Development of New Electrical Resistivity Method for Soil Survey

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A method to investigate the geological formation structure by measuring and analyzing earth electrical resistivity has been known well as the specific resistivity method. Now it is the most important method for underground sensing technology as well as the artificial seismic method. Recently they are also progressing more rapidly corresponding to development of computer technology, mew sensors and many measurement instruments. In this research we try to apply these techniques to soil survey and to develop a new method for it. The outline is as follows.1. Soil electric resistivity varies, closely related with physical and chemical characteristic of soil. First, relations between electric resistivity of soil, pore structure, grain size, physio-chemical properties of mineral surface, and soil structure (dispersion and aggregation system) are investigated and discussed. Then, it is concluded that the electrical resistivity would be very useful index in soil survey.2. Wenner Method and Shulunberger Method are generally applied to measure and analyze the earth electric resistivity. These methods require much experiences in analysis of observed apparent resistivity, and personal error is tend to be included depending on skill of analyst. Then, the new method is developed to analyze observed data automatically excluding human factor as possible.3. As conventional methods are generally applied to the geological survey, the objective geological formation is deep. But in soil survey the objective soil strata are relatively sallow on the contrary, and it is important to survey in wide horizontal extent. Under consideration of these conditions, a new method for soil survey using the electric potential distribution in place of electric current in conventional method is developed.4. The new method and conventional ones are compared and evaluated in field application test. Characteristics of these methods are discussed.