ＡＥ法とＤＲＡによるコアからの原位置地圧計測

Abstract

Experimental studies have been undertaken to explore the applicability of acoustic emission (AE) method and deformation rate analysis (DRA) to in situ stress estimation. Firstly, the paper discusses the influence of delay time and confining pressure on the recollection of the maximum previous stress based on laboratory experiments of Inada granite previously stressed under uniaxial or confining pressure. The main conclusions are: 1) The elapsed time, up to 7 years, does not produce any detrimental effects on the recollection of the maximum previous stress, and the stress could be estimated from AE method and DRA within 10% difference. 2) The specimen, previously stressed under the confining pressure, produced the significant change in AE and strain behaviors at the stress level which is close to the previous stress axially applied to the rock specimen. So, it was concluded that AE method and DRA allow us to estimate the previous stress along the loading axis of a specimen. Secondly, to show the applicability of the technique to in situ stress measurement, the paper discusses the results on drilled core rock obtained from two mines in Australia. Rock cores were obtained from two mines in Australia. The stresses were estimated using the AE method and DRA in different directions. The main conclusions are : 3) Although the uniaxial compression tests were carried out 30 to 40 days or 60 to 70 days after the drilling, the Kaiser effect in AE occurrence was clearly observed in the most tests. 4) The estimated stresses from the AE method were well consistent with that from DRA except one kind of rock core specimen, and also agreed well with the results obtained by hollow inclusion cell developed by CSIRO.