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Laboratory Test to Study the Eletric Resistivity in a Clean Sand

Grant number: 08/05879-2
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:Jônatas Menezes Costa
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 standart 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 contains a resistivity module that is located behind the standart 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 references 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 bibliography refers to typical soils from temperate climates, not reflecting soil behavior from tropical climates. The goal of this research to study, in laboratory, the behavior of the electric resistivity in pure sand, controlling the intervening factors, like humidity factor, compaction, porosity and saturation degree, providing subsidies for a extensive study involving among others the construction of laboratory equipment to compare the field results and, mainly, to attain reference values. This study is a part of a wider reserch "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 references values for the results gotten in field associating to laboratory tests that shows with security the need, or not, of detailing the geo-environmental investigation