ABSTRACT:

The present report deals with utilizing the strain energy stored in the rocks during loading to failure process. The strain energy stored in the rock and its dissipation is analyzed with damage as the criteria. The inherent flaws distribution contributing to damage and further fracturing process is addressed using the two-parameter Weibull distribution. Finally with the aid of stress-induced damage, the failure strength of rock is decreased by the amount of strain energy residual. To validate the results, unconfined compression tests were conducted on an Argillite sample at constant rate of strain using MTS compression testing machine.

INTRODUCTION

Amount of residual strain energy for a particular rock depends on the extent of ductility or brittleness and load intensity at the point of failure (refer to figure 1). On application of load the rock behaves elastically and then assumes ductility depending on degree of confinement (5). During the process some amount of energy is stored in the rocks as strain energy and released gradually after failure, which varies exponentially with time (7). This residual strain energy cannot be recovered after the failure of the material because of irregular shape of its fragments and random orientation of the stress directions in the fragments. Alternatively strain energy can be utilized by using it in the same fracturing process. Long-term loading is one process, which reduces the crushing energy drastically, but it is not practically feasible process due to very long periods of loading.

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