Stresses induced by a demolition agent in non-explosive rock fracturing

Stresses induced by a demolition agent in non-explosive rock fracturing was analysed using the theory of elasticity and the thick-walled cylinder principle. Circumferential and radial stresses in rock induced by an internally pressurized hole was first analysed under plane strain condition. Stresses perpendicular to the line connecting two adjacent holes were calculated based on coordinate transformation. A parametric study was carried out to investigate the influence of spacing and size of hole on the stress distribution. The analytical model provides a method to determine the optimum hole spacing and size as well as the time needed for fracturing rocks with properties similar to those employed to determine the pressure-time function of the demolition agent. It is found that tensile stress decreased dramatically with the increasing of hole spacing, while it increased with increment of hole size but the influence of spacing on stress changes was more significant than that of hole size. It is also concluded from the study that tensile stress in the middle of two holes decreased dramatically with a logarithmic distribution when solely increasing hole spacing. As can be anticipated more time is required for rock fracturing and breaking when hole spacing is increased for both soft and hard rocks.