The role of surface chemical effects in hydraulic fracturing of shale is studied using the results of unconfined compression tests and Brazilian tests on Mancos shale- cored at depths of 20-60 ft. The rock mineralogy, total organic carbon and cation exchange capacity were determined in order to characterize the shale. Adsorption tests to study the interaction of the shale and aqueous fluid mixture were also carried out using surface tension measurements. The uniaxial compressive strengths and tensile strengths of individual shale samples after four hours exposure to water, 2.85 x 10^-3 M cationic surfactant (dodecyltrimethylammonium bromide-DTAB) and 2.81 x 10^-3 M anionic surfactant (sodium dodecylbenzenesulfonate-SDBS) were analyzed using ANOVA and Bonferroni tests. These mechanical strengths were largely reduced on exposure to the aqueous environments studied, despite the relatively low clay and low swelling clay content of the Mancos shale. Further comparison of the uniaxial compressive strengths and tensile strengths of the shale on exposure to water, to the strengths when exposed to the surfactant solutions showed that their difference was not statistically significant indicating that exposure to water had the greatest effect on strength loss. The surface tension measurement of 2.85 x 10^-4 M DTAB and 2.81 x 10^-4 M SDBS solutions before and after equilibration with shale showed about 80% increase in surface tension in the DTAB solution and 10% increase in surface tension in the SDBS solution. The probable sorption mechanism is electrostatic attraction with negatively charged sites of the shale as shown by significant loss of the cationic surfactant (DTAB) to the shale surface, and the relatively minor adsorption capacity of the anionic surfactant (SDBS). Although these adsorption tests indicate interaction between the shale and surfactant solutions, within the number of tests carried out and the surfactant concentration used, the interaction does not translate into a significant statistical difference for impacts of surfactants on mechanical strength of this shale compared to the impact of water alone. The relevance of this work is to facilitate the understanding of how the strength of rock can be reduced by the composition of hydraulic fracturing fluids, to achieve improved fracture performance and higher recovery of natural gas from shale reservoirs.

Over the past 50 years, several advancements have been made in the research area of the mechanics of unsaturated soils. These advancements can be categorized into two groups; (i) development (or improvement) of testing techniques (or apparatus) to determine the mechanical properties of unsaturated soils and (ii) development of (numerical, empirical or semi-empirical) models to estimate the variation of mechanical properties of unsaturated soils with respect to suction based on the experimental results. Implementation of the mechanics of unsaturated soils in conventional geotechnical engineering practice, however, has been rather limited. The key reasons for the limited practical applications may be attributed to the lack of simple and reliable methods for (i) measuring soil suction in the field quickly and reliably and (ii) estimating the variation of mechanical properties of unsaturated soils with respect to suction. The main objective of this thesis research is to develop simple and reliable techniques, models or approaches that can be used in geotechnical engineering practice to estimate sol suction and the mechanical properties of unsaturated soils. This research can be categorized into three parts. In the First Part, simple techniques are proposed to estimate the suction values of as-compacted unsaturated fine-grained soils using a pocket penetrometer and a conventional tensiometer. The suction values less than 300 kPa can be estimated using a strong relationship between the compressive strength measured using a pocket penetrometer and matric suction value. The high suction values in the range of 1,200 kPa to 60,000 kPa can be estimated using the unique relationship between the initial tangent of conventional tensiometer response versus time behavior and suction value. In the Second Part, approaches or semi-empirical models are proposed to estimate the variation of mechanical properties of unsaturated soils with respect to suction, which include: - Bearing capacity of unsaturated fine-grained soils - Variation of bearing capacity of unsaturated fine-grained soils with respect to matric suction - Variation of initial tangent elastic modulus of unsaturated soils below shallow foundations with respect to matric suction - Variation of maximum shear modulus with respect to matric suction for unsaturated non-plastic sandy soils (i.e. plasticity index, Ip = 0 %) In the Third Part, approaches (or methodologies) are suggested to simulate the vertically applied stress versus surface settlement behavior of shallow foundations in unsaturated coarse-grained soils assuming elastic-perfectly plastic behavior. These methodologies are extended to simulate the stress versus settlement behavior of both model footings and in-situ plates in unsaturated coarse-grained soils. The results show that there is a reasonably good comparison between the measured values (i.e. soil suction, bearing capacity, elastic and shear modulus) and those estimated using the techniques or models proposed in this thesis research. The models (or methodologies) proposed in this thesis research are promising and encouraging for modeling studies and practicing engineers to estimate the variation of mechanical behavior of unsaturated soils with respect to matric suction.

Group of piles are widely used deep foundation systems to resist lateral and vertical loads. Seismic and static performance of pile groups mostly depend on soil type, pile spacing and pier rigidity. Not many pile lateral load tests have been performed due to high costs. Advanced and complex analytical methods were developed over the years to assess nonlinear lateral pile response. This research is conducted aiming at developing a practical analysis method to verify the lateral performance of pile groups and its effect on overall response of bridge utilizing the available pile lateral load test data. Empirical constants derived from evaluation of lateral load tests are used in a simple formulation to define the nonlinear behavior of the pile-soil system. An analysis guideline is established to model the nonlinear soil-bridge interaction by the help of a general purpose structural analysis program comprising recommendations for various cases. Results of the proposed method is compared to the results of industry accepted advanced methods using response spectrum and nonlinear time history analyses to assess the suitability of this new application. According to the analysis results, proposed simple method can be used as an effective analysis tool for the determination of response of the superstructure.

In this study, the load bearing behavior of piled raft foundations is investigated performing laboratory and field tests. Piled raft foundation of a multi storey building was also instrumented and monitored in order to study the load sharing mechanism of piled raft foundations. A small reinforced concrete piled raft of 2.3 m square supported by four mini piles at the corners was loaded and contribution of the raft support up to 41 % of the total load was observed. The soil was stiff fissured Ankara clay with no ground water. A building founded on a piled raft foundation was instrumented and monitored using earth pressure cells beneath the raft during its construction period. The foundation soil was a deep graywacke highly weathered at the upper 10 m with no ground water. The proportion of load that was carried by the raft was 21 to 24 % of the total load near the edge and 44 to 56 % under the core. In the laboratory tests, model aluminum piles with outerinner diameters of 2218 mm and a length of 200 mm were used. The raft was made of steel plate with plan dimensions of 176 mm x 176 mm and a thickness of 10 mm. The model piles were instrumented with strain gages to monitor pile loads. Model piled raft configurations with different number of piles were tested. The behavior of a single pile and the plain raft were also investigated. The soil in the model tests was half and half sand &ndash / kaolinite mixture. It has been observed that when a piled raft is loaded gradually, piles take more load initially and after they reach their full capacity additional loads are carried by raft. The proportion of load that was carried by the raft decreases with the increasing number of piles and the load per pile is decreased. Center, edge and corner piles are not loaded equally under rafts. It has been found that rafts share foundation loads at such levels that should not be ignored.

Damage and condition identi&amp / #64257 / cation of existing structures using non-destructive tests is a common challenge that has been worked on for a long time. In this study, two di&amp / #64256 / erent methods were developed to &amp / #64257 / nd existing force on cables as well as determine bending characteristics (EI coe&amp / #64259 / cients) of beam like structures (such as bridges). Comparing forces in symmetrically placed cables or against values obtained from design drawings would indicate structural imbalance as well as &amp / #64257 / nding EI coe&amp / #64259 / cients at a number of segments on a bridge girder might indicate weak regions that might possibly have undergone structural damage, having weak connections, lost composite action etc. With the help of the proposed algorithm, the sti&amp / #64256 / ness parameters of bridges can be assessed and the location of any damage that is in the magnitude which can a&amp / #64256 / ect displacement behavior of system can be located. The developed methods are demonstrated using the values analytically obtained from the created models and the e&amp / #64256 / ectiveness of the algorithm is criticized. Furthermore, several damage scenarios on a scaled lab beam was used to test the application using real experimental data / including tests on undamaged beam (for identi&amp / #64257 / cation) and tests on the damaged beam. Additional experiments were conducted on a cable stretched in the laboratory instrumented using a load cell to measure instantaneous axial load on the cable and compare these values against the values obtained from the developed tension measurement device. The results are compared and conclusions are derived.

Orientador: Miriam Gonçalves Miguel / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-17T14:10:40Z (GMT). No. of bitstreams: 1 Scallet_MarcellaMaschietto_M.pdf: 1855400 bytes, checksum: 6ec58c53afe478625fb1fa36239f671c (MD5) Previous issue date: 2011 / Resumo: Este trabalho tem como objetivo estudar o comportamento de estacas escavadas de pequeno diâmetro, submetidas a carregamentos axiais de compressão através de provas de carga estática realizadas no Campo Experimental de Mecânica dos Solos e Fundações 2 da Unicamp. O CEMSF2 apresenta um perfil geológico cuja primeira camada é constituída de argila siltosa, coluvionar, laterítica e colapsível. Pretendeu-se avaliar as capacidades de carga e os recalques dessas estacas nas condições: a) sem pré-inundação e sem melhoria de ponta; b) sem pré-inundação e com melhoria de 1 ponta, com o lançamento de um volume de 18 litros de brita 1 no fundo da estaca antes da concretagem; c) com pré-inundação e sem melhoria de ponta e d) com préinundação e com melhoria de ponta. Todas as estacas foram submetidas a dois carregamentos (ensaios e reensaios), sob uma mesma condição acima descrita. Foram instalados tensiômetros convencionais para a leitura das sucções matriciais do solo durante a realização das provas de carga. Através das curvas carga versus recalque foram definidas as capacidades de carga e as resistências ao atrito lateral e de ponta, por meio de métodos de interpretação dessas curvas com o solo sem inundação e préinundado por 48horas, considerando as reduções dos valores da sucção matricial do solo, devido às duas condições de umidade. A capacidade de carga das estacas nos ensaios foi menor do que nos reensaios, para as estacas sem pré-inundação, devido ao aumento da resistência de ponta nos reensaios. Nas provas de carga com préinundação, em geral, não houve aumento de resistência de ponta dos ensaios para os reensa ios. A resistência ao atrito lateral foi maior que a resistência de ponta em todas as provas de carga. O lançamento de brita 1 não trouxe melhorias na capacidade de carga. Reduções consideráveis na capacidade de carga foram observadas em função da pré-inundação do solo, sendo essas reduções mais expressivas para as estacas com melhoria de ponta / Abstract: This paper aims to study the behavior of bored piles of small diameters, subjected to axial compression loads by static load tests carried out at the Field of Experimental Soil Mechanics and Foundation 2 at Unicamp. The CEMSF2 has a geological profile whose first layer is composed of silty clay, with coluvionar, lateritic, and collapsible features.This study intended to evaluate the load capacities and the settlements of these foundations in such conditions: a) without any pre- wetting nor improvement in the tip; b) without any pre-wetting but with a tip improvement, placing a volume of 18 liters of stones 1 in the base of the pile before concreting c) with pre- wetting but without tip improvement and d) with pre-wetting and tip improvement. All these piles were subjected to two loading (tests and retests), under the same test condition described above. Conventional tensiometers were installed to read the matric suctions of the soil during the performance of the load tests. Throughout the load versus settlement curves the load capacities and the strength to lateral friction and tip were defined using methods of interpretation of these curves with the soil without any pre-wetting and 48-hour-pre wetting, considering the reductions of the values of the soil matric suction due to two moisture conditions. The load capacity of piles in the tests was smaller than the one in the retests for the piles without any pre-flooding, due to the increase of the tip strength in the retests. In the load tests with pre-flooding, in general, there was not any increase of strength in the tip of the tests for the retests. The strength to the lateral friction was greater than the tip strength in all loading tests. The placing stones 1did not result any improvement to the bearing capacity. Considerable reductions in bearing capacity were observed because of the pre-wetting soil, such reductions are more significant for the piles with improved tip / Mestrado / Geotecnia / Mestre em Engenharia Civil

Orientador: Paulo Jose Rocha de Albuquerque / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-13T04:04:46Z (GMT). No. of bitstreams: 1 Melo_BarbaraNardi_M.pdf: 6782464 bytes, checksum: 2db509605b90c7d9ce2ae5bbdafbb1c1 (MD5) Previous issue date: 2009 / Resumo: A dificuldade de se atingir a ruptura dos elementos de fundação nos ensaios estáticos fez com que, ao longo de várias décadas, diversos métodos de extrapolação da curva carga vs recalque fossem sugeridos por inúmeros pesquisadores, no intuito de determinar a carga de ruptura, destacando-se os métodos propostos por Van der Veen (1953), Mazurkiewics (1972), Décourt (1996) e NBR 6122/1996. Porém, a experiência confirma que os resultados podem variar consideravelmente entre um método e outro. Este trabalho destaca o Conceito de Rigidez proposto por Décourt (1996, 2008), método que, nos últimos anos, vem sendo utilizado pela comunidade geotécnica e é destacado pelo autor como um método que oferece informações de resistência de ponta e atrito lateral, além da carga de ruptura em provas de carga comuns, ou seja, sem instrumentação. Com a interpretação dos resultados, levantados em estacas do tipo escavadas, hélice contínua, raiz, ômega, pré-moldadas, apiloadas e metálicas em seis campos experimentais localizados nas cidades de Campinas/SP, Recife/PE, Vitória/ES, Londrina/PR, Ilha Solteira/SP e Brasília/DF obtiveram-se valores satisfatórios de carga de ruptura convencional em provas de carga levadas a grandes deslocamentos e algumas restrições em provas de carga interrompidas prematuramente. Os resultados de atrito lateral comparados com resultados de estacas instrumentadas trazem valores satisfatórios, ou seja, dentro dos domínios. / Abstract: The difficulty of reaching the rupture of the foundation elements in the static loading made that along several decades several methods of extrapolation of the load - settlement curve were suggested by many researchers, with the intent of determining the load failure, such as the methods proposed by Van der Veen (1953), Mazurkiewics (1972), Décourt (1996) and NBR 6122/1996. But the experience confirms that the obtained results can vary considerably from one method to another. This work details the Concept of Rigidity, proposed by Décourt (1996, 2008), a method that in the last years it has been used by the geotechnical community and which the author claims as a method that provides information on tip resistance and lateral friction, along with the load at failure in common load tests, it means, without instrumentation. Whit the interpretation results raised in bored piles, continuous flight auger, root, omega, driven concrete, "hamered" and metal pile in six experimental fields localized in Campinas/SP, Recife/PE, Vitória/ES, Londrina/PR, Ilha Solteira/SP and Brasilia/DF got satisfactory values of conventional load failure in load tests carried to big movements and some restrictions in load tests not carried to failure. The lateral friction results compared with load tests on instrumented piles results show satisfactory values, it means, in the domains. / Mestrado / Geotecnia / Mestre em Engenharia Civil

Orientador: Paulo Jose Rocha de Albuquerque / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-09T17:50:50Z (GMT). No. of bitstreams: 1 Zammataro_BrunoBraz_M.pdf: 5071414 bytes, checksum: 81ca663defad90551f9f175888acb63f (MD5) Previous issue date: 2007 / Resumo: Nesta pesquisa estudou-se o comportamento de estacas tipo escavada e hélice contínua, submetidas a prova de carga estática horizontal. Estes elementos encontram-se instalados no Campo Experimental da Feagri, Unicamp, cujo perfil compõe-se de solo estratificado predominantemente argiloso, porém com comportamento de arenoso. Como objetivo principal, obtiveram-se valores de nh, para um intervalo escolhido e através de valores de deslocamento horizontal e carga aplicada. Além disso, obtiveram-se, para diversos métodos, valores de carga de ruptura e carga admissível horizontal, verificando sua validade / Abstract: The behavior of bored and continuous flight auger piles was studied, under static horizontal load. These elements are installed in the Feagri Experimental Field, at the Unicamp campus, with a soil section profile which is predominantly stratified clay, but behaving as sandy soil. The main objective was to obtain values for nh,for a chosen interval and through values of horizontal displacement and applied load. Besides this, for various methods, values were obtained for horizontal loading at rupture and safe loading, verifying their validity / Mestrado / Geotecnia / Mestre em Engenharia Civil

Este trabalho apresenta resultados de provas de carga em placa com monitoramento do teor de umidade e da sucção matricial do solo, realizadas a 1,5 m de profundidade em um solo não saturado e colapsível, considerado representativo da região centro-oeste do estado de São Paulo. Foram executados ensaios com e sem inundação da cava, do tipo lento (SML), rápido (QML) e misto (lento até um determinado estágio, passando a rápido a partir de então). O acompanhamento do teor de umidade e da sucção durante os ensaios foi realizado através de pesagem de amostras, com a utilização da técnica de reflectometria no domínio do tempo (TDR) e com o auxílio de tensiômetros. A partir dos dados obtidos, procedeu-se a uma análise da influência da sucção na resposta do sistema solo-placa. Foi observado que o aumento da sucção provoca um crescimento substancial da capacidade de carga do solo. Comparando-se ensaios inundados com não inundados, observou-se que o colapso do solo mostra-se mais proeminente com o aumento da sucção. Com respeito à técnica de reflectometria no domínio do tempo, a mesma demonstrou um desempenho satisfatório para medidas de teor de umidade in situ. / This work presents results of plate load tests with measurements of soil moisture content and matric suction, carried out at a 1.5 m depth in an unsaturated collapsible soil, considered as representative of the middle-west region of the state of São Paulo, Brazil. The tests were performed with and without the wetting of the pit. Three test methods were used: slow maintained load (SML), quick maintained load (QML), and mixed tests (SML up to a certain stage, switched to QML from there on). Soil moisture content and suction were measured through gravimetric determination on samples, the time domain reflectometry technique (TDR), and tensiometers. The gathered data allowed an assessment of the influence of the soil suction over the soil-plate system response. It was observed that the increase in suction causes a substantial increase in soil bearing capacity. Comparisons between wet and non-wet tests showed that soil collapse is higher when suction rises. The time domain reflectometry technique showed a promising performance with respect to in situ water content measurements.

Apresenta-se um método para a previsão da curva tensão-recalque a ser obtida em provas de carga em placa circular, instalada a diferentes profundidades e com vários diâmetros, para diversos níveis de sucção em solo não saturado. Também é proposto um procedimento para correção dos recalques medidos em ensaio com carregamento do tipo rápido, para a obtenção dos correspondentes recalques estabilizados de um ensaio lento. A previsão realizada apresenta resultados bastante próximos dos obtidos em provas de carga, verificando-se assim a aplicabilidade do método proposto para reproduzir o comportamento do sistema solo-placa neste tipo de solo. Além disso, este trabalho apresenta um estudo do módulo de deformabilidade a partir de ensaios de campo e de laboratório, para o solo do campo experimental de fundações da EESC/USP, aplicando conceitos da mecânica dos solos não saturados. Em campo, o módulo de deformabilidade foi obtido por meio de provas de carga em placa circular com e sem inundação prévia do solo. Em laboratório, o módulo foi obtido a partir de ensaios de compressão confinada e triaxiais, ambos com sucção controlada. Observou-se que a sucção matricial tem grande influência no módulo de deformabilidade do solo. / This thesis presents a method for prediction the stress-settlement curve to be obtained in circular plate load tests, at different depths and with several diameters, to differents suction levels on unsaturated soil. A procedure is also proposed for correction the settlement measured with a quick maintained load (QML) tests to obtain the stabilized settlement in a slow maintained load (SML) tests. This prediction presents quite results of the real measured stress-settlement curve through load tests, thus verifying the applicability of the proposed method to reproduce the behavior the soil-plate system in this soil. Besides, this work presents a study of the deformation modulus using field and laboratory tests, to the soil of the foundations experimental field of EESC/USP, applying concepts of the unsaturated soil mechanics. In field, the deformation modulus was obtained by means of circular plate load tests with and without previous soaking of the soil. In laboratory, the modulus was obtained using confined compression and triaxial tests, both with controlled suction. It was observed that the matric suction has great influence in the soil deformation modulus.