Rock masses are initially stressed in their current in situ state of stress and to a lesser natural state. Whether one is interested in the extent on the monitoring of stress change. formation of geological structures (folds, faults, The subject of paleostresses is only briefly intrusions, etc. ), the stability of artificial struc- discussed. tures (tunnels, caverns, mines, surface excava- The last 30 years have seen a major advance our knowledge...