terceiros, mas que atendam às características impostas pelo guia. A interconexão entre a etapa analógica com a digital foi realizada através da utilização de módulos de conversão A/D com tecnologia Sigma-Delta e resolução de 24-bits. Todas as etapas de aquisição, processamento e armazenamento de dados são controladas através de um microcontrolador ARM Cortex-M de 32-bits, o qual provê os mais diversos e modernos periféricos. Os testes de laboratório demonstraram a eficácia dos circuitos analógicos, pois apresentaram resposta plana na banda de passagem, onde os filtros passa-baixa, do tipo Butterworth, proporcionaram uma atenuação de 36 dB/oitava a partir da frequência de corte de 500 Hz, enquanto os filtros passa-alta, do tipo passivo, proporcionaram uma atenuação de 6 dB/oitava abaixo da frequência de corte de 2 Hz. Os testes de operação confirmaram a fácil e rápida operação do conjunto sismográfico, enquanto os testes de campo demonstraram a praticidade de sua operação e confiabilidade e coerência dos resultados. Concluiu-se que o sistema é exequível, atendendo às necessidades de monitoramento de um processo de desmonte de rochas utilizando explosivos a um preço relativamente baixo, abrindo a possibilidade de utilizá-lo em monitoramentos permanentes em situações onde isto seja necessário. / This research presents the design, construction and laboratory and field testing of an engineering seismograph for monitoring vibration and acoustic pressure levels during rock blasting. Filters and amplifiers with characteristics that meet the specifications of ISEE Performance Specifications for Blasting Seismographs (ISEE, 2011) have been developed. Third part sensors (geophones and microphones) were selected to attend the characteristics suggested by the guide. The interconnection between the analog and the digital stages was accomplished with A/D conversion modules with Sigma- Delta technology and 24-bit resolution. All data acquisition, processing and storage steps are controlled by a 32-bit ARM Cortex-M microcontroller, which provides several and modern peripherals. Laboratory tests confirmed the effectiveness of the analog circuits that presented flat response between 2 and 500Hz. The low-pass filters developed are type Butterworth with an attenuation factor of 36 dB/octave for frequencies above 500 Hz. The high-pass filters are of passive type with rejection factor of 6 dB/octave below 2 Hz. The operation of the system presented to be easy and fast. Field tests demonstrated its friendliness and the results showed to be consistent. It was concluded that the system is feasible and applicable to monitor rock-blasting process. Its relatively low price opens up the possibility of using it for permanent monitoring in situations where this might be necessary.
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Influência do acoplamento de geofone nos parâmetros de vibraçãoGomes, Lucas Roncarati January 2017 (has links)
Os principais impactos ambientais decorrentes de desmontes de rochas com explosivos estão associados à geração de vibrações no maciço circundante e pressão acústica. Para o monitoramento sismográfico apropriado, é fundamental que o sensor esteja bem acoplado ao meio, possibilitando a medição acurada da vibração do terreno. Devido à existência de diversas recomendações a respeito da montagem dos sensores de vibração (geofones) em campo, este estudo tem o intuito de avaliar os métodos de acoplamento de geofone mais comuns, determinando quais são aceitáveis para um adequado monitoramento sismográfico. Dessa forma, foi estudada a influência de quatro métodos de fixação nos parâmetros de vibração. Para este propósito, o primeiro geofone foi colocado sob um saco de areia, o segundo foi enterrado no solo, o terceiro foi cravado no solo e o quarto foi livremente colocado sobre o solo. Estes geofones foram dispostos lado a lado e as vibrações de desmontes com explosivos de uma mina de carvão a céu aberto foram monitoradas. As vibrações foram analisadas em termos de velocidade de vibração de partícula de pico, históricos temporais e frequência associada à vibração. Os resultados obtidos indicaram o desacoplamento do geofone sob saco de areia, descartando o método. O enterramento do geofone se mostrou preferível, entretanto, o uso de cravos registrou bom acoplamento. A colocação do geofone sobre o solo se mostrou aceitável de acordo com o nível de aceleração de vibração, decorrente do desmonte. / The main environmental impacts from rock blasting are ground vibrations and air overpressure. For proper blast vibration monitoring, it is critical that the sensor be coupled to the medium, enabling accurate measurement of ground vibration. Due to the existence of several recommendations regarding the mounting of vibration sensors (geophones) in the field, this study intends to evaluate the most common geophone coupling methods, determining which are acceptable for adequate vibration monitoring. The influence of four mounting methods on vibration parameters was studied. For this purpose, the first geophone was sandbagged, the second one was buried in soil, the third one was spiked and the fourth one was placed freely on the ground. These geophones were mounted side by side and ground vibrations at an opencast coal mine were monitored. The vibrations were analyzed in terms of peak particle velocity, time histories and frequency spectra. The results indicated the decoupling of the sandbagged geophone, discarding the method. The burial of the geophone proved to be preferable, however, the use of spikes recorded good coupling. The free placement of geophone proved to be acceptable according to the expected acceleration level.
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Influência dos níveis de vibração e pressão acústica produzidos pelo desmonte de rochas com explosivos em construções de alvenariaRosenhaim, Vitor Luconi January 2015 (has links)
Desmonte de rochas com explosivos em áreas próximas a residenciais têm ocorrido com frequência em várias localidades em todo o Brasil. Atividades relacionadas a mineração e em especial as detonações causam muitos problemas visto que geram incômodo às comunidades vizinhas resultante de níveis elevados de pressão acústica (ruído) na atmosfera e reclamações de rachaduras em paredes das residências associadas com a propagação de vibrações no terreno. A necessidade de se obter uma melhor compreensão de como estruturas típicas da construção civil nacional respondem as vibrações geradas pelas detonações se torna evidente, bem como uma avaliação conjunta da influência de outras forças, tais como, condições meteorológicas (variações diárias de temperatura e umidade relativa do ar) que começam a agir sobre os materiais constituintes das estruturas desde o momento da construção e durante toda sua vida útil. Nesse contexto, definiu-se como meta dessa pesquisa investigar a resposta deformacional de construções de alvenaria frente aos estímulos provocados por diferentes níveis de vibração e pressão acústica gerados pelo desmonte de rochas com explosivos em diferentes condições geológicas, comparando-as com os efeitos das variações climáticas de temperatura e umidade. Visando o atendimento desta demanda, a resposta de três estruturas, duas residenciais e uma comercial, a diferentes operações com desmonte de rochas (mineração de carvão e pedreira) foram avaliadas. A movimentação das paredes de estruturas de alvenaria, comumente encontradas no entorno de empreendimentos mineiros, foi registrada com sensores de velocidade instalados nas paredes e os resultados foram correlacionados com os níveis de vibração no terreno e pressão acústica (ruído) na atmosfera que provocaram esta movimentação. A partir dos resultados das medições da movimentação das estruturas, deformações induzidas nas paredes, geradas durante trações no plano e flexões fora do plano das paredes, foram computadas e comparadas com os limites de ruptura do material mais fraco que constitui as paredes das estruturas. Em conjunto com o monitoramento da movimentação das estruturas, variações na abertura de rachaduras existentes no reboco no interior ou exterior das estruturas induzidas por forças dinâmicas (detonações) e estática (variações climáticas) foram registradas por meio de sensores de deslocamento instalados em ambos lados das rachaduras. As respostas das estruturas apresentaram excelente acoplamento da fundação com o terreno e nenhuma movimentação livre (ressonância) das paredes das estruturas foi observada após a passagem das ondas sísmicas, indicando que as estruturas seguem muito perto as excitações provocadas pelas vibrações no terreno do terreno e param de movimentar junto com o mesmo. Devido às ondas sísmicas e acústicas atingirem quase que ao mesmo tempo as estruturas, foi difícil separar a influência de cada estímulo. As deformações calculadas foram inferiores as necessárias para induzir rachaduras na argamassa utilizada como reboco nas paredes, considerada como o material mais frágil dentre os constituintes das paredes das estruturas. A resposta deformacional das rachaduras frente às variações climáticas diárias de temperatura e humidade relativa do ar foi superior as variações resultantes da influência das vibrações geradas pelas detonações. / Blasting near residential areas has become frequent in many locations throughout Brazil. Activities related to mining and in especial blasting have become a problem as they generate a potential nuisance to nearby communities resulting from high air sound pressure levels and can result in claims of wall cracking associated with ground vibrations. It was deemed necessary to have a better understanding of how structures of typical national construction respond to blast vibrations and compare this response to other forces, such as, environmental forces that naturally act on these structures since the moment they are constructed and throughout the entire life of the structure. The response of three structures, two residential and one office building, to different blasting activities (coal and quarry blasting) were evaluated in this study. Whole structure motions and the movement of existing cracks were measured in masonry built structures commonly found near mining operations. Whole structure and mid-wall motions were measured at upper and lower corners and on mid-walls using single-axis velocity transducers and compared with ground motions and air sound pressure excitations, measured next to the structures using a tri-axial geophone and microphone. Dynamic (blast-induced) and static (weather-induced) changes in crack width of existing interior and exterior wall cracks in the cement grout, typically used as wall coverage, were recorded. Dynamic structure and crack motions during blasting were time-correlated with ground vibrations and air sound pressure levels. Wall strains generated during out-of plane bending and in-plane tensile strains were computed and compared with the failure strains for the weakest material comprising the wall construction. Long-term crack movement with variations in temperature and humidity were compared with blast-induce peak crack displacements. The structures response showed good coupling of the foundations with the ground and no free-response was observed after the cessations of the ground excitations, indicating the structures are rigid following very close the ground excitation. Because air sound pressure levels and ground motions arrived at the same time in the structures, it was difficult to separate the influence of each stimulus. Calculated strains were lower than the required to induce cracks in the cement grout and environmental-induced crack response, resultant from daily changes in temperature and humidity, were greater than the response caused by blast-induced ground motions and air sound pressure levels in crack aperture.
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