Abstract: A tool for use in initiating a hydraulic fracture in a bore hole comprises an elongate cylindrical bore hole packer structure (11) having an inner longitudinal passage (12), a mid-portion (13) provided with ports (14) extending outwardly from passage (12) to the exterior periphery of the packer structure (11) and expandable circumferential well portions (15A) surrounding the inner longitudinal passage (12) to each side of the mid-portion (13). In use of the tool the circumferential wall portions (15A) can be expanded by injection of hydraulic fracturing fluid into passage 12) and exit of the injected fluid through the ports (14) to produce a pressure difference between the inside of the packer structure and the outside of the packer structure as the fluid passes through the ports (14) such that the hydraulic fluid exiting the packer structure can initiate a fracture.

Abstract: A tool for use in initiating a hydraulic fracture in a bore hole comprises an elongate cylindrical bore hole packer structure (11) having an inner longitudinal passage (12), a mid-portion (13) provided with ports (14) extending outwardly from passage (12) to the exterior periphery of the packer structure (11) and expandable circumferential well portions (15A) surrounding the inner longitudinal passage (12) to each side of the mid-portion (13). In use of the tool the circumferential wall portions (15A) can be expanded by injection of hydraulic fracturing fluid into passage 12) and exit of the injected fluid through the ports (14) to produce a pressure difference between the inside of the packer structure and the outside of the packer structure as the fluid passes through the ports (14) such that the hydraulic fluid exiting the packer structure can initiate a fracture.

Abstract: A method of mining that makes use of hydraulic fracturing. The method comprises fracturing an ore body hydraulically by introducing fluid rapidly into a bore or fissure in the ore body such that pressure in the bore or fissure builds up rapidly and it fractures the surrounding ore body. This enables the surrounding ore body to cave into a suitable space such as an undercut from which the ore can then be recovered. The method is particularly useful in block caving as a replacement for explosives.