DESTRESSING IN MINE ROADWAYS UNDER HIGH PRESSURE.

For the purpose of designing tunnel supports, the properties of the rocks in the roadway strata and the stress conditions therein can be divided into the following two extreme categories: rocks which are strong enough to withstand the imposed stress conditions as a rresult of tunnel drivage. Such an excavation will either not require any support or will require minimum support; and rocks which are very weak, with the pressures acting upon them being so high that they cannot be supported with the support systems available; or maintenance costs are so high as to make the project uneconomical. Paper discusses the suggested approaches to solution of either case based on destressing technique.