UBC Theses and Dissertations
Development of an electrical resistivity cone for groundwater contamination studies Weemees, Ilmar Andrew
The evaluation of groundwater quality has become increasingly important as more industrial waste and solid domestic refuse comes into contact with groundwater. Often the quantity and extent of contamination is determined by direct sampling of the groundwater and soil. An alternative method of detecting contaminated groundwater is by noting the electrical resistivity of the contaminated soil. The feasibility of logging resistivity while conducting cone penetrometer testing has been investigated in this research. To this end a two stage program was devised, consisting of lab testing and then field tests of a working tool. Lab testing was carried out using a prototype probe designed to evaluate the feasibility of the project. The lab testing consisted of determining the resistivity of a number of different soil, electrolyte, and organic contaminant mixtures while varying the configuration of the probe. On the basis of lab testing the necessary requirements for the module dimensions and electronics were chosen and were fine tuned by field tests. The module itself consists of an insulated four electrode array and is mounted behind a standard 15 sq cm piezo-cone (CPTU). Upon completion of the development phase the instrument was tested at four different sites. From field testing it was determined that the resistivity cone (RCPTU) was able to accurately map changes in groundwater chemistry on the basis of resistivity measurements. The results of the resistivity testing were verified by groundwater sampling. It was also found that changes in lithological properties, as determined by the cone penetration test (CPT), could influence the resistivity. Basic guidelines for the use of the RCPTU in contaminant investigations are presented.
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