Yieldable cambered arch support assembly

Abstract

An arch support assembly for withstanding the effects of rock burst in underground mines, which includes a spaced aligned series of arch supports, each support having a spaced pair of upright side support columns with an upwardly cambered cap beam arch having opposite ends therefore transversely meeting and secured respectively to the upper ends of the side columns at an obtuse angle. The arch supports are rigidly tied together and provided with a roof supported by the cap beams to provide in combination an arch support assembly. A yielding connection is provided between the upright side columns and the cap beam ends whereby the cambered cap beams are permitted to flex downwardly under an impact load on the roof and the cap beam ends are thereby permitted to extend transversely a controlled limited amount relative to the upright side columns under a yieldable interference friction securement

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/518,477, filed May 6, 2011, the entire content of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to mine roof control, and more particularly, it is directed to a yielding arch support for withstanding the effects of impact loading during rock burst occurring in underground mines or tunnels. This invention relates particularly to cambered steel arches capable capable of yielding instantly under sudden impact, such as to cushion the effect of rock burst, in such a manner so as to avoid distortion of the roof arch and maintain the integrety of the support assembly.

BACKGROUND OF THE INVENTION

As mining conditions continue to deteriorate due to depletion of easily accessible reserves, arch support installation is becoming more common. Currently all wide flange arch support assemblies are rigid. Cambered arch support assemblies are typically installed in an area where a roof fall has occurred and loose debris has been removed. In order to protect miners from secondary rock falls, arch support assemblies must be installed to protect the miners using the travel way. The object is for the cambered arch support system or assembly to absorb the impact of a rock burst impact load.

Typically, when an underground mine experiences a roof fall, the rock debris is removed from the area and the area of the roof fall is bolted and backfilled to reduce the risk of further rock fall. The process of bolting and backfilling the area of the roof that experience roof fall, however, is a time consuming process that requires the mine to stop production. In addition, backfill material is costly and backfilling the large roof fall area can become prohibitively expensive. Accordingly, steel arch support assemblies are more currently utilized as a simple and reliable system to protect personnel and moving vehicles from falling rocks.

Generally, these rigid arch support assemblies incorporate a roof structure spanning between adjacent arch supports of the assembly as lagging panels which are intended to absorb the impact loads from the falling rock. As an example, see the impact resistant lagging assembly disclosed in U.S. Patent Application Publication No. US 2010/0266349, published on Oct. 21, 2010.

Presently, wide flange arch support assemblies deform when an impact load is applied and the arch sets comprising the assembly are compromised and cannot be preserved and therefore have to be replaced.

SUMMARY OF THE INVENTION

The arch support assembly of the present invention can withstand the effects of rock burst in underground mines without being compromised, whereby the structural integrity of the steel sets making up the assembly is preserved. The arch support assembly of the present invention includes a spaced aligned series of arch supports, each support having a spaced pair of upright legs or side support columns with an upwardly cambered cap beam having opposite ends thereof transversely meeting and secured respectively to the upper ends of the side columns at an obtuse angle. The arch supports are rigidly tied together and provided with a roof that is supported by the cap beams to provide in combination an arch support assembly. The improvement of the present invention includes a yielding connection provided between each of the upright columns and the cap beam ends whereby the cambered cap beams are permitted to flex downwardly under an impact load on the roof and the cap beam ends are thereby permitted to extend transversely a controlled limited amount (generally a yield of not more than a few inches) relative to the upright side columns under a yieldable interference friction securement fit.

Tie rods tie adjacent of the spaced arch supports together with portions of the roof spanning therebetween under compression. Accordingly, extreme movement of the arch support assembly under impact loading is limited. The yielding cambered arch design allows adequate movement to absorb impact but not extreme yielding movement which would exert stress on the tie rod connections.

The cap beams are generally wide flange cap beams (metal I-beams), and the roof generally consists of parallel beam panels or segments which are confined at their opposite ends by the cap beam flanges and retained transversely to and between adjacent cap beams under longitudinal compression. These roof panels are generally constructed of wood, but may also be constructed of other appropriate materials, or combinations thereof, such as plastic and metal.

The side legs or upright support columns may also be constructed of flanged metal I-beams with parallel beam wall segments confined at their opposite ends by the upright column beam flanges.

The yielding connections between the cap beams and the upright column beams take on different configurations. As one example, the yielding connection may consist of fasteners secured through apertures which are elongated in the direction of extension of the cap beams in order to provide the yieldable interference friction securement fit between the cap beam ends and the upright side columns. As another alternative, the yielding connection may consist of a clamped connection, such as a connection known in the industry as a clamped TH-Profile connection.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages appear hereinafter in the following description and claims. The accompanying drawings show, for the purpose of exemplification, without limiting the scope of the invention or the appended claims, certain practical embodiments of the present invention wherein:

FIG. 1 is an isometric view of the arch support assembly according to one embodiment of the present invention;

FIG. 2 is a view in front elevation of one adjacent set of arch supports illustrating an embodiment of the present invention, for incorporation into the support assembly shown in FIG. 1;

FIG. 3 is a view in right side elevation of the arch support set shown in FIG. 2;

FIG. 4 is an enlarged isometric view of the left side yielding connection provided between the cap beam and left side upright support column shown in FIG. 2 before impact loading;

FIG. 5 is a view in front elevation of the yielding connection shown in FIG. 4;

FIG. 6 is a view in front elevation of the yielding connection shown in FIGS. 4 and 5 after impact loading;

FIG. 7 is an isometric view of the yielding connection shown in FIG. 4 after impact loading;

FIG. 8 is a view in front elevation of a set of adjacent arch supports for incorporation into the arch support assembly of FIG. 1, illustrating a second embodiment of the yielding connection between the cap beam and the upright side support columns;

FIG. 9 is a view in right side elevation of the arch support set shown in FIG. 8;

FIG. 10 is an enlarged front view of the yieldable connection provided between the left end of the cap beam and the top end of the left side support column of the support arch illustrated in FIG. 8 prior to impact loading; and

FIG. 11 is an enlarged view in front elevation of the yielding connection shown in FIG. 10 after impact loading.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, the arch support assembly 10 of the present invention is provided for withstanding the effects of rock burst in underground mines, and includes a spaced aligned series of arch supports 11. Each support 11 has a spaced pair of legs or upright side support columns 12 with upwardly arched or cambered cap beams 13 having opposite ends 14 meeting and secured respectively to the upper ends 15 at an obtuse angle as illustrated. Arch supports 11 are rigidly tied together with tie rods 16 and provided with a roof 17 supported by cap beams 13 to provide in combination the arch support assembly 10.

A yielding connection 18 is provided between the upright columns 12 and cap beam ends 14 whereby cambered cap beams 13 are permitted to flex downwardly under an impact load on roof 17 and cap beams 13 are thereby permitted to extend laterally at their ends 14 a controlled limited amount relative to upright columns 12 under a yieldable interference friction securement fit of yielding connections 18.

Cap beams 13 and upright side columns 12 are wide flanged steel beams of a generally I-beam configuration. The side columns 12 are supported on runner channels 19 which permit sliding of the entire arch support assembly 10 along a ground surface as a unit.

Roof 17 is comprised of parallel beam segments 20, which in this instance are constructed of wood, but may also be constructed of plastic or metal. These parallel beam segments 20 are confined at their opposite ends by the side flanges of cap beams 13 whereby they are retained transversely to and between adjacent cap beams 13. Tie rods 16 tie adjacent of the spaced arch supports 11 together with the roof panels or beams 20 therebetween under compression.

The sidewalls 21 are constructed in the same manner as the roof 17.

Two different example embodiments of the yielding connections 18 are illustrated. Referring first to FIGS. 2 through 7, the yielding connection for the assembly 18 of the present invention consists of fasteners secured through apertures elongated in the direction of extension of the cap beams 13 for thereby providing a yieldable interference friction securement fit. The yield is created by allowing a wedged or elliptical shape set of fasteners 23 to be slidably forced to and into corresponding wedge or elliptical shape slots 24, which creates a frictional load in the lower connection butt plate 25. Plate 25 is welded to the upper end 15 of upright side column 12. The torque as illustrated by arrow 26 is applied to fastener 18, and varies according to the size of the wide flange section of the steel I-beams utilized for the arch supports 11. It amounts generally from between 200 to 700 Ft. Lbs. When impact load is applied as indicated by arrow 26, yieldable connection 18 permits the ends 14 to yield or extend laterally or outward as indicated by arrow 27 in FIG. 5 relative to upright side support column 12 under the yieldable interference friction securement fit between the bottom of cap beam 13 and butt plate 25 due to the pre-torqued securement of fasteners 23. In beam arch support assemblies of the prior art utilizing wide flange supports, the arch supports were deformed when an impact load was applied and the arch supports had to be replaced. With the arch support assembly of the present invention the arches 11 are allowed to yield and the structural integrity of the steel set is preserved and the connections are not comprised. Movement of the upper portion of the wedge elliptical shape fasteners 23 into wedged or elliptical shaped slots 24 in the cap beams 13, prevents the fasteners from shearing.

Typically the cambered arches 11 are installed in courses of three or more units. The individual arch sets 11 are bound together by tie rods 16 pulling individuals adjacent sets of arch supports 11 tightly together, placing the roof beam segments 20 under compression. Because the individual arches 11 are tightly bound together, extreme movement under impact loading is limited. The yielding cambered arch support assembly 10 of the present invention allows adequate movement to absorb impact but not extreme yielding movement which would exert stress on the tie rod connections.

Referring next to FIGS. 8 through 11, a second embodiment of the yielding connection 18 is illustrated. In this embodiment, the yielding connection 18 consists of a clamped connection. In this embodiment, a TH-Profile 30 and clamps 31 are utilized to create a friction surface between the two profile sections 32 and 33 of TH-Profile 30. The TH-Profile is known in the industry as a seated combination of two U or V shaped channel sections which are clamped together in order to provide a yielding slidable friction fit. Generally the profile members or sections 32 and 33 are designed whereby the shifting of the profile members relative to one another is between the side flanges of the profiles rather than between the side walls of the profiles. The profile section 33 is secured to the upper end of leg or upright side column 12 and the other upper profile section 32 is secured to cap beam 13. The clamp 31 determines the yield load of the structure. As is best illustrated in FIG. 11, upper profile section 32 is secured by a weld fitment to the underside of cap beam 13 between the two welded gusset plates 34, and lower profile section 34 is welded to the top 15 of upright end column 12. During impact loading test with a 2,200 pound weight drop on a course of arches 11, as structured according to the illustration of FIG. 1, the deformation was only a few inches. By allowing the course of arches to yield only a few inches the structural integrity is maintained.

Accordingly, the yieldable connections 18 provided in the wide flange structure of arch support assembly 10 of the present invention easily absorbs impact energy from rock falls or rock bursts, and because of the connection of the tie rods 18 between adjacent arch supports 11, the unit is tied together so that the assembly can yield little. Accordingly, the integrity of the arches are maintained, eliminating the necessity for replacement.

Claims

1. In an arch support assembly for withstanding the effects of rock burst in underground mines, including a spaced aligned series of arch supports, each support having a spaced pair of upright side support columns with an upwardly cambered cap beam having opposite ends thereof transversely meeting and secured respectively to the upper ends of said columns at an obtuse angle, said arch supports rigidly tied together and provided with a roof supported by said cap beams to provide in combination said arch support assembly, the improvement comprising;

a yielding connection provided between said upright columns and said cap beam ends whereby said cambered cap beams are permitted to flex downwardly under an impact load on said roof and said cap beam ends are thereby permitted to extend transversely a controlled limited amount relative to said upright columns under a yieldable interference friction securement fit.

2. The arch support assembly of claim 1, including tie rods tying adjacent of said spaced arch supports together with portions of said roof spanning therebetween under compression.

3. The arch support assembly of claim 2, wherein said cap beams are flanged metal I-beams, said roof consisting of parallel beam segments confined at their opposite ends by said beam flanges and retained transversely to and between adjacent cap beams under longitudinal compression.

4. The arch support assembly of claim 3, wherein said beam segments are selected from one or more of wood, plastic and metal.

5. The arch support assembly of claim 3, wherein said support columns are also flanged metal I-beams with parallel beam wall segments confined at their opposite ends by said column beam flanges.

6. The arch support assembly of claim 1, said yielding connection including fasteners secured through apertures elongated in the direction of extension of said cap beams.

7. The arch support assembly of claim 6, wherein said fasteners have heads which correspond in shape to said apertures whereby said heads are drawn into said apertures after initially sliding with a frictional fit with an applied impact load.

8. The arch support assembly of claim 1, said yielding connection consisting of a clamped connection.

9. The arch support assembly of claim 8, wherein said clamped connection is a clamped TH-Profile of a predetermined limited length.

10. An arch support assembly for withstanding the effects of rock burst in an underground mine, comprising:

an aligned series of spaced arch supports, each support including a spaced pair of upright side support columns with an upwardly cambered cap beam having opposite ends thereof transversely secured to upper ends of said upright support columns with a yielding friction fit connection permitting a controlled limited amount of yield;

a roof structure spanning between each adjacent set of cap beams; and

tie rods tying said adjacent cap beams together with said roof structure thereby retained under compression.

11. The arch support assembly of claim 10, said roof structure comprised of a parallel series of beam segments.

12. The arch support assembly of claim 11, wherein said beam segments are selected from one or more of wood, plastic and metal.

13. The arch support assembly of claim 10, said yielding connection including fasteners secured through apertures elongated in the direction of extension of said cap beams.

14. The arch support assembly of claim 13, wherein said fasteners have heads which correspond in shape to said apertures whereby said heads are drawn into said apertures after initially sliding with a frictional fit with an applied impact load.

15. The arch support assembly of claim 10, said yielding connection consisting of a clamped connection.

16. The arch support assembly of claim 15, wherein said clamped connection is a clamped TH-Profile of a predetermined limited length.