1. 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.
2. Description of the Related Art
Over the past several years, Burred 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 vise 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 vise 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 containing a crushable or compressible core material that allows controlled yielding of the support along its length. A second elongate tube is coupled to the first elongate tube. The second elongate tube is movable in a telescopic manner relative to the first elongate tube and can be filled in situ with a crushable or compressible core material that allows controlled yielding of the support along the second elongate tube once the compressible core material in the first tube has been substantially compressed. 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 an elongate tube. An aerated or other lightweight concrete or cement is poured into the elongate tube to substantially fill the entire length of the tube. Once the concrete is set, the concrete will bond to the inside surface of the 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 outer shell thus allowing axial yielding of the support along its length as the lightweight concrete is compressed.
In another embodiment, a longitudinally yieldable support is comprised of a first support section having a first elongate outer shell filled with a first solid compressible filler material and a second support section having a second elongate outer shell extending above the first elongate outer shell. The second elongate outer shell has an outer diameter that is different than a diameter of the first elongate outer shell to allow the second elongate outer shell to slide relative to the first elongate outer shell. The second elongate outer shell is filled with a second solid compressible filler material having a density that is greater than a density of the first solid compressible filler material.
In one embodiment, a pair of attachment members are coupled to the second elongate outer shell and are configured for lifting the second elongate outer shell relative to the first elongate outer shell and for securing the second elongate outer shell relative to the first elongate outer shell once lifted.
In another embodiment, the second elongate outer shell is comprised of steel and is movable from a first position in which the second elongate outer shell is at least partially disposed within the first elongate outer shell to a second position in which a portion of the second elongate outer shell is positionable between the first elongate outer shell and a roof of a mine entry with a lower portion of the second elongate outer shell disposed within the first elongate outer shell.
In yet another embodiment, the second elongate outer shell is comprised of steel and is movable from a first position in which the second elongate outer shell is at least partially disposed over the first elongate outer shell to a second position in which a portion of the second elongate outer shell is positionable between the first elongate outer shell and a roof of a mine entry with a lower portion of the second elongate outer shell disposed over the first elongate outer shell.
In still another embodiment, the first compressible filler material has a first density and the second compressible filler material is comprised of a solidified compressible material having a second density that is greater than the first density of the first compressible filler material.
In yet another embodiment, the pair of attachment members are each comprised of an elongate strap that is coupled to the second elongate outer shell by wrapping around a lower end thereof and further comprises a securing portion for securing the second elongate outer shell relative to the first elongate outer shell.
In another embodiment, the attachment portion of each of the pair of attachment members laterally extends relative to a top end of the second elongate outer shell and is configured for attachment to a roof of a mine entry.
In still another embodiment, each of the pair of attachment members are bent over a top edge of the first elongate outer shell to maintain the second elongate outer shell relative to the first elongate outer shell.
In another embodiment, the first compressible filler material has a density of between about 40 and 50 lb/ft3 and the second compressible filler material has a density of between about 50 and 60 lb/ft3.
In yet another embodiment, the first support section will yield first under load until a first yield limit is reached at which time the second support section will begin to yield.
In another embodiment, the first support section is capable of supporting a load of between approximately 100,000 lbs and 300,000 lbs as the first support section yields under load.
In still another embodiment, the second outer shell will fold upon itself as the second support 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:
Aerated or “foamed” concrete or cement is particularly beneficial because it can be cast in the outer shell 14 substantially along its entire length and the strength or compressibility characteristics of the foamed concrete are 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 primary support section 12 is well proven and has been reliably used in roof supports for years. In addition, once set, 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 material 16 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 primary support section 12 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 the support 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, the secondary support section 18 is telescopically coupled to the primary support section 12. In use (as will be described in more detail), the secondary support section 18 can be lifted relative to the primary support section 12 until the top 24 of the secondary support section 18 abuts against the roof. The overall length of the secondary support section 18 is such that when raised relative to the primary support section 12, the bottom portion of the secondary support section 18 is still engaged with the primary support section 12. Once raised, the secondary support section 18 is then filled with the filler material 22. Attachment members 26 and 28 are coupled to the secondary support section 18 and are provided for both lifting the secondary support section 18 from the primary support section 12 and for securing the secondary support section in its lifted position until the secondary support section 18 is filled with the filler material 22, as through filling port 30 in the upper portion of the secondary support section 18. The filling port 30 may comprise a one-way valve that allows the filler material 22 to be pumped into the outer shell 20 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.
The attachment members 26 and 28 are formed from elongate steel straps that are bent and wrapped around the bottom edge 29 of the outer shell 20 with the distal ends 26’ and 28’ upwardly extending within the outer shell 20. The proximal ends 26″ and 28″ 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 26″ and 28″ can be bolted to the roof at least until the outer shell is filled with the filler material 22 and the filler material 22 has adequately cured so as to hold the outer sleeve 20 in position.
Referring now to
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The straps 110 and 112 are similarly configured to the attachment structures 26 and 28 illustrated in
Conversely, as shown in
Regardless of how the upper support section is secured in place relative to the roof and lower support section until filled,
The lower support section 210 is prefilled with a first filler material 220, such as a lightweight concrete, having a predetermined load bearing capability while yielding. The upper support section 208 is filled in situ with a second filler material 222 having a load bearing capability that is at least as great as the load bearing capability of the lower support section 210. By providing the upper support section 208 with a second filler material 222 that has a greater load bearing capacity than the first filler material 220 additional benefits and load bearing characteristics are realized. 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 primary support section includes a filler material formed from foamed concrete having density of approximately 40 to 50 lb/ft3. The secondary support section 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 tube or shell to fold upon itself in a plurality of folds as the filler material compresses. 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 support section 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 shell.
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 e support in accordance with the present invention.
Accordingly, each test support behaved in a predictable manner that continued to yield while supporting at least a particular load and that yielded a short distance before a significant load bearing capacity was 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. With respect to each test, the data shows 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). As illustrated, 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 sheds 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.
Number | Date | Country | |
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Parent | 13599428 | Aug 2012 | US |
Child | 14508032 | US |