Patent Application
20090010715
1. Field of the Invention
The present invention relates to permanent isolation seals for mining applications and, more particularly, to a permanent seal in an underground entry to isolate the atmosphere on one side of the seal from the atmosphere on the other side.
2. Description of Related Art
In underground mining, there is typically a need to isolate the atmosphere in a specific portion of the mine. A seal is provided to isolate areas of the mine for purposes such as to limit the area of the mine workings that need to be ventilated, to control the dissemination of any toxic or explosive gases in the mine, or to allow the atmosphere in an isolated part of the mine to change its composition to a less hazardous state. Seals are constructed across individual mining entries or tunnels to provide such isolation.
Seals have been traditionally constructed as walls of stacked concrete blocks that may be coated or joined together with a cementitious material, which is considerably weaker than the concrete blocks themselves. Further, the cementitious material typically shrinks over time creating leaks in the seal and possibly allowing dangerous gases to bypass the seal. Blocks are fitted across a mine opening in a staggered or overlapping relationship. Such seals, however, have not been found to withstand mine explosion overpressures of over 20 psi. More recently, a mine seal has been employed that incorporates concrete block walls sandwiching an inner core of a polymeric material containing aggregate. This composite structure of a core provided between two concrete block walls (described in U.S. Pat. No. 5,385,504, incorporated herein by reference), is constructed by dry-stacking concrete blocks to form walls between the roof, floor and ribs of a mine entry. A rear wall is first constructed and wedged into place. Next, a front wall is constructed to a height of 2-3 feet and construction continues by pyramiding the blocks until one or two blocks are in contact with the roof. The core material is installed between the fully constructed rear wall and the partially constructed front wall by providing a layer of aggregate material (gravel or the like) between the walls and coating the aggregate material with foamable polyurethane. As the polyurethane foams and cures, the polyurethane increases in height (with the aggregate mixed therein) and solidifies, adhering to the rear and front walls. Construction of the front wall continues and additional layers of the core material (polyurethane and aggregate) are provided between the rear wall and the growing front wall until the core material and the front wall reach the roof of the mine entry. The outside surface of the front wall is covered with a coating of a fire-resistant sealant satisfying the guidelines of the Mine Safety and Health Administration (MSHA). While this composite seal withstands mine explosion overpressures of at least 20 psi, a need has been identified to increase the pressure rating of mine seals.
This need is met by the mine seal of the present invention that includes a pair of walls, each wall including a plurality of blocks and a core provided between the walls and adhering to the walls. An adhesive is provided between adjoining surfaces of the blocks of the walls. The sealant has greater strength properties than the blocks. The main seal may further include at least one internal wall to provide additional strengthening of the seal. The present invention also includes a method of strengthening a wall that includes a plurality of blocks by providing a plurality of individual blocks, coating a surface of each block with an adhesive and stacking the blocks to form a wall with the adhesive being positioned between adjoining surfaces of the blocks, wherein the adhesive has greater strength properties than the individual blocks.
Referring to
The strength of the seal 2 may be enhanced by including an adhesive layer on one or more surfaces of the composite walls 14, 16, such as surface layers 28, 30 on respective walls 14, 16 facing the core member 18 and/or front surface layer 32 on front wall 16. It should be understood that the thickness of the layers 28, 30, 32 and the thickness of the adhesive 22 between the blocks 20 are exaggerated in the drawings for illustration and may be selected based on the design parameters for the strength requirements of a particular installation of the seal 2. The seal 2 may further include, in addition to the rear composite block wall 14, the front composite block wall 16, and the core member 18, one or more interior walls (such as a solid concrete block wall as described herein with respect to walls 14, 16) to provide additional strengthening of the seal. Additional core members 18 may be provided between each interior wall and between each interior wall and the walls 14, 16.
Additional adhesive 22 may be provided between walls 14, 16 and the surfaces of the mine entry 4 as at 34. This additional adhesive 34 can fill in gaps between the walls 14, 16 and floor 6, roof 8 and pillars 10, 12, particularly in rough mine entries. Additional adhesive 34 also serves to bind the seal 2 to the mine entry surfaces and increase the integrity of the seal 2 as the adhesive 34 seeps into cracks in the entry surfaces and cures therein. The exposed surface of front wall 16 or front surface layer 32 may be coated with a conventional MSHA-approved fire-resistant sealant layer 36.
The core member 18 provided between any two walls may be produced from a binding material 24, such as a foamable polyurethane (e.g., RokLok® 10 available from Micon, Inc.). A foamable polyurethane expands upon curing to produce a network of closed cell foam that fills in any void spaces between the two composite block walls 14, 16. Other binding materials may be used, such as plastics, polymeric foams and synthetic foams. The core member 18 binds to both composite block walls 14, 16, thereby creating an integral seal. The core member 18 may include aggregate material 26 (such as gravel, limestone, talc, glass, or other inert filler particulates). The aggregate material 26 is used in combination with the binding material 24 to increase the strength of the core member 18 at minimal expense. The proportion of aggregate material 26 to binding material 24 may be adjusted to ensure sufficient binding of the core member 18 to the composite block walls 14, 16.
The core member 18 is installed stepwise along with construction of the front wall 16. A layer of the aggregate material 26 is provided behind the partially constructed front wall 16 and the foamable polyurethane (or other binding material 24) is applied to the aggregate layer. As the polyurethane cures and foams, the aggregate material 26 moves therewith to fill the gap between the back and front walls 14, 16. Subsequent courses of the concrete blocks 20 are constructed and additional aggregate material 26 and binding material 24 are placed on top of the precedingly produced foamed polyurethane/aggregate layer between the two walls 14, 16 until the front wall 16 and core member 18 are completely constructed. Alternatively, the core member 18 may be constructed stepwise by applying layers of foamed polyurethane into the gap between the rear wall 14 and growing front wall 16 without the aggregate. The adhesive 22 may be applied to the backside of the front wall 16 as the first wall is constructed, creating surface layer 30, and/or may be applied to the exposed surface of the front wall 16 as front surface layer 32 for providing additional strength to the seal. The adhesive layers 28, 30 and 32, as well as additional adhesive 34 are used depending on the strength requirements for the seal 2. Finally, a fire-resistant sealant 36 is applied to the exposed surface of the front wall 16 or front surface layer 32.
In one embodiment of the present invention, shown in
The plurality of blocks 38 may be installed stepwise along with construction of the front wall 16 as shown in
A monolithic core structure of the blocks 38 adhered together with adhesive 22 may be produced in a few hours (such as about 2 hours) as compared to production of conventional block seals produced from cementatious materials that may require up to several days to cure and be useable. Further, the blocks may be cut and shaped at the installation site to fit the mine entry 4. Foamable polyurethane creates heat as it cures and foams through an exothermic reaction. The heat from this reaction may cause certain safety concerns, such as an increased risk of a fire, in an underground mine environment. Thus, forming the core member 18′ from the plurality of blocks 38 above ground minimizes the amount of heat created in an underground mine.
In a further embodiment of the present invention, shown in
The mine seal of the present invention provides a tight seal within the mine entry. The adhesive seals around the entire perimeter of the seal structure, thereby impeding movement of the mine atmosphere from one side of the seal to the other and increasing the integrity of the seal within the mine entry. It has been found that the mine seal of the present invention can withstand mine explosion overpressures of well in excess of 20 psi, such as in excess of 240 psi. The strength of the seal is partially a function of the adhesive material between the blocks, which greatly increases the strength of the block wall bound to the core member over prior seals. The adhesive material also has flexural properties, which allows the seal to better absorb energy and prevent the formation of cracks in the seal over prior seals. Further, the adhesive material does not shrink or degrade over time providing a longer life expectancy for the seal compared to prior seals formed with a cementitious material. Increased strength properties are achievable by coating the surfaces of the front and back walls with layers of the adhesive. In this manner, the strength of the seal may be selected depending on the particular conditions of a mine.
It should be appreciated that the composite wall of the present invention may also be used in the construction industry or the like, such as in foundations, dividing walls, or to provide damage resistance to extraneous explosions (i.e., as a security barrier). Instead of constructing block walls by dry stacking blocks or mortaring blocks, the adhesive used in the present invention creates composite block walls with strength properties heretofore unobtainable.
It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Such modifications are to be considered as included within the following claims unless the claims, by their language, expressly state otherwise. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
This application claims the benefit of U.S. Provisional Application No. 60/933,555, filed Jun. 7, 2007, the entire contents of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60933555 | Jun 2007 | US |
