Techniques Used in Studying the Fracture Mechanics of Rock

PARTIALLY BROKEN MATERIAL WAS OBTAINED TO STUDY THE GROWTH OF CRACKS DURING BRITTLE FRACTURE. IN UNIAXIAL COMPRESSION THIS WAS ACCOMPLISHED BY PLACING A SIMPLY SUPPORTED BEAM IN PARALLEL WITH THE ROCK SPECIMEN TO LIMIT THE ADVANCE OF THE RAM WHEN THE LOAD-CARRYING ABILITY OF THE SPECIMEN DECREASED. UNCERTAINTIES ASSOCIATED WITH STRAIGHT CYLINDRICAL SPECIMENS WERE AVOIDED BY USING CYLINDERS WITH A REDUCED CENTRAL SECTION. VOLUMETRIC STRAIN WAS COMPUTED FROM TWO PERPENDICULAR STRAIN GAGES. THE ONSET OF CRACK GROWTH AND THE WORK EXPENDED AGAINST CONFINING PRESSURE WERE FOUND WITH THE AID OF PLOTS OF VOLUMETRIC STRAIN VERSUS STRESS. MEASUREMENTS OF LINEAR COMPRESSIBILITY INDICATED THE PREDOMINANT DIRECTION OF CRACK GROWTH AND THE INCREASE IN POROSITY. /AUTHOR/