A rock fragmentation device and method is provided which includes a shaft and a plurality of expandable members positioned along a length thereof. The shaft has a hollow length therethrough for the passage of a pressurized fluid, and a plurality of feed apertures for delivery of the pressurized fluid to the expandable members. The shaft further includes a feed inlet for receiving the pressurized fluid from a hydraulic system. The plurality of expandable members each have an inner diameter dimensioned to receive the shaft in a tightly engaging connection, and are positioned on the shaft in fluid tight engagement effective for receiving pressurized fluid via the feed apertures without leaking fluid. The expandable members are expandable, upon filling with the pressurized fluid, to sufficient dimensions to break apart rock when fitted inside a cavity formed therein.