A prática da engenharia geotécnica dispõe de métodos consagrados para obtenção de parâmetros constitutivos através de ensaios de campo aplicados a solos argilosos, que apresentam resposta não drenada, e a solos granulares, que apresentam resposta drenada. Solos que possuem granulometria intermediária podem apresentar resposta parcialmente drenada, trazendo incertezas na obtenção de parâmetros geotécnicos estimados a partir destes ensaios. Este trabalho apresenta resultados de ensaios de campo conduzidos em diferentes velocidades, em dois depósitos de granulometria intermediária, para avaliar tanto a influência da velocidade sobre as medidas do ensaio, quanto a transição das condições de fluxo ao redor do piezocone. O primeiro local de estudo é caracterizado por um depósito natural localizado no município de Joinville/SC, constituído na camada analisada de solo siltoso. O segundo local é caracterizado por um depósito de resíduo de mineração de ouro localizado no município de Barrocas/BA, constituído na camada analisada de silte arenoso. Ensaios de piezocone em velocidade padrão buscaram primeiramente verificar a estratigrafia do terreno e definir uma camada mais homogênea para concentrar as análises. Ensaios de dissipação foram realizados para obtenção dos parâmetros de fluxo. Ensaios de piezocone com variação de velocidade compreenderam o intervalo de 0,5 mm/s a 45 mm/s no depósito natural e 0,3 mm/s a 57 mm/s no resíduo de mineração de ouro. Adicionalmente, amostras foram coletadas para caracterização dos materiais. Os resultados dos ensaios de piezocone nos dois depósitos estudados mostraram que a diminuição da velocidade gerou aumento da resistência e redução da poro-pressão e que o aumento da velocidade não gerou mudanças significativas, sugerindo que os ensaios em velocidade padrão são predominantemente não drenados. As análises em termos de velocidade adimensional mostraram que a transição de não drenado para parcialmente drenado ocorre em torno de uma velocidade normalizada V da ordem de 300 e a transição de parcialmente drenado para drenado ocorre em V inferior a 5 no resíduo de mineração de ouro. Já no depósito de solo natural a transição não pode ser avaliada com clareza devido ao sistema complexo de macrodrenagem, típico de solos residuais. Por fim, foi proposta uma metodologia que busca identificar o grau de drenagem ocorrido nos ensaios, com base na curva de drenagem estabelecida do solo, e converter a resistência à penetração parcialmente drenada em uma condição não drenada para permitir a utilização dos resultados e interpretação através das teorias consagradas. / In geotechnical engineering practice, a series of methods has been established for obtaining constitutive parameters from field tests applied to clay soils (considering the response fully undrained) and sandy soils (considering the penetration response as drained). Soils with intermediate particle sizes may present partial drained response, which introduces uncertainties in the assessment of constitutive parameters. This paper presents results of field tests carried out at different penetration rates in two silty deposits to assess both the influence of rate effects on measured test results, as well as the transition of flow conditions around the piezocone. The first site is characterized by a natural deposit located in the city of Joinville/SC. The second site is characterized by a deposit of gold mining tailings in the city of Barrocas/BA. Piezocone tests performed in standard velocity were used to verify the site stratigraphy and define the presence of more homogeneous layers to concentrate the analysis of rate effects. Dissipation tests were conducted to obtain flow parameters characteristics of the deposit. Piezocone were tested with penetration rates in the range of 0.5mm/s to 45mm/s in the natural deposit and 0.3mm/s to57mm/sin the gold mining tailing. Additionally, samples were collected for characterization of materials. The results of the piezocone tests showed that the cone resistance increases with decreasing penetration rate while pore pressure reduces, and that tests performed under standard penetration rate are mainly undrained in the tested field. The analysis in terms of normalized velocity showed that transition between undrained and partially drained occurs for value of V around 300 and the transition between partially drained and drained occurs for value of V lower than 5 in the gold mining tailing. The transition in the natural deposit cannot be verified clearly due to the complex system of macro drainage typical of residual soils. Finally, a method was proposed to identify the degree of drainage occurring in penetration tests based on the soil drainage characteristic curve, and to convert the cone tip resistance measured under partially drained conditions into a value that corresponds to undrained conditions. This correction would enable the use and interpretation of results following methods currently adopted in engineering practice.

A prática da engenharia geotécnica dispõe de métodos consagrados para obtenção de parâmetros constitutivos através de ensaios de campo aplicados a solos argilosos, que apresentam resposta não drenada, e a solos granulares, que apresentam resposta drenada. Solos que possuem granulometria intermediária podem apresentar resposta parcialmente drenada, trazendo incertezas na obtenção de parâmetros geotécnicos estimados a partir destes ensaios. Este trabalho apresenta resultados de ensaios de campo conduzidos em diferentes velocidades, em dois depósitos de granulometria intermediária, para avaliar tanto a influência da velocidade sobre as medidas do ensaio, quanto a transição das condições de fluxo ao redor do piezocone. O primeiro local de estudo é caracterizado por um depósito natural localizado no município de Joinville/SC, constituído na camada analisada de solo siltoso. O segundo local é caracterizado por um depósito de resíduo de mineração de ouro localizado no município de Barrocas/BA, constituído na camada analisada de silte arenoso. Ensaios de piezocone em velocidade padrão buscaram primeiramente verificar a estratigrafia do terreno e definir uma camada mais homogênea para concentrar as análises. Ensaios de dissipação foram realizados para obtenção dos parâmetros de fluxo. Ensaios de piezocone com variação de velocidade compreenderam o intervalo de 0,5 mm/s a 45 mm/s no depósito natural e 0,3 mm/s a 57 mm/s no resíduo de mineração de ouro. Adicionalmente, amostras foram coletadas para caracterização dos materiais. Os resultados dos ensaios de piezocone nos dois depósitos estudados mostraram que a diminuição da velocidade gerou aumento da resistência e redução da poro-pressão e que o aumento da velocidade não gerou mudanças significativas, sugerindo que os ensaios em velocidade padrão são predominantemente não drenados. As análises em termos de velocidade adimensional mostraram que a transição de não drenado para parcialmente drenado ocorre em torno de uma velocidade normalizada V da ordem de 300 e a transição de parcialmente drenado para drenado ocorre em V inferior a 5 no resíduo de mineração de ouro. Já no depósito de solo natural a transição não pode ser avaliada com clareza devido ao sistema complexo de macrodrenagem, típico de solos residuais. Por fim, foi proposta uma metodologia que busca identificar o grau de drenagem ocorrido nos ensaios, com base na curva de drenagem estabelecida do solo, e converter a resistência à penetração parcialmente drenada em uma condição não drenada para permitir a utilização dos resultados e interpretação através das teorias consagradas. / In geotechnical engineering practice, a series of methods has been established for obtaining constitutive parameters from field tests applied to clay soils (considering the response fully undrained) and sandy soils (considering the penetration response as drained). Soils with intermediate particle sizes may present partial drained response, which introduces uncertainties in the assessment of constitutive parameters. This paper presents results of field tests carried out at different penetration rates in two silty deposits to assess both the influence of rate effects on measured test results, as well as the transition of flow conditions around the piezocone. The first site is characterized by a natural deposit located in the city of Joinville/SC. The second site is characterized by a deposit of gold mining tailings in the city of Barrocas/BA. Piezocone tests performed in standard velocity were used to verify the site stratigraphy and define the presence of more homogeneous layers to concentrate the analysis of rate effects. Dissipation tests were conducted to obtain flow parameters characteristics of the deposit. Piezocone were tested with penetration rates in the range of 0.5mm/s to 45mm/s in the natural deposit and 0.3mm/s to57mm/sin the gold mining tailing. Additionally, samples were collected for characterization of materials. The results of the piezocone tests showed that the cone resistance increases with decreasing penetration rate while pore pressure reduces, and that tests performed under standard penetration rate are mainly undrained in the tested field. The analysis in terms of normalized velocity showed that transition between undrained and partially drained occurs for value of V around 300 and the transition between partially drained and drained occurs for value of V lower than 5 in the gold mining tailing. The transition in the natural deposit cannot be verified clearly due to the complex system of macro drainage typical of residual soils. Finally, a method was proposed to identify the degree of drainage occurring in penetration tests based on the soil drainage characteristic curve, and to convert the cone tip resistance measured under partially drained conditions into a value that corresponds to undrained conditions. This correction would enable the use and interpretation of results following methods currently adopted in engineering practice.

Stone column treatment is commonly used to mitigate liquefaction hazard in sandy soils. Research and experience indicate that this method is effective for clean sands but that it may not be effective for silts and sands with fines contents greater than 15-20%. An alternative to the stone column method involves supplementing stone column treatment with pre-fabricated vertical wick drains installed prior to the stone columns installation. Although this method is used in practice, there has not been a formal academic study of its effectiveness. This thesis evaluates seven different case histories where wick drains were used and one where wick drains were not used, for comparison purposes. The site locations varied as well as the soil properties and treatment plans. CPT testing was done at 3 sites and SPT testing was performed at the other 5 sites. CPT data were correlated to SPT data to facilitate comparisons. One of the case histories includes a unique study in which three different variations of the stone column treatment were applied at the same site, providing a direct comparison of the effectiveness of each method. A 26% area replacement ratio (Ar) with drains was determined to be more effective overall than a 26% Ar without drains and more effective in increasing low initial blow counts than the 34% Ar without drains. The areas with drains were more likely to exceed the minimum project criteria consistently throughout the site. Significant scatter were observed in the results and probable causes for the scatter are noted. Final blow count coefficients of variation ranged from 28% to 77%. Increased fines contents required increased Ar in order to maintain similar average final blow counts. Site improvements were evaluated separately and collectively. Individual site results were compared to clean sand curves developed by Baez (1995). Sites with average fines contents less than 20% which were improved using drains and an 11-15% Ar treatment were comparable to clean sand sites without drains and with 5-10% Ar. To achieve similar improvement at sites with 40-46% fines necessitated drains and Ar values of 23-26%. Design recommendations are provided.

Stone columns are an established method of liquefaction mitigation in clean sands (fines content <15%). Although stone columns are considered less effective in silty soils, an increase in the area replacement ratio or the addition of wick drains may still produce improvement in the normalized blow count. Limited case histories are available with a direct comparison of the use of stone columns with and without wick drains at one location. The Salmon Lake Dam Modification project provided such a scenario. Two test sections were completed at the site prior to construction to determine the area replacement ratio for the final design as well as to compare the application of stone columns with and without wick drains. Visual observations of water and air escaping from wick drains within a distance of 15 ft of the stone column construction confirmed that drains aided in pore pressure dissipation. Test results indicated that stone column treatment with wick drains produced greater improvement in blow count than stone column treatment without drains. For the overall site, there was an increase in improvement ranging from 3 to 8 SPT blow counts. When compared to the results of a similar evaluation of a site in Ogden, Utah, which had a comparable fines content and an area replacement ratio of 26%, the increase in stone column effectiveness produced by adding wick drains was lower at the Salmon Lake Dam site. The increase in improvement at the Ogden, Utah site ranged from 12 to 18 SPT blow counts. At the Ogden site, wick drains were placed between every stone column while they were only placed between vertical rows of columns at Salmon Lake dam. Despite the beneficial effects provided by using wick drains with stone column treatment in silty soils, the performance was below what would be expected for stone column treatment without wick drains in clean sands with less than 15% fines. Stone column treatment also proved less effective in layers of sandy silt than in layers of silty sand, which was indicated by lower average improvement and more points of negative improvement in layers of sandy silt. Although several different area replacement ratios were analyzed (23, 27, 31, and 35%), no consistent trend towards greater improvement in blow count was seen as the replacement ratio increased beyond 23%.

The static cone penetration tests are quite extensively used for carrying out in-situ geotechnical investigations both for onshore and offshore sites especially where the soil mass is expected to comprise of either soft to medium stiff clays or loose to medium dense sands. The wide use of the cone penetration tests (CPT) in geotechnical engineering has resulted in a great demand for developing necessary correlations between the cone penetration resistance and different engineering properties of soils. The successful interpretation of the cone penetration test data depends mainly on the various empirical correlations which are often derived with the help of a controlled testing in calibration chambers. The calibration chambers have been deployed in various sizes (diameter varying from 0.55 m to 2.10 m) by a number of researchers. It is quite an expensive and time consuming exercise to carry out controlled tests in a large size calibration chamber. The task becomes even much more difficult when a sample comprising of either silt or clay has to be prepared. As a result, most of the reported cone penetration tests in calibration chambers are mainly performed in a sandy material. Taking into account the various difficulties associated with performing tests in large calibration chambers, in the present study, it is attempted to make use of a miniature static cone penetrometer having a diameter of 19.5 mm. This cone was gradually penetrated at a uniform rate in a triaxial cell in which a soil sample of a given material was prepared; the diameter of the cone was intentionally chosen smaller so that the ratio of the diameter of the cell to that of the cone becomes a little larger. Two different diameters of the cells, namely, 91 mm and 140 mm, were used to explore the effect of the ratio of chamber (cell) size to that of the cone size. In addition, the rate of penetration rate was also varied from 0.6 mm/minute to 6.0 mm/minute (the maximum possible rate for the chosen triaxial machine with the larger cell) to examine the effect of the rate of the penetration of the miniature cone on the tip resistance. By using the chosen experimental setup, a large number of static miniature cone penetrometer tests were carried out on four different materials, namely, (i) clean sand, (ii) sand with 15% silt, (iii) sand with 25% silt, and (iv) sand with 15% fly ash. The cone tip resistance for each material was obtained for a wide range of three different relative densities. The effective vertical pressure (σv) for the tests on different samples was varied in between 100 kPa and 300 kPa. The variations of the tip resistance with axial deformation in all the cases were monitored so as to find the magnitude of the ultimate tip resistance. In contrast to the standard cone, the diameter of the piston shaft was intentionally kept a little smaller than that of the cone itself so as to restrict the development of the piston resistance. For each cell (chamber) size, two different sizes of the pistons were used to assess the resistance offered by the penetration of the piston shaft itself. It was noted that the resistance offered by the chosen piston shaft is not very substantial as compared to that of the cone tip itself. Most of the experimental observations noted from the present experiments were similar to those made by the penetration of the standard size cone in a large calibration chamber. The ultimate tip resistance of the cone was found to increase invariably with an increase in the magnitude of σv. An increase in the relative density of the soil mass leads to an increase in the value of qcu. For the same range of relative densities, an addition of fly ash in the sample of sand, leads to a considerable reduction in the magnitude of qcu. Even with the addition of 25% silt, the values of qcu were found to become generally lower as compared to clean sand and sand added with 15% silt. An employment of a larger ratio of the diameter of the cell to that of the miniature cone leads to an increased magnitude of qcu. An increase in the penetration rate from 0.6 mm/min to 6.0 mm/min, was found to cause a little increase in the magnitude of qcu especially for sand added with fly ash and silt. The effect of the penetration rate on the results was found to increase continuously with a reduction in the rate of penetration. At higher penetration rates, in a range closer to those normally employed in the field (20 mm/sec), it is expected that the rate of penetration of the cone will not have any substantial effects on the magnitude of qcu for clean sands. The magnitude of qcu obtained in this thesis at different values of σv for all the cases with the use of the miniature cone were compared with the two widely used correlations in literature. It is found that except for dense sands, in most of the cases, the present experimental data lie generally in between the two correlation curves from literature; for dense sands the measured values of qcu were found to be significantly lower than the chosen correlation curves. It was noted that with the use of the miniature cone penetrated in a given sample prepared in a triaxial cell, it is possible to obtain reasonably an accurate estimate of the tip resistance of the standard cone especially for loose to medium dense states of all the materials. Further, from the analysis of all the tests results, it was noted that approximately a linear correlation between qcu/σv and soil friction angle (φ) for different chosen materials exists provided the dependency of the φ on the stress level is taken into account. As compared to the standard cone penetrometer which is usually employed in the field, the miniature cone used in this study is expected to provide a little conservative estimate, of the tip resistance of the standard static cone penetrometer with reference to the different materials used in this study on account of the facts that (i) there is a reduced area behind the cone, (ii) the ratio of the diameter of the calibration chamber (cell) to that of cone is not very high, (iii) the chosen size of the cone is smaller than the standard cone, and (iv) the chosen penetration rate is much smaller than the standard rate of penetration. Further, in the case of clean sand, an attempt has also been made in this thesis, with the help of a number of direct shear tests at different stress levels, to generate an expression correlating peak friction angle, critical state friction angle, relative density of sand and vertical effective stress. A correlation has been generated with the help of which, the value of peak dilatancy angle can be obtained from the known values of peak friction angle and critical state friction angle. In confirmation with the available information in literature, this exercise on clean sand has clearly indicated that a decrease in the magnitude of vertical effective stress leads to an increase in the values of both peak friction angles and peak dilatancy angles.

O problema da disposição de resíduos de mineração e a ruptura de barragens de rejeitos preocupa engenheiros e órgãos ambientais nacionais e internacionais. Estes materiais possuem características geotécnicas distintas dos geomateriais encontrados em depósitos naturais, têm granulometria predominantemente siltosa e condutividade hidráulica intermediária. Como o ensaio de palheta constitui-se em uma técnica rotineira na estimativa da resistência ao cisalhamento não-drenada de argilas, procura-se através da presente pesquisa ampliar este conhecimento a solos siltosos. Dentre os fatores que influenciam as medições da resistência não-drenada, a velocidade de rotação pode ser considerada o mais importante, particularmente quando há ocorrência de drenagem parcial durante o cisalhamento. A ocorrência de drenagem parcial durante ensaios de campo em resíduos siltosos gera incertezas na interpretação e na estimativa de parâmetros de projeto. Assim, o objetivo deste trabalho consiste em avaliar a influência da velocidade de rotação da palheta na resistência não-drenada de um material siltoso, de granulometria semelhante aos resíduos de ouro, através de ensaios de laboratório utilizando uma mini-palheta. Para tal, procedeu-se a automatização e adaptação de um equipamento de palheta de laboratório, inicialmente manual, para aplicação de diferentes velocidades de rotação. Os ensaios de mini-palheta foram realizados a velocidades de rotação entre 0,5 e 54 rpm, que correspondem a velocidades adimensionais (V) entre 2 e 276. Os resultados dos ensaios de mini-palheta mostraram, de modo geral, um aumento na resistência com a diminuição da velocidade de rotação da palheta, devido à ocorrência do adensamento a baixas velocidades de rotação. O tempo de ruptura diminuiu e o deslocamento até a ruptura aumentou com o aumento da velocidade de rotação. Observou-se uma grande dispersão nos resultados dos ensaios, provavelmente devido à relação entre o tamanho da palheta e o tamanho dos grãos do solo. Com relação às condições de drenagem impostas ao solo durante o cisalhamento, observou-se que as condições não-drenadas foram satisfeitas para valores de V superiores a 10+2, enquanto as condições drenadas ocorrem para V inferior a 1. Assim, quando 1<V<10+2 há ocorrência de drenagem parcial durante o cisalhamento. A interpretação através da normalização de resultados, correlacionando a velocidade adimensional V ao grau de drenagem U, possibilita a identificação da ocorrência de drenagem parcial, evitando a superestimativa das propriedades geotécnicas dos solos em ensaios de campo. / The problem of tailings disposal and dams failure concerns engineers and national and international environmental agencies. These materials have geotechnical characteristics that differ from geomaterials found in natural deposits, are predominantly silty and have intermediate hydraulic conductivity. As the vane test is a usual technique to estimate the shear strength of clays, the present study extend this knowledge to silty soils. Among the factors that influence the undrained strength measurements, the rotation rate can be considered the most important, particularly when partial drainage during shear occurs. The occurrence of partial drainage during field tests on silty tailings generate uncertainties in the interpretation and estimation of design parameters. The purpose of this study is to evaluate the influence of mini-vane test rotation rate on the undrained strength of a silty soil, with a particle size similar to the gold tailings, through laboratory mini-vane tests. Thus, the automation and customization of a mini-vane test equipment initially manual was developed for the application of different rotation rates. Mini-vane tests were carried out at rotation rates between 0.5 and 54 rpm, corresponding to dimensionless velocities (V) between 2 and 276. The mini-vane tests results showed, in general, an increase in resistance with decreasing the rotation rate due to the occurrence of consolidation of soil at low shearing rates.The time to failure decreased and the displacement to failure increased with increasing rotation rate. There was a wide dispersion of test results, probably due to blade size to soil grain size ratio. Regarding the drainage conditions imposed to the soil during shear, the tests have shown that the undrained conditions are satisfied for V values greater than 10+2, while the drained conditions occurs for V values lower than 1. When 1<V<10+2 partial drainage occurs during shear. The interpretation using normalized results correlating the dimensionless velocity V to the drainage degree U allows the identification of partial drainage occurrence, avoiding the overestimation of soil geotechnical properties in field tests.

O problema da disposição de resíduos de mineração e a ruptura de barragens de rejeitos preocupa engenheiros e órgãos ambientais nacionais e internacionais. Estes materiais possuem características geotécnicas distintas dos geomateriais encontrados em depósitos naturais, têm granulometria predominantemente siltosa e condutividade hidráulica intermediária. Como o ensaio de palheta constitui-se em uma técnica rotineira na estimativa da resistência ao cisalhamento não-drenada de argilas, procura-se através da presente pesquisa ampliar este conhecimento a solos siltosos. Dentre os fatores que influenciam as medições da resistência não-drenada, a velocidade de rotação pode ser considerada o mais importante, particularmente quando há ocorrência de drenagem parcial durante o cisalhamento. A ocorrência de drenagem parcial durante ensaios de campo em resíduos siltosos gera incertezas na interpretação e na estimativa de parâmetros de projeto. Assim, o objetivo deste trabalho consiste em avaliar a influência da velocidade de rotação da palheta na resistência não-drenada de um material siltoso, de granulometria semelhante aos resíduos de ouro, através de ensaios de laboratório utilizando uma mini-palheta. Para tal, procedeu-se a automatização e adaptação de um equipamento de palheta de laboratório, inicialmente manual, para aplicação de diferentes velocidades de rotação. Os ensaios de mini-palheta foram realizados a velocidades de rotação entre 0,5 e 54 rpm, que correspondem a velocidades adimensionais (V) entre 2 e 276. Os resultados dos ensaios de mini-palheta mostraram, de modo geral, um aumento na resistência com a diminuição da velocidade de rotação da palheta, devido à ocorrência do adensamento a baixas velocidades de rotação. O tempo de ruptura diminuiu e o deslocamento até a ruptura aumentou com o aumento da velocidade de rotação. Observou-se uma grande dispersão nos resultados dos ensaios, provavelmente devido à relação entre o tamanho da palheta e o tamanho dos grãos do solo. Com relação às condições de drenagem impostas ao solo durante o cisalhamento, observou-se que as condições não-drenadas foram satisfeitas para valores de V superiores a 10+2, enquanto as condições drenadas ocorrem para V inferior a 1. Assim, quando 1<V<10+2 há ocorrência de drenagem parcial durante o cisalhamento. A interpretação através da normalização de resultados, correlacionando a velocidade adimensional V ao grau de drenagem U, possibilita a identificação da ocorrência de drenagem parcial, evitando a superestimativa das propriedades geotécnicas dos solos em ensaios de campo. / The problem of tailings disposal and dams failure concerns engineers and national and international environmental agencies. These materials have geotechnical characteristics that differ from geomaterials found in natural deposits, are predominantly silty and have intermediate hydraulic conductivity. As the vane test is a usual technique to estimate the shear strength of clays, the present study extend this knowledge to silty soils. Among the factors that influence the undrained strength measurements, the rotation rate can be considered the most important, particularly when partial drainage during shear occurs. The occurrence of partial drainage during field tests on silty tailings generate uncertainties in the interpretation and estimation of design parameters. The purpose of this study is to evaluate the influence of mini-vane test rotation rate on the undrained strength of a silty soil, with a particle size similar to the gold tailings, through laboratory mini-vane tests. Thus, the automation and customization of a mini-vane test equipment initially manual was developed for the application of different rotation rates. Mini-vane tests were carried out at rotation rates between 0.5 and 54 rpm, corresponding to dimensionless velocities (V) between 2 and 276. The mini-vane tests results showed, in general, an increase in resistance with decreasing the rotation rate due to the occurrence of consolidation of soil at low shearing rates.The time to failure decreased and the displacement to failure increased with increasing rotation rate. There was a wide dispersion of test results, probably due to blade size to soil grain size ratio. Regarding the drainage conditions imposed to the soil during shear, the tests have shown that the undrained conditions are satisfied for V values greater than 10+2, while the drained conditions occurs for V values lower than 1. When 1<V<10+2 partial drainage occurs during shear. The interpretation using normalized results correlating the dimensionless velocity V to the drainage degree U allows the identification of partial drainage occurrence, avoiding the overestimation of soil geotechnical properties in field tests.

O problema da disposição de resíduos de mineração e a ruptura de barragens de rejeitos preocupa engenheiros e órgãos ambientais nacionais e internacionais. Estes materiais possuem características geotécnicas distintas dos geomateriais encontrados em depósitos naturais, têm granulometria predominantemente siltosa e condutividade hidráulica intermediária. Como o ensaio de palheta constitui-se em uma técnica rotineira na estimativa da resistência ao cisalhamento não-drenada de argilas, procura-se através da presente pesquisa ampliar este conhecimento a solos siltosos. Dentre os fatores que influenciam as medições da resistência não-drenada, a velocidade de rotação pode ser considerada o mais importante, particularmente quando há ocorrência de drenagem parcial durante o cisalhamento. A ocorrência de drenagem parcial durante ensaios de campo em resíduos siltosos gera incertezas na interpretação e na estimativa de parâmetros de projeto. Assim, o objetivo deste trabalho consiste em avaliar a influência da velocidade de rotação da palheta na resistência não-drenada de um material siltoso, de granulometria semelhante aos resíduos de ouro, através de ensaios de laboratório utilizando uma mini-palheta. Para tal, procedeu-se a automatização e adaptação de um equipamento de palheta de laboratório, inicialmente manual, para aplicação de diferentes velocidades de rotação. Os ensaios de mini-palheta foram realizados a velocidades de rotação entre 0,5 e 54 rpm, que correspondem a velocidades adimensionais (V) entre 2 e 276. Os resultados dos ensaios de mini-palheta mostraram, de modo geral, um aumento na resistência com a diminuição da velocidade de rotação da palheta, devido à ocorrência do adensamento a baixas velocidades de rotação. O tempo de ruptura diminuiu e o deslocamento até a ruptura aumentou com o aumento da velocidade de rotação. Observou-se uma grande dispersão nos resultados dos ensaios, provavelmente devido à relação entre o tamanho da palheta e o tamanho dos grãos do solo. Com relação às condições de drenagem impostas ao solo durante o cisalhamento, observou-se que as condições não-drenadas foram satisfeitas para valores de V superiores a 10+2, enquanto as condições drenadas ocorrem para V inferior a 1. Assim, quando 1<V<10+2 há ocorrência de drenagem parcial durante o cisalhamento. A interpretação através da normalização de resultados, correlacionando a velocidade adimensional V ao grau de drenagem U, possibilita a identificação da ocorrência de drenagem parcial, evitando a superestimativa das propriedades geotécnicas dos solos em ensaios de campo. / The problem of tailings disposal and dams failure concerns engineers and national and international environmental agencies. These materials have geotechnical characteristics that differ from geomaterials found in natural deposits, are predominantly silty and have intermediate hydraulic conductivity. As the vane test is a usual technique to estimate the shear strength of clays, the present study extend this knowledge to silty soils. Among the factors that influence the undrained strength measurements, the rotation rate can be considered the most important, particularly when partial drainage during shear occurs. The occurrence of partial drainage during field tests on silty tailings generate uncertainties in the interpretation and estimation of design parameters. The purpose of this study is to evaluate the influence of mini-vane test rotation rate on the undrained strength of a silty soil, with a particle size similar to the gold tailings, through laboratory mini-vane tests. Thus, the automation and customization of a mini-vane test equipment initially manual was developed for the application of different rotation rates. Mini-vane tests were carried out at rotation rates between 0.5 and 54 rpm, corresponding to dimensionless velocities (V) between 2 and 276. The mini-vane tests results showed, in general, an increase in resistance with decreasing the rotation rate due to the occurrence of consolidation of soil at low shearing rates.The time to failure decreased and the displacement to failure increased with increasing rotation rate. There was a wide dispersion of test results, probably due to blade size to soil grain size ratio. Regarding the drainage conditions imposed to the soil during shear, the tests have shown that the undrained conditions are satisfied for V values greater than 10+2, while the drained conditions occurs for V values lower than 1. When 1<V<10+2 partial drainage occurs during shear. The interpretation using normalized results correlating the dimensionless velocity V to the drainage degree U allows the identification of partial drainage occurrence, avoiding the overestimation of soil geotechnical properties in field tests.

Ante la falta de materiales que cuentan con las propiedades mecánicas necesarias para ser usados como relleno estructural en algunas zonas en donde se realizan proyectos, surge la preocupación de mejorar las propiedades mecánicas del limo arenoso. En investigaciones anteriores adicionaron fibras de acero, fibras naturales y aditivos químicos para mejorar las propiedades mecánicas de los suelos. Por otro lado, el deterioro ambiental que actualmente viene sufriendo nuestra sociedad a causa del consumo masivo de productos descartables como el plástico, producto que se descompone en una media de 450 años, y que está compuesto principalmente con PET (Tereftalato de polietileno). Este material al ser arrojado al medio ambiente viene afectando a los animales acuáticos y al agua. Sin embargo, están surgiendo emprendimientos para darles un uso alternativo. La presente tesis se centra en la problemática de mejorar las propiedades mecánicas de la arena limosa de las inmediaciones de los Pantanos de Villa, con la inserción del PET reciclado en porcentajes de 1% al5%. Para desarrollar la hipótesis se realizaron ensayos de granulometría del suelo, PET, y en las mezclas de suelo más PET con porcentajes de 1%, al 5%; límite de Atterberg, gravedad especifica al suelo y al PET. También, se realizaron ensayos de proctor estándar y corte directo para todas las mezclas. Finalmente, se realizaron ensayos triaxiales CD de 3.5 mm al suelo puro y al porcentaje de la mezcla que mejor comportamiento mecánico obtuvo. / Due to the lack of materials that has the necessary mechanical properties to be used as a structural filler in some zones where projects are carried out, the concern arises to improve the mechanical properties of sandy silt. In previous investigations they added steel fibers, natural fibers and chemical additives to improve the mechanical properties of soils. On the other hand, the environmental deterioration that our society is currently suffering due to the massive consumption of disposable products such as plastic, a product that decomposes in an average of 450 years, which is mainly composed of PET (polyethylene terephthalate). This material, when released into the environment, has been affecting aquatic animals and water. However, ventures are emerging to give them an alternative use. This thesis focuses on the problem of improving the mechanical properties of the silty sand in the vicinity of the Pantanos de Villa, with the insertion of recycled PET in percentages of 1% to 5%. To carry out the development of the hypothesis, they were made soil granulometry tests, PET, and in the mixtures of soil plus PET with percentages of1% to 5%; Atterberg limit, specific gravity the soil and PET. Also, Proctor Standard and Direct Cut tests will be carried out for all mixtures. Finally, 3.5 mm Triaxial CD tests were performed to the pure soil and to the percentage of the mixture that obtained the best mechanically performance. / Tesis

El presente documento presenta un estudio basado en el análisis del comportamiento de las propiedades mecánicas de un suelo limo arcilloso con la incorporación de fibras de PET triturado. Para conocer el comportamiento de un suelo, es necesario conocer primero su génesis. Las muestras analizadas provienen de la capa de subrasante de una carretera que une las ciudades de Munichis y Yurimaguas, en el departamento de Loreto, Perú. El tipo de suelo en las zonas de selva baja suele tener características como bajo índice de soporte, media a elevada plasticidad, y demás características que lo hacen considerar como un suelo problemático, esto debido a factores como el clima, humedad, y ubicación geográfica. Para realizar un análisis preciso del comportamiento de este suelo en combinación con el PET, se llevó a cabo ensayos como la prueba del hidrómetro, Proctor modificado y CBR con porcentajes variables de PET respecto a la masa de la muestra de suelo. Cada uno de ellos, principalmente, para conocer bien el tipo de muestra, y el índice de soporte con cada porcentaje incorporado. Los resultados son evidencia que mientras mayor sea el porcentaje de PET, el suelo pierde características resistentes, por lo que su índice de soporte disminuye; por el contrario, mientras menor es el porcentaje de PET incorporado, el índice de soporte se incrementa. En suma, para poder conocer el comportamiento esperado, es necesario realizar distintas pruebas, y haciendo uso de distintos tipos de suelos. / This study is based on the analysis of the behavior of the mechanical properties of a silty clay soil with crushed PET fibers incorporated. To understand the behavior of a soil, it is necessary to know its origin. The analyzed samples come from the subgrade layer of a highway that connects the cities of Munichis and Yurimaguas, in the region of Loreto, Peru. The material in this area usually has characteristics such as low support index, medium to high plasticity, and other characteristics that make it considered a problematic soil, this due to factors such as climate, humidity, and geographical location. To perform a precise analysis of the behavior of this soil in combination with PET, tests such as the hydrometer test, Modified Proctor and CBR with different percentages of PET, were carried out. to the mass of the sample. Each of them mainly to know well the type of sample, and the support index with each percentage incorporated. The results show that as higher the percentage of PET, the soil loses resistant characteristics, so its support index decrease, on the other hand, the lower percentage of PET used, the support index increases. In summary, to know the expected behavior, it is necessary to carry out different tests, and make use of different types of soil. / Trabajo de investigación