Application of Conical-ended Borehole Technique to Discontinuous Rock and Consideration.

概要

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The combination of the 16-elements conical-ended borehole technique and the compact overcoring method is an excellent method to measure the three dimensional state of stress by means of stress reliving in hard rock. In the present paper, this method has been applied to the discontinuous rock and the characteristics of stress distribution on the periphery of faults have been examined by the systematic stress measurement at multipoints in a single borehole. Subsequently, it has been discussed that numerical simulation is indispensable to grasp macroscopic initial stress field.<BR>Firstly, it has been shown that the in situ stress measurement performed at 18 adjacent points by means of the combination of the 16-elements conical-ended borehole technique and the compact overcoring method within diorite and granodiorite, and it has been discussed that the present method is promising method to measure the absolute stress. Moreover, it has been clarified that the number of measuring points can be drastically increase by this method.<BR>Secondly, from comparison of the measured value with the results by the displacement discontinuity method (DDM) analysis, it has been clarified that the faults are the geological primary factor controlling the initial stress distribution and the cracks are the secondary cause of disturbance of the initial stress distribution.
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