METHOD FOR SURVEYING BOTTOM DEPTH OF UNDERGROUND BASE STRUCTURE

摘要

PROBLEM TO BE SOLVED: To measure the bottom depth of an underground base structure simply with high accuracy.;SOLUTION: An electrode sonde arranging three or more electrodes with constant intervals is inserted into an inspection hole by an underground base structure. Out of three selected equally-spaced electrodes, one is set to be a current electrode C1, while the other two are set to be potential electrodes P1, P2. A constant current is applied through between an infinite electrode C2 arranged on the surface of the earth and the current electrode C1 of the electrode sonde, and potential occurring within the earth is measured by the pair of potential electrodes P1, P2 as a potential difference. A curve which changes from the high resistivity side to the low resistivity side is found out of two kinds of apparent resistivity curves in the forward and backward directions of the three electrodes C1, P1, P2 within the electrode sonde used in the measurement by multiplying by a coefficient corresponding to the electrode arrangement and electrode interval from a measured current value and potential value. The bottom depth of the base structure is determined to be a position showing the maximum slope at a position nearest to the high resistivity side of the curve, thereby searching for the bottom depth of the underground base structure with higher accuracy regardless of experience.;COPYRIGHT: (C)2011,JPO&INPIT