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Laboratory Equipment Developingto Eletric Resistivity Measurement

Grant number: 08/05643-9
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): September 01, 2008
Effective date (End): August 31, 2009
Field of knowledge:Engineering - Civil Engineering - Geotechnical Engineering
Principal Investigator:Anna Silvia Palcheco Peixoto
Grantee:Antonio Carlos Canhada Lopes da Silva
Home Institution: Faculdade de Engenharia (FE). Universidade Estadual Paulista (UNESP). Campus de Bauru. Bauru , SP, Brazil

Abstract

The resistivity piezocone (RCPTU) is becoming a very important tool in the geo-environmental investigation of contamination plumes. The standard piezocone, considered quasi-static, consists on pushing the cone penetrometer into the ground with a constant rate of 2cm/sec (approximately 1m/min). The RCPTU include a resistivity sensor that is located behind the standard piezocone. This resource allows resistivity measurements of bulk soil. This electric current flux that can be measured as conductivity, or its inverse, resistivity, when measured in the soil, in a series of tests, allows the detection of a probable presence of certain substances by comparing to reference values. In areas where the reference values are exceeded, complementary evaluations may be made by samples collected in discrete depth for latter chemistry analysis. This reference values are established from field experience or from similar geological environments. However those found in the literature refers to typical soils from temperate climates, not reflecting soil behavior from tropical climates. This research goal is the development of a laboratory equipment to obtain the resistivity in order to control the intervening factors like wet, compaction, porosity and saturation degree, providing subsidies extensive analyses of the resistivity values obtained of RCPTU in situ test. In this way, it is necessary the development of some equipments like sensor and samplers. It is planning to study the resistivity measurement in two ways: with vertical plates located in the extremity sides of sample, leading to real resistivity; and a sensor like that one of RCTPU, but with minor dimensions, to compare with in situ results. The equipment details are in the report. This study is part of a wider research, Development of Electric Resistivity Equipment for Geotechnical and Geo-Environmental Soil Investigation; Fapesp Number 07/06085-7, of PhD Anna Silvia Palcheco Peixoto. In this way, the mainly objective of this research study a rational manner of obtaining reference values for results gotten in field associating to laboratory tests that shows with security the need, or not, of detailing the geo-environment investigation.