Patent Publication Number: US-10329911-B2

Title: Mine seal and method of construction for high resistance to transverse loads

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 14/108,892 filed Dec. 17, 2013 still pending, and is a continuation-in-part of U.S. patent application Ser. No. 12/584,429 filed Sep. 5, 2009, which application is still pending, 
     FIELD OF THE INVENTION 
     The present invention relates to devices for controlling the flow of air in mines or devices for sealing off passageways in mines and particularly to a mine ventilation wall or mine seal formed with a plurality of interlocking masonry blocks for high resistance to transverse loads. 
     BACKGROUND OF THE INVENTION 
     Walls are typically formed in mine tunnels for either controlling the flow of air through the mine or for sealing off abandoned sections of the mine. Mine ventilation walls, also known as brattice walls, are frequently constructed in mines to restrict the flow of air to certain passageways in order to maintain a flow of air to the mine face and all portions of the mine that are actively used by mine personnel. Mine seals or stoppings are typically constructed to seal off mined-out areas or abandoned portions of mines. 
     Previously, materials used to construct mine seals typically included conventional concrete blocks or prefabricated blocks or panels formed of foam or composites. However, the Sago mine disaster, which involved the failure of a mine seal formed of a dense foam product, proved the futility of constructing mine seals with foam. In that instance, an explosion occurred in a mined-out area that had been sealed only a short time before the disaster. Although mine seals may be constructed of conventional concrete blocks, conventional concrete blocks do not provide the shear strength necessary to withstand high transverse loads or shear forces, such as would be experienced in an explosion. 
     Accordingly, what is needed is a mine seal or stopping structure that is capable of being rapidly constructed while at the same time is capable of withstanding large transverse loads. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a mine seal or wall capable of retaining its integrity under a transverse load without the use of rebar or similar reinforcement materials. The mine seal is constructed of a plurality of interlocking masonry blocks. The interlocking blocks include a body with a top surface, planar sides, planar ends, and a bottom surface. A top shear lug extends longitudinally along the top of the block. An end shear lug extends vertically along each end of the block. The bottom surface and ends of the block include grooves therein for accommodating the shear lugs of adjacently stacked blocks. The blocks are dry-stacked in successive rows to construct a mine wall. When stacked end to end in successive rows, the top and end shear lugs of each interlocking block engage complimentary grooves in the adjacent blocks thereby enabling the blocks to self-align vertically and lock together as they are stacked. The resulting mine seal exhibits a high resistance to transverse loads. 
     OBJECTS AND ADVANTAGES 
     Several advantages are achieved with the mine seal of the present invention, including:
         a. The mine seal structure exhibits a high resistance to transverse loads. The shear strength of a mine seal constructed according to the present invention averages 1600 lbs/ft higher than the shear strength of a mine seal constructed of conventional solid concrete blocks.   b. Shear lugs on the individual blocks interlock with complimentary grooves in adjacent blocks to substantially increase the shear strength of the mine wall.   c. The shear lugs and complimentary grooves enable rapid alignment of a plurality of interlocking blocks to form a mine wall or seal.   d. The blocks include a self-alignment feature that results in straighter, tighter walls than those constructed of conventional blocks.   e. Blocks are easier to lay or stack than conventional blocks.   f. As only one embodiment of block is required to form a complete mine wall or seal, unit production costs of the block are minimized.   g. As only one embodiment of block is required to form a complete mine wall or seal, the task of transporting the materials required to construct an explosion resistant mine wall is greatly simplified.   h. The block and dry-stacking method of the present invention enables construction of a high shear strength mine seal with a single wall of blocks. Installation time is substantially faster than prior art seals that require pairs or higher numbers of walls.   i. The mine seal of the present invention is explosion-resistant.   j. Interlocking shear lugs and complimentary notches on the blocks result in a mine seal with less leakage than conventional mine seals and more coal mineable per CFM (ventilation flow) and vent setup.   k. The mine seal structure exhibits increased resistance to failure from roof crush, equipment damage, or air pressure differential.       

     These and other objects and advantages of the present invention will be better understood by reading the following description along with reference to the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of partially constructed mine wall according to the present invention. 
         FIG. 2  is a top isometric view of a preferred embodiment of a masonry block used to form the mine wall of  FIG. 1 . 
         FIG. 3  is an end view of the block of  FIG. 2 . 
         FIG. 3A  is a detail view depicting a shear lug and complimentary groove in the block of  FIG. 2 . 
         FIG. 4  is a top view of the block. 
         FIG. 5  is a bottom isometric view of the block of  FIG. 2 . 
         FIG. 6  is an end view of a portion of the mine wall of  FIG. 1 . 
         FIG. 7  is a front elevation view of the preferred embodiment of a mine seal within a mine entrance constructed with a plurality of masonry blocks according to the present invention. 
         FIG. 8  is a sectional view of a portion of the mine seal of  FIG. 7  taken along line  8 - 8  of  FIG. 7 . 
         FIG. 9  is a sectional view of a portion of the mine seal of  FIG. 7  taken along line  9 - 9  of  FIG. 7 . 
         FIG. 10  is a graph depicting a comparison of shear strengths of a mine seal constructed of conventional solid masonry blocks versus a mine seal constructed of the preferred embodiment of block according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1  there is shown a portion of a preferred embodiment of a mine wall or seal  20  according to the present invention. The mine seal  20  includes a base  22  with a level top surface  24  and a plurality of interlocking concrete blocks  26  erected on the level surface. The blocks  26  are preferably dry-stacked in successive layers on the level surface  24 . The blocks include a rapid alignment mechanism for enabling an installer to align the blocks in each successive row with the row of blocks immediately below it. 
     Referring to  FIG. 2 , there is shown a preferred embodiment of an interlocking masonry block  26  according to the present invention for use in constructing the mine seal of  FIG. 1 . The interlocking block  26  includes a solid body  28  with a top surface  30 , bottom surface  32 , end surfaces  34 , and side surfaces  36 . The top, bottom, end, and side surfaces  30 ,  32 ,  34 , and  36  are each substantially planar. A top shear lug  40  extends longitudinally along the top surface  30  and an end shear lug  42  extends vertically along each end  34  of the block. As shown in  FIG. 5 , a bottom groove  44  extends longitudinally along the bottom surface  32  of the block  26  and an end groove  46  extends vertically along each end surface  34 . 
     With reference to  FIGS. 3 and 3A , both the top shear lug  40  and end shear lugs  42  preferably include beveled sidewalls  48  and the grooves  44  and  46  preferably included beveled sidewalls  50 . The shear lugs and grooves are thus substantially trapezoid-shaped as viewed from their ends. The beveled sides of the shear lugs and grooves, as well as the fact that the farthest outward surface  52  of the shear lugs is smaller than the entry  54  of the grooves, enables rapid end-to-end joining of blocks and rapid dry-stacking of successive rows of blocks as the beveled sidewalls  48  of the shear lugs easily find and fit into the respective grooves. 
     Referring to  FIG. 2 , the end shear lugs  42  on each end  34  of the block  26  are on opposite sides of the end, making one end a mirror image of the opposing end. This arrangement gives a distinct advantage when dry-stacking a plurality of blocks as the block need not be rotated 180° on its bottom surface  32  in order to slide it into engagement with an adjacent block in a dry-stacked structure. Thus, an installer can quickly remove blocks from a pallet and stack them into a wall without needing to rotate any individual block into the proper orientation. 
     Most preferably, a substantially linear trench is dug in the floor of the mine tunnel to accommodate poured concrete for the forming of a base  22  with a level surface  24 . Conventional means, such as 2×6-inch boards, can be used to build a form for containing the concrete pour and obtaining the level surface. Furthermore, the concrete base can be formed at a height such that the subsequent rows of blocks will approximately top out substantially even with the mine roof. As mine roofs typically settle with time, the newly formed mine seal will eventually be held in place by overhead pressure. 
     With reference to  FIG. 7 , a plurality of blocks  26  according to the invention are dry-stacked on level surface  24  of base  22  to form a mine seal  20  within a mine entrance or tunnel  56 . In a mine seal  20  according to the present invention, half-length blocks  58  may be used if desired or strictly full-length blocks  26  to block the mine entrance  56 . The level surface  24  of base  24  maintains each succeeding row of blocks level and horizontally aligned with the row or rows below it. Most preferably, sealing materials  60  such as wood planks, foam, or similar materials can be used to seal any air spaces between the seal  20  and the tunnel roof or walls. Preferably, any air spaces may be filled with a coating of MSHA-certified sealant, such as Silent Seal available from Fomo Products, Inc. of Norton, Ohio. Furthermore, the exposed surfaces of either wall may be coated with a conventional MSHA flame retardant sealant layer. 
     As the ends of the blocks  26  of the present invention are minor-images of each other, any block can be swapped end-to-end without regard to fitting into the mine seal structure as each subsequent row of blocks is dry-stacked. The beveled sides of the shear lugs  40  and  42  and grooves  44  and  46 , as well as the fact that the farthest outward surface  52  of the shear lugs is smaller than the entry  54  of the grooves (see  FIG. 3A ), enables rapid end-to-end joining of blocks and rapid dry-stacking of successive rows of blocks as the beveled sidewalls  48  of the shear lugs  40  and  42  easily find and fit into the respective grooves  42  and  44 . As shown in  FIG. 7 , the dry-stacked blocks  26  are slid together end-to-end, with the end surfaces  34  of each adjacent block flush with each other and the bottom surface  32  of any block in an upper row flush with the top surfaces  30  of any adjacent row of blocks below it. Furthermore, the shear lugs  40  on the top of each block  26  and the shear lugs  42  on the ends  34  of each block interlock with their respective grooves  44  and  46  thereby provide a substantial increase in resistance to a shear force or sideways pressure P (see  FIG. 6 ) against either face  62  of the mine seal  20 . 
     With reference to  FIG. 6 , the interlocking shear lugs between all upper and lower surfaces of adjacent blocks and between all end surfaces of adjacent blocks form an effective mine seal that is substantially impervious to air penetration, which property is beneficial when a mine wall is erected as a ventilation wall. When a mine wall is erected to serve as a mine seal  20 , the interlocking shear lugs  40  and  42  enable the wall to resist a substantial a displacement force or shear force P (see  FIG. 6 ). The high shear strength is achieved without the use of reinforcement rods or masonry anchors. 
     Mine seals are constructed to seal off mined-out portions of a mine from the active mine. It is critical that such mine seals exhibit high shear strength or a strong resistance to a transverse load. A transverse load is defined as deflection from pressure exerted on one side of the seal. 
     For testing purposes, several mine seals were constructed with  1 ) conventional solid concrete blocks (control condition), and several with  2 ) mine seal blocks according the present invention (test condition) (see  FIG. 2 ). Resistance to transverse loads varies with the normal load applied at the top of the mine seal. Both sets of mine seals were tested at normal loads of 500, 1750, and 3000 lbs/ft. As shown in  FIG. 10 , a mine seal constructed with mine seal blocks according to the present invention recorded substantially higher shear strength at each of the three normal load conditions. The shear strength for both the control and test condition increased substantially linearly with the normal load. A wall constructed with the mine seal block of the present invention recorded on average 1600 lbs/ft higher shear strength at a given applied normal load than a wall constructed of conventional solid concrete blocks. According to the present invention, the mine seal of the present invention can withstand a shear strength of at least 1900 pounds per foot (lbs/ft) under an applied normal load of 500 lbs/ft, a shear strength of at least 2700 pounds per foot (lbs/ft) under an applied normal load of 1750 lbs/ft, and a shear strength of at least 3600 pounds per foot (lbs/ft) under an applied normal load of 3000 lbs/ft. 
     As shown in  FIG. 2  the blocks  26  of the present invention include a self-aligning structure. The single top shear lug  40  and the complimentary longitudinal groove  44  along the bottom surface  32  ensure that, when forming a mine seal, the blocks in each upper row align properly with the blocks there below to form a perfectly aligned vertical wall. Furthermore, when building the wall, it is not necessary for the installer to align the blocks such that the ends of each block in an upper row are staggered with respect to the ends in any of the lower rows of block. As the lugs substantially lock the blocks together at all seams in the constructed wall, there is no necessity to stagger the blocks, which enables an installer to rapidly construct a mine seal. 
     As the invention has been described, it will be apparent to those skilled in the art that the embodiments shown herein may be varied in many ways without departing from the spirit and scope of the invention. Any and all such modifications are intended to be included within the scope of the appended claims.