Study on stress redistribution around a rock chamber based on field measurements with progressive excavations

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Although stress redistribution due to excavation is most important phenomenon to assess stability of an underground chamber, it does not seem to be made clear sufficiently by field measurements. We took note of the two methods of field measurements for that ; one is Acoustic Emission monitoring, and the other one is the measurement of small strain changes in rock. We developed the two methods through small scale in situ tests and applied them to monitor three real chambers for underground powerhouses. As the results, we found these methods are applicable to investigate stress redistribution in fields. Furthermore, we observed that stress does not always concentrate in only one location near a chamber wall, and, in some cases, it concentrates in two or three locations around chamber depending on interlocking of rock masses separated by discontinuous planes.