No description available.

The stability of rock masses is influenced by the occurrence of rock joints. Therefore, the shear strength of rock joints must be considered in dimensioning of underground constructions. One way to predict the shear strength is through usage of failure criteria, which are validated from results of direct shear tests under controlled laboratory conditions. Consequently, the quality of the results from the tests are crucial to the accuracy with which the criteria will be able to predict the shear strength. Since rock joints are unique by nature usage of replicas (man-made copies of rock joints) is of importance in parameter studies. The overall objective of this work is to facilitate the development of improved criteria for predictions of the shear strength of rock joints. To support this objective, two sources of uncertainty have been investigated, namely the geometry of replicas and the influence of the normal stiffness of test systems. Two quality assurance parameters for evaluation of geometrical differences between replicas and rock joints based on scanning data have been derived. The first parameter describes the morphological deviations. The second parameter describes the deviations in orientation with respect to the shear plane. The effective normal stiffness approach, which compensates for the influence of the normal stiffness of the test system in direct shear testing, has been developed, validated, and applied. With help of the quality assurance parameters it is demonstrated that it is possible to reproduce replicas within narrow tolerances. Application of the effective normal stiffness approach basically eliminates the normal load error. In all, the results support generation of improved quality of test data and consequently, the development of shear strength criteria with improved accuracy will also be facilitated. / <p>Academic Dissertation which, with due permission of the KTH Royal Institute of  Technology, is submitted for public defence for the Degree of Licentiate of Engineering on Wednesday the 9th June 2021, at 9:00 a.m. in M108, Brinellvägen 23, Stockholm.</p><p><strong>Paper A</strong>: Larsson J, Flansbjer M, Portal N W, Johnson E, Johansson F, and Mas Ivars D. (2020) Geometrical Quality Assurance of Rock Joint Replicas in Shear Tests – Introductory Analysis. Paper presented at the ISRM International Symposium - EUROCK 2020, physical event not held. https://onepetro.org/ISRMEUROCK/proceedings-abstract/EUROCK20/All-EUROCK20/ISRM-EUROCK-2020-101/451187  In Diva: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-51987 </p><p><strong>Paper B:</strong> Larsson J, Johansson F, Mas Ivars D, Johnson E, Flansbjer M and Portal N W. (2021) Rock joint replicas in direct shear testing – Part 1: Extraction of geometrical quality assurance parameters. To be submitted to Rock Mechanics and Rock Engineering  In DiVA: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-53111 </p><p><strong>Paper C:</strong> Larsson J and Flansbjer M. (2020) An Approach to Compensate for the Influence of the System Normal Stiffness in CNS Direct Shear Tests. Rock Mechancis and Rock Engineering 53, 2185–2199 https://doi.org/10.1007/s00603-020-02051-0  In DiVA: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-44085  </p><p><strong>Paper D:</strong> Larsson J. (2021) Experimental investigation of the system normal stiffness of a 5 MN direct shear test setup and the compensation of it in CNS direct shear tests. Submitted to ISRM International Symposium - EUROCK 2021  In DiVA: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-53112 </p>

No description available.

The shear behavior of a specimen made of reinforced concrete is complex. The resisting mechanisms are affected by different factors such as section form, slimness of the specimen, longitudinal and transversal reinforcement arrangement, adhesion between concrete and steel, among others. Addition of steel fibers to the concrete improves the ductility as well as the tensile behavior; providing good control during the cracking process. Fibers also enhance the shear behavior of structural elements, increasing ultimate resistance and ductility. Push-off tests had been used to study the mechanisms of concrete shear transfer. Shear strength of the specimen depends on the contribution of both concrete and reinforcement. Aggregate interlock has a significant contribution to the concrete shear capacity. In the last decades new kinds of concrete have been developed for industrial use, such as high strength concrete (HSC), self-compacting concrete (SCC) or fiber reinforced concrete (FRC), among others. In these new materials aggregate interlock phenomenon may be different when compared to conventional concrete (CC). There is a lack of information in literature about the mechanisms of shear transfer in fiber reinforced concrete elements. / Echegaray Oviedo, JA. (2014). Upgrading the push-off test to analyze the contribution of steel fiber on shear transfer mechanisms [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/43723

[pt] Na geotecnia, os parâmetros de resistência do solo são essenciais para qualquer projeto. Os ensaios de campo e laboratório são essenciais, mas ainda enfrentam muitas limitações práticas e financeiras. Além disso, métodos tradicionais, apoiados em relações empíricas ou teóricas, frequentemente não conseguem abranger a complexidade comportamental do solo. Diante disso, destaca-se a necessidade de explorar alternativas para superar essas barreiras. Neste contexto, a inteligência artificial surge como uma abordagem inovadora. Este estudo propõe um modelo preditivo para analisar a curva tensão-deslocamento em ensaios de cisalhamento direto e tensão-deformação em ensaios de cisalhamento simples (Direct Simple Shear - DSS) em areia. Após coletar e digitalizar dados de diversas fontes acadêmicas, formou-se uma base experimental robusta para treinar três algoritmos de Machine Learning (ML): Support Vector Regression (SVR), Random Forest (RF) e Feedforward Neural Network (FNN). Foram realizadas análises comparativas dos modelos, com foco particular na avaliação de métricas de desempenho e curvas dos ensaios de validação. O RF destacou-se por sua precisão e confiabilidade. Embora os modelos SVR e FNN tenham demonstrado utilidade, o RF emergiu como o mais eficaz. Este resultado reforça a viabilidade dos modelos de ML, particularmente o RF, como ferramentas valiosas para engenheiros geotécnicos e pesquisadores na previsão do comportamento de areias, mesmo com um conjunto de dados limitado. / [en] In geotechnics, soil resistance parameters are essential for any project. Field and laboratory tests are essential, but still face many practical and financial limitations. Moreover, traditional methods, relying on empirical or theoretical relationships, often fail to encompass the soil s behavioral complexity. In light of this, there is a highlighted need to explore alternatives to overcome these barriers. In this context, artificial intelligence emerges as an innovative approach. This study proposes a predictive model to analyze the stress-displacement curve in direct shear tests and stress-strain in Direct Simple Shear (DSS) in sand. After collecting and digitizing data from various academic sources, a robust experimental base was formed to train three Machine Learning (ML) algorithms: Support Vector Regression (SVR), Random Forest (RF), and Feedforward Neural Network (FNN). Comparative analyses of the models were conducted, with a particular focus on the evaluation of performance metrics and validation test curves. RF stood out for its accuracy and reliability. Although the SVR and FNN models demonstrated utility, RF emerged as the most effective. This result reinforces the viability of ML models, particularly RF, as valuable tools for geotechnical engineers and researchers in predicting the behavior of sands, even with a limited data set.

[pt] Este estudo apresenta o comportamento de misturas de areia e solo argiloso com teores variados de cinza volante, proveniente do processo de queima de carvão mineral no Complexo Termelétrico Jorge Lacerda, localizado no município Capivari de Baixo, no estado de Santa Catarina. O objetivo da presente pesquisa consiste em avaliar a aplicabilidade do uso de misturas solo-cinza e solocinza- cal em obras geotécnicas, como camadas de aterros sanitários, solos de fundação e estabilização de taludes. Foram realizados ensaios de caracterização física, química e mecânica (ensaio de compactação e ensaio de cisalhamento direto). Os ensaios de cisalhamento direto foram realizados em amostras de solo argiloso compactadas na umidade ótima e no peso específico seco máximo correspondente, com teores de cinza volante de 15 por cento e 30 por cento em relação ao peso seco do solo. Já os ensaios em amostras de areia foram realizados para uma densidade relativa de 50 por cento e umidade ótima de 10 por cento, com teores de cinza volante de 15, 30 e 40 por cento em relação ao peso seco do solo. Para as misturas solo-cinza-cal, adicionou-se 3 por cento de cal em substituição ao peso seco da cinza. Foi analisada a influência do tipo de solo, teor de cinza, adição de cal e tempo de cura (0, 30, 100, 125 e 140 dias) para as misturas, sendo a cura adotada somente para as misturas com areia. Os resultados mostraram-se mais satisfatórios para as misturas com solo argiloso, sendo a adição de cal mais eficiente para a mistura com menor teor de cinza. Na ausência de cal, o melhor comportamento obtido foi para a mistura com 15 por cento de cinza. Quanto às misturas com areia e sem cal, os resultados foram inferiores à areia; já no caso das misturas areia-cinza-cal, não foi possível definir um padrão do comportamento com relação ao tempo de cura, pois ainda que tenha havido um aumento da coesão a determinados dias, este ganho veio acompanhado de uma redução no ângulo de atrito, fazendo com que a areia mantivesse um comportamento melhor. Contudo, o teor de 27 por cento de cinza, sob 140 dias de cura, proporcionou ao solo um aumento de ambos os parâmetros, sendo, portanto, o teor ótimo a ser utilizado. Dessa forma, ainda que o emprego da cinza volante em misturas com o solo argiloso tenha se mostrado mais satisfatório, este material também pode ser utilizado em misturas com areia, desde que submetido a elevados períodos de cura e que contenham uma porcentagem de cinza em torno do teor ótimo encontrado, o que viabiliza o emprego positivo deste material em aplicações geotécnicas, possibilitando uma destinação ambientalmente correta deste resíduo e dando um fim mais nobre a este material. / [en] This study presents the behavior of sand and clay soil mixtures with different contents of fly ash, which comes from the coal burning process in Thermoelectric Complex Jorge Lacerda, located in the city of Capivari de Baixo, in Santa Catarina. The aim of this research is to assess the applicability of using soil-ash and soil-ash-lime mixtures in geotechnical works, like landfill layers, foundation soils and slope stabilization. Physical, chemical and mechanical (compaction test and direct shear test) were performed. Direct shear tests were performed on clay soil samples compacted at the optimum moisture content and the corresponding maximum dry specific gravity, with fly ash contents of 15 and 30 per cent, related to the dry weight of soil. Tests on sandy soil samples were performed at the relative density of 50 per cent and optimum humidity of 10 per cent, with fly ash contents of 15, 30 and 40 per cent related to the dry weight of soil. For soil-ash-lime mixtures, it was added 3 per cent of lime to replace the dry weight of ash. It was studied the influence of different parameters: soil type, ash content, lime addition and curing time (0, 30, 100, 125 and 140 days) for the mixtures. Curing process was adopted only for sandy soil mixtures. Results were more suitable for clay soil mixtures, and lime addition was more efficient for the mixture with the lowest ash content, related to 12 per cent. In the absence of lime, the best performance was obtained for the mixture with 15 per cent of ash. For sandy soil mixtures and without lime, the results were inferior to sand; and in the case of soil-ash-lime mixtures, it was not possible to define a pattern of behavior to the curing time, because although there has been an increase in cohesion certain days, this gain was followed by a reduction in friction angle, which has maintained the best performance of sand. However, the ash content of 27 per cent, at 140 days of curing, caused an increase of both parameters, what means that this ash content is the optimum content to be used. Thus, although the use of fly ash in mixtures with clay soil has been more satisfactory, this material can also be used in mixtures with sandy soil, since it contains an ash content around the optimum content found, and since it has been submitted to elevated curing periods, what enables the positive employment of this material in geotechnical applications, providing an environmentally correct disposal of this waste and giving it a noblest destination.

Submitted by Edineia Teixeira (edineia.teixeira@unioeste.br) on 2017-08-24T19:35:51Z No. of bitstreams: 2 Daniele _Ficanha2016.pdf: 2114781 bytes, checksum: 4cf98bf8089cd41a33e68e5cfc4c1ba8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-08-24T19:35:51Z (GMT). No. of bitstreams: 2 Daniele _Ficanha2016.pdf: 2114781 bytes, checksum: 4cf98bf8089cd41a33e68e5cfc4c1ba8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-07-11 / The function of metal silos consists in storing and preserving the quality of the grains. For that, it is extremely important the correct dimensioning in order to guarantee efficiency and security of the set. The possibility of a metal silo implantation is based mainly in the cost and weight of the primary raw material, the steel. The side plates represent the biggest part of the raw material used. The feasibility of a new fixation element, the alternative bolt, responsible for the connections of the silo body’s elements increase the resistance of the side plate, becoming attractive and economic for all users of metal silos. The elaboration of an alternative bolt was based on ISO 4016 (2000) regarding chemical composition and mechanical properties. Mass from the hexagonal head of the traditional bolt was withdrawn and added in the cut plan of the alternative bolt, making it an oblong element and round head. Prototypes of the alternative bolt were developed with the same raw material, temper process and bichromatization as the executed in the traditional bolts. Twenty-three samples of the traditional bolt and sixteen samples of the alternative bolt were produced through the method of direct shearing. The model’s premises were verified, in which the increase in shearing area in the alternative bolt’s cutting plan produced effects in the shearing resistance in the traditional bolt. Through the result of the alternative bolt, it was possible to determine the random error average variable of the model , validating the theoretical functions of the probability distribution for the representation of the statistic information of this random variable, determining the correct strength of the alternative bolt as 107,40 kN. In order to use the alternative bolt in metal silos, 27 samples of the traditional bolt and 3 samples of the alternative bolt were compared, both using support plates of the same material used in the silos, to verify if the plate influences the bolt’s shearing resistance. The parameters used in the definition of the crushing and tearing resistance were determined by tensile tests on the support plates, quantification to the breaking point, as well as the distance between the hole and the edge were determined, to be superior to the resistance of the bolts calculations. It was not possible to determine the influence of the support plate in the resistance of the alternative bolt shear, since the support plate crushed it and it reached only deformed plastic state. The comparison between the averages for the sample of the alternative bolt may have produced positive effects in the shear bolt resistance. / A função dos silos metálicos consiste em armazenar e preservar a qualidade dos grãos. Para isso, é de suma importância o dimensionamento adequado, a fim de garantir a eficiência e a segurança do conjunto. A possibilidade de implantação de um silo metálico baseia-se principalmente no custo e no peso da matéria prima: o aço. As chapas laterais representam a maior parte da matéria prima utilizada. A viabilização de um novo elemento de fixação, o parafuso alternativo, responsável pelas ligações dos elementos do corpo do silo aumentam a resistência da chapa lateral, tornando-se atrativo e econômico para todas as fontes usufruintes dos silos metálicos. A elaboração do parafuso alternativo baseou-se na ISO 4016 (2000) quanto à composição química e às propriedades mecânicas. Retirou-se massa da cabeça sextavada do parafuso tradicional e adicionou-se no plano de corte do parafuso alternativo, formando um elemento oblongo de cabeça redonda. Confeccionaram-se protótipos do parafuso alternativo com a mesma matéria prima, processo de têmpera e bicromatização que a executada nos parafusos tradicionais. Ensaiaram-se 23 amostras do parafuso tradicional e 16 amostras do parafuso alternativo pelo método do cisalhamento direto. Foram verificadas as suposições do modelo, no qual o aumento da área de cisalhamento no plano de corte do parafuso alternativo produziu efeitos na resistência ao cisalhamento do parafuso tradicional. A partir do resultado do parafuso alternativo foi possível determinar a média da variável aleatória erro do modelo, validando as funções teóricas de distribuição de probabilidades para a representação da informação estatística dessa variável aleatória, determinando a força correta do parafuso alternativo, de 107,40 kN. Com o intuito de utilizar o parafuso alternativo nas chapas do corpo de silos metálicos, comparou-se através do ensaio de 27 amostras do parafuso tradicional e 3 amostras do parafuso alternativo, ambos utilizando chapas laterais de silos metálicos para verificar se há influência da mesma na resistência ao cisalhamento dos parafusos. Os parâmetros utilizados na definição da resistência ao esmagamento e rasgamento foram determinados a partir do ensaio de tração das chapas de apoio, quantificação da tensão de ruptura, tal que as distâncias entre furo e borda foram determinadas para serem superiores à resistência de cálculo dos parafusos. Não foi possível a determinação da influência da chapa de apoio na resistência ao cisalhamento do parafuso alternativo, visto que a chapa de apoio esmagou e o mesmo chegou apenas ao estado de deformação plástica. A comparação entre as médias para a amostra de parafuso alternativo produziu efeitos positivos na resistência ao cisalhamento dos parafusos

O município de Caxias do Sul está inserido em um importante contexto geológico-geotécnico do estado do Rio Grande do Sul e, em sua área urbana, são observados vários acidentes de ordem geotécnica. O conhecimento dos solos e das rochas que constituem os perfis da área urbana carece de uma caracterização mecânica que, diante de qualquer acidente geotécnico, possa servir como ponto de partida para a solução de tal evento. Esta dissertação apresenta um estudo a respeito do comportamento mecânico de um solo residual de Dacito Canyon encontrado na área urbana do município de Caxias do Sul – RS. Foram realizados ensaios de cisalhamento direto e compressão triaxial com corpos de prova indeformados e reconstituídos e também foram executados um ensaio edométrico com um corpo de prova remoldado com a umidade próxima ao limite de liquidez. Os resultados obtidos com a realização dos ensaios mostraram que o material possui uma forte influência da estrutura do solo que foi especialmente evidenciada nos resultados dos ensaios de cisalhamento Foi possível estabelecer, com base em ensaios remoldados, uma curva NCL coerente com os parâmetros N da ordem de 2,1452 e e λ similar a 0,135. Entretanto não foi possível a definição de uma CSL pelo fato do material apresentar uma forte estrutura e os ensaios em amostras remoldadas e indeformadas não indicaram uma estabilização dos índices de vazios finais. O comportamento mecânico dos ensaios indeformados varia de acordo com o nível de deformação e de acordo com os ensaios. Nos ensaios de cisalhamento direto houve uma redução da coesão (de 50kPa para ~24kPa) e aumento do ângulo de atrito com as deformações (de 23 para 24 graus). Com a remoldagem esta tendência aumentou (o ângulo de atrito alcançou 28,5 graus). Já no ensaios triaxiais, o ângulo de atrito se manteve em torno de 29-30 graus e a coesão reduziu de 26kPa para 15kPa para grandes deformações. / The municipality of Caxias do Sul is part of an important geological-geotechnical context in the state of Rio Grande do Sul and several geotechnical accidents have been observed in its urban area. The knowledge of the soils and rocks that make up the profiles of the urban area lacks a mechanical characterization which, in the face of any geotechnical accident, can serve as a starting point for the solution of such an event. This dissertation presents a study about the mechanical behavior of a residual soil of Dacito Canyon found in the urban area of the city of Caxias do Sul - RS. Direct shear and triaxial compression tests were carried out with undisturbed and reconstituted test specimens and an edometric test carried out with a test specimen remolded with humidity close to the liquidity limit. The results obtained with the tests showed that the material has a strong influence of the soil structure that was specially evidenced in the results of the shear tests It was possible to establish on the basis of remolded tests an NCL curve coherent, with the N parameter of the order of 2.1452 and λ similar to 0.135. However, it was not possible to define a CSL because the material had a strong structure and the tests on remolded and undisturbed samples did not indicate a stabilization of the final void ratios. The mechanical behavior of the undeformed tests varied according to the level of deformation and according to the test type. In the direct shear tests there was a reduction of cohesion (from 50kPa to ~ 24kPa) and an increase in the angle of friction with the deformations (from 23 to 24 degrees). In tests with the remolded soil this trend increased (the angle of friction reached 28.5 degrees). In the triaxial tests on undisturbed specimens the friction angle remained around 29-30 degrees, similar to peak, and the cohesion reduced from 26kPa to 15kPa for large deformations.

During shearing of stiff clays, plate-shaped clay particles are parallel-oriented in the direction of shear reaching the minimum resistance of &ldquo / residual shear strength&rdquo / . The residual shear strength envelopes of stiff clays are curved, but for practical purposes represented by linear envelopes. This study investigates the nonlinearity of the residual shear strength envelope using experimental evidence (i) from laboratory reversal direct shear tests on two stiff clays (Ankara clay and kaolinite) at 25 to 900 kPa effective normal stresses and (ii) from laboratory data collected from literature. To evaluate the importance of nonlinearity of the envelope for geotechnical engineering practice, by limit equilibrium method, (a) case histories of reactivated landslides are analyzed and (b) a parametric study is carried out. Conclusions of this study are: (1) The residual shear strength envelopes of both Ankara clay and kaolinite are nonlinear, and can be represented by a power function (cohesion is zero). (2) At least 3 reversals or cumulative 20 mm shear displacement of direct shear box is recommended to reach residual condition. (3) Empirical relations between plasticity index and residual friction angle can accurately estimate the residual strength of stiff clays. (4) Nonlinearity is especially important for landslides where average effective normal stress on the shear plane is less than 50 kPa, both for translational and rotational failures. For such slopes using a linear strength envelope overestimates the factor of safety (more significantly for the case of high pore pressures). (5) As the plasticity index increases, the power &ldquo / b&rdquo / of the nonlinear shear strength envelope decreases, indicating more significant nonlinearity. For less plastic materials, using linear and nonlinear shear strength envelopes does not affect the factor of safety.

The frictional behavior of soil-construction material interfaces is of significant importance in geotechnical engineering applications such as retaining structures, pile foundations, geosynthetic liners, and trenchless technologies. Since most failures initiate and develop on the interfaces, special attention is required to predict the capacity of these weak planes in the particular application. Pipe-jacking and microtunneling technologies are being more widely used over the past decade and there is significant interest to predict the jacking forces and jacking distances achievable in order to achieve more efficient design and construction. This study focuses on the evaluation of the frictional characteristics and factors affecting the shear strength of pipe-soil interfaces. Eight different pipes made from fiber reinforced polymer (FRP), polycrete, steel, concrete, and vitrified clay were tested in the experimental program. For this purpose, a new apparatus was designed to conduct conventional interface direct shear testing on pipes of different curvature. This device allows coupons cut from actual conduits and pipes to be tested in the laboratory under controlled conditions. The apparatus includes a double-wall shear box, the inner wall of which is interchangeable to allow for testing against surfaces of different curvatures. By considering a narrow width section, the circular interface of pipes was approximated with a surface along the axial direction and the boundary is defined by the inner box. Roughness tests were performed using a stylus profilometer to quantify the surface characteristics of the individual pipes and relate these to the interface shear behavior. The surface topography showed different degrees of variability for the different pipes. To extend the range of roughness values tested and force the failure to occur in the particulate media adjacent to the interface, two artificial pipe surfaces were created using rough sandpapers. Interface shear tests were performed using the new apparatus with air-pluviated dense specimens of Ottawa 20/30 sand. Additional tests were performed using Atlanta blasting sand to evaluate the effect of particle angularity. The effect of normal stress and relative density were also examined. The interface strength was shown to increase with surface roughness and finally reach a constant value above a certain critical roughness value, which corresponded to the internal strength of the soil itself. This represented the failure location moving from the interface into the soil adjacent to the interface. Both the strength and the shearing mechanism were thus affected by the surface topography. It was also shown that the interface shear strength was affected by particle angularity, relative density and normal stress.