Construção e avaliação de sonda de resistividade elétrica para investigação do subsolo dissertação
Carregando...
Data
2019-12-02
Autores
Bizarri, Marco Aurélio
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O sensor de resistividade elétrica acoplado ao Piezocone (CPTu) permite a obtenção do perfil de resistividade elétrica do solo, possibilitando a estimativa de alguns parâmetros tais como porosidade, grau de saturação e índice de comportamento do solo. Além disso, também é possível localizar preliminarmente a profundidade, tanto da intrusão de água salgada em aquíferos de água doce, e de plumas de contaminação, o que difundiu o uso do equipamento em investigações geoambientais. A técnica pode ser utilizada como um complemento ao caminhamento elétrico evidenciando anomalias no maciço que necessitem de uma análise mais criteriosa, direcionando ensaios de amostragem de água e solo. Contudo, um fato importante a ser mencionado, é que as sondas comerciais fornecem diretamente os valores da resistividade, não informando as variáveis de entrada, tais como forma, frequência e amplitude da onda do sinal gerado. Portanto, o objetivo dessa dissertação é apresentar a construção de uma sonda que realiza a leitura vertical da resistividade elétrica do solo, com dimensões externas similares ao do Piezocone de Resistividade Elétrica (RCPTu). A pesquisa considera o design das peças, análises mecânicas teóricas, a construção do equipamento, ensaios laboratoriais de calibração e campo elétrico em meio aquoso, e ensaios de campo. Além disso, foram realizados cálculos da probabilidade da ocorrência de cenários de falha estrutural, utilizando a teoria da confiabilidade. Por fim, os resultados dos ensaios de campo e do RCPTu foram comparados e as análises mostraram que os valores obtidos foram próximos.
The electrical resistivity sensor connected in the Piezocone (CPTu) allows the logging of the soil electrical resistivity, permitting the evaluation of parameters such as porosity, degree of saturation and soil behavior type. In addition, it is also possible to preliminarily locate the depth of both saltwater intrusion in freshwater aquifers and contamination plumes, which has widespread the use of the equipment in geo-environmental investigations. The technique can be used as a complement to the vertical electrical sounding, showing anomalies in the massif that require a more careful analysis, conducting soil and water sampling tests. However, an important fact to be mentioned is that the commercial probes provide the electrical resistivity values directly, not informing the input variables, such as waveform, frequency and amplitude of the generated signal. Therefore, the purpose of this dissertation is to present the construction of a probe that logs the electrical resistivity of the soil, with external dimensions similar to the Resistivity Piezocone (RCPTu). The research considered the design of the pieces, theoretical mechanical analysis, the construction of the equipment, laboratory calibration and electric field in aqueous environment, and field tests. In addition, it was done calculations of the probability of occurrence of structural failure scenarios, using the reliability theory. Further, the results of field tests and RCPTu were compared and the analysis lead to close values.
The electrical resistivity sensor connected in the Piezocone (CPTu) allows the logging of the soil electrical resistivity, permitting the evaluation of parameters such as porosity, degree of saturation and soil behavior type. In addition, it is also possible to preliminarily locate the depth of both saltwater intrusion in freshwater aquifers and contamination plumes, which has widespread the use of the equipment in geo-environmental investigations. The technique can be used as a complement to the vertical electrical sounding, showing anomalies in the massif that require a more careful analysis, conducting soil and water sampling tests. However, an important fact to be mentioned is that the commercial probes provide the electrical resistivity values directly, not informing the input variables, such as waveform, frequency and amplitude of the generated signal. Therefore, the purpose of this dissertation is to present the construction of a probe that logs the electrical resistivity of the soil, with external dimensions similar to the Resistivity Piezocone (RCPTu). The research considered the design of the pieces, theoretical mechanical analysis, the construction of the equipment, laboratory calibration and electric field in aqueous environment, and field tests. In addition, it was done calculations of the probability of occurrence of structural failure scenarios, using the reliability theory. Further, the results of field tests and RCPTu were compared and the analysis lead to close values.
Descrição
Palavras-chave
Solo, Sonda, Resistividade elétrica, Soil, Probe, Electrical resistivity