Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 160-167. / by Mark David Bucknam. / M.S.

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Undrained triaxial tests were conducted to develop the constitutive relationships for two agricultural soils, which could be used for the finite element analysis of multipass effects of vehicles on soil compaction. Sandy-clay and sandy-silt samples were loaded and unloaded three times to levels of 138 kPa to simulate three passes of an agricultural tractor. An axial loading rate of 200 mm/min was used to include the dynamic effects of rapid loading from the vehicles. An Instron Universal Testing Machine was used to provide this loading rate. During the tests, a microcomputer based data acquisition system recorded axial force and strain. The system recorded 28 values per second. Tests were conducted at four confining pressures; 17.2, 24.1, 34.4 and 41.4 kPa. Plots for deviatoric stress and axial strain were found to be bilinear. Initial and latter portions of the curve were assumed to represent the elastic and plastic deformations of the sample, respectively. Assuming an associated flow rule, an elastic-plastic constitutive model was developed based on a Mohr-Coulomb failure surface. The constitutive model developed was evaluated by simulating a triaxial test at a confining pressure of 28 kPa. Initial conditions were computed by substituting the boundary stresses into the model to determine the elastic-plastic matrix. Incremental loads were applied up to the maximum stress level. For each increment of load, the elastic-plastic matrix was updated from the previous load application. The simulated data compared fairly well with experimental results, but tended to overpredict at higher stress levels. Based on a comparison with existing elastic-plastic models, the derived model appears to be well suited for substitution into the finite element method for studying soil compaction resulting from multipass effects of tractors. / M.S.

When a jack-up foundation is installed on seabeds consisting of a sand layer overlying soft clay, potential for 'punch-through' failure exists. This happens due to an abrupt reduction in bearing resistance when the foundation punches a block of sand into the underlying soft clay in an uncontrolled manner. This can lead to a sudden large penetration that can cause temporary decommissioning and even toppling of the unit. This research has addressed this problem with the aim of developing a practical design method for the jack-up industry to assess potential punch-through hazards. This objective has been achieved with the successful development of a new conceptual model for predicting the peak penetration resistance and a consistent method for constructing a complete resistance profile of spudcan foundations penetrating through sand into the underlying clay. The analytical basis of the new conceptual model follows the approach for silo analysis, and takes into account the stress level and dilatant response of sand. It is therefore a significant improvement over the punching shear and load spread models recommended in the current industry guidelines SNAME (2002), which do not consider the strength properties of the sand. To provide relevant experimental data for the new model, an extensive series of 30 continuous penetration tests were performed using the UWA drum centrifuge. These experimental results were retrospectively simulated using finite element (FE) analysis, in order to back-calculate the stress-level dependent friction and dilation angles in the sand during peak penetration resistance. The back-analysis showed that larger values of peak resistance gave lower friction and dilation angles, which is consistent with gradual suppression of dilatancy under high confining stress. When compared to published results from visualisation experiments, the FE analysis showed a similar failure mechanism during peak resistance, where a frustum of sand was forced into the underlying clay, with the outer angle reflecting the dilation in the sand. This has formed the basis of the new conceptual model. The performance of the new model in predicting the experimental peak resistance was compared with other existing analytical methods. Additional experimental results, including those already in the literature, were incorporated in the comparative study. It was found that the new conceptual model generally gave a good prediction of the experimental values, while the prediction from SNAME (2002) was conservative, with the predicted values being about half the experimental results on average. It was also shown that the new model could be modified to predict the post-peak penetration resistance in the sand layer. Finally, an analytical method for predicting the resistance profiles in the underlying clay was devised based on new bearing capacity factors developed through FE analysis. By joining the values of peak resistance, post-peak resistance and the resistance profile in the underlying clay, a complete simplified penetration resistance profile for spudcan foundations in sand overlying clay can be generated. The predicted profiles were shown to match the experimental results well.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / One of the most important and modern technology currently used in agricultural production systems are fertigation, which consists in applying the necessary nutrients to the the crops, through the water irrigation system, providing an improvement in the production efficiency. The study aimed to evaluate possible changes in the soil physical attributes caused by drip fertigation cropped with watermelon (Citrullus lanatus L.) and located in the Irrigation Perimeter of the Low Acaraà in the state of CearÃ, Brazil. The soil samples were collected with both deformed and undisturbed structure in three different periods of the crop cycle (at the beginning of the cycle, in the middle of the cycle in the 34 days after planting (DAP) and in the late season with 59 DAP), in two depths (0 - 0.15 and 0.15 to 0.30 m) and in in three situations of irrigation / fertigation managements (area of influence of the wet bulb containing fertilized culture - DC, area of influence of the wet bulb fertigated without culture SC (received only fertigation) and only an irrigated area - SF (without fertigation)). Physical attributes of particle size were determined: total clay and clay dispersed in water, soil bulk density and particle porosity (total macro and micropores), aggregate stability and mean weighted diameter, saturated hydraulic conductivity and water retention curve in the soil; Chemical analysis were determined for pH (hydrogen potential) in water, calcium (Ca), sodium (Na), potassium (K), magnesium (Mg), aluminum (Al), total acidity (H + Al), phosphorus, total organic carbon, nitrogen, C / N ratio, organic matter and electrical conductivity in the saturation extract (CEes). The experimental data were analyzed considering a completely randomized design with a split plots with 10 replications and it was conducted tests to verify the normality of the data, the F for the analysis of variance, the Tukey test for comparison of means. It was concluded that: a) Despite the predominantly sandy soil, the nutrients contained in fertigation caused positive changes in some physical soil properties studied, causing greater clay flocculation and decreasing the amount of dispersed clay in water, especially in the first layer sampled; b) The irrigation practice tended to alter adversely the quality of the ground, increasing its density and reducing the porosity; c) As the nutrients and water for irrigation were applied predominantly in the first layer of soil it was where it was observed the greatest variations of the physical attributes, including amount of stored water. / Uma das mais importantes e modernas tecnologias atualmente usadas na produÃÃo agrÃcola sÃo os sistemas de fertirrigaÃÃo, que consiste em aplicar os nutrientes necessÃrios pelas culturas, juntamente com a Ãgua da irrigaÃÃo, proporcionando uma melhoria na eficiÃncia de produÃÃo. O presente trabalho teve como objetivo avaliar as possÃveis alteraÃÃes nos atributos fÃsicos de um solo, causadas pela fertirrigaÃÃo por gotejamento, em um cultivo de melancia (Citrullus lanatus L.) no PerÃmetro Irrigado do Baixo AcaraÃ, no Estado do CearÃ. Foram coletadas amostras de solo com estrutura deformada e indeformada em trÃs Ãpocas diferentes do ciclo da cultura (no inÃcio do ciclo da cultura (E1), com 34 dias apÃs o plantio (E2) e 59 dias apÃs o plantio(E3)); para duas camadas (0 â 0,15 e 0,15 â 0,30 m) em trÃs situaÃÃes de manejo de irrigaÃÃo (Ãrea de influÃncia do bulbo Ãmido fertirrigado contendo a cultura â CC, Ãrea de influencia do bulbo Ãmido fertirrigado sem a cultura - SC e Ãrea cultivada apenas irrigada - SF (sem fertirrigaÃÃo)). Foram realizadas anÃlises fÃsicas de granulometria, argila dispersa em Ãgua, densidade do solo e da partÃcula, porosidade (total, macroporosidade e microporosidade), condutividade hidrÃulica do solo saturado e curva caracterÃstica de Ãgua no solo; e anÃlises quÃmicas de pH (potencial hidrogeniÃnico) em Ãgua, cÃlcio (Ca), sÃdio (Na), potÃssio (K), magnÃsio (Mg), alumÃnio (Al), acidez total (H+Al), fÃsforo, carbono orgÃnico total, nitrogÃnio, relaÃÃo C/N, matÃria orgÃnica e condutividade elÃtrica no extrato de saturaÃÃo (CEes). Os dados experimentais foram analisados considerando o delineamento inteiramente casualizado com arranjo em parcelas sub-subdivididas com 10 repetiÃÃes. Foram realizados testes para verificar a normalidade dos dados, o teste âFâ para a anÃlise de variÃnciae o Tukey para a comparaÃÃo de mÃdias. O trabalho teve como conclusÃes: a) Apesar do solo predominantemente arenoso, os nutrientes contidos na fertirrigaÃÃo causaram alteraÃÃes positivas em alguns atributos fÃsicos do solo estudado, ocasionando maior floculaÃÃo da argila e diminuindo a quantidade de argila dispersa em Ãgua, principalmente na primeira camada estudada; b) A prÃtica da irrigaÃÃo tendeu a alterar de forma negativa a qualidade do solo, aumentando sua densidade e diminuindo a porosidade total; c) Como os nutrientes e a Ãgua para irrigaÃÃo foram aplicados predominantemente na primeira camada do solo, foi nela onde se observou as maiores variaÃÃes dos atributos fÃsicos, inclusive para quantidade de Ãgua armazenada.

O trabalho apresenta os resultados de pesquisa voltada à investigação de processos de erosão e de deslizamentos afetando taludes rodoviários em solos residuais arenosos. A abordagem do estudo combinou diferentes ferramentas de investigação e de caracterização geológica-geotécnica e utilizou escalas de trabalho regional e de detalhe (1:50.000 a 1:500). Ela foi aplicada na rodovia Castelo Branco (SP-280), que está localizada na região sudoeste do estado de São Paulo, Brasil. As principais etapas da pesquisa abrangeram: levantamento de dados existentes; elaboração de base cartográfica e mapas temáticos utilizando Sistema de Informação Geográfica (SIG); levantamentos de campo; identificação dos taludes mais críticos; realização de ensaios laboratoriais (análise granulométrica, erodibilidade, resistência ao cisalhamento direto natural e inundado) e de análises de estabilidade dos taludes. Os resultados obtidos nestas etapas do estudo permitiram a identificação das causas e dos mecanismos dos processos de instabilização e a indicação das diretrizes gerais para a recuperação dos taludes afetados. / The paper presents the results of research focused on the investigation of erosion and slides processes affecting highway cut slopes in residual sandy soils. The approach of the study combined the different engineering geological investigation and characterization tools and used regional and detail work scales (1:50,000 to 1:500). It was applied in the Castello Branco Highway (SP-280), which is located in the south-west region of the São Paulo state, Brazil. The main steps of the research included: survey of existent data; preparation of the cartographical base and the thematic maps using Geographical Information System (GIS); field surveys; identification of the most critical cut slopes; realization of laboratorial essays (granulometry, soil erodibility, shear strength in natural and flooded humidity conditions) and slope stability analysis of the highway cut slopes. The results obtained in these steps of the study allowed the identification of the causes and mechanisms of the slope instability processes and the indication of the general directives for the recuperation of the affected cut slopes.

O trabalho apresenta os resultados de pesquisa voltada à investigação de processos de erosão e de deslizamentos afetando taludes rodoviários em solos residuais arenosos. A abordagem do estudo combinou diferentes ferramentas de investigação e de caracterização geológica-geotécnica e utilizou escalas de trabalho regional e de detalhe (1:50.000 a 1:500). Ela foi aplicada na rodovia Castelo Branco (SP-280), que está localizada na região sudoeste do estado de São Paulo, Brasil. As principais etapas da pesquisa abrangeram: levantamento de dados existentes; elaboração de base cartográfica e mapas temáticos utilizando Sistema de Informação Geográfica (SIG); levantamentos de campo; identificação dos taludes mais críticos; realização de ensaios laboratoriais (análise granulométrica, erodibilidade, resistência ao cisalhamento direto natural e inundado) e de análises de estabilidade dos taludes. Os resultados obtidos nestas etapas do estudo permitiram a identificação das causas e dos mecanismos dos processos de instabilização e a indicação das diretrizes gerais para a recuperação dos taludes afetados. / The paper presents the results of research focused on the investigation of erosion and slides processes affecting highway cut slopes in residual sandy soils. The approach of the study combined the different engineering geological investigation and characterization tools and used regional and detail work scales (1:50,000 to 1:500). It was applied in the Castello Branco Highway (SP-280), which is located in the south-west region of the São Paulo state, Brazil. The main steps of the research included: survey of existent data; preparation of the cartographical base and the thematic maps using Geographical Information System (GIS); field surveys; identification of the most critical cut slopes; realization of laboratorial essays (granulometry, soil erodibility, shear strength in natural and flooded humidity conditions) and slope stability analysis of the highway cut slopes. The results obtained in these steps of the study allowed the identification of the causes and mechanisms of the slope instability processes and the indication of the general directives for the recuperation of the affected cut slopes.

As linhas de transmissão no Brasil são geralmente muito extensas, uma vez que os grandes centros de consumo de energia ficam distantes das usinas hidrelétricas. Por essa razão, a construção e manutenção de linhas de transmissão é de grande importância e, em uma grande porcentagem destas linhas, as estacas helicoidais são usadas como fundações. No entanto, a previsão da profundidade final de instalação destas estacas ainda é um grande desafio para os projetistas, fornecedores de estacas helicoidais e construtoras. A profundidade final destas fundações é controlada pelo torque de instalação; portanto, se o torque necessário para instalar uma estaca pudesse ser calculado com acurácia, com base em suas dimensões, e nos resultados de ensaios de investigação de solo in situ (SPT), a previsão de comprimentos de estaca para estimativas de custos, a definição de equipamentos adequados para instalação e a estimativa da quantidade de seções de estacas a serem transportadas para uma determinada linha de transmissão seriam mais acuradas. Além disso, a capacidade de carga de estacas helicoidais pode ser estimada usando os resultados do torque final de instalação. Sendo assim, para atender à necessidade de se determinar o torque de instalação de fundações helicoidais ainda na fase de projeto, um método simplificado foi desenvolvido e validado com os resultados de 752 estacas helicoidais multi-hélices instaladas em solos predominantemente arenosos, de uma linha de transmissão brasileira. O modelo desenvolvido baseia-se nos resultados de ensaios SPT e considera o efeito de instalação das estacas no solo penetrado. Nesta dissertação é apresentada uma descrição detalhada do método proposto e uma comparação entre os resultados medidos em campo e calculados pelo método. Os resultados da comparação mostram que o método proposto pode estimar com sucesso o torque de instalação de estacas helicoidais. / The transmission lines in Brazil are usually very extensive, since the centers of power consumption are often far from the most hydroelectric plants. For this reason, the construction and maintenance of transmission lines is frequent in this country, and in a large percentage of transmission lines, helical piles are used as guy wire anchors and foundations for transmission towers. However, the estimates of the final embedded depth of numerous helical piles to be used in several towers of the transmission lines is still a challenge for the designers, pile suppliers and contractors. The final depth of helical foundations is controlled by the installation torque; therefore, if the torque necessary to install a helical pile could be accurately calculated based on the pile dimensions and results of in-situ soil tests (SPT), the prediction of pile lengths for costs estimations, the definition of suitable equipment for pile installation, and the estimate of the quantity of helical piles sections to be transported for a particular transmission line would be more precise. Additionally, the uplift capacity of helical piles can be estimated using the results of final installation torque. In order to address the existed need of determining the installation torque of helical foundations during the design phase, a simplified method was developed and validated with the results of 753 multi-helix piles installed in predominantly sandy soils of a Brazilian transmission line. The model proposed is based on the results of SPT tests, and considers the installation effect of helical piles on the soil penetrated. This text presents a detailed description of such method and a comparison between measured and predicted results. The comparison shows that the method proposed can successfully estimate the installation torque of helical piles.

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.

Bibliography: p. 219-237.