U.S. patent number 4,581,712 [Application Number 06/440,574] was granted by the patent office on 1986-04-08 for roof pressure monitoring system.
Invention is credited to Billy R. Bruce, Huey J. Perry.
United States Patent |
4,581,712 |
Perry , et al. |
April 8, 1986 |
Roof pressure monitoring system
Abstract
A mine safety system and method of measuring and monitoring the
mine roof support stress levels. The information which is
continuously gathered is recorded and stored so that a
substantially complete history of each selected roof bolt is
available to mine management personnel so that a determination may
be made as to what action should be taken to protect the safety of
the people working in the mine.
Inventors: |
Perry; Huey J. (Huntington,
WV), Bruce; Billy R. (Huntington, WV) |
Family
ID: |
23749298 |
Appl.
No.: |
06/440,574 |
Filed: |
November 10, 1982 |
Current U.S.
Class: |
702/138;
299/1.05; 73/784 |
Current CPC
Class: |
G01L
5/243 (20130101); E21F 17/185 (20130101) |
Current International
Class: |
E21F
17/00 (20060101); E21F 17/18 (20060101); G01L
5/24 (20060101); G01N 007/00 (); E21C 041/00 () |
Field of
Search: |
;364/181,420,558,505
;299/1 ;405/302,291 ;340/690,666,686,825.06 ;73/784 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Krass; Errol A.
Attorney, Agent or Firm: Levy; Sherman
Claims
We claim:
1. A roof pressure monitoring system for use in a mine to
anticipate and prevent roof-fall accidents and increase the safety
of miners comprising a plurality of sensors located in intimate
contact with the mine roof and support roof bolts securing the
sensors to the mine roof, said sensors having a predetermined
pressure applied thereto, a module located adjacent to at least
certain of said sensors, means electrically connecting said sensors
to said module, said module having means for measuring the positive
and negative pressure characteristics of said sensors as compared
to said predetermined pressure and converting the same
characteristics into digital information of pounds and pressure,
said module having a memory for storing the information and
comparing the same information with previously received information
and further including a small dedicated computer having a processor
with a program stored in Read Only Memory and Random Access Memory,
a host computer electrically connected to at least one module and
being located in a position remote therefrom, said host computer
receiving information from said module including an On-line clear
signal on a regular basis and a signal presence indicative of
changes in said pressure characteristics at the sensors, if such be
the case, with reference to location, time and magnitude of change,
said dedicated computer having information storage means, a printer
connected to said host computer, and said printer printing a
complete record of change of a sensor when the change from said
predetermined pressure is greater than a predetermiend value,
whereby, significant changes in pressure on said sensors are
recorded indicative that a roof-fall accident may occur.
Description
TECHNICAL FIELD
This invention relates generally to mine safety systems and
apparatuses and relates specifically to a system and apparatus for
continuously measuring and monitoring the stress levels being
applied to the mine roof supports such as roof bolts, support
columns, and the like so that appropriate action may be taken to
ensure the safety of the miners as well as to prevent damage to the
equipment within the mine.
BACKGROUND ART
In the past, some effort has been made to provide an alarm or the
like which will warn miners and mine operators that some portion of
a mine structure has made a substantial change or shift in the
strata, and normally the alarm is activated after the change or
shift has occurred. Also, the alarm ordinarily is either in an "on"
condition or an "off" condition and does not signal an impending
change nor shift in the geological structure of the mine. These
alarms may be mounted on the roof supports which extend from the
floor to the roof of the mine or may be attached to conventional
roof support bolts which are embedded within the strata above the
top of the mine.
Some examples of this type of structure are disclosed in U.S. Pat.
Nos. 3,111,655 to Kortarsky, et al and 4,156,236 to Conkle.
Additional efforts, such as disclosed in U.S. Pat. No. 4,066,992 to
Butler et al, have been made to provide a continuous surveillance
system on the seismic disturbances in and around the mine in an
effort to determine when a disturbance of sufficient magnitude to
cause damage to the mine will occur.
DISCLOSURE OF THE INVENTION
The present invention is embodied in a roof pressure monitoring
system which continuously monitors the pressure loading on various
roof bolts and roof supports throughout the mine and will record
the time of the change in pressure loading as well as the amount of
change to indicate that certain conditions have altered in some
areas of the mine so that the mine operators may take preventive
steps to avoid injury and loss of life of the miners or damage to
expensive mine equipment. Changes in either positive or negative
pressure loading are monitored. A positive change may indicate that
the load on one or more roof bolts is increasing and may reach a
point exceeding the capacity of the bolts to support the roof. A
negative change may indicate that the anchor of a roof bolt is
losing its hold and may be providing no roof support. A positive
change in one bolt and a negative change in an adjacent bolt may
indicate uneven holding strength of the roof bolts.
In the system, selected roof bolts are provided with sensors, and
several of such sensors are connected to an associated or near-by
module which in turn is connected to adjacent modules and to a host
computer which collects data from the modules, records the data on
a storage media and provides a printout of significant changes in
the sensors.
It is an object of the invention to provide a mine safety system
which monitors the roof supports throughout the mine and provides a
printout of significant changes in the pressure loadings so that
safety steps and preventive steps may be taken prior to a mine
accident or roof cave-in.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic perspective view of the system installed in a
mine.
FIG. 2 is a fragmentary sectional view of one of the roof bolts
with a typical sensor associated therewith.
FIG. 3 is a block diagram of the system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With continued reference to the drawing, a mine 10 normally has a
plurality of tunnels 11 located at one or more levels or strata of
the earth, and usually each tunnel has one or more galleries, bays
or off-shoots 12 extending laterally therefrom. In order to support
the roof of each tunnel and each off-shoot therefrom, it is
conventional to provide a plurality of columns 13 which extend from
the floor to the roof and a plurality of roof bolts 14 which extend
into the stratum of earth above the roof where such bolts are
threaded or otherwise connected to anchors 15 with a roof bolt
plate 16 between the head of the bolt and the roof. The columns and
roof bolts are intended to prevent cave-ins or the collapsing of
the roof.
In the present system, a sensor 18 is associated with a selected
roof bolt 15 on column 13, and such sensor may be of a commercially
available device of special design for integration with this system
and is located in intimate contact between the mine roof and the
supporting bolt or column. It is to be understood that the sensor
may be of known construction and may include a pair of spaced
generally parallel plates 19 separated by a compressible dielectric
20. An axial load applied to the roof bolt causes a deflection of
one or both plates 19 which may be measured as a capacitance change
between such plates and is a direct reflection of the pressure load
exerted on the bolt as the bolt is tightened.
It is noted that any type of device capable of converting pressure
force, displaced movement, or the like may be used.
A selected number of sensors (usually four to eight sensors) are
connected electrically to an on-site module 21 which includes a
small dedicated computer having a processor with its program stored
in ROM (Read Only Memory), input-output lines for communication,
and RAM (Random Access Memory) for data storage and manipulation.
Further, the module 21 includes circuitry which measures the
electrical characteristics of the sensors connected thereto and
converts such measurements into digital information equating to
pounds of pressure. This information is transferred to memory to be
compared with previous readings from the same sensors. The
different sensors normally are polled by the module at
predetermined intervals of time such as, for example, every ten
seconds on a continuous basis.
Each of the modules 21 is connected electrically to a host computer
22 located in a remote position, such as the mine office, for a
purpose which will be described later. When a change occurs in any
of the sensors which exceeds a predetermined amount, the module
sends the information downstream forward to the host computer 22
for further handling and decision making. The module then logs the
new pressure reading in its memory and resumes normal polling until
there is another pressure change occuring. Each module usually is
connected to the next module closer to the host computer 22 as well
as to the module next farther away to provide a "daisy-chain"
arrangement of modules. Each monitor not only monitors its own
sensors but relays data received from other modules.
Additionally, each module communicates an "on-line, clear" signal
to the host computer 22 on a regularly scheduled basis. This may
occur each half-hour or hour or the like depending upon what is
found to be desirable. The purpose of this is for each module to
log in periodically to confirm that it is on-line and functioning
properly. Each module has its own code or identifying number so
that it may be identified by the host computer when reporting
in.
The host computer 22 collects data on pressure loads from
throughout the areas of the mine that is deemed important. Such
data is recorded on a storage media such as a magnetic disk 23 or
the like. In addition to the information being transmitted from the
modules 21, the host computer 22 records the day, date, and module
number with the pressure load.
When the pressure load on a sensor increases or decreases a
predetermined amount such as, for example, 10% such change is
detected by its associated module and forwarded to the host
computer. The host computers log the change in pressure for that
particular sensor and stores it with all previous information
regarding that sensor. When a substantial change is detected in a
sensor, the host computer not only logs the new information, but it
prints out a hard copy report on a printer 24 which includes a
complete history of the change for that sensor and its associated
bolt or support. A typical printout may look as follows:
______________________________________ Indicated Module Bolt # Date
Time Pressure Change ______________________________________ 245 4
6/18/82 21:35 875 lbs +78 245 4 6/22/82 07:14 962 lbs +87 245 4
6/23/82 11:47 1,058 lbs +96 245 4 6/23/82 22:06 1,163 lbs +105
______________________________________
This type of report provides the mine personnel with useable
information regarding the condition of the mine roof in a given
area, and this information may be used in determining what action,
if any, should be taken to protect the safety of the miners and to
prevent roof-fall accidents within the mine. A positive change in
the pressure load (as in the above example) may indicate that the
strata above the roof is shifting, and additional bolts or other
supports are needed in the area to prevent a possible cave-in or
roof-fall of a portion of the roof. Since most roof-falls are the
result of an increased build-up of pressure over a period of time,
the system provides a warning substantially before the accident
occurs so that preventive measures may be taken to either overcome
the fault or evacuate the miners and equipment. A negative change
in the pressure load may indicate that the anchor is losing its
hold.
In the operation of the system, a plurality of sensors 18 are
positioned throughout the mine or a portion of the mine, and such
sensors are located between the roof and a portion of a roof bolt
or a column. During installation, the roof bolt is torqued to a
known pressure load which preferably is similar to the pressure
load of other sensors. The sensors are electrically connected to an
on-site module 21 which is located within the area of the sensors,
and such module continuously polls the sensors to immediately
determine any substantial difference in the pressure load. If no
substantial change is noted, the module periodically sends a signal
to the host computer 22 indicating that the module and sensors are
functioning but that no substantial change in pressure load has
occurred in the vicinity.
If a pressure load on one or more of the sensors occurs, the axial
load is processed by the module which immediately sends a signal
toward the host computer. The host computer receives the
information and logs the pressure load, together with the time of
occurrence, and compares the reading with previously logged
readings from the same module and sensor. If the change is in
excess of such predetermined amount, the information is transmitted
to a printer together with a complete history of changes in
pressure load and such printer prints a hard copy report which is
available immediately to mine personnel so that appropriate action
may be taken. The module is the part that compares current pressure
to previous pressure. It will send information to the Host Computer
only if it detects a sufficient change. Any time the Host Computer
receives information about a bolt, it means that there has been a
change in pressure sufficient to report and a printout is generated
at that time.
Further, a positive change indicates that the load is increasing on
a particular roof bolt which may reach a point exceeding the bolt's
capacity to support the roof. A change in the negative direction
indicates that the bolt's anchor is losing its hold and may be
providing no roof support. In addition, the system consists of
three separate parts, or subsystems, that all work together to
provide useable information to the mine personnel. These parts are
(1) Sensor, (2) Module, and (3) Host Computer.
The Sensor
It is to be noted that the sensor is a device which is located in
the bolt pressure path in the same way as a "washer" would be. In
other words, its physical characteristics require it to have an
outside diameter of about ten inches, a thickness of from one inch
to one-half inch, and a hole in the center through which the roof
bolt passes. As the bolt is tightened, pressure is exerted on the
sensor which directly reflects the pressure exerted on the bolt.
The sensor may be of any suitable type and may be two plates
separated by an air gap as the dielectric. The plates yield with
pressure to vary the space between them, creating a change in
capacitance. Another type places the two plates in closer physical
proximity, and it uses a compressible dielectric that will vary its
thickness with the amount of pressure exerted thereby varying the
capacitance.
It is to be emphasized that the sensor can be of any possible type
and, for example, the sensor may be either a washer like device
placed in the bolts path, or it may be an integral part of the roof
bolt plate. The sensor is a device having electrical
characteristics that are varied by either changes in pressure or
displacement. Thus, in effect, the sensor functions as either a
pressure or displaced transducer.
The Module
Attention is directed to the fact that the module is a small
dedicated computer. It has a processor with its program stored in
ROM (Read Only Memory), I/O (Input/Output) lines for communication,
and RAM (Random Access Memory) for data storage and manipulation.
Also, the module will contain, in addition to the computer, unique
circuitry which will measure the electrical characteristics of five
sensors. Each sensor is placed on a different roof bolt. These
measurements are then converted into digital information (numeric
data), equating to pounds of pressure, then transferred to memory
to be compared with previous readings from these same bolts. The
different sensors will be polled by the module at some interval of
time, every ten seconds or so for example.
Further, a module continuously polls its associated sensors and
monitors the indicated pressure. The module will send the
information forward toward the host computer for further handling
and decision making when a change occurs in any of the bolts that
exceeds a predetermined amount. Next, the module will then log in
its memory the new pressure reading and resume normal polling until
another pressure change occurs which requires that it, once again,
inform the host computer.
It is to be noted that each module monitors five (or some fixed
number) sensors. Wires connect each module to its associated
sensors and to the next module closer to the host computer as well
as the module next farther away from the host computer. In this
way, a "daisy-chain" arrangement of modules is formed. Each module
not only monitors its own sensors, but it relays data received from
other modules. The monitors become a relay network for passing data
to the host computer over great distances within a mine. In
addition to the functions described above, the module will
communicate an "on-line clear" signal to the host computer on a
regularly scheduled basis. This may occur each half hour or once an
hour, depending on what is found desirable. The purpose of this is
to make sure that each module logs in periodically to confirm that
it is on-line and functioning.
Each module has its own identifying number, which is set via
configuration switches prior to installation so that it can be
identified by the host computer when reporting in.
The Host Computer
Collection of data on bolt pressures throughout the areas in the
mine where monitoring is deemed important is performed by the host
computer. As previously stated, the data is collected from the
bolts by the "modules" and is forwarded on to the host computer.
The computer then records the pressure of each bolt on some storage
media; initially this media will be magnetic disk. The computer
keeps track of time of day and date on an ongoing basis. The time
and date are logged in with the pressure data on each bolt. When
the bolt pressure increases or decreases a predetermined amount,
10% for example, this change is detected by the module and
forwarded to the computer. The computer logs this change in
pressure for that particular bolt, and stores it with all the
previous information on that bolt. When a change of this kind is
detected, the computer not only logs the new information but it
prints out a hard copy report of the computer history of change for
that bolt also. As previously noted, a typical printout has been
provided.
It is to be emphasized that the Roof Monitoring System, as
explained in detail above, has important differences and advantages
over previous attempts to provide a warning system for roof falls.
Other devices previously developed attempt to warn of a falling
roof by providing some kind of alarm signal when an indication of
"something" happening is detected at the roof level.
Certain of the information disclosed herein is believed meaningful
in anticipating a possible roof failure, and the same is believed
to be of interest to an agency such as the U.S. Bureau of Mines
about these problems. Thus, there is provided a system that
monitors the stress on a roof at selected points and reports
changes in pressure on the supporting roof bolts, reports the
pressure, and reports the time which these pressure changes
occur.
At the present time, no existing systems are capable of this level
of monitoring and reporting. Furthermore, any system short of this
level of monitoring and reporting is completely inadequate for the
foregoing reasons.
With further reference to the capacitive sensor, there is
illustrated mine roof bolts and mine roof parallel plates. A
similar approach can be applied to timber supports and the sensor
would be placed between the roof and timber.
It will be understood that after appropriate analog/digital
conditioning by conventional methods, the axial loads would be
processed. The module does the processing of the signal (which is
not necessarily analog to digital). Individual or multiple roof
support loads could be monitored by a single module. Multiple
modules would be linked together throughout the mine to provide
adequate roof bolt load/stress information. Further, the data from
each OSM would be transmitted in digital or analog form. Current
load/stress information would be easily accessible from the host
computer for various mine locations. Also, the digital data base
could be flexible enough to provide valuable information such as,
but not limited, to the following:
1. Changes in load/stress levels to warn of excessive loads and
potential roof falls.
2. Plotting of isostress countours could correlate the influence of
one mining operation on another.
3. Conformance to a predetermined roof support plan could easily be
evaluated without entering the mine.
4. In the event of a mine emergency, blocked--or fallen--or
hazardous escapeways could be identified. Conditions leading up to
the emergency could also be reviewed, as desired or required.
The roof bolt plate is standard on all roof bolts.
It is to be emphasized that the sensor may have any of a number of
configurations and can be of conventional construction. Thus, the
present invention is not limited to any specific type of
sensor.
Each module may include a "dedicated computer" with memory,
program, etc. A different concept in the module to lessen expense
may be used. Such a later development could not be called a
dedicated computer. It might simply be circuitry refined to the
point that it performs this one function and nothing else, and
therefore would not qualify under the term "dedicated
computer."
While several embodiments of the present invention have been
illustrated herein in particular detail, it will be understood that
variations and modifications may be effected without departing from
the spirit and scope of the novel concepts of this invention.
* * * * *