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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Supraspinatus Musculotendinous Architecture: A Cadaveric and In Vivo Ultrasound Investigation of the Normal and Pathological Muscle

Kim, Soo Young 24 September 2009 (has links)
The purpose of the study was to investigate the static and dynamic architecture of supraspinatus throughout its volume in the normal and pathological state. The architecture was first investigated in cadaveric specimens free of any tendon pathology. Using a serial dissection and digitization method tailored for supraspinatus, the musculotendinous architecture was modeled in situ. The 3D model reconstructed in Autodesk MayaTM allowed for visualization and quantification of the fiber bundle architecture i.e. fiber bundle length (FBL), pennation angle (PA), muscle volume (MV) and tendon dimensions. Based on attachment sites and architectural parameters, the supraspinatus was found to have two architecturally distinct regions, anterior and posterior, each with three subdivisions. The findings from the cadaveric investigation served as a map and platform for the development of an ultrasound (US) protocol that allowed for the dynamic fiber bundle architecture to be quantified in vivo in normal subjects and subjects with a full-thickness supraspinatus tendon tear. The architecture was studied in the relaxed state and in three contracted states (60º abduction with either neutral rotation, 80º external rotation, or 80º internal rotation). The dynamic changes in the architecture within the distinct regions of the muscle were not uniform and varied as a function of joint position. Mean FBL in the anterior region shortened significantly with contraction (p<0.05) but not in the posterior. In the anterior region, mean PA was significantly smaller in the middle part compared to the deep (p<0.05). Comparison of the normal and pathological muscle found large differences in the percentage change of FBL and PA with contraction. The architectural parameter that showed the largest changes with tendon pathology was PA. In sum, the results showed that the static and dynamic fiber bundle architecture of supraspinatus is heterogeneous throughout the muscle volume and may influence tendon stresses. The architectural data collected in this study and the 3D muscle model can be used to develop future contractile models. The US protocol may serve as an assessment tool to predict the functional outcome of rehabilitative exercises and surgery.
12

Projeto e construção de um scanner tridimensional baseado no método de triangulação a laser utilizando softwares livres /

Moreira, Sandro Silva January 2016 (has links)
Orientador: Ruis Camargo Tokimatsu / Resumo: A modelagem tridimensional muito já contribuiu com a indústria do entretenimento e agora tem sido amplamente utilizada na manufatura e criação de novos produtos. A possibilidade de se ter um modelo de um produto a um preço menor e com uma maior rapidez tem feito essa técnica ser cada vez mais aceita em todas as áreas da engenharia. Quando já se tem um modelo real e deseja-se realizar alguma modificação, simulação ou mesmo replicar o produto, a engenharia reversa muito pode contribuir, pois permite a obtenção do modelo tridimensional a partir do objeto real. Os equipamentos de digitalização tridimensional têm um alto custo de investimento, mesmo os de baixa precisão. A comunidade de entusiastas de software e hardware livre busca também distribuir e popularizar o conhecimento compartilhando suas descobertas e contribuindo abertamente com outras iniciativas. Buscamos nesse projeto construir um scanner 3D utilizando software e hardware livre utilizando componentes de baixo custo e fácil aquisição, estabelecendo seus limites técnicos, estimulando assim a adoção de técnicas de engenharia reversa. O processo de calibragem, captura e pós tratamento da nuvem de pontos obtidas foi detalhado na construção de modelos para comparação de dimensões e levantamento de características da superfície do material. / Mestre
13

Projeto e construção de um scanner tridimensional baseado no método de triangulação a laser utilizando softwares livres / Design and construction of a three-dimensional scanner based in laser triangulation method using free software

Moreira, Sandro Silva [UNESP] 06 December 2016 (has links)
Submitted by Sandro Moreira (moreira.sandro@gmail.com) on 2017-01-18T18:23:17Z No. of bitstreams: 1 SandroMoreira-DissertacaoMestradoFinal.pdf: 12934831 bytes, checksum: a63cb94b201b877dc272a7bccad284bc (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-01-23T19:48:34Z (GMT) No. of bitstreams: 1 moreira_ss_me_ilha.pdf: 12934831 bytes, checksum: a63cb94b201b877dc272a7bccad284bc (MD5) / Made available in DSpace on 2017-01-23T19:48:34Z (GMT). No. of bitstreams: 1 moreira_ss_me_ilha.pdf: 12934831 bytes, checksum: a63cb94b201b877dc272a7bccad284bc (MD5) Previous issue date: 2016-12-06 / A modelagem tridimensional muito já contribuiu com a indústria do entretenimento e agora tem sido amplamente utilizada na manufatura e criação de novos produtos. A possibilidade de se ter um modelo de um produto a um preço menor e com uma maior rapidez tem feito essa técnica ser cada vez mais aceita em todas as áreas da engenharia. Quando já se tem um modelo real e deseja-se realizar alguma modificação, simulação ou mesmo replicar o produto, a engenharia reversa muito pode contribuir, pois permite a obtenção do modelo tridimensional a partir do objeto real. Os equipamentos de digitalização tridimensional têm um alto custo de investimento, mesmo os de baixa precisão. A comunidade de entusiastas de software e hardware livre busca também distribuir e popularizar o conhecimento compartilhando suas descobertas e contribuindo abertamente com outras iniciativas. Buscamos nesse projeto construir um scanner 3D utilizando software e hardware livre utilizando componentes de baixo custo e fácil aquisição, estabelecendo seus limites técnicos, estimulando assim a adoção de técnicas de engenharia reversa. O processo de calibragem, captura e pós tratamento da nuvem de pontos obtidas foi detalhado na construção de modelos para comparação de dimensões e levantamento de características da superfície do material. / The three-dimensional modeling has contributed much to the entertainment industry and has now been widely used in manufacturing and creating new products. The possibility of having a model of a product at a lower price and a higher speed have made this technique is increasingly accepted in all fields of engineering. When there is already a real model and you want to make any changes, simulation or even replicate the product, reverse engineering can greatly contribute, as it allows to obtain three-dimensional model from the real object. The three-dimensional scanning equipment have a high investment cost, even low accuracy. The community of enthusiasts of open source and open hardware also distribute and popularize knowledge sharing his findings and openly contribute to other initiatives. We seek in this study, build a scanner 3D using free software and hardware components using low-cost and easy acquisition, establishing its technical limits, stimulating the adoption of reverse engineering techniques. The calibration, capture and post-treatment process of the cloud of points obtained was detailed in the construction of models for comparison of dimensions and survey of surface characteristics of the material.
14

Learning an Abstract STEM Concept by Constructing a Three-Dimensional Physical Model Compared with a Two-Dimensional Digital Model

Garofalo, Salvatore January 2022 (has links)
This study examined the effectiveness of three instructional and assessment strategies on conceptual understanding of the DNA molecule. Specifically, a model building task was utilized to determine if physical model construction, digital model construction with a touchscreen tablet computer, or paper worksheet activity effected conceptual understanding during the initial exposure to an abstract science concept. The DNA molecule was chosen as an exemplary three-dimensional, abstract concept with physical and digital model building interventions. Conceptual understanding was measured using an objective quiz, a drawing of a DNA molecule, and a hand-written explanation of DNA. Conceptual understanding was measured immediately after intervention and again two months later. The study examined effects to conceptual understanding of model building by comparing physical models constructed using foam pieces and digital models constructed using a touchscreen tablet computer. A control group completed a paper worksheet activity on the topic of DNA. In all conditions, an instructional video about DNA was used to standardize the content taught. To account for the potential covariates of spatial ability and attitudes to scientific inquiry, participants completed a mental rotation test to measure spatial ability and an attitudes to scientific inquiry survey. A total of 161 students across six intact 9th-grade Living Environment classrooms participated in the study. The results from the three conceptual understanding measures were compared among the three groups at both immediate and delayed post-test timepoints as well as across the two post-test timepoints. For both immediate and delayed post-test, there were no differences among the groups for the objective quiz measure. However, the physical model group outperformed the digital model and control groups in both the drawing and explanation measures at both timepoints (p < 0.01). Across the two timepoints, the control group showed a significant degree of forgetting for the objective quiz measure (p < 0.001) and the digital group demonstrated a significant degree of forgetting for the objective quiz measure (p = 0.03) and drawing measure (p < 0.001). There was a significant difference between the delayed post-test and pre-test of the objective quiz for the physical model group (p < 0.001) and no significant difference between the post-test and delayed post-test for the objective quiz for the physical model group suggesting long-term conceptual understanding and retention. Overall, the physical model group demonstrated greater conceptual understanding at immediate and delayed timepoints for the drawing and explanation measures as well as significant retention of conceptual understanding of DNA as measured by the objective quiz across three timepoints. The digital model group demonstrated a greater degree of forgetting for objective quiz and drawing measures as well as underperformed in the three conceptual understanding measures at both post-test and delayed post-test timepoints. This suggests that the greater degree of physical, haptic manipulation of a three-dimensional model aids in conceptual understanding at all three measures as well as long-term memory when compared with the limited haptic interactions with a two-dimensional touchscreen device.
15

Towards Constructing Interactive Virtual Worlds

Chang, Francis 17 March 2014 (has links)
Networked virtual reality environments including virtual worlds devoted to entertainment, online socializing and remote collaboration have grown in popularity with the rise of commercially available consumer graphics hardware and the growing ubiquity of the Internet. These virtual worlds are typified by a persistent simulated three-dimensional space that communicates over a computer network, where users interact with the environment and each other through digital avatars. Development of these virtual worlds challenges the limits of the networking infrastructure, 3D streaming graphics techniques, and the distributed computing design of the virtual world systems that manages the simulation. In this dissertation, we explore solutions to different aspects of the overall problem of developing a general purpose, networked virtual environment, focusing on the networking and software system issues. Specifically, we show how to improve the networking infrastructure to better support the high packet-rate traffic that is typical of virtual worlds, efficiently stream terrain data for remote rendering, and construct a dynamically adaptive distributed systems framework suitable for virtual world simulations.
16

Apport de la modélisation tridimensionnelle à la compréhension du fonctionnement des sépultures multiples : l'exemple du secteur central de la catacombe des Saints Pierre-et-Marcellin (Rome, Italie) (Ier-milieu IIIe s. ap. J.-C.) / Contribution of three-dimensional modeling to understand the operation of multiple burials : the example of the central sector of the catacomb of Saints Peter and Marcellinus (Rome, Italy) (Ist-IIId s A.D)

Sachau-Carcel, Géraldine 12 October 2012 (has links)
Cette thèse se propose de mettre au point, grâce aux nouveaux outils informatiques, une méthode d’étude originale de l’espace funéraire en offrant une restitution tridimensionnelle de la sépulture, de l’architecture aux sujets. La découverte en 2003, d’un secteur de la catacombe des Saints Pierre-et-Marcelin (Rome, Italie), encore inexploré et original dans son organisation, a initié ce travail. Plusieurs tombes, datées des Ier-IIIe s. ap. J.-C, accueillent une succession de dépôts d’un grand nombre d’inhumés. La complexité des ensembles funéraires de ce secteur a nécessité le recours à de nouvelles formes de représentation pour l’analyse. L’objectif de cette thèse est d’établir un protocole de modélisation des sépultures multiples adapté à la stratification complexe des dépôts. Nos recherches ont porté, dans un premier temps sur l’élaboration et le test d’un processus de modélisation adaptés aux deux tombes étudiées et dans un second temps sur l’analyse des temps chronologiques et de la gestion des dépôts. Nos recherches ont abouti à la mise au point d’une méthodologie d’acquisition et de restitution de l’ensemble des vestiges osseux, de l’appareil funéraire et de l’espace funéraire. La modélisation 3D a permis par la visualisation tridimensionnelle une étude fine individuelle, une analyse des relations entre les différents sujets et de l’évolution taphonomique des dépôts confirmant la simultanéité des dépôts au sein des niveaux et entre les niveaux en rapport avec une crise de mortalité.L’application d'un protocole d'enregistrement puis de restitutions sur cette catacombe pourra contribuer à l'élaboration d'une méthode pour l'approche des sépultures plurielles. / The aim of this thesis is to perform, with the help of new informatics tools, an original study method of funerary space and offers a three-dimensional modelling of burial from architecture to individuals. This work was initiated by the discovery in 2003 of Saint Peter and Marcellinus catacombs parts, unexplored and original in its organisation. Several tombs, dated of 1st-3rd s A.D, received many buried. The complexity of tombs of central sector catacombs needs a new type of representation for analysis. The thesis goal is to establish a modelling process for several burials, adapt with deposit complex stratification. At first, our study was about the conception and the test of a modelling protocol adapted to the two study tombs, and after, to analyze chronological times and deposit management. Our research has result to acquisition and restitution process development of all human remains, funerary device and funerary space. The 3D modelling permits by the 3D visualisation, an advanced study, analyses of relations between different individuals and taphonomic evolution of deposit which confirmed the simultaneous deposit into levels and between levels linked to death's crisis.The application of a record protocol then restitution on these catacombs must contribute to a conception method for the approach of plural burials.
17

Modelagem tridimensional da região da articulação temporomandibular a partir de tomografia computadorizada visando o projeto, estudo e análise de prótese personalizada /

Gregolin, Rafael Ferreira. January 2017 (has links)
Orientador: João Antônio Pereira / Resumo: O uso de ferramentas computacionais atualmente está auxiliando o aprimoramento dos processos e procedimentos de análise e simulações em inúmeras áreas do conhecimento humano. A tomografia computadorizada (TC) é uma ferramenta de diagnóstico já consolidada na área médica e atualmente começa a ser utilizada como uma ferramenta para algo ainda mais inovador, a geração de modelos tridimensionais de órgãos ou estruturas ósseas do paciente para uso na criação de biomodelos e fabricação de próteses personalizadas. Biomodelos são cópias físicas das estruturas anatômicas de regiões ou orgãos do corpo humano utilizados para diagnóstico e planejamento cirúrgico. O uso de imagens tomográficas para geração de modelos 3D tem despertado um grande interesse na área médica e de bioengenharia. Além da criação do biomodelo é possível, com o uso das imagens, a geração de modelos computacionais representativos, possibilitando com isso, a realização de diversas simulações e análises biomecânicas da região ou órgão de interesse, visando a fabricação de próteses ou órteses personalizadas. Neste trabalho é apresentada uma metodologia para a geração de modelos matemáticos tridimensionais a partir de tomografias computadorizadas com o objetivo de estudar e analisar um implante personalizado da ATM (Articulação Temporomandibular), solicitado mecanicamente e fabricado em liga de titânio (Ti6Al4V) pelo processo de manufatura aditiva rápida do tipo DMLS (Sinterização Direta de Metais a Laser). Através do m... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of computational tools is currently helping to improve the processes and procedures of analysis and simulations in many areas of human knowledge. Computed tomography (CT) is a diagnostic tool already consolidated in the medical field and is now being used as a tool for something even more innovative, the generation of three-dimensional models of organs or bone structures of the patient for use in the creation of biomodels and Manufacture of customized prostheses. Biomodels are physical copies of the anatomical structures of regions or organs of the human body used for diagnosis and surgical planning. The use of tomographic images for generating 3D models has aroused great interest in the medical and bioengineering field. Besides the creation of the biomodel it is possible, through the use of the images, the generation of representative computational models, making possible the accomplishment of several simulations and biomechanical analyzes of the region or organ of interest, aiming at the manufacture of customized prostheses or orthoses. In this work is presented a methodology for the generation of three-dimensional mathematical models from CT scans in order to build, study and analyze a custom implant TMJ (Temporomandibular Joint), requested mechanically and made of titanium alloy (Ti6Al4V) by the prototyping process of type DMLS (Direct Metal Laser Sintering). Through the model created for the TMJ region, computational simulations of stresses and deformations were ... (Complete abstract click electronic access below) / Doutor
18

Reconstrução tridimensional da mama feminina a partir de imagens médicas por infravermelho com auxílio de geometrias substitutas

VIANA, Mariana Jorge de Andrade 12 February 2016 (has links)
Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-10-04T19:09:24Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) tese mariana viana para BC revisado profa Rita.pdf: 5880006 bytes, checksum: 58b21f8952495e3aba8663b4efa5c48c (MD5) / Made available in DSpace on 2016-10-04T19:09:24Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) tese mariana viana para BC revisado profa Rita.pdf: 5880006 bytes, checksum: 58b21f8952495e3aba8663b4efa5c48c (MD5) Previous issue date: 2016-02-12 / Capes / O câncer de mama desenvolve-se de maneira silenciosa, podendo levar a óbito se não for tratado em sua fase inicial. Por este motivo, é necessário desenvolver técnicas para sua detecção precoce. A carcinogênese altera a temperatura dos tecidos na região afetada e o uso da simulação computacional calcula como ocorre tal fenômeno. A imagem por infravermelho é capaz de indicar a distribuição superficial de temperatura e a comparação destes valores com os cálculos obtidos na simulação computacional é uma ferramenta promissora para a detecção precoce do câncer de mama. O objetivo desta tese é construir a geometria substituta tridimensional (3D) da mama feminina a partir de imagens por infravermelho da paciente. Isso possibilita o cálculo da distribuição de temperatura através de software de dinâmica dos fluidos computacional (CFD – Computational Fluid Dynamics). O corregistro de uma prótese mamária externa aos contornos da paciente modelou a superfície da geometria tridimensional da mama. No interior dessa geometria existem os lóbulos mamários, os ductos lactíferos, o tecido adiposo da mama e a lesão conforme indicado no exame de ultrassonografia da paciente. Um software de CFD realizou o preparo da geometria e subsequente cálculo da distribuição de temperatura na mama. Um estudo de caso verificou o impacto da inserção das estruturas citadas na geometria substituta. O erro entre as temperaturas máximas indicadas pela imagem por infravermelho das pacientes na região da pele sobre a anomalia e a temperatura máxima alcançada no cálculo de temperatura sobre a região correspondente na geometria substituta foi de 0,20%. A geometria 3D aqui apresentada adequa-se aos contornos de cada paciente e é mais próxima da mama real do que a geometria substituta 3D obtida pelo escaneamento de próteses mamárias externas e outras apresentadas na literatura técnica. Além disso, a geometria desenvolvida permitiu o cálculo de temperatura nos casos em que não era possível com a geometria anteriormente utilizada. / Breast cancer develops silently and can lead to death if not treated in its early stages. For this reason, it is necessary to develop techniques for its early detection. The carcinogenesis changes the temperature of the tissue in the affected area, the use of computer simulation to evaluate how such a phenomenon occurs. The infrared image can indicate the surface temperature distribution, and the comparison of these figures with the calculations obtained in a computer simulation is a promising tool for early detection of breast cancer. The purpose of this thesis is to build three-dimensional (3D) surrogate geometry of the female breast from infrared images of the patient. It allows the calculation of the distribution of temperature through Computational Fluid Dynamics (CFD) software. The breast prosthesis co-registration to the contours of the patient modeled the external surface of the 3D geometry of the breast. Within this geometry, there are mammary lobules, lactiferous ducts and adipose tissue of the breast and the lesion as indicated in the ultrasound examination of the patient. CFD software performed the preparation of the geometry and subsequent calculation of the breast temperature distribution. A case study verified the impact of the insertion of such structures in the surrogate geometry. The error between the maximum temperature indicated by the infrared image of the patient in the area of the skin over the abnormality and the maximum temperature achieved in the temperature calculation in the corresponding region in the surrogate geometry were 0.20%. The 3D geometry presented here fits the contours of each patient, and it is closer to the real breast than the surrogate 3D geometries acquired by the scanning of external breast prostheses and others ones presented in the technical literature. Furthermore, the modeled geometry allowed the temperature calculation in cases where it was not possible with the geometry that was previously used.
19

No limiar da auto-mutilação: fatores ecológicos e morfológicos envolvidos na autotomia caudal em Tropidurus itambere (Rodrigues, 1987) (Sauria:Tropiduridae)

Amorim, Joana de Dornellas Cysneiros Gomes de 27 February 2013 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-04-04T15:04:20Z No. of bitstreams: 1 joanadedornellascysneirosgomesdeamorim.pdf: 1811388 bytes, checksum: 09763f5f5602a497decd667655eb0c68 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-04-24T03:56:58Z (GMT) No. of bitstreams: 1 joanadedornellascysneirosgomesdeamorim.pdf: 1811388 bytes, checksum: 09763f5f5602a497decd667655eb0c68 (MD5) / Made available in DSpace on 2016-04-24T03:56:58Z (GMT). No. of bitstreams: 1 joanadedornellascysneirosgomesdeamorim.pdf: 1811388 bytes, checksum: 09763f5f5602a497decd667655eb0c68 (MD5) Previous issue date: 2013-02-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A autotomia caudal é uma resposta anti-predação voluntária amplamente empregada por lagartos. Suas consequências estão bem descritas na literatura, mas os fatores envolvidos na sua ocorrência carecem de aprofundamento. Pretendeu-se então averiguar se há diferença tanto na propensão à autotomia quanto no padrão de crescimento corporal e caudal de indivíduos com tamanho corporal diferente durante as estações quente/chuvosa (verão tropical) e fria/seca (inverno tropical). Para tanto foram mantidos em terrários externos três grupos experimentais (n = 19) de massas corpóreas diferentes (P1, P2 e P3), cujas caudas foram autotomizadas por constrição mecânica, medindo-se a pressão exercida e o tempo até a soltura da cauda. Dados morfométricos foram aferidos semanalmente e avaliados usando o test T bicaudal para amostras não pareadas, comparando-se as variáveis em função do peso corporal. As porções caudais liberadas foram conservadas em álcool e dissecadas, assim como quatro lagartos que morreram ao longo dos experimentos. A anatomia caudal foi analisada e comparada com descrições existentes. Elaborou-se um modelo tridimensional passível de ser usado como ferramenta didática e analítica. Foram encontradas em média 32 vértebras caudais em T. itambere. A maioria dos parâmetros avaliados não apresentou significância estatística, devido ao pequeno número amostral, mas tendências e possibilidades são apresentadas e discutidas em vista da literatura atual. Foi significativa a relação inversa entre temperatura cloacal e tempo até a autotomia. / Autotomy is an anti-predator behavior widely employed by lizards. The energetic consequences of this process are vastly describe in literature, yet the details involved in it’s occurrence lack thoroughness. This study intent to evaluate if there are differences related to body weight in propensity to realize autotomy, in body and caudal growth, both during the hot/wet season (tropical summer) and the cold/dry season (tropical winter). To accomplish that three groups of lizards (n = 19) with different body mass (P1, P2 and P3) were kept in out-doors cages during cold (July to September 2012) and hot seasons (November 2012 to January 2013). Autotomy was induced by constriction of the tail, while measuring the pression applie to it’s surface as well as the time until it’s release. Morphometric data was assessed weekly and processed using two-tailed t-test for unpaired samples, comparing variables according to body weight. The released portion of the tail was preserved in alcohol and dissected, as were the four lizards that happened to die during the experimental process. Caudal anatomy was analyzed and compare with preexisting descriptions. A three-dimensional model with didactic and analytic potential was elaborated. We found an average of 32 caudal vertebraes in T. itambere. Most of the analyzed parameters did not present statistical significance, due to the small sample size. However we present and discuss every tendency and possibility in face of the current literature. We did found a significant inverse relation between cloacal temperature and the time subjects took to undergo autotomy.
20

Investigation of Rock Mass Stability around Underground Excavations in an Underground Mine in USA

Xing, Yan, Xing, Yan January 2017 (has links)
Underground excavations break the balance of the initial stress field and cause stress redistributions in the surrounding rock masses. Problems normally arise as the stress exceeds the rock mass strength. In addition, the rock mass contains preexisting defects, such as the fissures, fractures, joints, faults, shear zones, dikes, etc., which could significantly weaken the rock mass strength and make the rock mass behavior complicated. The stability of underground excavations is of great importance to an operating mine project since it ensures the safety of the working environment and the successful ore exploration. Due to the complex geological conditions and engineering disturbances, the assessment of rock mass stability for a practical engineering problem is extremely challenging and difficult, which needs to be solved by the modern numerical methods. In this dissertation, the rock mass stability around tunnels in an underground mine in the USA was investigated by performing three-dimensional modeling using the 3DEC 3-Dimensional Distinct Element Code. Comprehensive stress analyses were respectively carried out on a preliminary model and a more advanced model. In the preliminary study, the built model contains the inclined lithologies, a non-persistent fault, and a convoluted tunnel system. The geomechanical property values used for the rock masses and discontinuities in the numerical model were estimated using the available geotechnical information and the experience of the research group. The Mohr-Coulomb and strain softening constitutive relations were prescribed for the rock masses; the coulomb slip joint model was assigned for the discontinuities. The influence of the boundary conditions, block constitutive models, horizontal in situ stress and rock support system on the tunnel stability was investigated. The rock mass behavior was quantified using the results of stress, displacement, and yielded zones around the tunnels. It showed that the roller boundary conditions resulted in slightly different but comparable results with the combined boundary conditions (roller and stress combined) where K0 equals to 0.4 or 0.5. Whereas the in-situ stress field for a complex geological system can only be obtained by applying proper boundary stresses and then by performing stress analysis. The softening behavior of the rock masses caused more deformations and yielded zones around the tunnels; the rock masses around the tunnels were observed to reach the residual strength values, which can be treated as failed areas. In addition, the M-C and s-s rock masses reacted differently as the K0 value changed. At K0=1.0, the tunnels seemed to be the most stable; K0=1.5, however, provided the worst scenario with roof and floor problems. With respect to the effectiveness of the support system, a large amount of the bonds of the supports was failing, thus, the deformations and yielded zones around the tunnels were slightly improved. Finally, comparisons between the numerical modeling results and the field measurements implied the applicability of strain softening behavior and a K0 value between 0.5 and 1.0 for the mine. Based on the specific geological, geotechnical, and construction information, a numerical model incorporating accurate features was developed. It includes a non-planar, weak interlayer, the persistent and non-persistent faults, and the open and backfilled excavations. The mechanical property values used for the rock masses and faults were estimated based on the laboratory test results of the intact rock and smooth joints. The strain softening behavior was specified for the rock masses belonging to the average quality, and the rock masses that reached residual strengths were assumed to be failing. The linear relations between the fault stiffnesses and normal stress were described using the continuously yielding joint model. To simulate the mine construction process in the field, the sequential excavation, backfilling, and supporting procedures were numerically implemented; additionally, a novel routine was applied to account for the delayed installation of the supports. Results showed that the tunnels close to the fault and the backfilled area were less stable. Most of the displacements around the tunnels occurred within a distance of zero to 2 or 3 m from the tunnel surface. The varying K0 value caused great changes in the rock mass behavior and the shear behavior of the major fault; significant instability of the tunnels was triggered by the high horizontal in situ stress. Parametric studies on the rock mass condition, rock mass residual strengths, and fault property values showed that the tunnel stability was more sensitive to the former two factors than the last one. A systematic investigation was conducted to evaluate the current rock supports installed at the mine where the increasing stress relaxation was incorporated. The deformations and of the failure zone thicknesses around the tunnels were reduced up to 8% and 20% after applying the supports instantaneously, and the reductions were improved by the delayed installation of supports. Additionally, the safety of supports was evaluated by the bond shear and bolt tensile failures, which was also improved with incorporation of delayed supporting. It was found that the current rock supports are insufficient in length, bond and tensile strengths. Therefore, a stronger support system was suggested. The stronger supports worked better in stabilizing the tunnels. Based on the deformations and failures of the rock masses, the length of the bolts on walls was suggested to be 4-5 m. At the end, the horizontal convergence strain predicted by the numerical simulations were calculated at two locations where the tape extensometers were installed. Good agreements with the field measurements were obtained for the cases that have the average rock mass properties and K0 values in the range 0.5-1.25.

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