U.S. patent number 3,892,442 [Application Number 05/388,747] was granted by the patent office on 1975-07-01 for mining method.
This patent grant is currently assigned to Atlantic Richfield Company. Invention is credited to Albert T. Janssen.
United States Patent |
3,892,442 |
Janssen |
July 1, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Mining method
Abstract
A mining method includes removing material to be mined from one
wall of a mine, and spraying a foam of plastic, polystyrene,
polyurethane, or cement onto an opposite wall to continuously fill
the mined cavity, except for the required immediate working area of
the mining machinery. The foam controls roof fall and earth
subsidence into the mined area and obviates the need for temporary
roof support apparatuses and the required attending and maintaining
personnel. Since the foam entirely replaces the mined material and
provides its own roof support, the entire deposit area can be
safely and efficiently mined.
Inventors: |
Janssen; Albert T. (Thousand
Oaks, CA) |
Assignee: |
Atlantic Richfield Company (Los
Angeles, CA)
|
Family
ID: |
23535337 |
Appl.
No.: |
05/388,747 |
Filed: |
August 16, 1973 |
Current U.S.
Class: |
299/11; 299/12;
405/288; 405/264 |
Current CPC
Class: |
E21C
41/18 (20130101); E21F 15/00 (20130101) |
Current International
Class: |
E21F
15/00 (20060101); E21D 011/00 () |
Field of
Search: |
;61/45F,35
;299/11,18,34,12 ;169/2R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,081,685 |
|
Aug 1967 |
|
GB |
|
167,176 |
|
Dec 1953 |
|
AU |
|
1,953,777 |
|
May 1971 |
|
DT |
|
43,237 |
|
Feb 1959 |
|
PO |
|
602,406 |
|
May 1948 |
|
GB |
|
Other References
Konchesky et al., Pneumatic Transportation of Mine Run Coal
Underground, Mining Congress Journal, Dec. 1971, pp.
42-46..
|
Primary Examiner: Abbott; Frank L.
Assistant Examiner: Pate, III; William F.
Attorney, Agent or Firm: Betz; Robert M.
Claims
What is claimed is:
1. A method for underground mining comprising advancing a cutting
device along one longitudinal wall of a mine shaft to remove a
mining product therefrom and substantially concurrently advancing a
foam support material dispensing device within said shaft behind
said cutting device and in the same direction to progressively fill
at least a portion of the enlarged void of said shaft created by
the removal of said mining product so as to control roof fall and
subsidence of the overlaying earth.
2. A mining method comprising the steps of advancing a
material-removing plow along a wall of a mine, substantially
concurrently advancing an apparatus for spraying a supporting foam
onto an opposite wall from that along which said plow is advanced,
supplying the ingredients for making said supporting foam to said
spraying apparatus, mixing said foam making ingredients, and
spraying said mixed ingredients onto said opposite wall.
3. In a method for underground mining comprising removing a mining
product from a wall of a mine shaft and substantially concurrently
introducing within said shaft a foam support material adapted to at
least partially fill the portion of said mine shaft enlarged by the
removal of said product, the improvement comprising the steps of
advancing continuously along said mine shaft from one end to the
other an apparatus for cutting said mining product from said wall
and a sprayer for depositing said foam support material and
maintaining said sprayer at a constant distance behind said cutting
apparatus.
4. A method as in claim 1 wherein the direction of motion of said
sprayer and said cutting apparatus is periodically reversed.
5. A method as in claim 3 wherein the advancing of said cutting
apparatus and said sprayer is accomplished by means controllable
remotely from said shaft and wherein said cutting apparatus and
said sprayer are each towed by means of at least one cable
extending substantially through the length of said mine shaft.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to mining methods and more particularly to
improvements in methods for controlling roof fall, subsidence, and
the like.
2. Description of the Prior Art
In mining, especially for coal deposits or the like, normally one
or more access tunnels or entries are cut into the seam or deposit
to be mined. In one commonly used method, called the longwall
method, a plow, shearer, or other such mining apparatus is driven
or towed along one wall of an opening in the coal seam or face
between the access tunnels to cut into and remove a portion of the
wall of the opening, creating a new face at the depth cut. The
product cut is removed from the mine by a conveyor or other means,
and the process is repeated successively cutting away the wall
until the plow has been moved the required distance into the
deposit. As the cavity from where the mined product has been
removed becomes large, the roof begins to crumble and fall into the
mine. Usually a number of roof support apparatuses are employed to
control this falling in the immediate area of the plow. The mine
roof away from the plow, however, is ordinarily allowed to fall
directly into the mined cavity. Thus, each time the plow removes
portions of the wall, the roof supports and the conveyor or other
removal means are moved towards the new wall or face, and the roof
in the direction away from that of the plow progression crumbles
into the mined out seam.
Over a period of time, the earth to its surface above the mine
sinks or subsides into the voids created by the removal of the
subsurface mined product. In many instances controlling the amount
of subsidence is desirable or necessary, for example, in mining
under a river the course of which may be changed by subsidence of
the land areas adjacent its bed.
Because of the requirements for moving the roof support and the
product removing conveyors each time the mine wall is cut, commonly
a large number of underground workmen are needed, for instance, one
workman to attend a specified number, such as 10, of the roof
supports. Such underground work is difficult, heavy and dangerous,
and is found undesirable by many mine workers. Such extra men and
equipment also constitutes a direct expense of the mining
operations.
Another problem encountered in present mining methods is the low
extraction ratio with which the product to be mined can be removed.
Typically the extraction ratio of present methods is on the order
of 50 percent or less. This is because once a horizontal cavity has
been mined, the roof fall in the mined area precludes subsequent
mining at levels above or below the presently mined cavity, without
extensive artificial support. Such support is provided, for
instance, for a lower level mining effort by allowing a particular
ceiling thickness between the previous mined cavity and the area to
be mined, together, perhaps, with support columns or pillars in the
lower mine. Also, often large pillars of coal or mine product are
left to prevent caving in active mining areas.
The obtainable ceiling height or seam thickness is another factor
in the extraction ratio since less than all of the material desired
to be mined can be removed. Ideally, the seam thickness should be
as large as possible to remove as much mine material as possible.
However, there is a practical limit on the height at which the
ceiling or roof supports can be safely utilized. For increased
height, larger and harder to manage and move supports are required,
which need more attending personnel and take more time to move.
A hazard which should be considered, especially in coal mining
operations, is that poisonous or noxious fumes, explosive dusts,
and the like, are often generated in the mining processes. Such
fumes, dust, and the like, must be controlled or removed from the
mine to prevent injury to the mine workers. Ventillation techniques
used to control such fumes and dust typically employ systems which
are expensive to maintain and operate, and which require elaborate
stope planning to provide proper air flow paths.
SUMMARY OF THE INVENTION
In light of the above, it is, therefore, an object of the invention
to provide a method for underground mining. It is another object of
the invention to provide a method for supporting the roof of a mine
or the like. It is still another object of the invention to present
a method for controlling subsidence of overlying earth into an
underground mine. It is another object of the invention to present
a method for increasing mine safety. It is yet another object of
the invention to present a mining method which can be remotely
controlled. It is still another object of the invention to present
a method for underground mining with increased production
efficiency. It is still another object of the invention to provide
a method for underground mining of very thick seams.
These and other objects, features, and advantages will become
apparent to those skilled in the art from the following detailed
description, when read in conjunction with the appended claims and
accompanying drawing.
In accordance with the invention, a mining method is presented in
which the product to be mined is removed from a mine wall. As the
removal of the mined product progresses, a supporting foam material
is deposited onto an oppoisite wall. The foam essentially fills the
mined area, except as required for the operation of the mining
equipment. The preferred foams are of plastic, such as polystyrene,
polyurethane, or the like, or foam cement, or the like, to support
the ceiling and, where required, to control the subsidence of the
overlying earth. The compressive strength of the foam may be
determined in accordance with the desired degree of subsidence
control -- the deeper the mine, the greater the compressive
strength of the foam for an equal degree of subsidence control.
BRIEF DESCRIPTION OF THE DRAWING
The invention is illustrated in the accompanying drawing
wherein:
FIG. 1 is a top view of a mine panel cut away to show the entries
and coal face and the mining apparatus therein, in accordance with
the invention;
FIG. 2 is a cross-sectional side view of the coal face taken at
2--2 in FIG. 1 showing the mining apparatus in accordance with the
invention after one wall has been cut and the other wall sprayed
with foam;
FIG. 3 is a cross-sectional side view of the coal face taken at
3--3 in FIG. 1 showing the sprayer apparatus of the invention after
cutting one wall out prior to the deposit of foam onto the other
wall; and
FIG. 4 is a cross-sectional side view of the coal face taken at
4--4 in FIG. 1 prior to cutting.
In the figures of the drawing, various parts have been exaggerated
in size or dimensions for clarity of illustration and ease of
description. Also, like reference numerals are used to denote like
or similar parts.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the FIGS. 1-4 of the accompanying drawing, a mine
panel in which the method of the invention can be practiced
includes access haulways 10 and 11 at each end of an area 12 to be
mined. In accordance with well-known "longwall" mining methods, the
material in the area 12 to be mined is continuously cut and removed
from a wall 13 by a plow, blade, or shearer 14. The removed product
is directed by the shearer 14 onto a conveyor 15, typically a chain
conveyor, for removal from the mine. The shearer 14 is carried on
top of the chain conveyor 15 and is towed by a cable 21 drawn by
powered reels 22 and 23.
In accordance with the invention, foam plastic or other foam
material is sprayed, blown, or otherwise deposited onto a wall 24
opposite that on which the shearer 14 cuts, to fill the mined
cavity 25 with the foam material. To effect this foam deposit, two
sets of nozzles 31 selectable to be generally aimed rearwardly to
this direction of travel are provided on a mixer assembly 32 by
which the foam plastic is mixed and sprayed onto the roof and
opposite wall 24. The mixer assembly 32 rides upon the conveyor 15
and is towed a desired distance behind the shearer 14 by cable 40
between powered reels 42 and 43. Alternatively, the mixer assembly
32 can be tied directly to the shearer 14 by a cable, chain, or the
like (not shown) to be towed by the shearer 14 the desired distance
therebehind. The ingredients for making the foam plastic mix are
conducted under pressure from tanks (not shown) on the surface or
other convenient location, in one or more hoses, such as hoses 33
and 34, illustrated, to the mixer assembly 32 and the selected
nozzles 31.
To protect the hoses 33 and 34 from damage by dragging on the mine
floor, a trough or channel 36 is provided on the conveyor 15 on
which the mixer 32 rides. The hoses 32 and 34 can also be wound on
respective reels 44 and 45, to be unwound or wound, as necessary,
as the mixer assembly 32 is moved along the conveyor 15.
Thus, in operation, the shearer 14 is towed from one haulway 11 to
the other haulway 10, cutting material from the wall face 13 and
directing it onto the conveyor 15 for removal. The chemical mixer
32 is drawn along the opposite side of the conveyor 15 at a
trailing distance of several feet, to spray foam, filling the mined
area 25. Because the foam is directed onto the ceiling (See FIG. 2)
as well as the opposite wall, no roof support apparatuses are
needed. As the cutting and removal of the mined material continues,
the conveyor 15 and the shearer 14 and mixing assembly 32 are moved
toward the new face 19 cut by the shearer 14 by rollers 47 and 48
on the mixer assembly 32. The rollers 47 and 48 ride upon the foam
previously deposited onto the opposite wall 24, so that the mixer
assembly 32, riding in a fixed relationship at the side of the
conveyor 15 pushes the conveyor against the newly cut face 19, as
the mixer assembly 32 is towed behind the shearer 14. The rollers
47 and 48 additionally function to maintain the relative position
of the shearer 14 to the face 13 to be cut.
When the shearer 14 and chemical mixer 32 reach the haulway 10,
they are reversed in direction, cutting and spraying back to the
haulway 11. The cable reels 22 and 23, and 42 and 43, as well as
the hose reels 44 and 45 are advanced within their respective
haulways 10 and 11 in the overall direction of advance of the
shearer 14. The reels can be moved manually or by remote control,
as desired.
When the directions of the shearer 14 and chemical mixer 32 are
reversed, the mixer 32 again is towed the desired distance behind
the direction of travel of the shearer 14. Additionally, since in
the embodiment illustrated the foam plastic is sprayed behind the
mixer 14, the foam is directed to the selected rearwardly aimed
nozzels 31, and the operation continued. The process is continued
until the entire area 12 to be mined has been removed. It can be
seen that the method can be easily adapted to be remotely
controlled to eliminate the need for equipment operators in the
mine, since the only operation which needs to be performed is
drawing the shearer and sprayer back and forth.
The chemicals conducted to the mixer 32 by the hoses 33 and 34,
when combined, result in a foam material, such as polystyrene,
polyurethane, foam cement, foam plastic, or the like being
produced. By appropriate choice of materials, the foam sprayed onto
the wall 24 can have practically any desired compressive strength.
Of particular safety advantage is that by addition of appropriate
additives, the foam can be made fire retardant. Examples of
materials which can be used and their physical properties can be
found in the Encyclopedia of Chemical Technology, 2nd Edition at
page 860 and pages 864-867, which are incorporated herein by
reference. Thus, the subsidence of the overlying earth can be
controlled to practically any desired extent merely by regulating
the compressive strength of the foam material. It is known, for
example, that polyurethane can be made with a density of, for
example, 8 pounds per cubic foot, which will be sufficient to
adequately prevent the subsidence at a depth of approximately 200
feet and limit the extent of subsidence at even greater depths.
Thus, as the material 12 is removed from the mine and substituted
with foam, it can be seen that since the wall areas opposite that
being mined are sprayed with foam in a continuous process, the
entire material within the panel can be effectively removed. Also,
since the entire mined void is filled to the ceiling, the principal
limit on the height or seam thickness is that of the size of the
available shearer or cutter. Thus, since no roof supports are used
the ceiling limit can be increased with increased extraction ratio,
and the personnel previously required to attend the supports are
not needed for that purpose.
If desired, the material cut from the wall 13 by the shearer 14 can
be removed from the mine with pneumatic suction or vacuuming
devices known in the art, not shown, such as by an apparatus
similar to that described in Mining Congress Journal, Dec. 1971,
pp. 42 et seg. Such suction or vacuum means is a desirable method
of removing the cut material, especially in coal mining operations,
since noxious methane gas liberated by mining the coal can be
controlled as well as any other noxious gases which might be
produced by the manufacture of the foam. Furthermore, such
vacuuming or pneumatic apparatuses can sufficiently control the
dust which may be produced in the mining operation which can create
undesired explosive atmospheres. The density of the teeth on the
cutter head may be designed to cut the mined material into a small
enough size to facilitate transportation of the mined material in
the suction pipes to the surface.
One particular advantage of the apparatus of the invention is that
it can be operated remotely, for instance, from a central control
room, without personnel at the actual cutting site. Additionally,
the method is much more efficient than those heretofore since no
supporting or separating walls need be provided for roof support.
Furthermore, since each mined cavity is completely filled with the
foam generated, it is possible to mine in layers; that is, mine a
fist layer, go back and mine the next upper (or lower) layer and so
forth.
Although the invention has been described and illustrated with a
certain degree of particularity, it is understood that various
modifications and changes in the apparatus and method may be
employed without departing from the spirit and scope of the
invention as hereinafter claimed.
* * * * *