Possibility of prestressing rocks in Underground excavations

Abstract

In civil engineering the prestressing methodology enables the engineer to induce in the structure states of stress that are equal and opposite to those due to the applied forces. In underground excavations, when this modifies the state of stress of the rock masses, it is also possible to apply compression stresses which, if rightly orientated, improve the stability of the rock. In this paper details are given of the methods of calculation and execution technology of a project which sought to nullify the thrusts of the vault of an underground power station, so that the stability of the side walls should not be impaired. It is reasoned why it was decided to prestress the rock as a method of achieving this object, and the features and factors which were involved are described. Information is also given of how the factors of safety of certain mountain massifs were improved, after the excavation of the above mentioned power station gave reason to believe that parts of the mountain rock might thereby become heavily overloaded.