Electronic blasting systems typically employ one or more blasting apparatuses located in or near a vicinity of the blast site, in communication with a blasting array comprising a plurality of detonators or detonator assemblies positioned at the blast site. Typically, each detonator includes an outer casing, a base charge, and means to achieve instantaneous or delayed actuation of the base charge upon receipt from a blasting machine of a command signal to FIRE. If required, each detonator may form a component of a larger detonator assembly adapted to cause actuation of a larger explosive charge to achieve rock fragmentation at the blast site. For example, each detonator may be positioned in a booster, such that actuation of the base charge of the detonator causes actuation of a portion of explosive material in the booster. Moreover, the booster may be located adjacent, for example, an explosive emulsion composition located down a borehole, such that actuation of the booster causes ignition of the explosive emulsion composition.
Prior to blasting machine/detonator communication, the blasting array is established at the blast site. The detonators, and optionally associated components, are positioned at desired locations in or near rock at the blast site, either at or near a surface of the ground, or underground. The detonators are usually placed in boreholes which are subsequently charged with explosive. Communication is then established between each blasting machine and its associated detonator assemblies. Such communication may involve wired communication, or any means of wireless communication. In any event, it is desirable to achieve two-way communication with the detonator assemblies, so that the blasting machine may communicate with the detonator assemblies, and if required the detonator assemblies may respond. For example, a blasting machine may transmit command signals (e.g. ARM, DISARM, or FIRE signals) to a detonator assembly that require no response. However, at other times a blasting machine may send an inquiry signal to assess a status of a detonator assembly at the blast site, wherein the inquiry signal requires the detonator assembly to respond in some way, for example to confirm the operating status of the detonator, information programmed into the detonator assembly (e.g. detonator identity, delay times for firing etc.), or the environmental conditions of the detonator assembly. Reliable two-way communication between one or more blasting machines, and a plurality of detonators at a blast site, either via wired or wireless communication, is of increasing importance for modern electronic blasting systems.
Each blasting machine may be programmed with identity information for each associated detonator assembly, so that detonators can be addressed by a blasting machine on an individual basis. For example, each blasting machine may retrieve identity information directly from a detonator assembly via direct two-way communication therewith. Alternatively, each blasting machine may be pre-programmed with detonator identification information, such as factory allocated detonator identification codes that are programmed into the detonator assemblies upon manufacture. In other mining operations, each detonator assembly (or corresponding detonator assembly) positioned at the blast site may be ‘visited’ by a blast operator carrying a portable electronic device such as a logger. A logger communicates via short-range communication with each detonator to generate and store a detonator list for the blast array comprising, for example, detonator identification codes, and optionally firing times for the detonators, which may be optionally programmed into the detonator assemblies by the logger. The detonator list may then be transferred from the logger to each blasting machine, thereby to make each blasting machine ‘aware’ of the detonators in the blasting array. Once the blasting machines are programmed in some way with the detonator identification information, the detonator assemblies are ready to be individually addressed by their associated blasting machine.
Typically prior to blasting machine/detonator assembly communication, the blast site is made safe for blasting by clearing all blasting personnel, mining equipment and vehicles a sufficient distance from the blast site to avoid any hazards (e.g. flyrock) resulting from the blast. As a result, all production operations within or near the blast zone must be stopped, to provide a time window for checking the operability of the blasting array, and execution of the blasting event. It is desirable for the time window to be as short as possible, so that stoppage of production operations can be minimized. In addition, a shorter time window would reduce the possibility that the safety and security of the blast site is compromised, for example by a person entering the blast zone before the blasting event is complete.
There remains a continuing need to develop methods of blasting, and corresponding blasting apparatuses suitable for application of such methods, that permit a blasting event to be conducted more rapidly, more efficiently, and more safely. In particular, two-way communication between a blasting machine and detonator assemblies can be time consuming. Therefore, there remains a need to shorten the time window required for a blasting event, including the time required to establish and/or verify communication between one or more blasting machines, and a plurality of detonators or detonator assemblies.