A New Method for Determining the Physical Parameters of Large Soil and Rock Samples in Situ

A new method is introduced for determining the electrical and mechanical parameters of large samples of materials in situ. A set of linear electrodes in boreholes forms a square pattern; positive and negative electrical potentials on alternate electrodes create symmetry planes which define several 'cells'; a given fraction of electric current leaves an electrode and reaches a corresponding electrode. It is thus possible to obtain an impedance characteristic for each cell. The situation is basically two-dimensional, so a Schwarz-Christoffel transformation may be used followed with electrical calculations to obtain the conductivity and the permittivity of the cell material. The mechanical parameters of the cells are obtained in a similar manner. A mechanical disturbance is generated in the central borehole and the travel time to the other boreholes is measured along with the attenuation. The mechanical parameters are computed and correlated with the electrical parameters. (Author Modified Abstract).