WO1998008113A1

WO1998008113A1 - Method and apparatus for monitoring ground vibration and air-blast

Info

Publication number: WO1998008113A1
Application number: PCT/AU1997/000538
Authority: WO
Inventors: Allan Coyne
Original assignee: Allan Coyne
Priority date: 1996-08-21
Filing date: 1997-08-21
Publication date: 1998-02-26
Also published as: AUPO178496A0

Abstract

An improved method is provided for monitoring and recordal of air-blast and/or ground vibration from an operation which produces these effects, the method including: disposing a plurality of monitors for air-blast and/or ground vibration in predetermined positions over a given area, at least one of said monitors being located in closer proximity to the operation than the remainder of said monitors; setting the operating mode of said at least one monitor relatively high when compared with the remainder of said monitors, such that said at least one monitor is triggered or activated only by significant air-blast and/or ground vibration; all said monitors being in communication with one another such that, when said at least one monitor is activated, said at least one monitor generates a control signal which also triggers the remaining monitors. An apparatus for carrying out such a method is also provided, such apparatus including a plurality of monitors for air-blast and/or ground vibration effects, adapted to be disposed in a predetermined manner or pattern around and in the vicinity of a site for an air-blast and/or ground vibration event, the monitors being in communication with one another and with a suitable processing unit (of any given type), and wherein at least one of said monitors, disposed in close proximity to said air-blast and/or ground vibration epicentre, acts as a trigger for the remaining monitors, said at least one monitor, in the event of an air-blast and/or ground vibration event, also serving to generate a control signal to the remainder of said monitors.

Description

METHOD AND APPARATUS FOR MONITORING GROUND VIBRATION AND AIR-BLAST

FIELD OF THE INVENTION The present invention relates, in general terms, to an improved method and apparatus for use in the monitoring of ground vibrations, air-blast and/or the like. More particularly, but not exclusively, the present invention relates to an improved method, and associated apparatus, for detecting, monitoring and perhaps ultimately minimising the effects of blasting and the like procedures, of the type often employed in mining operations, ground clearing operations, pre-construction clearing of land sites, etc. It should be realised, however, that the method and apparatus in accordance with the present invention may also be utilised where ground vibration is produced by operations where blasting, as by means of explosives, does not occur, for example in pile driving operations, where compacting machinery is being used etc.. These operations do not normally produce air-blast, but can produce significant levels of ground vibration. Often, conditions are imposed by regulatory authorities with respect to these operations. These conditions usually take forms that require:

( 1 ) that ground vibration must be monitored and results be available on request; and

(2) that vibration levels must not exceed a particular level. For ease of explanation, throughout the ensuing description reference will be made to an especially preferred embodiment of the present invention, in the form of a method and apparatus for monitoring/determining the effects of blasting in mining operations, such as in open-cut mines. It should be understood, however, that the method and apparatus in accordance with the invention are not restricted to open-cut mining, being equally applicable to underground mining, for example. It should be realised, however, that under no circumstances is the invention to be considered to be restricted to such a preferred embodiment. Indeed the method and apparatus in accordance with the present invention lend themselves to usage in a variety of different contexts, in effect any context wherein it is desired to be able to monitor and record the effects on the surrounding environment, in terms of levels of induced ground vibration, air-blast and the like, arising from a working operation, regardless of whether or not such operation involves the use of explosives. Nowadays, and for a variety of reasons, open-cut mining operations are becoming more and more the norm . Such mining operations, whether intended to win coal or other minerals from the soil for subsequent use, or whether of the quarry-type, have been found to be in most ways much more effective and efficient than more conventional underground mining operations. More often than not, explosives of any known type enjoy frequent usage in such operations, by virtue of such explosives being by far the most efficient and effective way of gaining access to the relevant material being mined, quarried or the like. The effects of blasting, in operations such as open-cut mining, quarrying etc., are and can be many and various, dependent upon the site of the overall operation. The overall impact of such blasting on the environment in general, not to mention the creatures of all types, animal as well as human, occupying that environment, as well as on any and all structures within that environment, can neither be underestimated nor neglected. This is most especially the case in situations wherein the relevant mining or like operation, including blasting, is taking place in close proximity to inhabited areas. There are in existence statutory limits on the allowable magnitude of ground vibration and air-blast attributable to blasting procedures. Mining companies, quarrying companies etc, by monitoring ground vibration and air-blast levels, attempt to satisfy the statutory or regulatory requirements. At the same time such monitoring allows for the collection and collation of information which will (or may) ultimately lead to the development/institution of blasting practices which will minimise the deleterious effects of blasting on the environment. In this day and age everybody is, and indeed should be, more and more conscious of the environment and factors that impinge thereon. DESCRIPTION OF THE PRIOR ART

For the sake of clarity the following definitions are made:

(1 ) the emanating air-blast and/or ground vibration phenomena which are the result of blasting or other operations and which are the phenomena that, by utilisation of the preferred embodiments, it is intended to measure and record, will be referred to hereinafter as "an air-blast and/or ground vibration event";

(2) the point from which the air-blast and/or ground vibration event emanates will be referred to hereinafter as "the air- blast and/or ground vibration epicentre"; and

(3) the area over which the air-blast and/or ground vibration event monitors are stationed will be referred to hereinafter as "the monitored site".

In the past a number of different procedures and apparatus have been employed for purposes of monitoring/measuring air- blast and/or ground vibration events. Traditionally the apparatus concerned is specifically designed to be stand-alone and portable, and its operation is initiated by the monitored air-blast and/or ground vibration exceeding preset thresholds . In one method now in use, prior to each air-blast and/or ground vibration event a field technician will be required to locate, at strategic places within an area where the effects of the air-blast and/or ground vibration event is considered to be of importance, one or more monitors of any given and known type. That technician must adjust the threshold levels of the monitoring equipment so as to ensure that it can in fact record or capture on record the air-blast and/or ground vibration event. Subsequent to the air-blast and/or ground vibration event the or each monitor is checked and the results recorded extracted therefrom, such results then being taken elsewhere for collation and analysis. Such a procedure has been found to be both a costly and time-consuming exercise.

In an alternative procedure, one or more monitors can be set up more or less permanently at specific monitoring sites around or in the vicinity of the mine, quarry or the like, with the threshold levels of such monitors being set sufficiently low to ensure that all air-blast and/or ground vibration events are captured. Locating such monitors permanently at given sites, whilst removing the need for them to be separately set prior to any air-blast and/or ground vibration event, nonetheless gives rise to its own problems. Field trips by appropriate personnel are still required to collect the results from the various monitoring equipment. Furthermore, in the instance of there being any failure in any of the equipment, in the worst possible scenario such failure can perhaps go undetected for long periods of time. Perhaps even more importantly, in terms of results likely to be achieved, the need for lowering the thresholds and thus increasing the sensitivity with distance from the air-blast and/or ground vibration epicentre can give rise to many false triggers and readings. By way of example only, false readings or triggers may be initiated by high winds, the passage of heavy-duty vehicles too close to the monitoring equipment, etc. Again, data collected from such permanently located monitoring apparatus still needs to be collated and cross-referenced against actual air-blast and/or ground vibration events so as to detect and remove false triggers from any analysis. In the result, the situation is often that the time lag which exists between an actual air-blast and/or ground vibration event and the generation of any meaningful results does not lend itself to any significant benefits being gained from the overall monitoring process.

OBJECT OF THE INVENTION

The present invention seeks to improve over the known techniques and apparatus by providing a method and apparatus for continuously and accurately monitoring air-blast and/or ground vibration events.

In accordance with one aspect of the present invention, therefore, there is provided a method for monitoring and recordal of air-blast and/or ground vibration from an operation which produces these effects, said method including the steps of: locating or disposing a plurality of monitors for air-blast and/or ground vibration in predetermined positions over a given area, at least one of said monitors being located in closer proximity to said operation than the remainder of said monitors; setting the operating mode of said at least one monitor relatively high, when compared with the remainder of said monitors, such that said at least one monitor is triggered or activated only by significant air- blast and/or ground vibration; all said monitors being in communication with one another such that, when said at least one monitor is activated, said at least one monitor also triggers the remaining monitors.

In accordance with another aspect of the present invention there is provided a method for monitoring and recordal of air-blast and/or ground vibration phenomena from an operation which produces these effects, said method including the steps of: locating or disposing a plurality of monitors for air-blast and/or ground vibration in predetermined positions over a given area, at least one of said monitors being located in closer proximity to the air-blast and/or ground vibration epicentre than the others; setting the trigger level or operating mod of said at least one monitor to such a high level that, by virtue of its close proximity to the air- blast and/or ground vibration epicentre, these thresholds will only be exceeded by an air-blast and/or ground vibration event; all said monitors being in communication with one another such that, when said at least one monitor is activated, said at least one monitor generates a control signal which is transmitted to the remainder of said monitors.

In accordance with a further aspect of the present invention there is provided a method for monitoring and recordal of air-blast and/or ground vibration phenomena which result from various operations such as blasting, pile-driving, use of compacting machinery and the like, said method including the steps of: locating or disposing a plurality of air-blast and/or ground vibration event monitors in predetermined positions over a given area, at least one of said monitors being located in closer proximity to the air-blast and/or ground vibration epicentre than the remainder of said monitors; setting the operating mode of said at least one monitor such that when air-blast and/or ground vibration levels exceed the respective preset thresholds of said at least one monitor, said at least one monitor issues a trigger signal- setting the respective air-blast and/or vibration thresholds of said at least one monitor to such a high level that, by virtue of its close proximity to the air-blast and/or ground vibration epicentre, these thresholds will only be exceeded by an air-blast and/or ground vibration event; setting an additional operating mode of said at least one monitor such that, on receipt of a command from a remote source, it will issue a trigger signal regardless of whether or not its respective air-blast and/or ground vibration thresholds have been exceeded; setting the operating mode of the remainder of said monitors such that they are activated solely by reception of the trigger signal issued by said at least one monitor, or by reception of a trigger signal issued by any other of the remainder of said monitors; and setting an additional operating mode of selected monitors of the remainder of said monitors such that these selected monitors will, on reception of the trigger signal issued by said at least one monitor or a trigger signal relayed from another of the remainder of said monitors, relay that trigger signal to other selected monitors of the remainder of said monitors.

In accordance with a further aspect of the present invention there is provided apparatus for the monitoring and recordal of air-blast and/or ground vibration events, said apparatus being made up of a plurality of monitors for air-blast and/or ground vibration effects, adapted to be disposed in a predetermined manner or pattern around and in the vicinity of an air-blast and/or ground vibration event, said monitors being in communication with one another and with a suitable processing unit (of any given type), and wherein at least one of said monitors, disposed in close proximity to said air-blast and/or ground vibration epicentre, acts as a trigger for the remaining monitors, said at least one monitor, in the event of an air-blast and/or ground vibration event, also serving to generate a control signal for the remainder of said monitors.

THE DRAWINGS

In order that the invention may be more clearly understood and put into practical effect there shall now be described in detail preferred embodiments of an apparatus in accordance with the present invention, and the method for monitoring associated therewith. The ensuing description is given by way of non- limitative example only and is with reference to the accompanying drawings, wherein:

FIG 1 shows, not to scale but in schematic form, a proposed lay-out for use in practising the method of the present invention; and

FIG 2 illustrates, in schematic form and in side elevation, a monitoring unit for use with the present methods.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference now to Fig 1 , there is set out thereon a proposed lay-out employing the method and apparatus in accordance with the present invention. Over a given area of land a plurality of monitors, preferably of the type illustrated in Fig 2 of the drawings, are disposed in a pre-determined manner. In the lay-out illustrated the monitors involved can be made up of two types dependent upon their actual location. A first type, generally designated 1 , is adapted to be located in reasonably close proximity to the air-blast and/or ground vibration epicentre. A second type, generally designated 2, is adapted to be located at positions more remote from the air-blast and/or ground vibration epicentre and are intended to give constructive data concerning the air-blast and/or ground vibration event at such sites which are more remote from the air-blast and/or ground vibration epicentre. The first type of monitor 1 will hereinafter be referred to as an early warning unit. The second type of monitor 2 will be referred to hereinafter as a slave unit.

In accordance with the present invention the various monitors 1 ,2 are in communication with one another using any known technology, such as for example radio-based telemetry, electronic means etc. In turn in an especially preferred embodiment the or each monitor 1 ,2 is similarly linked to an appropriate recording means of any given type, as for example a personal computer, also disposed at a position remote from the air-blast and/or ground vibration epicentre.

The or each early warning unit, being disposed relatively close to the air-blast and/or ground vibration epicentre, can have the air-blast and/or vibration threshold levels thereof adjusted to or set at a relatively high level, thereby eliminating the possibility of false triggering through the medium of localised high winds, passage of heavy traffic, etc. Indeed the or each early warning unit 1 is preferably so disposed and set as to only be triggered for purposes of recording the air-blast and/or ground vibration event by the air-blast and/or ground vibration event itself. Turning now to Fig 2, thereon there is illustrated a preferred form of monitoring unit, suitable for use as either a slave unit or an early warning unit. Such monitoring unit is preferably solar powered (to avoid the possibility of failure through lack of power) . The unit preferably includes a transceiver of any known type - as for example a high speed data radio - for the transmission of signals to and from a central processing unit and/or to and from other monitors as desired.

The typical monitoring unit, as illustrated for example in FIG 2, is adapted to be located at a given site in any known manner. Such a monitoring unit includes, as its principal components, a mast 30, a microphone 31 for the detection of air-blast, a geophone 32 for the detection of ground vibration, a data logging unit 33 of the type available under the trade mark DYNAMATE, high speed data radio transmission means 34, an antenna 35 to facilitate reception and transmission of signals, and suitable cabling 36 for electrically/electronically interconnecting the various components. In an especially preferred embodiment a solar panel or the like means 37 may be included.

The principle of operation of the method in accordance with the present invention is that, within milliseconds of any early warning unit 1 detecting excedence of either of its air-blast and/or ground vibration thresholds by an air-blast and/or ground vibration event, such unit 1 directs a triggering signal - via radio telemetry or other electronic means - to all other units, both early warning and slave units 1 ,2, which can then begin to record the air-blast and/or ground vibration event. In a practical sense, and since an electronic signal can travel much faster than the ground and air pressure waves which constitute the air-blast and/or ground vibration event, all monitoring units 1 ,2 can be triggered so as to be in monitoring mode long prior to the arrival at the site of such units of the air-blast and/or ground vibration data.

In an especially preferred embodiment of the method in accordance with the present invention the information regarding the air-blast and/or ground vibration event is received by a Central Recording Unit, which automatically displays results on a geographic map of the monitored site, and surrounds, within a finite time of the air-blast and/or ground vibration event, thus providing immediate feedback of air-blast and/or ground vibration event measurements. In a practical sense the impact on those involved with air-blast and/or ground vibration events produced by, say, blasting, seeing the results of that blast mere moments after feeling such blast cannot be over-emphasised. When the air- blast and/or ground vibration event has finished and the monitored site settled down, the Central Recording Unit in communication with the radio telemetry network automatically collects the air- blast and/or ground vibration event data from each monitor, early warning type 1 and slave type 2, displaying the peak air-blast and/or ground vibration event results on the aforementioned screen map and adding those results to an existing database. Appropriate software can be employed to allow for analysis of the results thus recorded. In addition to the peak air-blast and/or ground vibration event results, data representing the variation of the air-blast and/or ground vibration event with respect to time is also retrieved from each monitor, early warning type 1 and/or slave type 2. This data used to produce time scaled graphical waveforms of the air- blast and/or ground vibration event recorded by each monitor.

The Central Recording Unit also continually interrogates and records the status of each monitor, early warning type 1 and slave type 2, and reports any condition of any monitor which could cause it to be incapable of performing its designated function. This feature enables personnel to take appropriate action to correct the condition as soon as it occurs.

In accordance with an especially preferred embodiment, the thresholds or other settings of the or each monitor unit, be it either an early warning and/or slave unit, can be controlled/adjusted by, and from, the Central Recording Unit, through the medium of an appropriate remote signal, thus eliminating the need to have personnel in regular attendance at each monitor site. In real terms, the operation of any monitor as either an early warning unit or a slave unit can be varied dependent upon the location of the air-blast and/or ground vibration epicentre relative to that monitor. In accordance with a further preferred feature each monitor unit has the capability of also acting as a relay, whereby to assist in transmission of comments, early warning unit trigger signals and/or data between the various monitor units - both early warning and slave type. This is especially advantageous in the situation (which may sometimes occur) wherein there is an obstacle in place between the Central Recording Unit and a given monitor, or between given monitors, which will interfere with any signals/commands being transmitted therebetween. In accordance with yet another preferred embodiment the communication network, and monitoring system in general, may also be used for the capture, transmission and analysis of other types of data which can be collected, as for example: dust levels at any given site at any time, both before and subsequent to an air-blast and/or ground vibration event; noise level measurement; wind speed and direction; temperature; numidity; and water quality. In fact any number of different environmental parameters can be monitored, recorded and then analysed.

The early warning type units are intended to serve a variety of purposes, and principally to activate the monitoring units so as to allow for recordal of relevant information. To do this, or achieve this result, the sensitivity of such early warning units is (are) appropriately adjusted by means of their threshold levels. The principle of operation of the method and apparatus in accordance with the present invention is that, upon detecting an air-blast and/or ground vibration event the early warning unit issues a "go" signal to all slave or monitor units, in fact to all other monitoring units re the circuit or system, thereby initiating recordal procedures. It has been determined, however, that even the method and apparatus as previously described may miss an air-blast and/or ground vibration event, and hence not record possibly valuable data, in the instance of the amplitude of the air-blast and/or ground vibration event being insufficient to activate the early warning unit and hence generate the "go" signal. In order to avoid altogether this possibility or potential, in accordance with an especially preferred embodiment of the present invention all units are commanded such that they continuously record air-blast and/or ground vibration phenomena in such a manner that, at any point in time, they retain data pertaining to air-blast and/or ground vibration phenomena which have occurred from some previous point in time up to the present time. By way of example only, the air-blast and/or ground vibration data retained by all units would be that collected during , say, the previous 60 seconds of time. Upon receipt of a "go" signal, all units continue to collect air-blast and/or ground vibration data until the expiration of their predetermined logging periods. In the instance of the relevant early warning unit not generating a "go" signal the operator, located at a site remote from the air-blast and/or ground vibration epicentre, will himself detect that an air-blast and/or ground vibration event has occurred, by sensing the ground vibration and/or air-blast resulting therefrom. Alternatively, the operator can be informed by another observer that an air-blast and/or ground vibration event has occurred. By way of example - in the case of a blasting operation, a prearranged countdown communicated by means of a two-way radio from the shotfirer to the operator. The operator can then intervene to manually transmit, to a selected early warning unit, a command to force it to issue a "go" signal. The result of this action is that all other units respond as if the "go" signal was the result of the air-blast and/or ground vibration event exceeding either of the respective thresholds of an early warning unit. Since the Central Recording Unit automatically collects all data retained by the monitors, the forced "go" signal ensures that the data pertaining to the air-blast and/or ground vibration event is captured.

Thus, it should be understood that the early warning facility made available by the method and apparatus in accordance with the present invention should not be limited to detecting whether ground vibration or air-blast thresholds are exceeded.

The method and apparatus in accordance with the present invention can be seen to be responsible for a number of important advantages, when compared with the prior art, including:

(i) elimination of the possibility of false triggering of the monitors and the problems involved therewith, including isolating such events from results being analysed;

(ii) a substantially fail-safe early warning or trigger is made available;

(iii) remote control of monitoring equipment to suit differing monitoring requirements;

(iv) increased overall flexibility of use and utility; and

(v) a "system" concept is employed, this in contrast to the prior art arrangements wherein the tendency has always been to treat monitoring requirements as a collection of individual standalone units.

These advantages give rise to benefits, not only in practical terms but also in terms of experience, safety, etc. Finally it is to be understood that the aforegoing description refers merely to preferred embodiments of the invention and that variations and modifications will be possible thereto without departing from the spirit and scope of the invention, the ambit of which is to be determined from the ensuing claims.

Claims

CLAIMS 1 . A method for monitoring and recordal of air-blast and/or ground vibration from an operation which produces these effects, said method including the steps of: locating or disposing a plurality of monitors for air-blast and/or ground vibration in predetermined positions over a given area, at least one of said monitors being located in closer proximity to said operation than others; setting the operating mode of said at least one monitor relatively high, when compared with the remainder of said monitors, such that said at least one monitor is triggered or activated only by significant air-blast and/or ground vibration; all said monitors being in communication with one another such that, when said at least one monitor is activated, said at least one monitor also actuates or triggers the remaining monitors.

2. A method for monitoring and recordal of air-blast and/or ground vibration phenomena from an operation which produces these effects, said method including the steps of: locating or disposing a plurality of monitors for ground vibration and/or air-blast in predetermined positions over a given area, at least one of said monitors being located in closer proximity to the air-blast and/or ground vibration epicentre than the others; setting the trigger level or operating mode of said at least one monitor to such a high level that, by virtue of its close proximity to the air- blast and/or ground vibration epicentre, these thresholds will only be exceeded by an air-blast and/or ground vibration event; all said monitors being in communication with one another such that, when said at least one monitor is activated, said at least one monitor generates a control signal which is transmitted to the remainder of said monitors.

3. The method as claimed in claim 1 or claim 2, wherein said control signal generated by said at least one monitor is an early warning signal which serves to activate all said monitors whereby to have said monitors commence logging or recording data.

4. The method as claimed in ciaim 1 or claim 2 wherein, at a predetermined time before said air-blast and/or ground vibration event all said monitors are actuated to commence recording or logging data, and wherein at a predetermined time after said air-blast and/or ground vibration event, a signal is generated to de-activate all said monitors, thereby to halt recording or logging of data.

5. The method as claimed in claim 4, wherein all units are commanded such that they continuously record air-blast and/or ground vibration phenomena in such a manner that, at any point in time, they retain data pertaining to air-blast and/or ground vibration phenomena which have occurred from some previous point in time up to the present time, and wherein at a predetermined time after said air-blast and/or ground vibration event a signal is generated to de-activate all said monitors, thereby to halt recording or logging of data.

6. The method as claimed in claim 1 or claim 2, wherein said method is used to monitor the effect of the use of explosives at an operating site,

7. A method for monitoring and recordal of air-blast and/or ground vibration phenomena which result from various operations such as blasting, pile-driving, use of compacting machinery and the like said method including the steps of: locating or disposing a plurality of air-blast and/or ground vibration event monitors in predetermined positions over a given area, at least one of said monitors being located in closer proximity to the air-blast and/or ground vibration epicentre than the remainder of said monitors; setting the operating mode of said at least one monitor such that when air-blast and/or ground vibration levels excess the respective preset thresholds of said at least one monitor, said at least one monitor issues a trigger signal; setting the respective air-blast and/or ground vibration thresholds of said at least one monitor to such a high level that, by virtue of its close proximity to the air-blast and/or ground vibration eipcentre, these thresholds will only be exceeded by an air-blast and/or ground vibration event; setting an additional operating mode of said at least one monitor such that, on receipt of a command from a remote source, it will issue a trigger signal regardless of whether or not its respective air-blast and/or ground vibration thresholds have been exceeded; setting the operating mode of the remainder of said monitors such that they are activated solely by reception of the trigger signal issued by said at least one monitor, or by reception of a trigger signal issued by any other of the remainder of said monitors; and setting an additional operating mode of selected monitors of the remainder of said monitors such that these selected monitors will, on reception of the trigger signal issued by said at least one monitor or a trigger signal relayed from another of the remainder of said monitors, relay that trigger signal to other selected monitors of the remainder of said monitors.

8. The method as claimed in claim 7, wherein said control signal generated by said at least one monitor is an early warning signal which serves to activate all said monitors whereby to have said monitors commence logging or recording data.

9. The method as claimed in claim 7 wherein, as a predetermined time before said air-blast and/or ground vibration event all said monitors are actuated to commence recording or logging data, and wherein at a predetermined time after said air- blast and/or ground vibration a signal is generated to de-activate all said monitors, thereby to halt recording or logging of data.

10. The method as claimed in claim 7, wherein said method is used to monitor the effect of the use of explosives at an operating site.

1 1 . The method as claimed in claim 7, wherein all units are commanded such that they continuously record air-blast and/or ground vibration phenomena in such a manner that, at any point in time, they retain data pertaining to air-blast and/or ground vibration phenomena which have occurred from some previous point in time up to the present time, and wherein at a predetermined time after said air-blast and/or ground vibration event a signal is generated to de-activate all said monitors, thereby to halt recording or logging of data.

12. Apparatus for the monitoring and recordal of air- blast and/or ground vibration, said apparatus being made up of a plurality of monitors for air-blast and/or ground vibration effects, adapted to be disposed in a predetermined manner or pattern around and in the vicinity of a site for an air-blast and/or ground vibration event, said monitors being in communication with one another and with a suitable processing unit (of any given type), and wherein at least one of said monitors, disposed in close proximity to said air-blast and/or ground vibration epicentre, acts as a trigger for the remaining monitors, said at least one monitor, in the event of an air-blast and/or ground vibration event, also serving to generate a control signal for the remainder of said monitors.

1 3. The apparatus as claimed in claim 12, wherein said monitoring units are solar-powered.

1 4. The apparatus as claimed in claim 1 2, wherein said monitoring unit includes a means for generating and transmitting signals to each, or selected ones, of the remaining monitor units.

1 5. The apparatus as claimed in claim 1 2, wherein said processing unit is a personal computer, located at a site removed from the air-blast and/or ground vibration epicentre.

1 6. The apparatus as claimed in claim 1 2, wherein the sensitivity of each said monitoring unit may be adjusted, either manually or electronically, dependent upon the proximity of each unit to the air-blast and/or ground vibration eipcentre.

1 7. The apparatus as claimed in claim 1 2, wherein each monitor is in communication with each other monitor.

1 8. The apparatus as claimed in claim 1 2, wherein said control signal generated by said at least one monitor is an early warning signal which serves to activate all said monitors whereby to have said monitors commence logging or recording data.

1 9. The apparatus as claimed in claim 1 2 wherein, at a predetermined time before said air-blast and/or ground vibration event, all said monitors are actuated to commence recording or logging data and wherein, at a predetermined time after said air- blast and/or ground vibration event a signal is generated to deactivate all said monitors, thereby to halt recording or logging of data.

20. The apparatus as claimed in claim 1 2, used to monitor the effect of the use of explosives at an operating site.