EXPLORATION : ITS EVALUATION IN HARD ROCK TUNNELLING

THE AUTHOR RECALLS THE IMPORTANCE OF GEOLOGY AND GEOLOGICAL FORECASTS IN TUNNEL CONSTRUCTION. HOWEVER, IT IS DIFFICULT TO JUSTIFY GEOLOGICAL INVESTIGATIONS IF THE RESULTS ARE OUT OF PROPORTION WITH THE COST OR OVERALL TIME OF A CONSTRUCTION PROJECT. THE AUTHOR PROPOSES A MATHEMATICAL MODEL DESCRIBING TUNNEL CONSTRUCTION COSTS AND THE USE OF THE NOTION OF PROBABILITY. GEOLOGICAL INVESTIGATION IS STUDIED, PARTICULARLY THE DIFFERENT PHASES OF THE INVESTIGATION PROGRAMME, THE SELECTION OF THE GEOLOGICAL PARAMETERS FOR EVALUATING THE EXCAVATION AND ITS SUPPORT, AND THE TECHNIQUES USED TO DETERMINE THESE PARAMETERS. THE UNCERTAINTY AND LIMITS OF SITE INVESTIGATION ARE DISCUSSED. THE TECHNIQUE IS APPLIED TO A REAL CASE, THE HAROLD D ROBERTS TUNNEL.