GB2302951A

GB2302951A - Strata movement indicator

Info

Publication number: GB2302951A
Application number: GB9513446A
Authority: GB
Inventors: Alan Stuart Bloor; Paul Alan Fletcher
Original assignee: STRATA CONTROL TECHNOLOGY Pty; Rock Mechanics Technology Ltd
Current assignee: STRATA CONTROL TECHNOLOGY Pty; Rock Mechanics Technology Ltd
Priority date: 1995-07-01
Filing date: 1995-07-01
Publication date: 1997-02-05
Also published as: GB9513446D0

Abstract

A strata movement indicator 1 includes a reference guide 6, having a coil 7, fixed within the mouth of a borehole 5, and an indicator element 2 in the form of a ferromagnetic core, the element and the reference guide forming a linear displacement transducer from which signals indicative of the movement of the strata local to the indicator are fed to a computer for processing. Visual indication of strata movement is provided by coloured bands 2a.

Description

STRATA MOVENENT INDICATOR This invention concerns improvements in or relating to strata movement indicators.

In particular, the present invention relates to indicators of the type described in United Kingdom Patents No 2 253 707 and No 2 268 809 for use in underground mines in which an indicator element is suspended from an anchor within a borehole formed in the strata, the element carrying reference banding, specifically chromatic banding, registering with a guide fixed in the mouth of the borehole. The degree of extension of the element from the guide indicates the strata movement, the chromatic banding providing a ready visual indication as to the severity of the strata movement.

These earlier indicators provided simple and yet effective visual means of showing strata movement. However, their efficacy is compromised should inspection be less than regular and of course their use tends to be manpower intensive.

An object of the invention is therefore to provide a strata movement indicator which gives the requisite information without the need for visual inspection, while retaining a visual inspection facility.

According to the invention a strata movement indicator includes a flexible suspension member, an anchor for anchoring the suspension member in use within a borehole, a reference guide for securement within the mouth of the borehole, and an indicator element carried by the suspension member, the reference guide and indicator element together forming an inductive displacement transducer whereby in use any change in the inductance is occasioned by movement of the indicator element which is thereby indicative of strata movement.

The invention further consists of a strata movement indicator system which includes at least one strata movement indicator as aforesaid, monitoring means for monitoring the inductance of the transducer thereby to generate a signal indicative of the condition of the local strata, and computer or other suitable means for processing the signal and providing information thereon relating to the condition of the local strata.

The monitoring means of the system may include at least one interface unit between the or each transducer and the computer means, the computer means being adapted to process, store and display information derived from the or each strata movement indicator. The computer means may be further adapted to generate warning signals in the event that the information received from the or each strata movement indicator reports strata movement of a potentially dangerous magnitude.

The indicator element of the strata movement indicator conveniently has visible markings providing a gauge of the degree of movement in relation to the reference guide.

The visible markings may be in the form of chromatic banding, preferably reflective.

By way of example, one embodiment of strata movement indicator and a strate movement indicator system according to the invention are described below with reference to the accompanying drawings in which: Figure 1 is a schematic representation of the indicator; and Figure 2 is a schematic representation of the system.

Referring to the Figure 1, a strata movement indicator is depicted at 1 and includes an indicator element in the form of a ferromagnetic core 2 which in use is carried by a suspension member for example a wire 3 depending from an anchor 4 disposed within a borehole 5 at a suitable distance from its mouth. The core 2 is provided externally with chromatic banding 2a, for example green, orange and red.

A reference guide 6 is fixable within the mouth of the borehole and is in the form of a tube around which is wound a coil 7 with connections 8 for an interface unit 9 which monitors the inductance changes in the coil 7.

A strata movement indicator system as shown in Figure 2 includes a number of the indicators 1 each connected to an interface unit 9 which are in turn connected to a computer 10 provided remotely from the strata movement indicator; in the case of application in an underground mine, the computer would be located on the surface in an appropriate control room dealing with the operations of the mine in general.

In use, the anchor 4 is securely disposed within the borehole remote from its mouth and has suspended therefrom the wire 3 carrying the core 2. The reference guide 6 is fixed within the mouth of a borehole preformed in the strata to be monitored with the connections 8 of the coil 7 suitably arranged for connection with the interface unit 9 which is positioned in an appropriate location. The interface unit 9 is itself connected to the computer 10.

The core 2 lies within the reference guide 6 in spaced apart manner. At the time of installation the interface unit 9 and thus the computer 10 are calibrated and thereafter any variation in the inductance of the coil 7 is monitored by the interface unit 9. The unit 9 generates a signal representative of the change in inductance and accordingly indicative of the degree of strata movement. The signal passes to the computer wherein it is processed and is stored for retrieval and display. The interface unit and/or the computer are adapted to yield an audible or visual warning should the variation in the inductance suggest imminent danger from strata movement so detected.

The ferromagnetic core 2 bearing its chromatic banding 2a also gives a ready local and visual indication of any strata movement which takes place, the colour of the banding revealed denoting the severity of the strata movement on an escalating scale from for example green through orange to red.

It is to be understood that a plurality of strata movement indicators as indicated in Figure 2 incorporating linear displacement transducers can be located in appropriate sites within a mine, the signals from each being fed to the computer for processing and information presentation, thereby giving a comprehensive profile of the strata movement within the mine without the need for manpower to inspect the indicators visually on as regular a basis as has hitherto been desirable if not essential.

It is to be further understood that more than one transducer can be included within one strata movement indicator. In particular, an indicator of the type described in British Patent No 2 268 809 which includes at least two anchors with their pendant indicator elements, would necessarily incorporate a transducer corresponding to each reference guide and anchor point thereby to give a comprehensive overview of strata activity in the region of the relevant borehole at different heights.

The present invention thus provides a simple and yet effective means of transmitting important information to a location remote from the monitoring site.

Claims

CLAIMS:

1. A strata movement indicator includes a flexible suspension member, an anchor for anchoring the suspension member in use within a borehole, a reference guide for securement within the mouth of the borehole, and an indicator element carried by the suspension member, the reference guide and indicator element together forming an inductive displacement transducer whereby in use any change in the inductance is occasioned by movement of the indicator element which is thereby indicative of strata movement.

2. An indicator according to claim 1 in which the indicator element has visible markings providing a gauge of the degree of movement in relation to the reference guide.

3. An indicator according to claim 2 in which the visible markings are in the form of chromatic banding.

4. An indicator according to any one of the preceding claims in which at least two indicator elements with associated anchors and suspension members are provided, each indicator element having a respective reference guide and each combination of indicator element and reference guide forming an inductive displacement transducer.

5. A strata movement indicator system including at least one strata movement indicator as claimed in any of the preceding claims, monitoring means for monitoring the inductance of the transducer thereby to generate a signal indicative of the condition of the local strata, and computer means for processing the signal and providing information thereon relating to the condition of the local strata.

6. A system according to claim 4 in which the monitoring means of the system includes at least one interface unit between the or each transducer and the computer means, the computer means being adapted to process, store and display information derived from the or each strata movement indicator.

7. A system according to claim 5 in which the computer means is further adapted to generate warning signals in the event that the information received from the or each strata movement indicator reports strata movement of a potentially dangerous magnitude.

8. A strata movement indicator substantially as herein before described with reference to Figure 1 of the accompanying drawings.

9. A strata movement indicator system substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.