A self-drilling rock bolt assembly including a drill head mechanism and a fluid delivery system operatively associated with each other and adapted in use to secure with pre-tension, chemically, via injection, a self-drilling rock bolt into a strata; the rock bolt including a shaft having a cutting end and a driving end; the assembly including: a. the drill head mechanism having: a bolt coupling portion to releasably engage with the driving end of the rock bolt, wherein rotation of the bolt coupling portion rotates the rock bolt, wherein the bolt coupling portion is located in a central axial position of the drill head mechanism; a central hollow portion providing access to a fluid connection port of the rock bolt; and a nut coupling portion to releasably engage with a nut element located on the shaft of the rock bolt, wherein rotation of the nut coupling portion rotates the nut element, wherein the bolt coupling portion sits inside the nut coupling portion; b. the fluid delivery system having: an injection nozzle in communication with one or more sources of fluid (319, 321) for delivering measured quantities of one or more fluids to a predetermined location about said assembly, each source of fluid (319, 321) including a reservoir (310, 311, 312) in fluid communication with a priming pump (316, 317, 318), the priming pump (316, 317, 318) being in fluid communication with the displacement pump (313, 314, 315), the displacement pump (313, 314, 315) being in fluid communication with the injection nozzle, so that said fluid from said reservoir (310, 311, 312) is adapted to be pumped to said predetermined location; a cleaning flush phase for each separate internal passage (331, 332) within the injection nozzle, that has each cleaning fluid sourced from a different reservoir pressure source; whereby in use said drill head mechanism drives the rock bolt into the strata by rotating in a drilling direction the rock bolt and nut element at the same rate such that the nut element remains in the same position relative to the shaft of the rock bolt. a. the drill head mechanism having: a bolt coupling portion to releasably engage with the driving end of the rock bolt, wherein rotation of the bolt coupling portion rotates the rock bolt, wherein the bolt coupling portion is located in a central axial position of the drill head mechanism; a central hollow portion providing access to a fluid connection port of the rock bolt; and a nut coupling portion to releasably engage with a nut element located on the shaft of the rock bolt, wherein rotation of the nut coupling portion rotates the nut element, wherein the bolt coupling portion sits inside the nut coupling portion; a bolt coupling portion to releasably engage with the driving end of the rock bolt, wherein rotation of the bolt coupling portion rotates the rock bolt, wherein the bolt coupling portion is located in a central axial position of the drill head mechanism; a central hollow portion providing access to a fluid connection port of the rock bolt; and a nut coupling portion to releasably engage with a nut element located on the shaft of the rock bolt, wherein rotation of the nut coupling portion rotates the nut element, wherein the bolt coupling portion sits inside the nut coupling portion; b. the fluid delivery system having: an injection nozzle in communication with one or more sources of fluid (319, 321) for delivering measured quantities of one or more fluids to a predetermined location about said assembly, each source of fluid (319, 321) including a reservoir (310, 311, 312) in fluid communication with a priming pump (316, 317, 318), the priming pump (316, 317, 318) being in fluid communication with the displacement pump (313, 314, 315), the displacement pump (313, 314, 315) being in fluid communication with the injection nozzle, so that said fluid from said reservoir (310, 311, 312) is adapted to be pumped to said predetermined location; a cleaning flush phase for each separate internal passage (331, 332) within the injection nozzle, that has each cleaning fluid sourced from a different reservoir pressure source; an injection nozzle in communication with one or more sources of fluid (319, 321) for delivering measured quantities of one or more fluids to a predetermined location about said assembly, each source of fluid (319, 321) including a reservoir (310, 311, 312) in fluid communication with a priming pump (316, 317, 318), the priming pump (316, 317, 318) being in fluid communication with the displacement pump (313, 314, 315), the displacement pump (313, 314, 315) being in fluid communication with the injection nozzle, so that said fluid from said reservoir (310, 311, 312) is adapted to be pumped to said predetermined location; a cleaning flush phase for each separate internal passage (331, 332) within the injection nozzle, that has each cleaning fluid sourced from a different reservoir pressure source;