BLAST CONFIRMATION

Abstract

A communication module which is linked to a detonator which is initiated in response to a fire command signal, and wherein the communication module includes a transmitter which transmits a wireless signal which is dependent upon initiation of the detonator and which contains or conveys an identifier which uniquely identifies the detonator.

Claims

1-19. (canceled)

20. A blast system which includes a blast controller, a plurality of boreholes at a blast site, each borehole being charged with explosive material, a plurality of detonator assemblies respectively associated with said plurality of boreholes, each detonator assembly including a communication module, a detonator which in use is positioned inside a borehole exposed to the explosive therein, and conductors which connect the detonator to the communication module, wherein the communication module includes a control circuit which in response to receipt of a blast signal from the blast controller transmits a fire command signal at a time A via the conductors to the detonator thereby to cause initiation of the detonator at a time B, and a transmitter for transmitting a wireless signal, to the blast controller, which wireless signal contains or conveys an identifier which uniquely identifies the detonator assembly from which the wireless signal originated, said wireless being dependent, at least upon initiation of the detonator, wherein the transmission of said wireless signal from the detonator is selected from the following: (a) the transmission of the wireless signal commencing at the time B; (b) the wireless signal is transmitted at least for a period within which a measurement is made of a characteristic which is generated upon initiation of the detonator at the time B; (c) the wireless signal is transmitted continuously at or after the time A up to the time B; (d) the wireless signal is transmitted at the end of a time interval after the time B which interval is of sufficient duration to enable a measurement to be made of at least one event which is associated with initiation of the explosive, and wherein at least said wireless signals which are transmitted simultaneously by said transmitters from said plurality of detonator assemblies are modulated to promote multiplexing of the signals.

21. A blast system according to claim 20 wherein each of the wireless signals is modulated by a technique selected from time-, frequency-, and amplitude-modulation, and phase shifting.

22. A blast system according to claim 21 wherein the modulation technique is used to identify one or more specific blast events.

23. A blast system according to claim 20 wherein each detonator assembly respectively includes a memory unit in which is stored a unique identifier for the detonator assembly.

24. A blast system according to claim 20 wherein each transmitted wireless signal is adapted to identify the detonator assembly from which the wireless signal was transmitted.

25. A blast system according to claim 20 wherein the respective wireless signal transmitted from each detonator assembly contains information on the time of initiation of the detonator, and wherein the blast controller compares said time of initiation of the detonator to a programmed initiation time of the detonator to assess the response of the detonator assembly to the fire command signal.

26. A blast system according to claim 20 wherein the blast controller is configured to correlate receipt of each respective wireless signal with information relating to one or more of the following effects of blasting: electromagnetic pulse generation, sound generation, vibration generation, and visual observation.

27. A blast system according to claim 20 wherein in (a) the said characteristic is the velocity of detonation of the explosive in the borehole from what the wireless signal originates.

28. A blast system according to 20 wherein in (d) the said at least one event is the velocity of detonation of the explosive in the borehole from which the wireless signal originates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention is further described by way of examples with reference to the accompanying drawings in which:

[0044] FIG. 1 illustrates aspects of a blasting system according to the invention,

[0045] FIG. 2 illustrates in block diagram form some components of a detonator assembly according to the invention, and

[0046] FIG. 3 is a graphical depiction of different inventive techniques upon which the operation of the detonator assembly of the invention can be based.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0047] FIG. 1 of the accompanying drawings schematically illustrates aspects of a blasting system 10 in which the principles of the invention are implemented.

[0048] The blasting system 10 includes a blast site 12 at which are formed a plurality of boreholes 16A, 16B . . . 16N at predetermined locations. Each borehole is charged with an explosive 18, as is known in the art.

[0049] The blasting system 10 includes a plurality of detonator assemblies 20A, 20B . . . 20N. Each detonator assembly is located in a respective borehole 16 exposed to the explosive 18 in the borehole.

[0050] The blasting system 10 includes a blast controller 22, and a receiver 24 which may be one of a number of similar receivers which are positioned at predetermined remote locations around the blast site 12. Alternatively the receiver is located at, or forms a part, of the blast controller 22. Depending on operational requirements it is possible to configure a selected detonator assembly to provide the function of a receiver 24 as is described hereinafter.

[0051] The detonator assemblies are physically substantially identical to one another although the operations thereof are not necessarily identical.

[0052] The detonator assembly 20A includes a communication module 34A which is configured to be positioned at an operative location relative to the borehole 16A at which the detonator assembly is to be used. Conveniently the module 34A is at a mouth 36A of the borehole 16A. The communication module 34A is connected by conductors 38A to a detonator 40A which is positioned at a desired depth in the borehole exposed to the explosive material 18.

[0053] FIG. 2 shows in block diagram form a detonator assembly 20.

[0054] The communication module 34 includes a power source 42, a signal generator 44, a transmitter/receiver module 46 which comprises a transmitter 46A and a receiver 46B and a control circuit 48. The listing of these components is not exhaustive and is given to enable the principles of the invention to be understood. An identifier 50 which uniquely identifies the detonator assembly is stored in a memory unit 52 which is in the communication module 34 or in the detonator.

[0055] The blast controller 22 is used to execute a blasting sequence in the blasting system according to predefined protocols. After all prescribed initial checking and programming steps have been taken a stage is reached at which the blast controller 22 transmits a blast signal 54 to the various detonator assemblies 20A . . . 20N. In each case the blast signal 54 is received by the receiver 46B and validated by the control circuit 48. In accordance with predetermined rules, the control circuit 48 then transmits a fire command signal 56 via the conductors 38 to the detonator 40. The fire signal 56 causes the detonator 40 to initiate at a predetermined time and the explosive 18, exposed to the detonator, is ignited.

[0056] In order to obtain confirmation that a detonator 40 has been initiated and that there has not been a misfire the transmitter 46A is used to transmit a wireless signal 60 to the receiver 24. The operation of the transmitter 46A is made dependent at least upon initiation of the detonator in any of a number of ways which are depicted graphically in FIG. 3.

[0057] The wireless signal 60 includes the identifier 50 which uniquely identifies the detonator assembly 20. This identifier 50 is linked to an identifier of the borehole 16 at which the detonator assembly 20 is used. The borehole can be numerically designated or it can be designated by means of its geographical position i.e. through the use of appropriate coordinates. That information is kept in a database which is accessible by a control computer, not shown, linked in any suitable way to the blast controller 22 and to the receiver 24.

[0058] The wireless signal 60 is produced in a controlled manner by the function of the control circuit 48 which actuates the signal generator 44. A signal produced by the signal generator is subjected to a modulation technique by a modulator 66, as is described hereinafter. The resulting modulated signal 70 is applied to the control circuit 48 and combined with the identifier 50 to produce a signal 72 which then, via the transmitter 46B, constitutes the wireless signal 60 which is transmitted from the detonator assembly 20.

[0059] At a blast site which includes a large number of boreholes and detonator assemblies, of the order of several thousand, technical challenges arise in distinguishing a wireless signal 60X sent from a detonator assembly 20X, from a wireless signal 60Y sent from a detonator assembly 20Y. The difficulty is compounded when the respective wireless signals, possibly from a large number of detonator assemblies, are sent simultaneously or substantially simultaneously i.e. with only a very small time interval between the actual transmission times of the wireless signals.

[0060] Despite this difficulty the transmission of a wireless signal from a detonator assembly 20 which confirms initiation of the detonator 40 presents an opportunity for information on one or more selected aspects of the detonation process, which can be collected or observed within a short time interval, to be included in the wireless signal 60.

[0061] FIG. 3 graphically depicts different methods for controlling a transmitter to generate a confirmatory wireless signal, optionally with the inclusion of data which is generated by the blasting process.

[0062] FIG. 3 shows a horizontally extending timeline with spaced apart transversely extending dotted lines marked A, B, C and D respectively. In respect of any given detonator assembly 20 the time A is the time at which the fire command signal 56 is sent by the control circuit 48 via the conductors 38 to the associated detonator 40.

[0063] The time B is the time at which the detonator is initiated, after a predetermined and programmed time delay interval, in response to the fire command signal 56.

[0064] The time C is a time at which the detonator assembly 20 has been consumed after ignition of the explosive 18.

[0065] The time D is a parameter which marks the end of a time interval, after the time B, which time interval is optionally used and which is of sufficient duration to enable measurements to be made of one or more events which are associated with the initiation of the explosive 16.

[0066] In a first technique designated M1 in FIG. 3, the transmitter 46A is caused to transmit a wireless signal 601 of relatively short duration starting at the time B.

[0067] In accordance with a second method M2 the transmitter 46A is caused to transmit a signal 602 starting at the time A or at any time after the time A but before the time B. What is important in this respect is that the signal 602 terminates at the time B i.e. when initiation is detected.

[0068] In a third method M3 the transmitter 46A is kept inoperative until the time D. A signal 603 is then transmitted. This is before the time C for, at the time C, the detonator assembly is destroyed by the ignited explosive 18.

[0069] In a method M4 transmission of a wireless signal 604 commences at the time B and ends at the time D. As may be appropriate selected information on the detonator and detonation process can be included in the signal 604.

[0070] In a method M5 transmission of a first signal 605A commences at the time A, or at any time after the time A but before the time B. Transmission of the signal 605A ends at the time B. Thereafter a second signal 605B is transmitted from the time B up to the time D.

[0071] The signals 605A and 605B can be distinguished from each other through the use of an appropriate modulation technique (MOD1, MOD2). For example the signal 605A may comprise an up-chirp signal while the signal 605B may comprise a down-chirp signal.

[0072] A method M6 is similar to the method M5 in that transmission of a first signal 606A commences at or after the time A and is continued up to the time B. This is followed by a second signal 606B the transmission of which commences at the time B and ends at the time D or prior thereto. The signals 606A and 606B are distinguished from each other by using different frequencies (F1, F2) for their transmissions.

[0073] A method M7 is similar to the method M5 in that transmission of a first signal 607A commences at or after time A and is continued up to the time B. This is followed optionally, after an interval of duration T, by transmission of a second signal 607B which can continue for a predetermined time interval which ends before the time C e.g. up to the time D. The signals 607A and 607B do not necessarily have to be distinguished from each other in that the receiver 24 associated with the blast controller has the capability to detect the stop-start in the transmission i.e. the stopping of the transmission of the signal 607A at the time B and the starting of the transmission of the signal 607B at or after the time B.

[0074] The blast confirmation process which has been described is based on the transmission of a signal where such transmission is dependent on detecting the ignition of a detonator. Also the transmission must take place before the transmitter which is used for transmitting the signal is destroyed by the explosive process. If the signals which are transmitted in the aforementioned way are reliably generated and transmitted and detected then the blast confirmation process as described herein works effectively. It does however fall within the scope of the invention for one or more additional techniques, linked to the effects of blasting, to be used in conjunction with the detection of the blast confirmation signal. These additional techniques are used to enhance the accuracy of the blast confirmation process for despite careful design errors can arise in signal generation, transmission, receipt and interpretation. As indicated hereinbefore an electromagnetic pulse is generated when an explosive is fired. Detection of that pulse is confirmatory of successful initiation. Audio signals and vibratory signals caused by an explosive process also indicate successful initiation. Visual surveys which rely for example on the use of cameras can monitor a blast site. These processes, taken in isolation can be defective in that due to various physical factors closely timed detonator firings are not easily distinguishable from each other. Despite inherent limitations in the observational methods they can however, with benefit, where possible be used in conjunction with the blast confirmation signal transmission technique described herein, and correlated therewith, in order to improve the reliability of blast detection.

[0075] FIG. 3 thus graphically depicts different ways in which a wireless signal can be transmitted from a detonator assembly to confirm initiation of the associated detonator and, where required, to transfer information relating to the velocity of detonation. This facility is implemented for each detonator assembly 20 in the blasting system. The different techniques in FIG. 3 are implemented at least by making the operation of the transmitter 46A dependent on initiation of the detonator. In the methods M2, M5 and M6 the transmissions of signals which commence prior to the time B are terminated at the time B. In the methods M1, M4, M5 and M6 the wireless signals are transmitted commencing at the time B. In the method M3 a signal is transmitted starting at the time D.

[0076] The confirmatory signals which are transmitted in any of the ways described in connection with FIG. 3 contain the respective identifiers 50 of the detonator assemblies 20 from which the wireless signals originated. In this way misfired detonators 40 in the blasting system can be identified in real time or after blasting by post-processing the signals received at a common point e.g. at the receiver 24 or, if multiple receivers are used, at a single node to which the receivers are linked. The boreholes at which the misfired detonators were placed can also then be identified and appropriate remedial or corrective action in respect of the misfires can take place.

[0077] In a large blasting system with several thousand detonators the confirmatory signals coming from the various detonator assemblies must be distinguished from one another even though at least some of such signals may have been transmitted at the same time or within closely spaced time intervals from one another. To achieve this type of discrimination the wireless signals 60 coming from the different detonator assemblies are multiplexed using various techniques.

[0078] The preceding description relates generally to a blast confirmation process wherein a wireless signal is transmitted from a detonator to a central controller (the receiver) to confirm that it has blasted. In some embodiments this transmission of the signal occurs immediately before initiation at the time B. As the confirmatory signal is transmitted at a precisely determined time it is possible to measure the accuracy of the detonator's response to a fire command signal from the control circuit 48. For example if a detonator were programmed to initiate with a delay of 2000 milliseconds after receipt of the fire command signal and a signal confirming initiation is received indicating, say, a delay of 2003 milliseconds then it can be determined that the firing accuracy was 3 milliseconds after the specified time. The accuracy of firing can then be calculated. Similar calculations can be done for all of the detonators in the blasting system. This type of information can be used to verify the effectiveness of the blast process and can provide data which allows for future blasting processes to be enhanced.