Patent Publication Number: US-10774641-B2

Title: Load support drum with resilient core member

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/299,396 entitled “LOAD SUPPORT DRUM WITH RESILIENT CORE MEMBER” filed on Feb. 24, 2016, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The application generally relates to load bearing supports. The application relates more specifically to load bearing columns constructed of multiple stacked drums with a resilient core member surrounded by filler material. 
     Various devices disclosed in the prior art are designed and used to provide support to a mine roof. Underground mining results in removal of material from the interior of a mine, thereby leaving unsupported passageways of various sizes within the mine. The lack of support in such passageways may cause mine roof buckling and/or collapse. Thus, it has been desirable to provide support to mine roofs to prevent, delay, or control collapse thereof. 
     In both underground mining and areas of seismic activity, supports must be engineered to withstand enormous forces propagating through the earth. Building and bridge structures may include modified foundations designed to isolate the superstructure from major ground motion during an earthquake. Such supports for building structures are intended to avoid the transmission of high seismic forces. 
     Bridges and building structures which are located in an earthquake zone are capable of being damaged or destroyed by seismic forces. In general bridge structures may be constructed with bearings between the bridge&#39;s deck or superstructure and the bridge supporting columns to permit relative movement between the two. It is also known to provide damping for the movement upon these bearings of superstructure relative to supports, however the permitted relative movement is not large and furthermore it is not always preferred to attempt to hold a superstructure in a position around a neutral point with respect to the supports. 
     In underground mining applications, supports of aerated concrete in a hollow tube have been used to permit a support to yield axially in a controlled manner that prevents sudden collapse of an underground mine roof. Such supports yield axially as the aerated concrete within the product is crushed and maintains support of a load as it yields. 
     An oak wood post having a length of 6.5 feet and a diameter of 6 inches will have a slenderness (height to width) ratio of 26. Such a post will have a maximum axial load capacity of about 16,000 lbs. For a post formed from spruce, the maximum safe axial load handling capability for a post that is 6.5 feet in length and 6 inches in diameter is about 13,600 pounds. In addition, when a wood post yields by kneeling or buckling, such yielding will result in catastrophic failure of the post in which the post can no longer support the load. 
     Because of the obvious problem associated with such catastrophic failure of posts, various mine props have been developed in the art for supporting the roof of an underground mine. Such mine props have included, various configurations of wood beams encased in metal housings, and complex hydraulically controlled prop devices. Such props, however, do not allow for controlled axial yielding while preventing sideways buckling or kneeling in a simple, lightweight prop that can be hand carried by a user. 
     U.S. Pat. No. 5,308,196 to Frederick discloses a prior art mine roof support comprising a container that is placed between the mine roof and the mine floor and filled with a load-bearing material. 
     In instances where a support is compressed, whether due to seismic forces or geological forces, the support generally is incapable of rebounding when the load is reduced or removed. What is needed is a support that can compress under extreme loads and rebound to maintain contact with the load, and which satisfies one or more of these needs or provides other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs. 
     BRIEF SUMMARY OF THE INVENTION 
     In one embodiment a load bearing support is disclosed. The load bearing support includes a cylindrical drum, comprising a top portion, a bottom portion, a tapered cylindrical sidewall extending between said top portion and said bottom portion, at least one core member extending between the top portion and the bottom portion, and a load-bearing material disposed between the sidewall and the core member ; an opening extending through the top portion of the cylindrical drum for receiving the load-bearing material therethrough; and each of the top portions and the bottom portions comprising a reinforcing chime; the at least one core member comprising a lateral transfer zone defined at one or more points along a vertical axis of the core member, the lateral transfer zone arranged to distribute a portion of an axial load on the drum to the cylindrical sidewall, the cylindrical sidewall providing a radial expansion area for compression of the at least one core member and the load-bearing material. 
     Another embodiment discloses a method of supporting a load comprising: providing a cylindrical drum having a top portion, a bottom portion, a tapered cylindrical sidewall extending between said top portion and said bottom portion, at least one core member extending between the top portion and the bottom portion, and a load-bearing material disposed between the sidewall and the core member; removing at least a portion of the at least one core member to define a lateral transfer zone along a vertical axis of the core member, applying a load on the cylindrical drum in an axial direction compressing the core member under the applied load to yield partially at the defined lateral transfer zone; distributing the axial load laterally through the core member as the core member yields, expanding the tapered cylindrical sidewall as axial compression of the core member and the load-bearing as the applied load increases; and in response to a reduction or axial displacement in the applied load after compression, extending the core member axially to retain a support contact between the drum and the load by rebounding in the core member axial direction. 
     The disclosure relates to a mine roof support including at least one core member or segments, e.g., a wood post or log—inserted vertically in a cladding or continuous metal cylinder, with the direction of wood grain coinciding with the axis of the cylinder or drum. The cylinder is preferably a conventional 55 gallon drum with cylinder walls having chimes or hoop stiffeners, or a frusto-conical drum with tapering sidewalls. After the core segments are inserted into the drum or drums (drums may be stacked to achieve a desired height for the roof support), flowable filler such as a cementitious material, e.g., foam cement is poured into the drums to occupy the gaps between the core segments so as to encapsulate the timber segments within the drum cylinder. Dry, flowable aggregate or sand may be used as gap filler instead. The support is placed vertically between a mine bottom and a mine roof to provide support in mine entries to prevent or control the collapse of a roof in a mine entry. The metal cladding in the form of one or more stacked drums provides an elastic expansion that allows the assembled support to partially compress—e.g., 12 inches (30.5 cm) of roof sag—and yield gradually, allowing the internal contents of the drum cladding to expand laterally under roof loading before the roof collapses. The roof support rebounds partially upon removal of the load to maintain contact with the roof surface if the roof moves away from the support. 
     Certain advantages of the embodiments described herein include a controlled yielding of the drum support without releasing the load, up to at least 200 tons and to as much as 300 tons. 
     Another advantage is the ability to use the disclosed drum support in various applications including underground mining, bridge construction and repair, and seismic supports for buildings and other structures, as permanent or temporary load supports for very large loads, using inexpensive materials and assembly methods. 
     Still another advantage is the ability to customize the load bearing characteristics by designing the core members to yield according to weight and desired load deflection profile, as well as rebounding effect of the core members, by inserting slits or drill patterns in predetermined configurations along the core member axis or axes. 
     Yet another advantage is the ability to design a matrix of bound components working in harmony to provide support for massive loads. 
     Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The application will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements, in which: 
         FIG. 1  shows a cross-sectional elevational view of an exemplary embodiment of a roof support of the present invention. 
         FIG. 2  shows a perspective view of a mine roof support set according to the present invention showing a plurality of empty nested drums with tapered sidewalls. 
         FIG. 3  shows an alternate embodiment of a mine roof support set having straight sidewalls. 
         FIG. 4  shows a cross-sectional plan view of a support drum with core members and filler material inside. 
         FIG. 5  shows an exemplary core member having three post sections in abutment. 
         FIG. 6  shows an elevational view of a single post section of a core member. 
         FIG. 7  shows an alternate embodiment of a core member comprised of three post sections without slits. 
         FIG. 8  shows an alternate embodiment of a core member having apertures. 
         FIG. 9  shows a load profile of a drum support. 
         FIG. 10  shows a deformed support after loading. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Before turning to the figures which illustrate the exemplary embodiments in detail, it should be understood that the application is not limited to the details or methodology set forth in the following description or illustrated in the figures. It should also be understood that the phraseology and terminology employed herein is for the purpose of description only and should not be regarded as limiting. 
     Commonly owned U.S. patent application Ser. No. 14/456, 497 having a filing date of Aug. 11, 2014, entitled “NESTED MINE ROOF SUPPORTS”; U.S. Pat. No. 8,801,338 issued Aug. 12, 2014, entitled “NESTED MINE ROOF SUPPORTS” and U.S. Pat. No. 8,851,804 issued Oct. 7, 2014, entitled “PUMPABLE SUPPORT WITH CLADDING”, disclose various mine roof supports and methods, and are hereby incorporated by reference in their entirety. 
     The present invention includes a mine roof support set comprising a plurality of containers having a longitudinal axis and adapted to be placed in a passageway in a mine, with the longitudinal axis extending between the mine roof and the mine floor, and filled with a load-bearing material. 
       FIG. 1  shows a cross-sectional elevational view of an exemplary embodiment of a roof support  10 . Roof support  10  includes two drums or containers  14  has a bottom end  12 , a top end  13 , and a sidewall  17  extending from the bottom end  12  to the top end  13 . The bottom end  12  and/or the top end  13  may be substantially open or may be covered by an end cap (not shown). The sidewall  17  defines an internal cavity  16  of the hollow drum  14 . In the embodiment shown in  FIG. 1 , roof support  10  is made up of two stacked drums  14  to achieve the desired proximity to the roof surface  20 . Roof support  10  may be made of a single drum  14  or multiple stacked drums as needed to obtain the height of the mine roof  20  from the mine bottom  22 . In addition, a yield ring, beam, footing or wedges may be inserted on top of the roof support  10  to take up any gap between the roof support  10  and the mine roof surface  20 , such that the weight of the mine roof is transferred to the roof support  10 . Other shims may include pumpable containment structures (e.g., bags) or a pumpable telescoping structure such as disclosed in U.S. Pat. No. 6,394,707, incorporated herein by reference. 
     Drums  14  may have a frusto-conical shape with slightly tapered outer walls to facilitate nesting for transportation and to allow a margin or gap around the interior of the nested containers. Drums may also include a reinforcing chime or ring  21 , located at one or more locations about the periphery of the sidewall  17 .  FIG. 2  shows a mine roof support set according to the present invention showing a plurality of empty nested drums with tapered sidewalls  17 . Alternately, sidewalls may have substantially straight sidewalls  17  such as conventional 55 gallon drums. 
     In use, the container is placed with its longitudinal axis  18  extending between a mine roof  20  and a mine floor  22  such that the bottom end  12  of the container  10  is in contact with the mine floor  22 . A core member or members  25  is disposed vertically inside the cavity  16  at the approximate center of drum coaxial with axis  18 , or if multiple core members are used, parallel with axis  18 . The cavity  16  is then filled with a load-bearing material  24  surrounding core member or members  25 . In one exemplary embodiment core member  25  may be composed of wood sections of circular, square or rectangular cross-section. Preferably the wood grain is aligned vertically, i.e., parallel with axis  18 , to provide resiliency and rebounding properties as will be discussed in greater detail below. Alternative materials for the core members may be used, such as steel or other high-strength post material. Various wood species may be used depending on the loading properties, cost and availability. E.g., oak and cherry wood exhibit greater hardness and may be capable of higher load capacity, whereas pine may be a less expensive wood with lower load capacity than hardwood species. Each support may be customized accordingly, based on desired load capacity. 
     In one exemplary embodiment, the load-bearing material  24  may be particulate and flowable which provides efficient filling of the cavity  16 . By using particulate and flowable materials, a maximum amount of space is filled in the cavity  16 , unlike if larger rocks or objects were to be used. Exemplary and non-limiting load-bearing materials  24  include pea gravel, sand, foamed cement (FOAMCRETE), concrete, polyurethane, coal from a mine entry, mine slack (i.e., wash plant refuse), and crushed mine tailings (e.g., discarded excavated mine material). 
     Although the container  10  shown in  FIG. 1  preferably has a circular cross-section, the container of the present invention may have any cross-sectional shape including, but not limited to, circular, oval, square, rectangular, and polygonal. It may be made from any suitable material including, but not limited to, metal. It may include chimes or other cladding or reinforcing features to allow it to be compressible or improve its load-bearing capability when placed in the mine entry or improve its stiffness when being transported including, but not limited to, ribbing. The ribbing of the container  10  may include, but is not limited to, a continuous helical rib, a plurality of discontinuous ribs or a plurality of spaced apart ribs. Alternatively, the container sidewall  17  may have a substantially smooth surface, without ribs, corrugation, or the like, although certain dents and other imperfections may be present which do not affect operation of the present invention. 
       FIG. 2  shows a perspective view of one embodiment of a mine roof support set  100  according to the present invention. As can be seen in  FIG. 2 , three drums  14  are nested partially inside another, with rings  21  supported on the top surface or edge  13  of the adjacent drum for ease of handling, such as in transportation to a mine site. The tapered sidewall  17  allows the remainder of the drum  14  to slip into the lower portion of the adjacent drum. In an alternate embodiment shown in  FIG. 3 , the outside dimension of each container may be progressively smaller than the next, with straight sidewalls  17 . As shown in  FIG. 3 , containers  14  have progressively smaller outside diameters. Four containers  10  are shown in  FIG. 3 , but this is not meant to be limiting. The quantity of containers  10  nested in a set  100  may be varied depending on the underground roof conditions and related logistics. 
     In one embodiment, the containers  10  all possess the same or similar sidewall  17  thickness. In a preferred embodiment the sidewall thickness may be 1.2 millimeters (mm), to provide a desired elasticity under load for containing the filler material  24  and core member  25 . Drums  14  may all have the same height or the drums  14  may have decreasing outer dimensions taken in the direction from the outermost container  10  to the innermost container  10  or some other arrangement, including random heights, provided that the containers  10  nest in each other. 
     Referring next to  FIG. 4 , a cross-sectional view taken along the lines  4 - 4  in  FIG. 1  shows the filler material  24  and core members  25  disposed within the drum  14 . In the example shown in  FIG. 4 , the inside diameter (I.D.) of drum  14  is 22.5 inches (in.), and the wooden core members  25  are 6 in.×5 in. posts cut to the length of the drum  14  before loading and deformation occurs, i.e., about 36 in. As shown, three core members  25   a,    25   c,  are positioned in a row with both end members abutting a vertical surface  27  of the middle core member  25   b.  Filler material  24 , e.g., gravel, surrounds the core members  25  and fills the cavity  16  between the sidewall  17  and core members  25 . Air gaps occurring naturally between the compacted gravel allows the drum  14  to slowly compress under load, with core members providing additional reinforcing strength that increases the load bearing limit of the support  10 . 
     Referring next to  FIGS. 5-8 , core members  25  may include control zones defined by slits  30  or apertures  32  inserted in the respective core member  25 . Slits  30  are made by placing a pair of saw cuts at acute angles on opposing sides of a core member  25 . Opposing slits may penetrate a portion of the radius or thickness of the core member  25  without intersecting the opposite slit, i.e., so that at least a portion of the core member is not cut completely through. The depth of the opposing slits  30  may be more or less depending on how quickly lateral load transfer within the support is desired, and the degree of rebound capability that is desired when the load is removed from the support  10 . Similarly, apertures  32  may be drilled in various patterns, as illustrated in  FIG. 8 .  FIG. 8  shows three sets of apertures at right angles, each set of apertures comprising three bore holes parallel and tangent to one another. More or less bore holes, and different angles may be used to customize various properties of the support  10 , such as failure load limit, distribution of lateral load points on the sidewall, and rebound capability of the core member. 
       FIG. 5  shows an elevational view of an exemplary core member  25  having three wooden post segments  25   a,    25   b  and  25   c,  bound together to form a single core member  25 . Each post segment has a pair of slits  30  cut into the post segment on opposing sides. The slits in each pair are angled towards one another, to allow vertical compressive forces coming from the mine roof to be transferred laterally along the sidewall  17  through the filler material  24 . As the weight of the earth overburden is applied to the support through the mine roof, or alternately from the mine bottom, the support  10  is gradually compressed and the metal sidewalls  17  of the drums  14  slowly stretch while the vertical load compresses and pulverizes the filler material  24  within the drum  14 , and at the same time the core members  25   a - 25   c  are compressed and begin to expand laterally in the area of the designated slits  30 . 
     A typical load profile of a roof support of the type shown in  FIG. 4  is shown in  FIG. 9 . As the load on the support drum increases from 0 to about 390 kips, the drum support compresses by about 2 in. (5.08 cm). The load remains relatively constant, between 390 and 440 kips until the height of the drum support is reduced to about 9.6 in. (24.4 cm), then increases to about 493 kips until the maximum displacement of 12 in. (30.5 cm) occurs. Additional loading may be possible before failure, as the test results did not continue to increase the load above 493 kips. At 493 kips, the load was gradually removed, and the drum rebounded about 2 in. (5.08 cm) from the height at the maximum displacement. 
     Without being bound by theory, the rebound results as a property of the matrix formed between the metal sidewall  17  of the drum  14 , which has an elastic property under such great force, the filler material  24 , in this instance gravel that is partially pulverized to displace air pockets within the drum  14 , and the core member, which folds between the slits or drill holes as the yield sections are laterally displaced within the drum  14 . The core members  25  provide controlled deformation that prevents the release of the load and allows the metal sidewalls  17 , typically a sheet metal skin of between 1 mm to 2 mm thickness, to fold over itself slowly. Referring to  FIG. 9 , the folding of the steel sidewalls occurs in peripheral bands  38  adjacent to the lateral transfer zone defined by the slits  30  or drill holes  32 , and as the sidewall folds over itself the lateral strength is increased due to the additional sidewall thickness that is created by the three-ply fold  39 . As shown in  FIG. 8 , as the support  10  yields core members  25  deform in an S-shaped section  41  and the slits  30  form a keystone-like section  43  displaced laterally of the S-shape section, as indicated by arrows  45 . When the load is reduced or released, e.g., where the mine roof heaves or buckles due to mine conditions, or in the case of a bridge structure, a shifting of the load displaces a portion of a horizontal beam, the core member and filler material, and possibly the sidewalls, rebound to extend partially towards their original height prior to loading. The rebound property of the support may be further enhanced or controlled by binding the matrix of filler, sidewall and core member with a settable material such as polyurethane, adhesives or grout. 
     It should be noted that while the roof support  10  has been described in the context of an underground mine roof support, the roof support may be used to reinforce a bridge or building structure, e.g., in a seismic zone or as a temporary or permanent column support during construction, replacement or maintenance of the structure. 
     While the exemplary embodiments illustrated in the figures and described herein are presently preferred, it should be understood that these embodiments are offered by way of example only. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims. The order or sequence of any processes or method steps may be varied or re-sequenced according to alternative embodiments. 
     It is important to note that the construction and arrangement of the load support drum with resilient core member, as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application.