TELESCOPIC MINE ROOF SUPPORT

Abstract

A longitudinally yieldable support for underground roof support includes a first support section with a first elongate outer shell partially filled with a solid compressible filler material and a second support section at least partially filled with a second solid compressible filler material. The second support section is at least partially disposed within the first elongate outer shell and is telescopically extendable relative thereto. A bladder is interposed between the first and second support sections that is fillable in situ to cause extension of the second support section relative to the first support section when filled under pressure with a filler material.

Claims

1. A longitudinally yieldable support, comprising: a first support section comprising a first elongate outer shell partially filled at a first end portion with a first solid compressible filler material and defining a opening at a second end of the first elongate outer shell between a second end and a top of the first solid compressible filler material; and a second support section comprising a second elongate outer shell at least partially filled with a second solid compressible filler material positioned in the opening of the first outer shell, the second elongate outer shell having an outer diameter that is slightly smaller 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; a port in communication with a space between the top of the first compressible filler and a bottom of the second compressible filler configured for filling the space with a third filler material under pressure to cause the second support section to rise relative to the first support section in order to span a space between a floor and a roof of an underground entry.

2. The support of claim 1, wherein the first and second elongate outer shells are comprised of steel and wherein the first and second solid compressible filler materials are cast in the first and second elongate outer shells respectively.

4. The support of claim 3, wherein the second elongate outer shell is movable in a telescopic manner 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 maintained within the second elongate outer shell and a top of the second elongate outer shell is in contract with a roof of a mine entry.

5. The support of claim 1, wherein the first and second compressible filler materials have substantially the same density.

6. The support of claim 5, wherein the third compressible filler material is comprised of a solidified material having a second density that is greater than the densities of the first and second compressible filler materials.

7. The support of claim 1, further comprising a fillable bladder interposed between the top of the first compressible filler material and a bottom of the second compressible filler material, the fillable bladder having an inlet accessible through the port for filling the bladder in situ.

8. The support of claim 7, further comprising a one-way valve coupled to the inlet of the bladder to allow the filler material to enter the bladder but prevent the filler material from escaping from the bladder.

9. The support of claim 8 wherein the port is positioned proximate the top of the first compressible filler of the first support section.

10. The support of claim 5, wherein the first and second compressible filler materials have a density of between about 40 and 50 lb/ft.sup.3 and the third filler material has a density of between about 50 and 60 lb/ft.sup.3.

11. The support of claim 5, wherein the bottom end of the first support section and the top end of the second support section will yield under load before a center portion of the support where the third filler material resides begins to yield.

12. The support of claim 1, wherein the first and second support section are capable of supporting a load of at least 100,000 lbs.

13. The support of claim 12, wherein the first and second support sections are capable of supporting a load of between approximately 100,000 lbs and 300,000 lbs as the first and second support section yield under load.

14. The support of claim 10, wherein the first and second outer shells will fold upon themselves as the first and second support sections yield.

15. A method of installing a longitudinally yieldable support in an underground entry, comprising: providing a first support section comprising a first elongate outer shell partially filled at a first end portion with a first solid compressible filler material and defining a opening at a second end of the first elongate outer shell between a second end and a top of the first solid compressible filler material; providing a second support section comprising a second elongate outer shell at least partially filled with a second solid compressible filler material positioned in the opening of the first outer shell, the second elongate outer shell having an outer diameter that is slightly smaller 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; and pumping a third filler material through a port in communication with a space between the top of the first compressible filler and a bottom of the second compressible filler configured for filling the space with a third filler material under pressure to cause the second support section to rise relative to the first support section until the support abuts against a roof of an underground entry.

16. The method of claim 1, further comprising providing the first and second elongate outer shells of steel and separately casting the first and second solid compressible filler materials into the first and second elongate outer shells respectively.

17. The method of claim 16, further comprising moving the second elongate outer shell in a telescopic manner 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 maintained within the second elongate outer shell and a top of the second elongate outer shell is in contract with a roof of a mine entry.

18. The method of claim 15, further comprising providing the first and second compressible filler materials with substantially the same density.

19. The method of claim 18, further comprising providing the third compressible filler material as a solidified material having a second density that is greater than the densities of the first and second compressible filler materials.

20. The method of claim 15, further comprising providing a fillable bladder interposed between the top of the first compressible filler material and a bottom of the second compressible filler material, the fillable bladder having an inlet accessible through the port for filling the bladder in situ.

21. The method of claim 20, further comprising providing a one-way valve coupled to the inlet of the bladder to allow the filler material to enter the bladder but prevent the filler material from escaping from the bladder.

22. The method of claim 21, further comprising providing the port in a position proximate the top of the first compressible filler of the first support section.

23. The method of claim 18, further comprising providing the first and second compressible filler materials with a density of between about 40 and 50 lb/ft.sup.3 and the third filler material with a density of between about 50 and 60 lb/ft.sup.3.

24. The method of claim 18, further comprising configuring the support so that the bottom end of the first support section and the top end of the second support section will yield under load before a center portion of the support where the third filler material resides begins to yield.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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:

[0021] FIG. 1 is a perspective side view of a first embodiment of a support in accordance with the principles of the present invention.

[0022] FIG. 2 is a perspective side view of the support shown in FIG. 1 in an unfilled and collapsed state.

[0023] FIG. 3 is a perspective side view of the support shown in FIG. 1 in an unfilled and collapsed state coupled to a pump system.

[0024] FIG. 4 is a perspective side view of the support shown in FIG. 3 in a filled state coupled to a pump system.

[0025] FIG. 5 is a perspective side view of a bladder in an unfilled and collapsed state in accordance with the principles of the present invention.

[0026] FIG. 6 is a perspective side view of the bladder of FIG. 5 in a filled and expanded state.

[0027] FIG. 7 is a cross-sectional side view of a nozzle port in accordance with the principles of the present invention.

[0028] FIG. 8 is a cross-sectional side view of the nozzle shown in FIG. 7 coupled to a nozzle in accordance with the principles of the present invention.

[0029] FIG. 9 is a perspective side view of an embodiment of a support in an expanded and non-collapsed state installed in a mine entry in accordance with the principles of the present invention.

[0030] FIG. 10 is a perspective side view of the support illustrated in FIG. 8 in an expanded and partially collapsed state installed in the mine entry.

[0031] FIG. 11 is a perspective side view of the support illustrated in FIG. 9 in an expanded and further partially collapsed state installed in the mine entry.

[0032] FIG. 12 is a perspective side view of the support illustrated in FIG. 9 in an expanded and still further partially collapsed state installed in the mine entry.

[0033] FIG. 13 is a perspective side view of the support illustrated in FIG. 9 in an expanded and substantially fully collapsed state installed in the mine entry.

[0034] FIG. 14 is a perspective side view of a second embodiment of a support in accordance with the principles of the present invention.

[0035] FIG. 15 is a cross-sectional side view of a third embodiment of a support in accordance with the principles of the present invention in a collapsed state.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0036] FIG. 1 illustrates a first embodiment of a mine roof support in expanded form, generally indicated at 10 in accordance with the principles of the present invention. The support 10 may be utilized in various underground support situations including without limitation underground mine roof support, various tunnel applications or the like. The support 10 is comprised of a lower support section 12 that is comprised of an outer shell 14 in the form of a tube that is partially prefilled with a first compressible filler material 16, such as an aerated concrete aerated grout, foam or other suitable material known in the art and an upper support section 18 that is coupled to the lower support section 12 in a telescopic manner. The outer shell 14 may be comprised of a sheet of metal, such as steel, that is rolled into a cylinder and welded along a seam 15 that extends the longitudinal length of the outer shell 14. The upper support section 18 is comprised of an outer shell 20 that is substantially prefilled with a second compressible filler material 22. The second filler material may be of the same composition as the first compressible filler material. The upper support section 18 is also comprised of a sheet of a metal, such as steel, that is rolled into a cylinder and welded along a seam 19 that extends the longitudinal length of the outer shell 20.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Referring now to FIG. 2, there is illustrated the support 10 in a pre-expanded position where the outer shell 20 of the upper support section 18 is positioned or disposed at least partially within the lower support section 12 and the bladder 32 is collapsed and not yet filled with a filler material. The outer shell 20 of the upper support section 18 may be fully, substantially (i.e., with a small portion or few inches of the outer shell 20 exposed) or partially disposed (i.e., with several inches of the outer shell 20 exposed) within the lower support section 12. The outer shell 20 has an outer diameter that is slightly smaller (e.g., 0.125-0.5 inch smaller or less) than the inner diameter of the outer shell 14 of the lower support section 12, thus forming a small annular gap 28 between the outer shell 14 and the outer shell 20. This allows the support 10 to be transported and moved into position while protecting the outer shell 20 of the upper support section 18 from being damaged and to provide the support 10 in a more compact state. The bladder 32 is in a compressed state and sandwiched between the upper and lower sections 18 and 12.

[0045] 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.

[0046] As further illustrated in FIG. 3, once the support 10 is moved into position between the roof 40 and the floor 42, a pump system, generally indicated at 44, is coupled to the support 10 via the nozzle port 30. The pump system 44 includes a nozzle 46 configured for coupled to the nozzle port 30, a hose 48 coupled between the nozzle 46 and a pump 50. The pump 50 is in fluid communication with a filler material supply vat or tank (not shown) that contains the filler material in liquid form so as to be pumped with the pump system 44 into the bladder 32 under pressure. This operation is performed in situ with the support 10 in the desired position to provide support between the roof 40 and floor 42.

[0047] As shown in FIG. 4, once the pump system 44 is engaged and filler material is pumped into the bladder 32 under pressure, the filler material 52 causes the bladder 32 to expand and forces the upper support section 18 away from the lower support section 12 in a telescopic manner. The upper support section 18 is lifted until the top 24 of the upper support section 18 abuts against the roof 24. By utilizing a relative quick setting filler material 52, the support 10 can begin bearing a load in a relatively short period of time (e.g., 1 to 2 hours). Obviously, the filler material 52 is made not to cure too rapidly so that larger batches of the filler material can be prepared in advance for installing several supports 10 at a time before the batch of filler material starts to cure. For example, a batch of filler material 52 that cures in two hours allows those installing supports to premix enough filler material 52 to adequately install a significant number of supports during that time (e.g., ten supports) before a new batch of filler material is needed. Also, this provides enough curing time to allow the pump system 44 to be properly cleaned between batches so that the filler material does not cure inside the pump system 44.

[0048] FIGS. 5 and 6 illustrate a bladder 60 in accordance with the principles of the present invention. In FIG. 5, the bladder 60 is shown in a pre-expanded state and in FIG. 6, the bladder is illustrated in an expanded state. The bladder 60 is comprised of a flexible bag portion 62 and a nozzle port 64 coupled to the bag portion 62 at a lower end thereof. The bag portion 62 may have a generally cylindrical shape with a diameter approximately equal to the inside diameter of the lower support section. The bag portion 62 may be of a baffle-type design as illustrated or a simple cylindrical shape. The bag 62 is formed from a flexible yet strong material having a thickness capable of maintaining pressure exerted on the bag 62 when filled so as to prevent rupture of the bag 62 during the filling process and until the filler material pumped into the bag 62 cures. As shown in FIG. 6, when filled, the bag 62 has a generally cylindrical shape so as to fill the space between the upper and lower support sections as previously described. It is also contemplated that the bladder 60 may have a maximum filling capacity to limit the extension of the upper support section relative to the lower support section. Typically, the distance between the roof and the floor of a mine entry are known and the support is manufactured in sizes to match the distance. As such, the required extension of the upper support section relative to the lower support section may only require about six to eighteen inches of extension of the upper support section. As such, the bladder 60 could have a maximum expansion of approximately twenty-four inches so that there is a limit to the expansion between the upper and lower support sections. Once the bag 62 of the bladder 60 is fully filled, a pressure sensor on the pump system will cause the pump to disengage, alerting the user that a maximum bladder expansion has been reached. This feature is also useful to alert the user that the support is sufficiently expanded between the floor and the roof. That is, when the pump senses sufficient pressure, as when the upper support section has been expanded until it firmly abuts against the roof, the pump will shut off to alert the user that the support has been properly installed.

[0049] FIG. 7 illustrates a nozzle port 80 is attached to the outer shell 14 of the lower support section 12 in a hole 82 formed therein. The nozzle port 80 is comprised of an externally threaded tube 84 to which first and second nuts 86 and 88 attach the tube 84 to the outer shell 14 and nuts 88 and 90 attach the nozzle port to the bag 62 of the bladder 60. A one way valve 92 comprised of a flexible plate 94 is attached in a cantilevered manner to the end of the tube 84 that allows filler material to flow into the bag 62 but that prevents the filler material from flowing back out through the tube 84. As sown in FIG. 8, when pressurized filling material flows through the tube as indicated by the arrow, the filling material forces the flexible plate to bend away from the tube allowing the filling material to flow into the bag 62 only in one direction as indicated by the arrow. When the nozzle 96 is removed from the tube 84, the valve 92 closes to prevent the filler material from escaping through the tube 84.

[0050] Referring now to FIG. 9, once the support 10 is positioned and the outer shell 20 of the upper support section 18 is raised using the filling nozzle 96 shown in FIGS. 7 and 8 is used to engage with the orifice or port 80 so that the upper support section 18 can be lifted with a compressible filler material, such as a lightweight grout or cement, a foam or other materials known in the art. The port 80 is positioned proximate the top surface 100 of the precast filler material 102 in the bottom portion of the lower support section 12. As such, the bladder 60 can rest upon the top surface of the filler material 102 while being filled. The bladder 60 is filled until the filler material forces the upper support section 18 into engagement with the roof 40. Once it is evident that the upper support section 18 is sufficiently engaged with the roof, the nozzle 96 can be removed. By using a filler material that is in an at least partially liquefied form that will relatively quickly harden once pumped into the upper support section 18, once cured, settling of the filler material can be minimized if not eliminated. It is also contemplated that once the bladder is filled with a filler material, the orifice or port 80 can simply be plugged with a tapered plug that will prevent any filler material from escaping from the port 80. Those of skill in the art will appreciate that other mechanisms and/or structures may be used to effectively close the port once the filling process is completed to prevent the filler material from escaping through the port and such other mechanisms and/or structures are incorporated herein.

[0051] 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.

[0052] FIG. 9 illustrates a support 10 according to the present invention in a fully extended position with the bottom end 107 of the support 10 in contact with the floor 42 and the upper end 24 of the support 10 engaging the roof 40. Once the center section 109 of the support that was filled in situ with filler material 111 through the nozzle port 80 as previously described has adequately cured, the support 10 can begin bearing a load as the roof 40 and floor 42 converge as is typically the case in underground mine entries.

[0053] As shown in FIG. 10, as the roof 40 and floor 42 converge, either by the roof moving toward the floor or the floor heaving toward the roof, the support 10 will begin to collapse upon itself in a controlled and predictable manner. That is, the upper and lower ends 24 and 107 of the support 10 will begin to yield as the filler material is compressed and the outer shells 14 and 20 fold upon themselves in an accordion-like manner. More specifically, the upper and lower sections 18 and 12 will yield along their length typically from the ends 24 and 107 toward the center.

[0054] 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 FIGS. 10 and 11, as the support 10 first begins to yield, the support 10 is more likely to begin yielding from the top and bottom ends 24 and 107 of the support 10. The outer shells 14 and 20 will begin folding upon themselves in an accordion-style manner due to plastic deformation of the outer shells 14 and 20 as illustrated and the filler material 22 begins crushing to form sections within the accordion-style folds 119 of higher density as illustrated. Because the center support section 109 that is filled in situ is filled with a filler material 111 of higher density it will likely not begin yielding until the precast portions of the upper and lower sections 18 and 12 have undergone significant yielding. It is also less likely that the central section of the support 10 where the outer shells 14 and 20 overlap will yield initially since an effective double wall is formed that will provide additional load bearing strength along this section.

[0055] As illustrated in FIG. 12, the upper and lower sections 12 and 18 will continue to yield along their lengths while the outer shells 14 and 20 maintain sufficient hoop strength to contain the compressed filler 22 without bulging or lateral buckling. Once the lower and upper sections 12 and 18 have substantially been compressed as shown in FIG. 12 and a first yield limit has been reached, the center section 109 will then begin yielding until a second yield limit is reached as shown in FIG. 13. Again the outer shells 14 and 20 will begin folding upon themselves in an accordion-style manner due to plastic deformation of the outer shells 14 and 20 as illustrated and the second filler material 111 will begin crushing to form another section of higher density. Once the center section 109 begins to yield, as can be visibly observed, mine operators are alerted that complete failure of the support 10 is approaching and that all personnel and mining equipment should be removed from the area. The support 10 will continue to yield to the second yield limit until the filler material contained in the bladder is substantially fully compressed causing either the support 10 to fail or the support 10 to effective punch through the roof or the floor in which case the roof will collapse around the support 10. At this point, however, the support has effectively performed as expected.

[0056] As shown in FIG. 14, a second embodiment of a support, generally indicated at 200, is illustrated. The support 200 has a configuration similar to the configuration of the support 10 illustrated in FIG. 1, but rather than having a bladder system interposed between the upper and lower support sections 202 and 204, an air space 206 is formed between the precast filler materials 208 and 210 of the upper and lower support sections 202 and 204, respectively. A small block 220 of filler material may be interposed between the precast filler materials 208 and 210 of the upper and lower support sections 202 and 204, respectively, to form the air space gap 206 therein between. As another filler material 225 in liquid form is pumped through the port 226 as previously described, the filler material 225 will first completely fill the gap 206 and then subsequently cause the upper support section 202 to rise relative to the lower support section 204 until adequately extended between the floor and roof of a mine entry or other underground tunnel.

[0057] 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 FIG. 15 that a support 300 according to the present invention may comprise an outer shell 302 of an upper support section 301 that is disposed over the outer shell 304 of the lower support section 303. In this case, the upper support section is precast with a filler material, inverted and then placed over the top of the lower support section. This configuration has the advantage that the upper support section 301 will have less weight that the upper section previously described herein as only a portion of the upper section 301 is filled with compressible filler material. In addition, if the support 300 is stored outside prior to use, the gap between the outer shell 302 of the upper support section 301 and the outer shell 304 of the lower support section 303 will not accumulate water as may be the case when the support is inverted. Effectively, the support 300 is the same as the support 10 but simply inverted. Thus, while reference has been made to upper and lower support sections, it is noted that the orientation of the resulting support is not critical and can properly function in either orientation.

[0058] 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/ft.sup.3. 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/ft.sup.3. 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.