Capacidade de carga de fundações superficiais assentes sobre camada finita de solo cimentado

O uso de uma camada de reforço de solo cimentado é uma alternativa para melhorar a capacidade de suporte de fundações superficiais em solos com baixa capacidade de suporte. Pesquisas recentes com ensaios em modelo reduzido destacaram a influência da geometria e da resistência à tração da camada do solo cimentado na previsão da capacidade de suporte de sapatas apoiadas nas camadas tratadas. Este trabalho apresenta a avaliação de ensaios de carga estática em campo com bases circulares de aço assentes sobre camadas de solo cimentado acima de um solo coesivo-friccional com baixa capacidade de suporte. Nesta pesquisa foram utilizados dois tipos de agentes cimentantes: CP-V ARI e mistura Vidro moído-Cal de carbureto a fim de avaliar, pela primeira vez em campo, a performance desse cimento alternativo em substituição ao cimento Portland CPV-ARI. Neste trabalho, desenvolve-se uma metodologia de previsão da capacidade de carga de fundações superficiais circulares assentes em solo reforçado de geometria circular com solo cimentado, tendo em consideração tanto a espessura do reforço, assim como a sua extensão lateral, bem como se utilizam métodos tradicionais (Vésic e Hansen) para prever o comportamento em campo dessas camadas. Uma curva única (normalizada) de tensão equivalente versus deslocamento relativo é estabelecida para todos os ensaios de campo estudados, sob o solo natural e sob camadas de solo cimentado compactadas, considerando diferentes diâmetros de placas, resistência do reforço, áreas circulares e espessura tratadas. O mecanismo de ruptura pode ser previsto calculando a tensão máxima de tração no fundo da camada de reforço na carga de fundação prescrita. Uma equação para essa finalidade é sugerida e comparada com sucesso em relação aos resultados de ensaios de campo em tamanho real. Finalmente, uma nova abordagem analítica é proposta para o projeto de fundações superficiais assentes em camadas de areia cimentada sobre solo residual com baixa capacidade de suporte.The addition of a soil reinforcing cemented layer is an alternative to improve the bearing capacity of shallow foundations in soils with low bearing capacity. Recent research in small model has highlighted the influence of geometry and the tensile strength of the cemented soil layer in the prediction of bearing capacity of shallow foundation supported on the treated layers. This work presents the evaluation of static load tests in the field with circular steel plates on layers of cemented soil above a cohesive-frictional soil with low support capacity. In this research, two types of cementing agents were used: Portland cement-Type III and Ground waste Glass-Carbide Lime binder in order to test, for the first time, in the field performance of this green cements to replace Portland cement-Type III. In this work, a methodology for predicting the bearing capacity of circular surfaced foundations based on circular geometry cement reinforced soil is developed, taking into account both the thickness of the reinforcement, as well as its horizontal extension, including the use of traditional methods (Vésic and Hansen) to predict the field behavior of these layers. A unique (normalized) curve of equivalent stress versus relative displacement is established for all field tests, over natural soil and compacted cemented layer, considering different plates diameters, reinforcement strengths, circular areas and treated thickness. The rupture mechanism can be predicted by calculating the maximum tensile stress at the bottom of the reinforcement layer at the prescribed foundation load. An equation for this purpose is suggested and successfully tested against the results of actual field tests. Finally, analytical solutions to determine load capacity were effective predicting field values

Spread footings bearing on circular and square cement-stabilized sand layers above weakly bonded residual soil

The practice of soil-cement reinforced layers to bear shallow foundations is a feasible option in low bearing capacity soils. This paper addresses the interpretation of plate load tests bearing on compacted artificially cemented sand layers of distinct sizes and shapes (cylindrical and prismatic) overlaying a weakly bonded residual soil stratum. Static load tests were carried out on a rigid circular steel plate (diameter of 300-mm) resting on sand-cement reinforced layers with distinct areas (diameters/widths of 450, 600, and 900-mm) and constant thickness of 300-mm. The results have shown two distinct failure modes that rely on the cemented layer’s diameter/width: (a) the steel plate and the artificially cemented layer punch together into the weakly bonded residual soil, without the failure of the cemented layer, and (b) the artificially cemented layer fails. The combination of two traditional methods for predicting bearing capacity in soils was successfully applied considering the shape (and geometry) of the improved layer and the existence (or not) of interaction of the lateral of the cemented layers and the residual soil. Finally, this study highlights the importance of considering the shapes and sizes of soil-cement layers in the bearing capacity estimation (combining analytical solutions) of spread footings resting on treated layers above weakly bonded residual soils

Literary review on tailings dams in Brazil

O setor minerário brasileiro representa uma parcela importante na geração de recursos através da comercialização no mercado nacional e internacional. Este setor movimenta outros setores através do suprimento da matéria-­‐prima extraída, como é exemplo das indústrias da construção civil, automobilística, aeroespacial e outras. Muito embora sua importância seja relevante e estratégica na economia, a geração de resíduos é significativa e para tanto é necessário que sejam viabilizados métodos de disposição destes materiais obedecendo as restrições ambientais, sociais e econômicas. Com isso, diante ao enorme vulto de materiais residuais gerados, as barragens de contenção rejeitos minerais representam uma das técnicas mais optadas por mineradoras e geotécnicos. Logo, este artigo tem como proposta fornecer informações quanto a conceitos, métodos construtivos, técnicas e outros aspectos que envolvam o assunto barragem de contenção de rejeitos a partir de uma revisão literária.The Brazilian mining sector represents an important part in the generation of resources through the commercialization in the national and international markets. This sector moves other sectors through the supply of raw materials, such as the civil construction, automobile, aerospace and other industries. Although its importance is relevant and strategic in the economy, the generation of waste is significant and for that it is necessary that methods of disposal of these materials be made feasible obeying the environmental, social and economic restrictions. In view of the huge amount of waste materials generated, mineral retention dams represent one of the most preferred mining and geotechnical techniques. Therefore, this article aims to provide information on concepts, construction methods, techniques and other aspects that involve the subject dam retention from a literary review

Optimización de CO2 y costo de zapatas de concreto reforzado sobre un suelo tratado con cal usando algoritmo de recocido simulado modificado

Introduction: The design of spread footings over a lime-treated soil is studied as an important topic in geotechnical and environmental engineering. With the emergence and use of algorithms, it is possible to solve optimization problems in engineering, leading, for example, to decreased amounts of materials, time, energy, and work. Objective: This research aims to optimize the CO2 emission and cost of building spread footings over a treated soil with hydrated lime using the modified simulated annealing algorithm (MSAA). Method: The parameters for shear strength (cohesion and friction angle) was calculated of a silty soil of the Guabirotuba geological formation of Curitiba (Brazil) stabilized with different lime contents (3, 5, 7 and 9%) at different curing times (30, 90, and 180 days). Then with these parameters, the geometry of the spread footings was optimized with MSAA minimizing the cost and CO2 emissions of their construction. For the design constraint of the structures the ultimate bearing capacity of the soil was used as criteria, the settlements produced by the service load, and the base safety factor Results: The results show that most of the problems converge to the same solution for costs and CO2 emissions without depending on curing time and lime content used, due to the solutions being restricted primarily by the maximum permissible settlements. Conclusions: With the increase in lime content, the cohesion of the mixtures increased for all curing times studied ant the friction angle had no major variations in relation to the amount of lime administered or to the curing time employed. Costs and carbon dioxide emissions for spread footing construction converge to the same results. In this sense, 9% lime can be avoided, and small percentages of lime (i.e. 3-5%) are appropriated to ground improvement and reduce the costs of this procedure. On the other hand, the MSAA can be designated as a robust algorithm due to having achieved almost equal results and, in some cases, better results compared with other algorithms to solve problems reported in the literature.Introducción: El diseño de cimentaciones sobre suelo tratado con cal se estudia como un tema importante en ingeniería geotécnica y ambiental. Con la aparición y el uso de algoritmos, es posible resolver problemas de optimización en ingeniería, lo que lleva, por ejemplo, a la disminución de cantidades de materiales, tiempo, energía y trabajo. Objetivo: Esta investigación tiene como objetivo optimizar la emisión de CO2 y el costo de la construcción de zapatas sobre un suelo tratado con cal hidratada utilizando el algoritmo recocido modificado (MSAA). Metodología: Se calcularon los parámetros de resistencia al corte (cohesión y ángulo de fricción) de un suelo limoso de la formación geológica Guabirotuba de Curitiba (Brasil) estabilizada con diferentes contenidos de cal (3, 5, 7 y 9%) a diferentes tiempos de curado (30, 90, y 180 días). Luego, con estos parámetros, la geometría de las zapatas se optimizó con MSAA minimizando el costo y las emisiones de CO2 de su construcción. La capacidad de carga final del suelo, los asentamientos producidos por la carga de servicio y el factor de seguridad de base fueron usados como restricciones de diseño. Resultados: Los resultados muestran que la mayoría de los problemas convergen a la misma solución para los costos y las emisiones de CO2 sin depender del tiempo de curado y del contenido de cal utilizado, debido a que las soluciones están restringidas principalmente por los asentamientos máximos permitidos. Conclusiones: Con el aumento del contenido de cal, la cohesión de las mezclas aumentó para todos los tiempos de curado estudiados y el ángulo de fricción no tuvo variaciones importantes en relación con la cantidad de cal administrada o con el tiempo de curado empleado. Los costos y la emisión de dióxido de carbono para la construcción de zapatas convergentes coinciden con los mismos resultados. En este sentido, se puede evitar el 9% de cal, y pequeños porcentajes de cal (es decir, 3-5%) se destinan a la mejora del suelo y reducen los costos de este procedimiento. Por otro lado, MSAA puede ser considerado como un algoritmo robusto debido a que ha logrado resultados casi iguales y, en algunos casos, mejores resultados en comparación con otros algoritmos para resolver problemas reportados en la literatura

Literary review on tailings dams in Brazil

O setor minerário brasileiro representa uma parcela importante na geração de recursos através da comercialização no mercado nacional e internacional. Este setor movimenta outros setores através do suprimento da matéria-­‐prima extraída, como é exemplo das indústrias da construção civil, automobilística, aeroespacial e outras. Muito embora sua importância seja relevante e estratégica na economia, a geração de resíduos é significativa e para tanto é necessário que sejam viabilizados métodos de disposição destes materiais obedecendo as restrições ambientais, sociais e econômicas. Com isso, diante ao enorme vulto de materiais residuais gerados, as barragens de contenção rejeitos minerais representam uma das técnicas mais optadas por mineradoras e geotécnicos. Logo, este artigo tem como proposta fornecer informações quanto a conceitos, métodos construtivos, técnicas e outros aspectos que envolvam o assunto barragem de contenção de rejeitos a partir de uma revisão literária.The Brazilian mining sector represents an important part in the generation of resources through the commercialization in the national and international markets. This sector moves other sectors through the supply of raw materials, such as the civil construction, automobile, aerospace and other industries. Although its importance is relevant and strategic in the economy, the generation of waste is significant and for that it is necessary that methods of disposal of these materials be made feasible obeying the environmental, social and economic restrictions. In view of the huge amount of waste materials generated, mineral retention dams represent one of the most preferred mining and geotechnical techniques. Therefore, this article aims to provide information on concepts, construction methods, techniques and other aspects that involve the subject dam retention from a literary review

Effects of porosity, dry unit weight, cement content and void/cement ratio on unconfined compressive strength of roof tile waste-silty soil mixtures

One of the conventional ways to improve the mechanical behavior of soils is to mix them with cementing agents such as cement, lime and fly ash. Recently, introduction to alternative materials or sub-products that can be adopted to improve the soil strength is of paramount importance. Therefore, the present study aims to investigate the effects of porosity (η), dry unit weight (γd) of molding, cement content (C) and porosity/volumetric cement content ratio (η/Civ) or void/cement ratio on the unconfined compressive strength (qu or UCS) of silty soil–roof tile waste (RT) mixtures. Soil samples are molded into four different dry unit weights (i.e. 13 kN/m3, 13.67 kN/m3, 14.33 kN/m3 and 15 kN/m3) using 3%, 6% and 9% cement and 5%, 15% and 30% RT. The results show that with the addition of cement, the strength of the RT–soil mixtures increases in a linear manner. On the other hand, the addition of RT decreases qu of the samples at a constant percentage of cement, and the decrease in porosity can increase qu. A dosage equation is derived from the experimental data using the porosity/volumetric cement content ratio (η/Civ) where the control variables are the moisture content, crushed tile content, cement content and porosity. Keywords: Roof tile waste (RT), Voids/cement ratio, Reuse, Ground improvemen

Effects of lime addition on geotechnical properties of sedimentary soil in Curitiba, Brazil

The soil of the Guabirotuba geological formation (Paraná Basin, Brazil) has physico-mechanical properties which are not suitable for its utilization in pavement construction, in protection of hillsides and slopes, or as shallow foundation support. Treatment of this soil by lime addition would improve its usability. The present context intends to determine the ratio between the splitting tensile strength (qt) and the unconfined compressive strength (qu) of clayey soil in the metropolitan region of Curitiba City, which has been treated with different lime contents and curing times. The control parameters evaluated include lime content (L), curing time (t), moisture content (w), and ratio of porosity to volumetric lime content (η/Lv). It was observed that the qt/qu ratio is between 0.17 and 0.2 in relation to the curing time, and an exponential relation exists between them. Meanwhile, the unconfined compressive strength of lime-treated soil was found to be approximately four times the initial value