Geological conditioning aspects for piezocone test interpretation for stratigraphical identification in geotechnical and geo-environmental site investigation / Condicionantes geológicos na interpretação de ensaios de piezocone para identificação estratigráfica na investigação geotécnica e geoambiental

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In situ tests for geotechnical and geo-environmental site investigation embraces a variety of soundings and tests to map and define stratigraphic logging and specific design parameters for each kind of job. Stratigraphic logging and soil classification are a common stage to all investigation programs and frequently they are performed throughout logging tests which results in local vertical information. The main objective of this research is to evaluate the influence of geological history in the interpretation of piezocone tests for stratigraphic logging. Seismic piezocone tests were carried out to try to identify difference response between lateritic and non lateritic soils. Resistivity piezocone tests were carried out to evaluate salt-water intrusion within a shallow sedimentary aquifer. In this sense, nine sites with different geologic conditions, representing extensive area from Brazil, were selected and investigated. They include quaternary sediment sequences on the brazilian coast, tafrogenic sedimentary sequences and tropical soils originated from weathering of Paraná basin sedimentary and igneous rocks. Piezocone tests were effective for stratigraphic logging, sediment classification as well as to estimate geotechnical design parameters based on correlations for sedimentary sediments. For these type of soils, the international experience developed for sedimentary soils from North America and Europe can be used. Resistivity piezocone tests were effectively useful to identify salt-water intrusion within a sedimentary aquifer and contributed to refine soil stratigraphy. Consistent relations between geologic history and geotechnical properties were established based on piezocone test results. In the other hand, the weathering process produces profile transformations in the tropical soils and imposes limitations to stratigraphy definition, soil classification and to estimate geotechnical soil parameters based on these correlations. For tropical soils, the resistivity piezocone test was not efficient to identify the groundwater level and to refine stratigraphic logging, probably due to the presence of iron oxides and deep groundwater. The seismic piezocone tests were effective to separate lateritic and non-lateritic soils throughout the relation between maximum shear modulus and poit resistance (Go/qc). It is concluded that the geological information is fundamental for the interpretation of piezocone results, especially to integrate several logging test data, to identify spatial distribution and variability of soil layers. In this sense, combined tests, such as the seismic piezocone, where more than one parameter can be measured at the same location, contribute to minimize variability effects in the estimation of geotechnical soil parameters

ASSUNTO(S)

piezocone história geológica resistividade estratigrafia resistivity piezocone stratigraphy variability sísmica seismic geological history

ACESSO AO ARTIGO

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