WO1996039610A1

WO1996039610A1 - A system for monitoring an earth and/or rock body

Info

Publication number: WO1996039610A1
Application number: PCT/AU1996/000337
Authority: WO
Inventors: Robert Kevin Butcher
Original assignee: Powercoal Pty. Ltd.
Priority date: 1995-06-05
Filing date: 1996-06-03
Publication date: 1996-12-12
Also published as: ZA964539B; GB9724811D0; JPH11506540A; GB2317907A; AUPN338295A0; CA2221492A1; GB2317907B; PL324692A1

Abstract

A system (10) for monitoring an earth and/or rock body (12) includes a plurality of sensors (14) spaced apart on a surface (16) of the body (12) for providing respective first signals indicative of the displacement of the surface (16) with respect to the body (12). A plurality of interfaces (18) are respectively associated with the sensors (14) for receiving the first signals and producing second signals derived from the first signals. Control means (20) remote from and successively actuating the interfaces (18) provide the second signals to the control means (20).

Description

ΗTLE: "A SYSTEM FOR MONITORING AN EARTH AND/OR ROCK

BODY"

The present invention relates to a system for monitoring an earth and/or rock

body.

The invention has been developed primarily for monitoring roof displacement

in underground mining passages and will be described hereinafter with reference to

that application. However, it will be appreciated that the invention is not limited to

this particular field of use and is also suitable for monitoring displacement of passage

walls and other excavated surfaces. The roof and walls of underground mining passages often deform due to

stresses imposed by the surrounding earth and rock. To prevent collapse of the roof or

walls it is known to install roof support such as rock bolts, reinforcing and grouting or

the like.

For economic reasons it is desirable to only install the minimum amount of

roof support needed to safely support the roof. To aid mine personnel in determining the amount of roof support required it is

also known to install roof monitoring instruments in holes drilled at intervals along a

passage. However, to monitor roof displacement the instruments must be individually

manually examined and the data recorded and processed. This involves a significant

time and labour cost as a typical mine may have several hundred roof monitoring

instruments. Additionally, the time lag between data recordal and processing can

result in dangerous rock conditions remaining undetected for undesirable time periods.

It has been attempted to monitor roof displacement by wiring electric

instruments to a surface based processing unit. However, the cost of the instruments

and the cabling required renders this approach unsuitable for mining conditions.

It is an object of the invention to overcome or ameliorate at least one of these

deficiencies of the prior art.

According to a first aspect of the invention there is provided a system for

monitoring an earth and/or rock body including:

a plurality of sensors spaced apart on a surface of the body for providing

respective first signals indicative of the displacement of the surface with respect to the

body; a plurality of interfaces respectively associated with the sensors for receiving

the first signals and producing second signals derived from the first signals; control means remote from and successively actuating the interfaces to provide

the second signals to the control means.

Each interface preferably contains a unique address recognisable by the control

means. Each such address may be fixed or programmable. Desirably, the body contains a fixed portion and a movable portion and the

surface is located on the movable portion.

Preferably, the surface is the roof or wall of a passageway through the body.

The first signal is preferably provided by the sensor at a predetermined first

rate.

In an embodiment, the control means actuates the interface at a second rate,

less than or equal to the first rate, and the second signal is the most recent first signal.

Alternately, the second signal may be all the first signals since the last

actuation.

Desirably, the control means includes a data storage means connected to the

plurality of interfaces by a single four core data transmission means. More preferably,

the interfaces are each connected in parallel to the data transmission means.

The control means preferably actuates an alarm when the second signal falls

within a predetermined range.

In a preferred form, the sensors, the interfaces and the data storage means are

located below ground level, and the control means communicates the second signal to

a data storage and processing means located above ground level. If required, a second

data storage and processing means also may be located below ground level.

In an embodiment the roof may include an upwardly extending bore through

both the fixed and movable portions. The bore preferably has an end opening into the

roof surface of the movable portion. An anchor is preferably located towards the

upper end of the bore in the fixed portion. In this way, any displacement the anchor may undergo may be considered negligible when compared to the roof surface

displacement.

In a preferred embodiment, a cable extends from the anchor and terminates in a

tensioning weight. The cable is of sufficient length for the weight to be, at least

initially, positioned in the underground passage. The weight may include a visual

displacement indicator.

The sensor may include a signal generator mounted to the roof surface adjacent

the open end of the bore. The generator is preferably associated with the cable. In this

way, displacement between the anchor and the roof surface causes displacement

between the cable and the signal generator resulting in the first signal that is indicative

of the displacement between the anchor and the roof surface.

The signal generator is preferably a rotary encoder having a pulley in a looping

connection with the cable. The signal generator is desirably mounted in a protective

casing which includes a gripping means adapted to locate the protective casing and

signal generator at the roof surface adjacent the open end of the bore.

Each of the interfaces may also include an auditory or visual display means

which is energised when the control means actuates a particular interface. The

purpose of this display is to provide an indication to personnel near an interface that it

is functioning. According to a second aspect of the invention there is provided a method of

monitoring an earth and/or rock body, said method including the steps of: generating a first signal indicative of the displacement of a surface of the body

with respect to the body at a plurality of spaced apart locations; receiving the first signals at an interface respectively associated with each of the locations;

producing second signals derived from the first signals in each of the

interfaces;

successively accessing the second signals from the interfaces.

Preferably, the data is successively accessed and from each of all the plurality

of interfaces.

A preferred embodiment of the invention will now be described, by way of

example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a surface displacement monitoring system

according to the invention; and

Figure 2 is a partial enlarged view of the system shown in Figure 1.

Referring to Figure 1 there is shown a system 10 for monitoring an earth

and/or rock body 12. The system includes a plurality of sensors 14 (only one shown

for clarity) spaced apart on a surface 16 for providing respective first signals indicative

of the displacement of surface 16 with respect to the body 12. A plurality of interfaces 18 are respectively associated with sensors 14 for receiving the first signals and

sending second signals derived from the first signals.

Control means in the form of an underground data logger 20 is positioned

remote from the interfaces 18 for successively actuating each of the interfaces to provide the second signal to the logger 20. Each of the interfaces 18 contain a unique

address recognisable by data logger 20. Preferably, data logger 20 is connected in parallel to each interface 18 by a

four core cable 21. The cable 21 extends from the data logger 20 to the first interface

and thereafter between successive interfaces.

In the embodiment shown, the data logger 20 is connected via the existing

mine programmable logic controller (PLC) 22 to an above ground computer system 24

via interfaces 26. The computer system 24 includes a printer 28 and a plotter 30. In

other embodiments, the logger 20 is connected directly to the above ground computer

system 24.

The data logger 20 is also connected to a remote computer system 34 via

modem 36 and to an underground computer system 38 by interface 40.

Referring to Figure 2 the sensor 14 is located in a bore 42 extending through

fixed earth 44 and movable earth 46. By way of example, the boundary between the

fixed and movable earth is shown by broken line 48.

The sensor includes an anchor 50, located in fixed ground 44, from which

extends cable 52 terminating in a tensioning weight in the form of graduated marker

54. The cable is looped around the pulley 56 of a rotary encoder 58.

The rotary encoder 58 is mounted inside a housing 59 which is attached to a

protective casing 60. The casing 60 is generally manufactured from steel or plastic. A

shaft 62 extends from casing 60 which has barbs 64 to grip the bore wall and locate

the casing adjacent the open end of the bore. The housing 59 includes an electronic

address system 61 for communicating the rotary encoder signal to the interface 18. In another embodiment, the address system 61 can be located within the same housing as the interface 18. If desired, the interface 18 may be mounted to the casing 60, or

alternatively, contained in the same housing 59 as the encoder 58.

After shaft 62 of the sensor 14 has been positioned in hole 42 and the pulley 56

has been connected with cable 52, the encoder 58 is electrically connected to interface

18, calibrated and activated Calibration is performed by connecting the potentiometer

of the rotary encoder to a resistance meter and rotating the pulley 56 until the meter

indicates that the potentiometer is at the beginning of its range. During any

displacement of surface 16 relative to body 12 rotary encoder 58 is similarly displaced

from anchor 50 causing rotational travel of pulley 56 along cable 52. This in turn

causes variation in the first signal produced by the encoder that is sampled at a

predetermined rate and sent to interface 18.

The data logger 20 identifies each particular interface 18 by its unique address

and selectively actuates these interfaces to provide respective second signals indicative of the relative displacement between surface 16 and body 12. In an embodiment the

second signal contains data representing all the first signals that were recorded since

the last actuation of the interface. In another embodiment, the second signal contains data representing the most recent first signal recorded before the actuation of the

interface.

The second signals are then communicated to the surface computer system 24

to provide an almost instantaneous and continuously updated indication of roof

displacement in multiple locations throughout the mine.

Underground mine personnel can also examine the data using underground

computer system 34, and act accordingly,. Preferably, the data is shown in a graphical format illustrating the roof

displacement occurring at each sensor along a particular passage or group of passages.

By examining the graphs the mine personnel can decide how much roof support is

needed in different regions of the passages and whether or not roof collapse is

imminent..

Additionally, by progressively monitoring the displacement of the passage roof

as it is excavated mine personnel can determine if they are advancing towards a stable

or unstable region. This procedure is readily achievable using the monitoring system

according to the invention as extra sensors and interfaces can be added to the single

data cable as the passage extends. That is, the existing data cable is extended and the

newly installed interfaces are connected to the cable to provide the respective second

signals when actuated by the control means.

In another embodiment (not shown), the marker 54 is configured to lie, and be

dragged by rock movement, horizontally to avoid the parallax error associated with

reading the vertical roof mounted markers.

The system according to the invention provides several advantages over

existing methods of monitoring roof displacement.

A first advantage is provided by all the interfaces being connected in parallel

to the single data cable leading to the data logger. This results in a system with

significant capital and installation costs over previously attempted dedicated

underground-to-surface lead wire systems.

The system according to the invention also provides added flexibility due to

the data cable being able to transmit analogue or digital signals. Further capital cost savings result from the equipment used in the present

invention being approximately 90% reclaimable. Components of existing systems are

generally regarded as consumable items.

Another advantage is the labour saving realised by the mine not requiring any

specially trained staff to perform regular instrument reading and/or data processing.

Further, mine operation is more efficient and safer due to the continuously updated

data being available almost instantaneously in a useable format to both surface and

underground personnel.

Also, the components of the system according to the invention are less

expensive than existing systems. Accordingly, either a cost reduction is achieved or a

greater number of sensors are installed to provide a more accurate indication of roof

displacement.

Additionally, the monitoring system can also accommodate the graduated

visual markers already familiar to mine personnel. Further auditory or visual displays

can be used, for example audible beeps or flashing LED's, to indicate that the system

is functioning correctly. Moreover, in some embodiments the system includes alarms that instantly alert personnel either remote from and/or adjacent to a sensor which

indicates a potentially hazardous roof condition. Such an alarm may be activated by a predetermined roof displacement or, alternatively, a predetermined rate of roof

displacement occurring.

In embodiments where the data logger is connected directly to the above

ground computer system, the intermediate PLC is not required. Such a monitoring system is appropriate for use in underground hazardous areas therefore further

reducing risk to personnel.

The capital and labour cost savings, the convenience and speed of the data

logging and result processing and the enhanced mine safety afforded by the

monitoring system according to the invention result represent a commercially

significant advance over the prior art.

Although the invention has been described with reference to a specific example

it will be appreciated by those skilled in the art that it may be embodied in many other

forms.

Claims

CLAIMS:-

1. A system for monitoring an earth and/or rock body including:

a plurality of sensors spaced apart on a surface of the body for providing

respective first signals indicative of the displacement of the surface with respect to the body;

a plurality of interfaces respectively associated with the sensors for receiving

the first signals and producing second signals derived from the first signals;

control means remote from and successively actuating the interfaces to provide

the second signals to the control means.

2. A system as claimed in claim 1 wherein each said interface contains a unique address recognisable by the control means.

3. A system as claimed in claim 2 wherein each said address is fixed.

4. A system as claimed in claim 2 wherein each said address is programmable.

5. A system as claimed in any one of the preceding claims wherein the body

contains a fixed portion and a movable portion and the surface is located on the

movable portion.

6. A system as claimed in claim 5 wherein the surface is the roof or wall of a

passageway through the body.

7. A system as claimed in any one of the preceding claims wherein said first

signal is provided by the sensor at a predetermined first rate.

8. A system as claimed in claim 7 wherein the control means actuates the

interfaces at a second rate, less than or equal to the first rate, and the second signal is

the most recent first signal.

9. A system as claimed in claim 7 wherein the second signal is all of the first

signals since the last actuation.

10. A system as claimed in any one of the preceding claims wherein the control

means includes a data storage means connected to the plurality of interfaces by a

single data transmission means.

11. A system as claimed in claim 10 wherein the data transmission means is a four

core cable.

12. A system as claimed in claim 10 and 11 wherein the interfaces are each

connected in parallel to the data transmission means.

13. A system as claimed in any one of the preceding claims wherein the control

means actuates an alarm when the second signal falls within a predetermined range.

14. A system as claimed in any of claims 10 to 13 wherein the sensors, the

interfaces and the data storage means are located below ground level, and the control

means communicates the second signal to a data storage and processing means located

above ground level.

15. A system as claimed in claim 14 wherein a second data storage and processing means is located below ground level.

16. A system as claimed in any one of the preceding claims wherein the roof

includes an upwardly extending bore through both the fixed and movable portions.

17. A system as claimed in claim 16 wherein the bore has an end opening into the

roof surface of the movable portion.

18. A system as claimed in claim 17 wherein an anchor is located towards the

upper end of the bore in the fixed portion.

19. A system as claimed in claim 18 wherein a cable extends from the anchor and

terminates in a tensioning weight.

20. A system as claimed in claim 19 wherein the cable is of sufficient length for

the weight to be, at least initially, positioned in the underground passage.

21. A system as claimed in claim 19 or 20 wherein the weight includes a visual

displacement indicator.

22. A system as claimed in claim 21 wherein the sensor or sensors may include a

signal generator mounted to the roof surface adjacent the open end of the bore.

23. A system as claimed in claim 22 wherein the generator is associated with the

cable such that displacement between the anchor and the roof surface causes

displacement between the cable and the signal generator resulting in the first signal

indicative of the displacement between the anchor and the roof surface.

24. A system as claimed in claim 23 wherein the signal generator is a rotary

encoder having a pulley in a looping connection with the cable.

25. A system as claimed in claim 24 wherein the signal generator is mounted in a protective casing which includes a gripping means adapted to locate the protective

casing and signal generator at the roof surface adjacent the open end of the bore.

26. A system as claimed in any of the preceding claims wherein the interfaces

include an auditory or visual display means which is energised when the control

means actuates a particular interface so as to provide an indication to personnel near

one of the interfaces that the interface is functioning.

27. A method of monitoring an earth and/or rock body, said method including the

steps of: generating a first signal indicative of the displacement of a surface of the body

with respect to the body at a plurality of spaced apart locations;

receiving the first signals at an interface respectively associated with each of

the locations; producing second signals derived from the first signals in each of the

interfaces;

successively accessing the second signals from the interfaces.

28. A method as claimed in claim 27 wherein the data is successively accessed and from each of all the plurality of interfaces.