IMPROVEMENT IN THE INTERPRETATION OF STRESS MEASUREMENTS BY USE OF THE OVERCORING METHOD - DEVELOPMENT OF A NEW APPROACH

Determination of the state of the initial stresses in a rock formation is still one of the most important and complex problems in geotechnic s. The over-coring method of measuring the stresses is one of the meas urement methods most frequently used in geotechnics. It has been shown to be highly suitable for measuring the stresses in ''hard and sound' ' rocks. However, applied to rocks which have a partialy elastic behav iour the method comes up against many problems the biggest of which ar e. (1) the non-elastic behaviour of the rock; and (2) the presence of natural fractures or those caused by the overcoring operation. These p roblems make it impossible to obtain correct deformation measurements which can be interpreted in terms of stresses. To overcome these probl ems, a new method has been developed based on the use of the deformati ons recorded at the start of the overcoring tests this method is the s ubject of the present article. (C) 1998 Elsevier Science B.V. All righ ts reserved.