AU2002301535B2 - Warning of impending collapse of unstable geotechnical structure - Google Patents
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Description
P/001011 Regulation 3.2
AUSTRALIA
Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Warning of impending collapse of unstable geotechnical structure The following statement is a full description of this invention, including the best method of performing it known to us: Melbourne 004158862 r 2 THIS INVENTION relates to warning of impending collapse of an unstable geotechnical structure. It relates more specifically to a method of providing such warning, to a micro-seismic activity monitoring apparatus, and to a warning system.
In accordance with a first aspect of this invention, there is provided a method of providing a warning of an impending collapse of an unstable geotechnical structure, including sensing ground motion by means of a sensor proximate a zone prone to collapse and generating a first signal representative of said ground motion; conditioning said first signal at least partially to isolate signal content representative of ground motion induced by failure in the matter proximate the unstable geotechnical structure, from signal content representative of ground motion induced by other causes, and noise induced in the sensor, to yield a conditioned signal; processing said conditioned signal to determine at least one predetermined attribute of micro-seismic activity induced by failure in the matter proximate the unstable geotechnical structure; analyzing said at least one attribute of said micro-seismic activity to identify conditions precursive of collapse of said geotechnical structure; generating a warning signal when said conditions indicate a likelihood above a determined level of collapse of the unstable geotechnical structure.
Sensing the ground motion may be by means of a sensor adapted to sense micro-seismic activity in preference to non-micro-seismic activity, such as a geophone having a resonant frequency below about 32 Hz, and which is preferably critically damped.
The method preferably includes transmitting ground motion to the sensor via a wave guide coupled micro-seismically to the matter proximate said unstable geotechnical structure. Micro-seismically coupling the wave guide to said matter may advantageously be by anchoring the wave guide in competent material coupled micro-seismically to the matter proximate said unstable geotechnical structure, the method including mounting the sensor on the wave guide. The wave guide may conveniently be a rock bolt or tendon.
Conditioning said first signal to yield said conditioned signal, may include at least some of filtering out signal content of a frequency exceeding a predetermined frequency; converting signal content to a digital signal; adjusting the level of the signal content by combining the signal content with a DC value at a value determined by said signal content; recording sampling values of said signal content at a predetermined sampling rate.
The method may include monitoring at least one predetermined attribute of said micro-seismic activity to recognize said conditions precursive of collapse of the unstable geotechnical structure, said at least one attribute being selected from amplitude, duration, rate, spectral content, wave form, time lapse between successive activities, the relationship between different attributes of an activity and the relationship between attributes of successive activities or a series of activities.
Identifying said conditions precursive of collapse of said unstable geotechnical structure may include recording the number of micro-seismic events over a recent, relatively short time interval; recording the number of micro-seismic events over a relatively longer time interval; obtaining the ratio of the number of micro-seismic events over said short time interval and the number of micro-seismic events over said longer time interval; generating a warning when said ratio exceeds a predetermined level.
Instead, the method may include identifying said condition precursive of collapse of the unstable geotechnical structure by recording the duration over which a relatively small number of recent micro-seismic events were detected; recording the duration over which a relatively larger number of recent micro-seismic events were detected; obtaining the ratio of the duration of said small number of micro-seismic events and the duration of said larger number of micro-seismic events; generating a warning when said ratio falls below a pre-determined level.
Analyzing said at least one attribute of said micro-seismic activity to recognize said conditions precursive of collapse of the unstable geotechnical structure may include sampling a value of said at least one attribute repetitively over time, calculating an average value of said at least one attribute over a short time period, calculating an average value of said at least one attribute over a longer time period, comparing the short term average with the longer term average, and recording discrepancies between the short term average and the longer term average.
Instead, analyzing said at least one attribute of said micro-seismic activity may include sampling a value of said at least one attribute repetitively over time, calculating an average value of said at least one attribute over a small number of recent activities, calculating an average value of said at least one attribute over a larger number of recent activities, comparing the average value over the small number of activities with the average value over the larger number of activities, and recording discrepancies between the average value over the small number of activities and the average value over the larger number of activities.
If desired, more than one attribute of said micro-seismic activities may be analyzed in conjunction.
Said at least one attribute may be selected from amplitude, duration, rate, spectral content, wave form and time elapsed between successive micro-seismic activities.
By way of development, the relation between more than one attribute of successive micro-seismic activities may be analyzed.
The method may include comparing values of said at least one attribute recorded respectively over a plurality of recent pre-determined time ranges. The values of said at least one attribute may be compared over a plurality of time periods defined by predetermined numbers of events. The warning signal may be generated when the value of said discrepancies moves outside a predetermined range of values. Instead, or in addition, the warning signal may be generated when the rate of change of said discrepancies moves outside a predetermined range of rates of change.
The method may be applied in conditions in which said unstable geotechnical structure is one or more masses of rock surrounding a mining excavation, for example, when said mining excavation is in an underground mine, especially when said underground mine is a coal mine. The Applicant believes that the method may advantageously also be applied to the working zone in pillar extraction operations.
The method may be applied when collapse of the overlying strata is a planned and integral part of the mining operations.
The method may be applied when said unstable geotechnical structure is a slope or wall created as a result of opencast mining operations, for example when said unstable geotechnical structure is a beam of rock above a naturally-formed opening, or is above an opening created by human intervention.
In accordance with a second aspect of the invention, there is provided a micro-seismic activity monitoring apparatus for warning of impending collapse of an unstable geotechnical structure, the apparatus including a sensor adapted to generate a first signal representative of measured ground motion; conditioning logic arranged to receive said first signal, the logic being pre-programmed to condition the first signal at least partially to isolate signal content representative of ground motion induced by failure in matter proximate the unstable geotechnical structure, from signal content representative of ground motion induced by other causes, and noise induced in the sensor to yield a conditioned signal; processing logic arranged to receive the conditioned signal and to process the conditioned signal to identify and characterize micro-seismic activity resulting from failure of the matter proximate the unstable geotechnical structure; analysis logic arranged to analyze the pattern and said at least one attribute of activities in a series of micro-seismic activities to yield a quantified result, the analysis logic comprising a comparator adapted to generate a warning signal when said comparison results in a discrepancy between said quantified result and a determined value; and a warning device responsive to said warning signal to give a warning.
The sensor may be a transducer in the form of a geophone having a resonance frequency of not more than about 32 Hz, preferably between about 14 Hz and about 28 Hz. The geophone may be critically damped.
Said sensor may have a mounting formation for mounting the sensor snugly to a wave guide, such as a rock bolt or tendon. The mounting formation may be a socket formation. It may be threaded so as to be screwthreadingly secured to the rock bolt.
The warning device may include at least one of a siren and a light.
In one species of embodiment, the apparatus may include a dedicated power pack. The apparatus may then be a self-contained or stand-alone apparatus.
The conditioning logic may include a low pass filter to filter out signal content having a frequency higher than a predetermined frequency, for example, advantageously, about 1 kHz.
The conditioning logic may include one or more of an analogue-to-digital converter to convert the first signal to a digital signal; a circuit for establishing a DC level of the first signal for a predetermined relatively long time period, and a circuit for adjusting a level of the first signal by adjusting the DC level of the signal to a predetermined level; an amplifier for amplifying the first signal to enhance distinction between the first signal and noise; a sampling circuit for sampling and recording values of the first signal at a predetermined sampling rate; an averaging circuit for establishing an average of sampling values over a predetermined time period.
Said analyzing logic may be adapted to implement the method as claimed in any one of Claim 7 to Claim 17.
The invention extends to a warning system for warning of impending collapse of an unstable geotechnical structure, including a micro-seismic activity monitoring apparatus in accordance with the second aspect of this invention, the apparatus being installed proximate said unstable geotechnical structure.
Preferably, the sensor may be mounted at a projecting end of a rock bolt or support tendon anchored in a competent material micro-seismically coupled to matter proximate said unstable geotechnical structure.
Said unstable geotechnical structure may be in a mining excavation underground in a mine. The mine may be a coal mine. Collapse of overlying strata may be an integral and planned part of a mining method employed in the mine.
The apparatus may be intrinsically safe for operation in a fiery mine.
The invention is now described by way of example with reference to the accompanying diagrammatic drawings. In the drawings Figure 1 shows, schematically, in three-dimensional side view, a micro-seismic activity monitoring apparatus in accordance with the invention; Figure 2 is a schematic flow chart representing operation of the apparatus of Figure 1; and Figure 3 is a flow chart of a practical example of operation of the apparatus of Figure 1.
With reference to Figure 1 of the drawings, reference numeral 10 indicates generally a working zone underground in a mine.
The working zone is defined in-between a hanging wall 12, and a foot wall 14. Micro-seismic activity takes place in mother material or rock in the vicinity of the working zone, especially in mother material or rock generally indicated by reference numeral 16 above the hanging wall 12.
It is important to appreciate that the invention is not limited to application in underground mines, or even mines (although such applications are important, possibly even most important), and that the invention can generally be applied to all situations where there is a risk of a collapse of an unstable geotechnical structure.
In accordance with the invention, a micro-seismic activity is monitoring apparatus, generally indicated by reference numeral 20, is installed in the working zone to monitor micro-seismic activity and to create a warning in the event of an imminent collapse of an unstable geotechnical structure to allow personnel and machinery to be removed from the working zone in anticipation of a collapse.
In accordance with one aspect of the invention, preferably, the apparatus 20 is mounted on a wave guide which, in this embodiment, is in the form of a rock bolt or tendon 22 anchored in the mother material or rock 16 and having a projecting portion 22.1 projecting below the hanging wall 12. The significance of this will be explained below.
The apparatus 20 comprises a mounting element 24 for mounting the apparatus 20 to a free end of the rock bolt 22.
The apparatus 20 further comprises a micro-seismic transducer indicated via a housing thereof by means of reference numeral 26. The micro-seismic transducer, in this embodiment, is a geophone for sensing ground motion and having a resonance frequency of 14 Hz. For convenience, the geophone will herein be identified by reference numeral 26. The Applicant prefers a geophone having a resonant frequency of 14 Hz to 28 Hz, and which is critically damped.
Shown via its casing, and immediately below the geophone 26, there is provided logic indicated by reference numeral 28. As will be explained below, the logic serves to condition, process and analyse signal generated by the geophone 26.
Immediately underneath the logic casing 28, there is provided a further casing generally indicated by reference numeral 30 and which represents a power pack. In this embodiment, the power pack is in the form of a battery of cells which are conveniently rechargeable.
Immediately underneath the power pack casing 30, there are provided alarm units for giving a warning, more specifically a siren 32 and a light 34. The power pack drives not only the logic 28, but also the alarm units.
The apparatus 20, in this embodiment, is intrinsically safe for operation in a fiery mine, for example a coal mine. Thus, the whole of the apparatus including the casings 28 and 30, and the alarm units 32 and 34 are rendered intrinsically safe in accordance with an appropriate standard.
Very briefly, in use, ground motion or micro-seismic activity in the mother material or rock is transmitted or guided via the rock bolt 22, acting as a wave guide, to the geophone 26. Furthermore, mine workings within the working zone produces acoustic activity, for example, sound generated by a continuous miner and other machinery, by personnel, tools used by the personnel, and the like, which, unintentionally, is also sensed by the geophone 26. In accordance with the invention, a first signal, which is generated by the geophone 26 in response to the micro-seismic activity and acoustic activity sensed by the geophone 26, is conditioned by conditioning logic forming part of the logic 28, in a number of respects, inter alia by means of a low pass filter to filter out signal above a predetermined cut-off frequency which, in this embodiment, is about 1 kHz. The signal is also conditioned to remove noise and signal content unrelated to micro-seismic activity. The signal is pre-amplified and digitized in a digital-to-analogue converter forming part of the conditioning logic. In short, the conditioning logic produces a conditioned signal in digital form which has been beneficiated, or refined to comprise mostly, ideally only, signal representative of particular micro-seismic activity which is pre-cursive of or indicative of an impending collapse of unstable geotechnical structure or rock fall.
Further in accordance with the invention, the conditioned signal is processed and analyzed as will be described in more detail with reference to Figures 2 and 3 to enhance the integrity of predicting an impending collapse so as to maximize the integrity of prediction and to minimize spurious or false alarms. It is regarded as the ideal to predict each collapse and to have no spurious or false alarms. This may not be possible in practice, and the Applicant regards triggering an alarm spuriously as less harmful than not warning against an actual collapse.
When, in accordance with the invention, a warning situation is declared in anticipation of a collapse, the alarm units are actuated to warn personnel within the working zone to allow them to evacuate the zone, both in person and in respect of machinery which may be damaged in a collapse.
It is important to appreciate that mounting the apparatus on a wave guide, more specifically a rock bolt or rock tendon anchored in the mother material or rock in which micro-seismic activity is expected to take place, creates an excellent coupling between the geophone and the material in which the micro-seismic activity takes place. Thus, such signal is very effectively transmitted to the geophone. This is in contrast to acoustic activity within the working zone, for example by personnel and by implements or tools or machinery, which is transmitted as sound waves through air and which transmission is relatively less efficient.
Furthermore, it is of importance that a geophone having a low natural frequency of no more than about 32 Hz, preferably of about 14 Hz to 28 Hz, is used which is inherently biassed toward sensing microseismic activity in preference to ordinary acoustic activity related to working in the working zone.
It is regarded as most important that signal generated by the geophone is conditioned to remove background noise and signal content not related to micro-seismic activity and is processed to identify particular micro-seismic activity which is pre-cursive of an impending collapse, i.e. to discriminate between such particular micro-seismic activity and other activity which would also be sensed by the geophone. Such conditioned signal only is then used during processing and analyzing to enhance the integrity of predicting a collapse.
It is an important aspect of the invention that the apparatus is self-contained in as much as it does not rely on an external power source, external logic, or the like but provides for all of the operations required from sensing micro-seismic activity to giving a warning, preferably in an integral package.
It is to be appreciated that deviation from the above preferred embodiment is possible within the ambit of this invention, for example under certain circumstances, or in certain applications, it may be appropriate to serve the apparatus by means of an external power pack, or to have an alarm unit spaced from, or an additional alarm unit spaced from, the sensor.
Refer now to the flow chart in Figure 2 which is a schematic, simplified rendition of steps in performing the invention and to Figure 3 which is in the form of a practical example. In Figure 2, the respective steps or step combinations are set out in boxes numbered 26, 28.1 to 28.9, 32 and 34 in following the numbers of the features or components in Figure 1. In Figure 3, the steps are marked Figure 3a to Figure 3j.
Ground motion (unintentionally together with acoustic and other activity unrelated to ground motion) is detected by the micro-seismic transducer 26 (Figure 3a), which generates a corresponding signal (referred to as the first signal) which is transmitted to the logic 28, more specifically the signal conditioning portion of the logic. As reflected in box 28.1 and Figure 3b, the first signal passes through a low pass filter having a cut-off at 1 kHz to filter out most of undesired acoustic activity picked up by the geophone and which does not relate to ground motion or microseismic activity. The filter is an 8 th order filter.
Pre-amplification takes place to a desired level.
As indicated at 28.2 and Figure 3c, the filtered signal is digitized by means of an analogue-to-digital converter which, in this embodiment, samples at a rate of at least 1 kHz.
As indicated at 28.3 and 28.4 (Figures 3d and 3e), in respect of each sample in the digitized signal, a DC average is calculated and recorded over the most recent ten second increment and a DC corrected signal is recorded to compensate for long term drift by subtracting the DC average from the digitized signal, to form a conditioned signal (Figure 3f).
As indicated at 28.5 (Figure 3f), the conditioned signal is rectified to form a rectified conditioned signal. An average value of the rectified conditioned signal over time periods of the most recent one hundred milliseconds is calculated and is referred to as "LTA" (long term average), illustrated at time t in Figure 3f. Similarly a STA (short term average over the most recent ten milliseconds) is calculated, also illustrated at time t in Figure 3f.
With reference to 28.6 and Figure 3g, the ratio of STA and LTA is compared with a pre-determined threshold level whose value depends on peak noise levels and minimum processable signal levels. A trigger is generated when the ratio of STA and LTA exceeds the threshold level.
With reference to box 28.7 and Figure 3h, processing the trigger output as in 28.6 (Figure 3g) uses a "persistence output" to guard against a single or a few transient peaks triggering the system. Thus, a value or level of "persistence output" is calculated in respect of each sample taken. If, for a sample, the trigger has been generated, the value of the "persistence output" is incremented by a predetermined persistence increment. If, for a sample, the trigger has not been generated, the "persistence output" is decreased by one, with the proviso that the "persistence output" cannot be decreased below zero. If the level or value of the "persistence output" exceeds a predetermined value or level, then an "event" is declared and is recorded. For a pre-determined time period after an "event" is recorded, the "persistence output" continues to be updated, but no further "events" are recorded, despite that the "persistence output" exceeds the pre-determined level.
For each event which is recorded, various attributes or parameters are detemined to characterize the event. These attributes include magnitude, spectral content, duration and wave form.
The number of events per time unit is stored in a moving 1o buffer of predetermined size or duration.
The Applicant regards it as of particular importance that "persistence" is used as a factor in determining whether or not an event is established thus to prevent transient micro-seismic activity, not of particular significance in respect of an impending collapse, from having undue effect in establishing an "event".
With reference to 28.8 and Figure 3i, at any particular moment or point in time, the time period for a relatively small number of events which have taken place immediately prior to the point in time, indicated as Etimeo is calculated, referred to as the "short buffer". An event rate i.e. number of events per time period, over the duration of the "short buffer" is calculated. Similarly, a time period during which a predetermined larger number of events, having a ratio of n relative to the m number of events during the short buffer, took place, is determined, referred to as the "long buffer". The event rate over the duration of the "long buffer" is calculated. When the ratio of the event rate during the "short buffer" to the event rate during the "long buffer" is higher than a predetermined value, a warning situation is declared, and the alarm units are triggered as rendered in box 28.9, 32, 34 and Figure 3j.
0 17 Methods for declaring a warning situation may also include examination of the differences between the short and long term values of the attributes or parameters used to characterize events, including combinations thereof.
If desired, the alarm units may be actuated for a predetermined length of time, then de-actuated, and if required actuated again after a predetermined time lag.
It is regarded by the Applicant as most important that the ultimate factor determining whether or not a warning condition is declared, is determined on the ratio of a most recent short term event rate to a recent longer term event rate.
005199805 17a 00 Reference to any prior art in the specification is not, and C-i should not be taken as, an acknowledgment, or any form of suggestion, that this prior art forms part of the common general Z knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.
SAs used herein, except where the context requires otherwise, CI the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to c exclude other additives, components, integers or steps.
exclude other additives, components, integers or steps.
Claims (33)
1. A method of providing a warning of an impending collapse of an unstable geotechnical structure, including sensing ground motion by means of a sensor proximate a zone prone to collapse and generating a first signal representative of said ground motion; conditioning said first signal at least partially to isolate signal content representative of ground motion induced by failure in the matter proximate the unstable geotechnical structure, from signal content representative of ground motion induced by other causes, and noise induced in the sensor, to yield a conditioned signal; processing said conditioned signal to determine at least one predetermined attribute of micro-seismic activity induced by failure in the matter proximate the unstable geotechnical structure; analyzing said at least one attribute of said micro-seismic activity to identify conditions precursive of collapse of said geotechnical structure; generating a warning signal when said conditions indicate a likelihood above a determined level of collapse of the unstable geotechnical structure.
2. A method as claimed in Claim 1 in which sensing the ground motion is by means of a sensor adapted to sense micro-seismic activity in preference to non-micro-seismic activity.
3. A method as claimed in Claim 1 or Claim 2 which includes transmitting ground motion to the sensor via a wave guide coupled micro- seismically to the matter proximate said unstable geotechnical structure. A method as claimed in Claim 3 in which micro-seismically coupling the wave guide to said matter is by anchoring the wave guide in competent material coupled micro-seismically to the matter proximate said unstable geotechnical structure, the method including mounting the sensor on the wave guide. A method as claimed in any one of Claim 1 to Claim 4 inclusive, in which conditioning said first signal to yield said conditioned signal, includes at least some of filtering out signal content of a frequency exceeding a predetermined 1o frequency; converting signal content to a digital signal; adjusting the level of the signal content by combining the signal content with a DC value at a value determined by said signal content; recording sampling values of said signal content at a predetermined sampling rate.
6. A method as claimed in any one of Claim 1 to Claim inclusive, which includes monitoring at least one predetermined attribute of said micro-seismic activity to recognize said conditions precursive of collapse of the unstable geotechnical structure, said at least one attribute being selected from amplitude, duration, rate, spectral content, wave form, time lapse between successive activities, the relationship between different attributes of an activity and the relationship between attributes of successive activities or a series of activities.
7. A method as claimed in any one of Claim 1 to Claim 6 inclusive, in which identifying said conditions precursive of collapse of said unstable geotechnical structure includes recording the number of micro-seismic events over a recent, relatively short time interval; recording the number of micro-seismic events over a relatively longer time interval; obtaining the ratio of the number of micro-seismic events over said short time interval and the number of micro-seismic events over said longer time interval; generating a warning when said ratio exceeds a pre-determined level.
8. A method as claimed in any one of Claim 1 to Claim 6 inclusive, in which identifying said condition precursive of collapse of the unstable geotechnical structure includes recording the duration over which a relatively small number of recent micro-seismic events were detected; recording the duration over which a relatively larger number of recent micro-seismic events were detected; obtaining the ratio of the duration of said small number of micro- seismic events and the duration of said larger number of micro-seismic events; generating a warning when said ratio falls below a pre-determined level.
9. A method as claimed in any one of Claim 1 to Claim 6 inclusive in which analyzing said at least one attribute of said micro-seismic activity to recognize said conditions precursive of collapse of the unstable geotechnical structure includes sampling a value of said at least one attribute repetitively over time, calculating an average value of said at least one attribute over a short time period, calculating an average value of said at least one attribute over a longer time period, comparing the short term average with the longer term average, and recording discrepancies between the short term average and the 00 Slonger term average. 0 Z 10. A method as claimed in any one of Claim 1 to Claim 6 c inclusive in which analyzing said at least one attribute of said micro-seismic 5 activity includes In q sampling a value of said at least one attribute repetitively over time, an average value of said at least one attribute over a small q number of recent activities, Scalculating an average value of said at least one attribute over a larger number of recent activities, comparing the average value over the small number of activities with the average value over the larger number of activities, and recording discrepancies between the average value over the small number of activities and the average value over the larger number of activities.
11. A method as claimed in claim 9 or claim 10 in which more than one attribute of said micro-seismic activities are analyzed in conjunction.
12. A method as claimed in any one of Claim 9 to claim 11 inclusive in which said at least one attribute is selected from amplitude, duration, rate, spectral content, wave form and time elapsed between successive micro-seismic activities.
13. A method as claimed in claim 12 in which the relation between more than one attribute of successive micro-seismic activities is analyzed.
14. A method as claimed in any one of Claim 6 to Claim 13 inclusive in which values of said at least one attribute recorded respectively over a plurality of recent pre-determined time ranges, are compared. 00 c-I O 15. A method as claimed in any one of Claim 6 to Claim 14 z inclusive in which the values of said at least one attribute are compared over plurality of time periods defined by pre-determined numbers of events. c 16. A method as claimed in any one of Claim 9 to Claim Sinclusive in which the wamrning signal is generated when the value of said discrepancies moves outside a predetermined range of values. S 10 17. A method as claimed in any one of Claim 9 to Claim 16 inclusive in which the wamrning signal is generated when the rate of change of said discrepancies moves outside a predetermined range of rates of change.
18. A method as claimed in any one of Claim 1 to Claim 17 inclusive in which said unstable geotechnical structure is one or more masses of rock surrounding a mining excavation.
19. A method as claimed in Claim 18 in which said mining excavation is in an underground mine. A method as claimed in Claim 19 in which said underground mine is a coal mine.
21. A method as claimed in Claim 20 which is applied to the working zone in pillar extraction operations.
22. A method as claimed in any one of Claim 18 to Claim 21 inclusive in which collapse of the overlying strata is a planned and integral part of the mining operations.
23. A method as claimed in Claim 18 in which said unstable geotechnical structure is a slope or wall created as a result of opencast mining operations.
24. A method as claimed in any one of Claim 1 to Claim 17 inclusive in which said unstable geotechnical structure is a beam of rock above a naturally-formed opening. A method as claimed in Claim 24 in which said unstable geotechnical structure is above an opening created by human intervention.
26. A micro-seismic activity monitoring apparatus for warning of impending collapse of an unstable geotechnical structure, the apparatus including a sensor adapted to generate a first signal representative of measured ground motion; conditioning logic arranged to receive said first signal, the logic being pre-programmed to condition the first signal at least partially to isolate signal content representative of ground motion induced by failure in matter proximate the unstable geotechnical structure, from signal content representative of ground motion induced by other causes, and noise induced in the sensor, to yield a conditioned signal; processing logic arranged to receive the conditioned signal and to process the conditioned signal to identify and characterize micro-seismic activity resulting from failure of the matter proximate the unstable geotechnical structure; analysis logic arranged to analyze the pattern and said at least one attribute of activities in a series of micro-seismic activities to yield a quantified result, the analysis logic comprising a comparator adapted to generate a warning signal when said comparison results in a discrepancy between said quantified result and a determined value; and a warning device responsive to said warning signal to give a warning.
27. An apparatus as claimed in Claim 26 in which the sensor is a transducer in the form of a geophone having a resonance frequency of not more than about 32 Hz.
28. An apparatus as claimed in Claim 26 or Claim 27 in which said sensor has a mounting formation for mounting the sensor snugly to a wave guide.
29. An apparatus as claimed in Claim 28 in which said mounting formation is a socket formation dimensioned for snug receipt over an end of a rock bolt or tendon. An apparatus as claimed in any one of Claim 26 to Claim 29 inclusive in which the warning device includes at least one of a siren and a light.
31. An apparatus as claimed in any one of Claim 26 to Claim inclusive which includes a dedicated power pack.
32. An apparatus as claimed in Claim 31 which is a self-contained or stand-alone apparatus.
33. An apparatus as claimed in any one of Claim 26 to Claim 32 inclusive, in which the conditioning logic includes a low pass filter to filter out signal content having a frequency higher than a predetermined frequency.
34. An apparatus as claimed in Claim 33 in which said predetermined frequency is about 1 kHz.
35. An apparatus as claimed in any one of Claim 26 to Claim 34 inclusive in which the conditioning logic includes one or more of an analogue-to-digital converter to convert the first signal to a digital signal; a circuit for establishing a DC level of the first signal for a predetermined relatively long time period, and a circuit for adjusting a level of the first signal by adjusting the DC level of the signal to a predetermined level; an amplifier for amplifying the first signal to enhance distinction between the first signal and noise; a sampling circuit for sampling and recording values of the first signal at a predetermined sampling rate; an averaging circuit for establishing an average of sampling values over a predetermined time period.
36. An apparatus as claimed in any one of Claim 26 to Claim inclusive in which said analysing logic is adapted to implement the method as claimed in any one of Claim 7 to Claim 17.
37. A warning system for warning of impending collapse of an unstable geotechnical structure, including a micro-seismic activity monitoring apparatus according to any one of Claim 26 to Claim 36 inclusive, installed proximate said unstable geotechnical structure. A warning system as claimed in Claim 37 in which the sensor 00 C(N is mounted at a projecting end of a rock bolt or support tendon anchored in a o competent material micro-seismically coupled to matter proximate said Z unstable geotechnical structure.
39. A warning system as claimed in Claim 37 or Claim 38 in which 5 the unstable geotechnical structure is in a mining excavation underground in i~ a mine. A warning system as claimed in Claim 39 in which the mine is O a coal mine.
41. A warning system as claimed in Claim 39 or Claim 41 in which the apparatus is intrinsically safe for operation in a fiery mine.
42. A warning system as claimed in any one of Claim 39 to Claim 41 in which collapse of overlying strata is an integral and planned part of a mining method employed in the mine.
43. A micro-seismic activity monitoring apparatus substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.
44. A method of providing a warning of an impending collapse of an unstable geotechnical structure having the steps substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings. A warning system substantially as hereinbefore described.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA200107654 | 2001-10-18 | ||
| ZA2001/7654 | 2001-10-18 |
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| AU2002301535A1 AU2002301535A1 (en) | 2003-06-12 |
| AU2002301535B2 true AU2002301535B2 (en) | 2009-01-22 |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2528304C1 (en) * | 2013-07-23 | 2014-09-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Кузбасский государственный технический университет имени Т.Ф. Горбачева" (КузГТУ) | Method of determining outburst sites in coal beds |
| CN108824409A (en) * | 2018-07-28 | 2018-11-16 | 中铁二院工程集团有限责任公司 | Railway high precipitous rock slope micro seismic monitoring method and system |
| CN109441547A (en) * | 2018-12-29 | 2019-03-08 | 煤炭科学技术研究院有限公司 | A kind of getting working face coal and gas prominent real-time system for monitoring and pre-warning and method |
| CN113850975A (en) * | 2021-09-26 | 2021-12-28 | 重庆交通大学 | Early warning method and early warning system of dumping dangerous rock collapse based on sonar |
| CN114856709A (en) * | 2022-05-31 | 2022-08-05 | 中铁隧道局集团有限公司 | System and method for rock burst and unfavorable geological real-time forecasting simultaneously |
| CN114876578A (en) * | 2022-06-20 | 2022-08-09 | 广西大学 | Anchor rod stress-micro-shock simultaneous time-space integrated deep-buried tunnel collapse real-time early warning system and method |
| CN115271555A (en) * | 2022-09-27 | 2022-11-01 | 山东省地质矿产勘查开发局八〇一水文地质工程地质大队(山东省地矿工程勘察院) | Information platform system for comprehensive treatment of karst collapse emergency disposal multiple elements |
| CN117031531A (en) * | 2023-08-04 | 2023-11-10 | 华东交通大学 | A sound barrier anti-collapse monitoring method and its monitoring device |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107784795A (en) * | 2017-11-28 | 2018-03-09 | 桂林电子科技大学 | A kind of microseismic signals intellectual monitoring identification equipment and recognition methods |
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| US6807862B2 (en) * | 2002-02-21 | 2004-10-26 | Sekos, Inc. | Device and method for determining and detecting the onset of structural collapse |
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| US6292108B1 (en) * | 1997-09-04 | 2001-09-18 | The Board Of Trustees Of The Leland Standford Junior University | Modular, wireless damage monitoring system for structures |
| US6807862B2 (en) * | 2002-02-21 | 2004-10-26 | Sekos, Inc. | Device and method for determining and detecting the onset of structural collapse |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2528304C1 (en) * | 2013-07-23 | 2014-09-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Кузбасский государственный технический университет имени Т.Ф. Горбачева" (КузГТУ) | Method of determining outburst sites in coal beds |
| CN108824409A (en) * | 2018-07-28 | 2018-11-16 | 中铁二院工程集团有限责任公司 | Railway high precipitous rock slope micro seismic monitoring method and system |
| CN109441547A (en) * | 2018-12-29 | 2019-03-08 | 煤炭科学技术研究院有限公司 | A kind of getting working face coal and gas prominent real-time system for monitoring and pre-warning and method |
| CN109441547B (en) * | 2018-12-29 | 2024-03-19 | 煤炭科学技术研究院有限公司 | A real-time monitoring and early warning system and method for coal and gas outbursts in mining working faces |
| CN113850975A (en) * | 2021-09-26 | 2021-12-28 | 重庆交通大学 | Early warning method and early warning system of dumping dangerous rock collapse based on sonar |
| CN113850975B (en) * | 2021-09-26 | 2023-02-07 | 重庆交通大学 | Sonar-based dumping type dangerous rock collapse early warning method and early warning system |
| CN114856709A (en) * | 2022-05-31 | 2022-08-05 | 中铁隧道局集团有限公司 | System and method for rock burst and unfavorable geological real-time forecasting simultaneously |
| CN114876578A (en) * | 2022-06-20 | 2022-08-09 | 广西大学 | Anchor rod stress-micro-shock simultaneous time-space integrated deep-buried tunnel collapse real-time early warning system and method |
| CN115271555A (en) * | 2022-09-27 | 2022-11-01 | 山东省地质矿产勘查开发局八〇一水文地质工程地质大队(山东省地矿工程勘察院) | Information platform system for comprehensive treatment of karst collapse emergency disposal multiple elements |
| CN117031531A (en) * | 2023-08-04 | 2023-11-10 | 华东交通大学 | A sound barrier anti-collapse monitoring method and its monitoring device |
| CN117031531B (en) * | 2023-08-04 | 2024-04-26 | 华东交通大学 | A sound barrier collapse prevention monitoring method and monitoring device |
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