Abstract
In previous experiments, we observed that granite increases in volume near and in the fracture range in simple compression. This volume increase diminishes as the confining pressure is increases. Under 1800atm. confining pressure, the rock becomes rearly elastic and breaks down showing high brittleness. The bulk expansion is very much reduced. These phenomena are considered to be in a close connection with the porosity of rocks. An extraordinary increase in rupture strength with confining pressure was observed. The observed value of rupture strength is in a good agreement with Robertson's formura σD=6PH for sillicate rocks.
