Patent Application
20170130580
Field of the Invention
The present invention relates generally to an underground mine roof support for supporting the roof, and, more particularly, to a yieldable mine roof support that allows for adjustment of the overall length of the mine roof support to fit between a roof and a floor of a mine entry.
Description of the Related Art
Over the past several years, Burrell Mining Products, Inc. of New Kensington, Pa. has successfully marketed and sold a mine roof support product sold under the trademark THE CAN®. THE CAN support is comprised of an elongate metal shell that is filled with aerated concrete. The use of aerated concrete in THE CAN support allows the support to yield axially in a controlled manner that prevents sudden collapse or sagging of the mine roof and floor heaving. THE CAN support yields axially as the aerated concrete within the product is crushed and maintains support of a load as it yields.
A typical size of THE CAN support is approximately six feet (1.8 meters) in height and two feet (0.6 meters) in diameter. The overall height of THE CAN supports is based on the average size of the mine entry with each support being of a height that is less than an average height of the mine entry in which the supports are to be installed. In order to install each support, wood planks (or other appropriate cribbing materials such as aerated concrete blocks) are placed beneath THE CAN support to level the support and additional wood planks or other cribbing materials are placed on top of the support until the space between the support and the roof is filled. Essentially, the cribbing materials are tightly wedged between the support and the roof so as to cause each THE CAN support to bear a load of the roof upon installation. Even though these cribbing materials can be installed by mine personnel in a manner that ensures that each support begins bearing a load of the mine roof upon installation, there still exists a need in the industry to provide a mine roof support that is capable of being installed in a manner that substantially fills the space between the mine roof and the mine floor without requiring the installation of cribbing materials above the roof support. In addition, even though cribbing materials may be tightly inserted between the top of the mine roof support and the roof of the mine, there is still an amount of movement of the mine roof relative to the mine floor (or vice versa in the case of floor heaving) that can occur before the mine roof support is able to fully bear the load. Thus, there still exists a need in the art to provide a mine roof support that is capable of bearing a load of the mine roof support shortly after installation but before the roof begins converging toward the floor or vice versa.
Thus, it would be advantageous to provide a mine roof support that is installable within a mine entry that substantially fully extends between the mine roof and the mine floor when properly installed. It would be a further advantage to provide a mine roof support that is installable within a mine entry that is capable of bearing a load of the mine roof shortly after installation without the need of cribbing materials placed above the support in order to decrease installation time and to increase the initial load bearing capacity of the mine roof support.
These and other advantages will become apparent from a reading of the following summary of the invention and description of the illustrated embodiments in accordance with the principles of the present invention.
Accordingly, a support is comprised of first elongate tube partially containing a crushable or compressible core material in a bottom portion thereof that allows controlled yielding of the support along its length. A second elongate tube is telescopically received within the first elongate tube. The second elongate tube is movable in a telescopic manner relative to the first elongate tube and is filled with a crushable or compressible core material of the same consistency as the material in the first elongate tube. A fillable bag or bladder is inserted between the first elongate tube and the second elongate tube with a filling port or nozzle extending through a side wall of the first elongate tube. The bag or bladder is then filled under pressure in situ with a crushable or compressible core material that causes the second elongate tube to rise relative to the first elongate tube in a telescopic manner until the upper end of the second elongate tube contacts a roof of a mine entry in which the support is positioned. Once the core material in the bag or bladder cures, the support allows controlled yielding of the support along the second elongate tube as the compressible core material compresses due to convergence of the mine entry roof and floor. By being able to raise the second tube relative to the first tube, the support of the present invention is provided with a length adjustment feature.
In one embodiment, the support is comprised of a first outer steel shell formed in the shape of a first elongate tube. An aerated or other lightweight concrete or cement is poured into the bottom of the first elongate tube to fill a portion thereof. Once the lightweight concrete is set, the lightweight concrete will bond to the inside surface of the first elongate tube so as to prevent the concrete from disengaging from the tube during transport or use. The use of a lightweight cement containing lightweight aggregate or air pockets allows the cement to be crushed within the first outer shell thus allowing axial yielding of the support along its length as the lightweight concrete is compressed. The support is further comprised of a second outer steel shell formed the shape of a second elongate tube. Aerated or other lightweight concrete is poured into the second outer steel shell so that the second outer steel shell is completely filled from top to bottom with lightweight concrete. The outer diameter of the second outer steel shell is slightly less than an inner diameter of the first outer steel shell so that the second outer steel shell can be slid into the first outer steel shell but that restricts lateral movement of the second outer steel shell relative to the first outer steel shell under load.
A fillable bag or bladder is positioned within the first outer steel shell and on top of the compressible filler contained in the first outer steel shell. The fillable bag or bladder may have a generally cylindrical shape when filled with a diameter approximately equal to the inner diameter of the first outer steel shell. The bladder has an filling port or nozzle that extends through a hole or aperture formed in a sidewall of the first outer steel shell to allow the bladder to be filled in situ from outside the first outer steel shell. The second outer steel shell that has been filled with the compressible filler is positioned at least partially within the first outer steel shell and on top of the bladder.
Filling the bladder under pressure with a filler material, such as cement, lightweight cement, grout or other materials known in the art that can be pumped into the bladder, causes the second outer steel shell to rise relative to the first outer steel shell from a first position to a second position where the top of the second outer steel shell abuts against a roof of a mine entry.
In another embodiment, the second elongate outer shell is partially filled with a compressible filler in an upper portion thereof and is disposed over the first elongate outer shell that is completely filled with the compressible filler. The bladder is disposed within the second outer shell between the compressible filler in the second outer shell and the top of the compressible filler within the first outer shell. This provides less compressible filler above the bladder and thus less weight that must be lifted as the bladder expands to raise the second outer shell relative to the first outer shell.
In still another embodiment, the compressible filler material in the first and second outer shells is formed from the same material and thus has substantially the same density. The filler material in the bladder may have a density that is substantially the same as or greater than the compressible filler material in the first and second outer shells. This ensures that the support when installed will yield in a controlled and predictable manner by allowing the top and bottom portions of the support to yield before the center section containing the bladder begins to yield.
In yet another embodiment, rather than employ the use of a bladder, the filler materials contained in the first and second outer shell sections are spaced apart to form an air gap between the upper surface of the filler material in the bottom section and the bottom surface of the filler material in the upper section. The filler materials may be spaced apart with blocks of the filler material. The filling nozzle is in fluid communication with the air gap so that filler material in liquid form can be pumped under pressure into the air gap to force the upper section away from the lower section, thus causing the upper section to rise. By maintaining a relatively close tolerance between the inner diameter of the first shell and the outer diameter of the second shell and providing the filler material in an uncured and liquefied form having a particle size that is greater than a gap between the first and second shells, the filler material will cause the upper section of the support to rise without substantially flowing through the gap. Once the upper section abuts the roof of the mine entry, the filling process can cease.
In another embodiment, the precast compressible filler material in the upper and lower sections has a density of between about 40 and 50 lb/ft3 and the compressible filler material that is pumped into the support in situ has a density of between about 50 and 60 lb/ft3.
In yet another embodiment, the top and bottom ends of the support will yield first under load until the precast filler materials have yielded and then the filler material filled in situ will yield.
In another embodiment, the support is capable of supporting a load of between approximately 100,000 lbs and 300,000 lbs as the support yields under load.
In still another embodiment, the first and second outer shells will fold upon themselves as each section yields.
The foregoing summary, as well as the following detailed description of the illustrated embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings several exemplary embodiments which illustrate what is currently considered to be the best mode for carrying out the invention, it being understood, however, that the invention is not limited to the specific methods and instruments disclosed. In the drawings:
The lower support section 12 also include a nozzle port 30 that is coupled to the lower support section 12 and in fluid communication with the inside of the lower support section 12 through a hole formed in the outer sell 14. The nozzle port 30 is configured to be coupled with a filling nozzle (as further described herein) for filling a bladder 32 positioned between the lower and upper filler materials 16 and 22, respectively. Once the support 10 is positioned in a desired location within a mine entry to support the roof of the mine and control convergence between the floor and the roof of the mine entry, the upper section 18 can be expanded relative to the lower section 12 in a telescopic manner by inflating the bladder 32 with filler material pumped through the nozzle port 30 until the top 24 of the upper section 18 abuts against the roof of the mine entry.
The upper support section 18 is thus lifted to be in contact with the roof of the mine entry as the space between the filler materials 16 and 22 is filled with a filler material 34 such as aerated concrete, aerated grout, foam or other suitable materials known in the art. The filler materials 16, 22 and 34 provide the principle load bearing capabilities of the support 10 while the outer shells 14 and 20 provide upper longitudinal or load bearing support while also maintaining adequate hoop strength of the mine support 10 to prevent any significant lateral or radial expansion of the filler materials 16, 22 and 34 as the support 10 is compressed. Thus, the tubes 12 and 18 and filler materials 16, 22 and 34 work in tandem as the support 10 yields under load to allow vertical or longitudinal compression of the support 10 while maintaining support of the load. That is, the support 10 will longitudinally yield for a given displacement or yield dimension without catastrophic failure under load.
Aerated or “foamed” concrete or cement is particularly beneficial because it can be cast in the outer shells 14 and 20 as necessary and the strength or compressibility characteristics of the foamed concrete can be controlled and relatively uniform and predictable to produce a desired compressive strength to weight ratio. The use of foamed concrete, in which small air cells are formed within the concrete, in the bottom portion 36 of the lower support section 12 and in the entire upper section 18 is well proven and has been reliably used in roof supports for years. In addition, foamed concrete once cured forms a solidified, unitary structure that will remain contained within the outer shell 14 during handling and will not settle within the outer shell 14, as may be the case when using loose materials, such as saw dust or pumas. In a support application, settling of the filler materials 16 and 22 is a major concern since any settling will result in larger displacement or yielding of the support before the support begins to carry a load.
As previously mentioned, while cylindrical supports in the form of the support sections 12 and 18 have been successfully used in underground mines for a number of years, the space between the top of the support and the roof must be occupied with a material that will transfer the forces applied by the roof to the support without any significant lag between when the roof moves and the support begins bearing a load. Most commonly, wood planks have been stacked on top of supports and effectively wedged to the best extent possible between the roof and the support. As movement within the mine entry occurs, the wood planks are compressed until they effectively begin bearing a load and can fully transfer that load to the support. Moreover, as the space between the support and the roof increases, more wood is required between the roof and the support. As more wood is stacked upon the support, the roof of the mine can move a greater distance before the support will begin fully supporting the load. Ideally, a load supported by a support should be fully supported within approximately the first inch (2.5 centimeters) of movement.
In order to maximize the load bearing capability of the support 10 of the present invention while also making the support 10 adjustable in length, the upper support section 18 is telescopically coupled to the lower support section 12. In use (as will be described in more detail), the upper support section 18 is lifted relative to the lower support section 12 until the top 24 of the upper support section 18 abuts against the roof. The overall length of the upper support section 18 is such that when raised relative to the lower support section 12, the bottom portion of the upper support section 18 is still engaged with the lower support section 12. The upper support section 18 is raised by pumping filler material into the support 10 through the nozzle port 30.
The filling port 30 may comprise a one-way valve that allows the filler material to be pumped into the outer shell 14 while preventing the filler material 22 from exiting through the port 30 when the nozzle being used to fill the outer shell 20 is removed. By using a nonflammable filler material, such as aerated concrete, lightweight grout, self-hardening foam or other materials known in the art, the support 10 provides a significant improvement over prior art supports that utilize wood products alone or in combination with other nonflammable support structures. In the case of a fire, any supports that are made in whole or in part from wood could fail as the fire burns any flammable materials from the support. With the present invention, the supports are more likely to remain in place and continue to support the roof even during a fire. Furthermore, use of filler materials that are not susceptible to shrinkage continue to support the roof even after long periods of time.
Until the filler material pumped through the nozzle port 30 has cured, attachment members may be provided that are formed from, for example, elongate steel straps that are bent and wrapped around the bottom edge of the outer shell 20 with the distal ends upwardly extending within the outer shell 20. The proximal ends extend to the top end 24 of the outer shell 20 and are outwardly bent to form attachment tab portions. The attachment tab portions are provided with a hole so that the proximal ends can be bolted to the roof at least until the filler material that has been pumped through the nozzle port 30 has adequately cured so as to hold the upper section 18 in position.
Referring now to
Once placed on a support surface, such as the floor of a mine entry where the support 10 is to be installed, the upper support section 18 can be lifted in a telescoping manner relative to the lower support section 12 until the top edge 24 of the upper support section 18 abuts against the roof (not shown). Lifting of the upper support section 18 relative to the lower support section 12 may be facilitated by lubricating the sides of the outer shell 20 during the manufacturing process. Such lubricants may include non-flammable lubricants such as those made from synthetic materials, such as polyolefin or polytetrafluoroethylene, or other lubricants approved for use in the industry. The support 10 is configured to rest directly on the support surface 32 without the need for wood cribbing or the like in order to provide a non-flammable support 10 over its entire length when installed in a mine entry or other underground tunnel where support is required. While a substantial portion of the upper support section 18 is shown protruding from the lower support section 12, it is contemplated that the upper support section 18 in it pre-expanded state could be entirely contained in the upper portion 38 of the lower support section 12. Also, because the upper support section 18 is prefilled with a compressible filler and contained within the upper portion 38 of the lower support section 12, the upper support section 12 provides internal structural support to the upper portion 38 of the lower support section 12. As such, during transport or installation, it is less likely that damage will occur to the hollow upper portion 38 that could otherwise prevent the upper support section 18 from being extendable relative to the lower support section 12. That is, an inadvertent impact to the outer shell 14 of the lower support section 12 that could dent the outer shell 14 is resisted, if not prevented, by the added support from the outer shell 20 and compressible filler 22 contained in the upper support section 18.
As further illustrated in
As shown in
Referring now to
In order to prevent over extension of the upper support section 18 relative to the lower support section 12, the upper support section 18 may include a brightly colored indicator ring 104 that may be pained around the upper support section a predetermined distance from the bottom edge 105 of the upper support section 18. That is, if the upper support section 18 were extended to a point where the upper section 18 could easily disengage from the lower support section 12, the support 10 may not provide support in a predicted manner by allowing the upper support section from fully or partially disengaging from the lower support section. The indicator ring 104 provides a visual indicator when the upper support section has reached its maximum safe extension position, even if the upper support section 18 has not yet engaged the roof. In such a situation, the support 10 should be removed and a longer support utilized or the space between the top of the support 10 and the roof should be filled with wood timbers or other approved materials.
As shown in
As previously discussed, the lower and upper support sections 12 and 18 are at least partially prefilled with a first filler material 22, such as a lightweight concrete, having a predetermined load bearing capability while yielding. The center section 109 of the support 10 is filled in situ with a second filler material 115 having a load bearing capability that is at least as great as the load bearing capability of the first filler material 22. By providing the center section 109 of the support 10 with a second filler material 115 that has a greater load bearing capacity than the first filler material 22 additional benefits and load bearing characteristics are realized. As shown in
As illustrated in
As shown in
While the foregoing illustrated embodiments show the outer shell of the upper support section being disposed within the lower support section, it is equally contemplated, as shown in
The supports of the present invention are designed to carry an average load of at least approximately between about 100,000 lbs and about 350,000 lbs depending on the size of the support. The upper and lower support section includes a precast filler material formed from foamed concrete having density of approximately 40 to 50 lb/ft3. The central support section, which may include the bladder of the present invention, includes a filler material formed from lightweight cement, grout our other materials known in the art having density of approximately 50 to 60 lb/ft3. Each support section is comprised of an outer tube that is formed by sheet rolling techniques to form a tube from a flat sheet of steel. Such steel may have a thickness of approximately 0.075 to 0.09 inches of 1008 steel. The tube is then welded at a seam along the entire length of the tube. Likewise, each section may be formed by an extrusion process or other methods known in the art. The support generally will longitudinally yield when subjected to a longitudinal force or load. The support will yield in one or more yield zones by allowing the outer tubes or shells to fold upon themselves in a plurality of folds as the filler materials compress. Thus, the support longitudinally yields without releasing the load.
Various fillers and combinations of fillers may be employed in the supports. For example, the filler material may comprise aerated concrete mixtures of one or more densities. Likewise, the upper and lower support sections may include compressible fillers, such as pumas or hollow glass spheres that may be encapsulated within other binding agents or other materials, such as cement, grout or foam to hold the filler material together and to the inside of the outer shells.
By way of example of the loads that can be supported by a support in accordance with the present invention, several tests have illustrated the impressive load supporting capabilities of the mine support in accordance with the present invention. Supports comprised such filler materials such as with a lightweight concrete have been subjected to vertical force tests in the NIOSH mine simulator to compress the support sand record the load bearing capability of each support. Typically, after less than 2 inches of compression, the supports are able to support a load of over 200 kips and continue to maintain that load bearing capacity over its entire range of yielding up to 22 inches of vertical displacement. As illustrated by such tests, such supports are able to support a significant load within 2 inches of compression. Prior art supports that use wood planks to fill the gap between the top of the support and the roof will typically allow more movement before the same load bearing capacity is reached.
Accordingly, each test support will behave in a predictable manner and continue to yield while supporting at least a particular load. Moreover, such supports will only yield a short distance before a significant load bearing capacity is realized. This allows mine engineers to place the supports at various locations and distances throughout a mine entry where the loads to be supported are relatively predictable, with the assurance that very little movement of the roof will occur before the support is fully loaded. Moreover, because each support gradually increases in load bearing capacity while continuing to yield, there is no unexpected drop in load bearing capacity of the supports that could result in a localized failure. Such tests often reveal data with a sine-type wave pattern where the load bearing capacity varies as the support is compressed. This is a result of the folding of the outer shell of the support. That is, when the outer shell of the support is experiencing plastic deformation when the shell is forming a fold, the load bearing capacity will decrease slightly until the fold is complete at which point the load bearing capacity will slightly increase. This repeats with each successive fold of the outer shell of the support until the support has reached its maximum compression (typically about half its original height). However, while the occurrence of each fold changes the load bearing capacity of the support, the upper and lower load bearing capacity of the support during and after a fold is within a relatively constant range, again producing a predictable load bearing capacity of the support even as the support yields.
The supports according to the present invention can also maintain a support load of even during several inches of vertical displacement of the upper end of the support relative to the bottom end. This allows the support to continue to bear a load even if the floor and roof of the mine entry laterally shift relative to one another. Thus, even in a condition where horizontal shifting of the mine roof or floor occurs, the mine support according to the present invention continues to support significant loads.
While the present invention has been described with reference to certain illustrative embodiments to illustrate what is believed to be the best mode of the invention, it is contemplated that upon review of the present invention, those of skill in the art will appreciate that various modifications and combinations may be made to the present embodiments without departing from the spirit and scope of the invention as recited in the claims. It should be noted that reference to the terms “shell” or “tube” are intended to cover shells or tubes of all cross-sectional configurations including, without limitation, round, square, or other geometric shapes. In addition, reference herein to a use of the support in a mine entry or underground mine according to the present invention is not intended in any way to limit the usage of the support of the present invention. Indeed, the support of the present invention may have particular utility in various tunnel systems or other applications where a yieldable support post is desired. The claims provided herein are intended to cover such modifications and combinations and all equivalents thereof. Reference herein to specific details of the illustrated embodiments is by way of example and not by way of limitation.
This application is a continuation-in-part of U.S. patent application Ser. No. 14/659,086, filed on Mar. 16, 2015, which claims priority to U.S. Provisional Patent Application No. 61/954,746, filed on Mar. 18, 2014, and is a continuation of U.S. patent application Ser. No. 14/508,032, filed on Oct. 7, 2014, which is a continuation of U.S. patent application Ser. No. 13/599,428, filed on Aug. 30, 2012, now U.S. Pat. No. 8,851,805, the entirety of each of which is incorporated by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 61954746 | Mar 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14508032 | Oct 2014 | US |
| Child | 14659086 | US | |
| Parent | 13599428 | Aug 2012 | US |
| Child | 14508032 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14659086 | Mar 2015 | US |
| Child | 15216126 | US |
