Abstract Engineering always deals with uncertainties, and efforts are needed to quantify them. A probabilistic analysis considers the statistical information of the problem to this quantification. In the geotechnical area, uncertainties play a particular role in structure design because it deals with naturally formed materials. Evaluating spatial variability has become progressively important. However, studies on the correct reproduction of this variability and conditional simulations are limited. In this paper, a geostatistical-based enhancement of the Random Finite Element Method (RFEM) is presented. The main aim of this study is to incorporate an advanced multivariate geostatistical technique (i.e., Turning Bands Co-simulation, TBCOSIM) to reproduce the coregionalization model of soil properties correctly in order to investigate the effects regarding this reproduction. It is illustrated in a real case of soil slope. The results showed that, for the unconditional simulation, the presented approach reached a perfect agreement with the coregionalization model, while the conditional simulation inserted some disturbances to this agreement, but it still satisfactorily reproduced the model. The original RFEM failed to reproduce this structure, leading to lower variances than the presented approach, which would cause a non-conservative design. Furthermore, disregarding the local uncertainty (i.e., the nugget effect) may introduce bias to analysis and, depending on its magnitude, may also lead the conditional analysis to not show a worthwhile reduction in variances of results. Finally, this paper shows that correctly determining the coregionalization model and reproducing it on probabilistic analysis may meaningfully influence the results.

RESUMO A concentração de óleos e graxas em amostras de águas contaminadas com resíduos oleosos pode ser determinada pelos procedimentos estabelecidos no Standard Methods for the Examination of Water and Wastewater. No entanto, sua aplicação nem sempre resulta em valores adequados ou níveis de precisão satisfatórios para atendimento de padrões normativos. Nesse sentido, este artigo apresenta uma proposta de ensaio para determinação da concentração de óleos minerais em águas provenientes de áreas pavimentadas, sujeitas ao derramamento de óleos e graxas. Tal método tem por base o método de partição gravimétrica (5520 B), estabelecido pelo Standard Methods. No novo procedimento, a etapa de separação entre o solvente de extração contendo os resíduos e o restante da fase aquosa foi substituída pela evaporação de toda a água da amostra, em estufa a 85ºC. Para avaliar a eficiência do método, foram preparadas amostras com concentrações conhecidas de óleo de 200, 100, 50, 25 e 15 mg.L-1 em água destilada e realizados ensaios de laboratório para determinação do teor de óleo, conforme tal procedimento. Os valores obtidos para as concentrações de óleo são bastante satisfatórios, apresentando comportamento linear em relação às concentrações de referência. Esse fato evidencia a confiabilidade do método proposto e sua aplicabilidade na determinação da concentração de óleos em amostras de águas contaminadas provenientes do escoamento superficial em pavimentos.

ABSTRACT Oil and grease concentration in water samples contaminated by oily residues can be determined by the procedures established in the Standard Methods for the Examination of Water and Wastewater. However, its application does not always result in adequate values or satisfactory accuracy levels in order to meet regulatory standards. In this sense, this paper presents a test-method proposal for determining mineral oil concentration in water samples from runoff of paved areas subject to oil and grease spillages. This method is based on the partition-gravimetric method (5520 B) established by the Standard Methods. In the new procedure, the separation between the extraction solvent containing residues and the aqueous phase remainder was replaced by the whole water sample evaporation in an oven at 85ºC. In order to assess the proposed method’s efficiency, samples were prepared with known oil concentrations of 200, 100, 50, 25 and 15 mg.L-1, in distilled water and laboratory tests were performed to determine the oil content, according to the new procedure. The values obtained for the oil concentrations through the proposed procedure are quite satisfactory, presenting linear behavior in relation to the reference concentrations. This fact evidences the reliability of the new method and its applicability in determining the oil concentration in contaminated water samples from runoff in pavement surfaces.

RESUMO O objetivo deste trabalho é apresentar coeficientes de desagregação para chuvas intensas diárias do posto E2-046, situado em Caraguatatuba - SP. Os dados obtidos por meio do pluviógrafo se referem a um período contínuo (31 anos de série) e possuem forte correlação com as leituras do pluviômetro, validando as leituras do pluviógrafo, o que atribuiu maior confiabilidade aos resultados. O coeficiente médio “24 horas”/“1 dia” encontrado para a região de estudo foi 1,075, o qual difere dos valores encontrados na literatura. O desvio relativo considerando outras durações, e consequentemente outros coeficientes de precipitação, em relação à média da literatura chegou a 22,06% (18 horas/“24 horas”). O desvio relativo de coeficientes de desagregação para pequenas durações do posto estudado em relação à média de coeficientes para as cidades do Estado de São Paulo foi bastante elevado, atingindo quase 50% (10 minutos/“24 horas”). Tais desvios reforçam a necessidade de utilização de coeficientes de desagregação locais.

ABSTRACT The objective of this study is to present disaggregation coefficients for intense daily rainfalls for E2-046 rainfall station, located at Caraguatatuba, São Paulo state. The data obtained through rain gauge refer to a continuous period (31 years of series) and had a strong correlation with the measurements of the rain gauge, validating the pluviographs reading, which attributed greater reliability to the results. The average coefficient “24 hours”/“1-day” found for the study region was 1.075, which differs significantly from the values found in literature. The relative deviation considering other durations, and consequently other precipitation coefficients in relation to the mean values of the disaggregation values of the E2-046 station reached 22.06% (18 hours/“24 hours”). The relative deviation of rainfall disaggregation coefficients of the station studied in relation to the mean coefficients for the cities of São Paulo State to small durations was quite high, reaching almost 50% (10 minutes /“24 hours”). This reinforces the need of using local disaggregation coefficients.