Stress measurements in Scandinavian bedrock-conditions, results and interpretation

In situ stress measurements in Scandinavian bedrock are reviewed and discussed. The conditions precedent in order to obtain reasonably reliable three - dimensional stresses in the rock mass space mosaic structure are analyzed. It is concluded that measurements with the LEEMAN three - dimensional or door - stopper method and with the modified LEEMAN - HILTSCHER method give within a very small volume (less than a few hundreds of cm3). Generally, it can be stated that the stress measurements indicate higher horizontal compression stresses and shear stresses than should be expected from elastic theory. Most of the stress values obtained with the measuring methods judged to be reliable can be interpreted as residual stresses caused by creep phenomena in the rock mass during late glaciations. It is concluded that it will probably be fairly easy to find Swedish bedrock, where qualified rock tunnels (chambers) with moderate span can be cut out at 100-1000 m depth without any manifest stability problems, excavation difficulties or heavy reinforcements to be anticipated from rock stress conditions