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| | Abstract | | TTSP has been developed as the method to investigate the geological situation ahead of the tunnel face. Signal source and geophone placement is inside the holes of about 25m long, which are drilling perpendicular to the tunnel axis, unlike that which the conventional HSP and TSP have been done. By this arrangement, signal processing, which was not able to be used by the conventional method, becomes possible to capture the changes in the physical properties of rock at the position of the seismic reflecting surface in front of the tunnel face. Also, TTSP data will be processed in a manner used in the AVO. In this paper, using the data from the field, the applicability of the method of averaging approximation of elastic wave velocity will be confirmed. In addition, under the assumption that Poisson's ratio is about two-fifths, the S-wave reflection coefficients and change rates of Poisson's ratio are calculated. In comparison with the result and that calculated under the assumption about one-third of Poisson's ratio, the improvement of the analysis is confirmed. By a further experiment, it is aiming that the result by TTSP to be the higher precision. |
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