INSTABILITY PHENOMENON

UNDERGROUND EXCAVATIONS IN HARD ROCK SUBJECT TO DYNAMIC LOADING CAUSED BY NUCLEAR DETONATION MAY EXPERIENCE VIOLENT COLLAPSE (ROCKBURSTING) SIMILAR TO WHAT IS OBSERVED IN DEEP MINING OPERATIONS. THIS PROPOSAL AIMS AT DEVELOPING A METHODOLOGY TO DETERMINE THE CIRCUMSTANCES FOR WHICH ROCKBURST WILL OCCUR, BASED ON THE ASSUMPTION THAT COLLAPSE OF THE CAVITY IS TRIGGERED BY A SURFACE BUCKLING OF THE WALLS OF THE EXCAVATIONS. THE METHODOLOGY WILL RELY ON A FINITE ELEMENT DISCRETIZATION TO DETERMINE THE CONDITIONS OF INSTABILITY, BY SEARCHING THE CONDITIONS FOR WHICH ONE OF THE EIGENVALUES OF THE INCREMENTAL STIFFNESS MATRIX VANISHES. THE OBJECTIVES OF THIS PHASE I PROPOSAL ARE TO ASSEMBLE A FINITE ELEMENT CODE, IMPLEMENT CONSTITUTIVE EQUATIONS TO MODEL PRESSURE-SENSITIVE DILATANT ROCK, AND VALIDATE THE NUMERICAL MODEL AGAINST THEORETICAL SOLUTIONS ON THE SURFACE INSTABILITY OF A HALF-PLANE SUBJECT TO LATERAL LOADS.