US20140348596A1

US20140348596A1 - Nested mine roof supports

Info

Publication number: US20140348596A1
Application number: US14/456,497
Authority: US
Inventors: David A. Hussey; George A. Watson; Stephen G. Sawyer
Original assignee: MICON
Current assignee: MICON
Priority date: 2010-04-22
Filing date: 2014-08-11
Publication date: 2014-11-27

Abstract

This invention is directed to a means for transporting a mine roof support set including a plurality of nested containers. Each container in the set has a progressively smaller cross-sectional dimension, or a tapered, frusto-conical shape, to allow the containers to be nested one within the other. The plurality of nested containers allows more efficient transportation of the mine roof support set to a mine site. The containers can be separated at the mine site and filled with a load-bearing material. The containers filled with the load-bearing material are then placed with their longitudinal axis between a mine roof and a mine floor.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application is a continuation-in-part of co-pending U.S. application Ser. No. 13/684,773 having a filing date of Nov. 26, 2012, entitled “NESTED MINE ROOF SUPPORTS”, which application claims priority to U.S. Provisional Application No. 61/563,976 having a filing date of Nov. 28, 2011, entitled “NESTED MINE ROOF SUPPORTS”; and of co-pending U.S. application Ser. No. 13/091,849 having a filing date of Apr. 21, 2011, entitled “PUMPABLE SUPPORT WITH CLADDING”, which claims priority to U.S. Provisional Application No. 61/326,847 and having a filing date of Apr. 22, 2010, entitled “PUMPABLE SUPPORT WITH CLADDING”, all of which applications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates generally to mine roof supports and, more particularly, to a set of mine roof supports designed to be nested.
2. Description of Related Art
Various roof support devices in the prior art have been designed and used to provide support to a mine roof. Deep mining results in removal of material from the interior of a mine, thereby leaving unsupported voids of various sizes within the mine. These unsupported voids are conducive to mine roof buckling and/or collapse. Thus, it has been desirable to provide support to mine roofs to prevent, delay, or control collapse thereof
U.S. Pat. No. 5,308,196 to Frederick, herein incorporated by reference, discloses one commonly used prior art mine roof support. Specifically, the Frederick patent discloses a container that is placed between the mine roof and the mine floor and filled with a load-bearing material.
It is not economical to transport such containers for a mine roof support from the manufacturing site to the mine because of their overall size, which can be up to 15 feet in length and 72 inches in diameter, and weight. Because the containers are hollow, their weight is small relative to their volume. Therefore, the number of these containers which may be placed on a truck or railcar for transportation is limited by the volume of space that they occupy and not by their weight. Transportation costs are usually computed based on the distance that a load travels and not how efficiently it uses the available capacity of the transportation vehicle. Thus, the inefficient utilization of the available transportation capacity due to the combination of the high volume and low weight of the containers for the mine roof support results in high transportation costs relative to a load which more efficiently utilizes the capacity of the transportation vehicle.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method of transporting a mine roof support for efficient use of the capacity of a transportation vehicle. The method includes assembling a plurality of hollow individual containers, by placing individual open top containers together such that each individual container fits inside of an adjacent container; placing the plurality of individual containers on a vehicle for transportation from a manufacturing site of the containers to an underground mine site; transporting the plurality of containers via the transportation vehicle to the underground mine site; and separating the plurality of containers at the mine site to provide individual hollow containers.
Also disclosed is a transportable mine roof support. The transportable mine roof support comprising: a container member having a bottom portion and a side portion upwardly extending from the bottom portion; a support member movably received within the container member; and a bore defined within the support member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a container used in the mine roof support set according to the present invention;

FIG. 2 is a perspective view of one embodiment of a mine roof support set according to the present invention showing the mine roof support set in the nested condition;

FIG. 3 is a plan view of the mine roof support set shown in FIG. 2;

FIG. 4 is a cross-sectional view of one embodiment of the mine roof support set shown in FIG. 2 taken along line 4-4; and

FIG. 5 is a perspective view of one embodiment of two un-nested containers filled with a load-bearing material according to the present invention.

FIG. 6 is a cross-sectional view of an extensible mine roof support according to a third embodiment of the invention.

FIG. 7 is a cross-sectional view of the mine roof support of FIG. 8 in a partially installed state with respect to a mine.

FIG. 8 is a cross-sectional view of the mine roof support of FIG. 8 in a fully installed state with respect to the mine.

FIG. 9 is a schematic cross-sectional view of one embodiment of an extensible mine roof support.

FIG. 10 is a schematic cross-sectional view of one embodiment of an extensible mine roof support.

DESCRIPTION OF THE PREFERRED EMBODIMENT

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 void 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 one embodiment of such a container 10. The container has a bottom end 12, a top end 13, and a sidewall 14 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 14 defines a cavity 16.
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. The cavity 16 is then filled with a load-bearing material 24. In one embodiment of the invention, the load-bearing material 24 is 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, coal from a mine entry, mine slack (i.e., wash plant refuse), foamed cement (FOAMCRETE), concrete, polyurethane, and crushed mine tailings (e.g., discarded excavated mine material). Footing material (not shown), such as wood timber or other material, may be placed between either or both ends 12, 13 of the container 10 and the respective mine roof 20 and/or floor 22 to account for differences between the height of the container 10 and the height of the void in the mine Alternatively, a cap or a base (not shown) having a thickness may be used in the manner of a shim to assure that the container 10 contacts both the roof and the floor of the mine The cap or base may be a rubber ring or of any other suitable shape and/or material that effectively fills a gap between the mine roof 20 or floor 22 and the ends 12, 13 of the container 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.
Although the container 10 shown in FIG. 1 is cylindrical, 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 features to allow it to be compressible or improve its load-bearing capability when placed in the mine void 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, as shown in FIGS. 2-5, the container sidewall 14 may instead have a substantially smooth surface. By substantially smooth surface, it is meant that the sidewall does not include any 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 200 according to the present invention. As can be seen in FIG. 2, containers 10 a-10 d are nested one within another for ease of handling, such as in transportation to a mine site. The outside dimension (for the cylinders of set 200, 10 a being the outside diameter) of each container is progressively smaller than the next. As shown in FIGS. 2-4, container 10 a has the largest outside diameter, with containers 10 b, 10 c and 10 d having progressively smaller outside diameters. Four containers 10 are shown in FIGS. 2-4, but this is not meant to be limiting. The quantity of containers 10 nested in a set 200 may be varied depending on the underground conditions and related logistics, including the roof control plan.
In one embodiment, the containers 10 all possess the same or similar sidewall 14 thickness. The outer dimension of each subsequently smaller container 10 is determined at least in part by the inside diameter of the larger container 10 into which it is received, as well as the sidewall thickness. The difference in the cross-sectional dimension between each container 10 and the next smaller container 10 and, thus, the gap between the inner surface of the container 10 and outer surface of the next smaller container 10 is minimized. The cross-sectional dimension of the container 10 is one factor that determines the load-bearing capability of the mine support. Therefore, when it is desired that all of the mine supports in the set have load-bearing capability within a specific engineering tolerance, the difference in cross-sectional dimension between each container 10 and the next smaller container 10 may be minimized to allow the maximum number of containers 10 having a cross-sectional dimension providing load-bearing capability within the engineering tolerance to be nested. To accomplish this, the cross-sectional dimension of each successively smaller container 10 is reduced by the minimum amount necessary to allow it to be inserted into and removed from the container 10 having the next larger cross-sectional dimension, without binding or getting stuck. In one embodiment, a first container 10 is sized to be received within a second container 10 as a frictional fit. By frictional fit, it is meant that the respective surfaces of the first and second containers 10 may abut each other during insertion into or removal of the first container into the second container yet without binding therebetween or otherwise becoming stuck. To the extent that one or more of the smaller diameter containers 10 of the set 200 provides reduced load-bearing capabilities compared to other containers in the set, the roof support plan incorporating such containers may be adjusted as necessary. For example, the smaller diameter containers 10 may be spaced slightly closer together or closer to other such containers than larger diameter containers 10. The differences in the cross-sectional dimension between one container 10 and the next smaller container 10 may be of any magnitude and may be uniform or vary throughout the set. The lengths of the containers 10 may also be constant or vary from container to container. The containers may have the same cross-sectional shape or the shape of the cross-section may vary from container to container as long as the containers may still be nested one inside the other. In general, when nested, the cavity 16 of each container 10 is empty. In one embodiment, the cavity 16 is filled with the load-bearing material once the containers are separated at a mine site.
Referring to FIGS. 3 and 4, the mine roof support set 200 includes the plurality of containers 10 nested one within another, with each container 10 having a progressively smaller cross-sectional dimension than the container 10 in which it is nested. While no gap is shown between the inside of one container (e.g., 10 a) and the outside of a progressively smaller container (e.g., 10 b), there is at least some gap therebetween so that container 10 b may be fitted into container 10 a and then removed therefrom without becoming stuck. In FIGS. 2 and 4, the containers 10 a-10 d are shown as having progressively reduced heights, such that container 10 a receives all of containers 10 b-10 d and container 10 b receives all of containers 10 c and 10 d. This is not meant to be limiting. For example, the containers 10 may all have the same height or the containers 10 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.
FIG. 5 shows perspective views of one embodiment of containers 10 a, 10 b separated from each other and filled with load- bearing material 24 a, 24 b. Two containers are shown and described here (10 a, 10 b) for simplicity. However, it is contemplated that each nested set 200 could include up to ten containers 10. The mine roof support set 200 according to the present invention includes nested containers 10 for transportation. This allows for more efficient use of the capacity of a transportation vehicle. By nesting the containers 10 inside of each other, more space on a transportation vehicle is available than if each individual container 10 were to be transported separately. By providing additional space on the transportation vehicle the user is able to transport more items to the mine site with fewer trips and at a lower cost. After the nested container set 200 has been unloaded at the mine site, the container set 200 is transported into the mine and the containers (e.g., 10 a, 10 b) are separated from one another. Each container 10 a, 10 b is then filled with load- bearing material 24 a, 24 b, which may be the same or different material from each other. The load- bearing material 24 a, 24 b may be flowable, thereby providing an efficient manner in which to fill the containers 10. By using particulate and flowable material, the user can deliver the material 24 a, 24 b into the top of each container 10 a, 10 b with minimal effort. After the containers 10 a, 10 b have been filled, each container 10 a, 10 b is positioned with its longitudinal axis 36 a, 36 b between the mine roof and the mine floor. The containers 10 may be shimmed above and below ends 12 and 13 as needed to fit within the mine opening.
In one desired embodiment, the support member 100 defines an enclosure having a body 322, with a top portion 13, and a bottom portion 12 disposed at respective distal ends of the body 72. Desirably, the support member 100 is substantially hollow to receive a filler 328 therein. Therefore, it is to be understood, that the support member 100 may include suitable openings or ports (not shown) for introducing the filler 328 into the support member 100. Alternatively, the support member 100 may be partially solid or entirely solid. A partially solid support member 100 may, therefore, accommodate less filler 328 than a substantially hollow support member 100. It is to be understood that the internal structure of the support member 100 may assume various configurations. Exemplary and non-limiting filler 328 includes foamed cement (such as FOAMCRETE.RTM.), concrete, polyurethane, or crushed mine tailings (i.e., discarded excavated mine material). In the desirable embodiment as shown in FIG. 6, the support member 100 includes a bore 50 defined therein. The bore 50 includes a first opening 52 defined along a side portion 14 of the support member 100 and a second opening 56 defined along the bottom portion 12 of the support member 100. As shown in FIGS. 7 and 8, the bore 50 is adapted to receive a material 24 therethrough. For example, the bore 50 may be a plastic pipe that is approximately ½ inch to one inch in diameter. The bore 50 may be routed through the filler 328 in any suitable configuration. Alternatively, the bore 50 may be situated within the side portion 14 of the container member 10 c.
Desirably, the shape of the support member 100 substantially corresponds to the shape of the container member 10 c. For example, both the container member 10 c and the support member 100 are substantially cylindrical in shape, however, it is to be understood that the support member 100 may be embodied as other shapes. For example, with respect to a cylindrical shape, the top and bottom portions 13, 12 may be substantially circular bases. Desirably, an 8×8 foot piece of 16 gauge cold roll sheet steel may be curved, such that two opposing ends thereof are brought together to form the body 72 of the support member 100. Thereafter, the top and bottom portions 13, 12 are attached to the respective distal ends of the body 72. It is to be understood that the support member 100 may be of unitary construction or may be a multiple piece construction. Desirably, the support member 100 is constructed of relatively rigid or other suitable material including, but not limited to, steel. The top portion 13 of the support member 100 may be contoured or be adapted to correspond to a specific grade or grade variations of a mine roof.
The height of the support member 100 may be greater than the container member 10 c. For example, a desirable height of the support member 100 may be eight feet, as compared to the three feet height of the container member 10 c. Thus, when the support member 100 is inserted into the container member 10 c, the support member 100 extends beyond the opening 70 of the container member 10 c. In the exemplary use of an 8×8 foot piece of sheet steel, the body 72 of the support member 100 is approximately thirty inches in diameter. The diameter of the support member 100, or width along the widest portion thereof, is less than the diameter or width of the container member 10 c. Thus, in the case of a thirty-inch diameter body 72, the diameter of the container member 10 c may be anything greater than thirty inches. Desirably, the variation in diameters differs only to the extent that there exists a minimal sufficient clearance between the side portion 14 a and the side portion 14 c.
An operation of the mine roof support 100 in accordance with a desirable embodiment of the present invention will now be discussed. With continuing reference to FIG. 8, the mine roof support 100 is used in a mine 60 having a mine roof 62 and a mine floor 64, as shown in FIGS. 7 and 8. In the desirable embodiment, the container member 10 c is positioned on the mine floor 64 below the mine roof 62. Thereafter, the support member 100 is inserted into the container member 10 c. A hose 46 or suitable equivalent may be attached to the first opening 52 of the bore 50. A pressurized machine (not shown) may be connected to the hose 46 and operated to introduce the material 24 into the bore 50. It is to be understood that any suitable machine configured to entrain solids into an air cavity may be utilized. For example, an air stream may be delivered into a container of the material 24 with an airstream exiting the container having the material 24 entrained therein. The material 24 is delivered through the bore 50 such that the material is deposited via the second opening 56 into the container member 10 c. Consequently, as more material 24 is deposited into the container member 10 c, the support member 100 is increasingly moved closer to the mine roof 62. Specifically, the support member 100 is upwardly displaced within the container member 10 c by the material 24 pushing against the bottom portion 12. An exemplary amount of material 24 may be at least two feet. However, it is to be understood that the raised height of the support member 100 may vary based upon the distance of the void between the top portion 13 of the support member 100 and the mine roof 62. Other factors determining the raised height include, but are not limited to, the height of the container member 10 c, the type of material 24, and the amount of weight to be supported by the mine roof support 100. It has been determined that the support member 100 may be raised with a force corresponding to as little as 1.6 PSI and that raising thereof may be accomplished in approximately one second. Once the top portion 13 of the support member 100 contacts the mine roof 62, the weight of the mine roof 62 is distributed to and supported on the mine roof support 100. In the case of an uneven mine roof 62, wedges (not shown) may be introduced between the top portion 13 and the mine roof 62 to obtain a substantially even contact surface. However, it is to be understood, that the wedges are not intended to support the weight of the mine roof 62, as is the case in the prior art. After installation of the mine roof support 100, the hose 46 may be removed and the first opening 52 of the bore 50 may be sealed.
In an alternative embodiment of the present invention, the support member 100 may be raised substantially with air alone so that the material 24 is introduced into the container member 10 c only after the support member 100 has been raised. It is also envisioned that the present invention may be modified to operate as a primarily hydraulic or pneumatic telescoping mine roof support. Accordingly, the material 24 may be substituted by water or air, respectively.
In some applications, it may be beneficial to provide the underside of the bottom portion 12 (facing the material 24) with patterning or other surface texturing. Surface texturing on the underside of the bottom portion 12 can enhance the filling and spreading of the material 24 entrained in air as the container member 10 c is filled. The surface texturing may be formed in the material of the bottom portion 12 (in the steel) or may be applied as a separate layer, such as a layer of patterned or roughened foamed concrete.
Referring next to FIG. 9, in another embodiment a plurality of nested containers 10 a, 10 b and 10 c may be nested and filled with a pumpable load-bearing material or filler 24. Container 10 a is filled to the open top end 13, and disposed on container 10 b, which is also filled to top end 13. Container 10 b is disposed within container 10 c, which is partially filled with load-bearing material 24, e.g., to a predetermined height h. Height h is adjusted by injecting or pouring load-bearing material into container 10 c, thus allowing the stacked containers 10 a, 10 b and 10 c to form a customized roof support member 100. As disclosed above with respect to FIGS. 6-8, the support member 100 may include suitable openings or ports (not shown) for introducing the filler 24 into the support member 100. Alternatively, the support member 100 may be partially solid or entirely solid. A partially solid support member 100 may, therefore, accommodate less filler 24 than a substantially hollow support member 100. It is to be understood that the internal structure of the support member 100 may assume various configurations. Containers 10 a-10 c 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.
In one aspect, a support member may be constructed on site by pumping flowable load-bearing material into nested containers 10 a-10 c in sequence, beginning with the top-most container 10 a, then one or more intermediate containers 10 b, if any, and finally the bottom-most container 10 c. Preferably the bottom container 10 c will be used as the height adjustment container, and may be partially empty, while the remaining containers are filled substantially to the respective top end. Thus the roof support when constructed in on site may be tailored in height to suit variable roof conditions and heights in the underground mine. This method of height adjustment of the roof support member 100 allows the supports to be fit precisely to the desired height for loading the support. The support may be adjusted to fit exactly from the mine bottom to the mine roof, or alternately, may be adjusted to within a close distance from the mine roof to allow for placement of a yield ring or similar device for loading the roof support. Wedge locks 15 may be provided around the periphery of each of the lower level nested containers 10 a-10 c, to maintain a minimum vertical spacing between nested containers and to provide openings 70 to allow fill conduits for insertion of flowable material 24. Wedge locks 15 permit upward movement of containers 10 when material 24 is introduced into a lower level container 10. Wedge locks 15 may also laterally secure the containers 10 a-10 c relative to one another, and reduce or eliminate horizontal movement of the nested containers 10 a-10 c. For example, as shown in FIG. 9, one or more wedge locks 15 may be placed in the open top end 13 of the bottom container 10 c, in the space between the intermediate container 10 b and the bottom container 10 c. Likewise, one or more wedge locks 15 may be placed in the open top end 13 of the intermediate container 10 b, in the space between the top-most container 10 a and the intermediate container 10 b.
While the example illustrated in FIG. 9 shows three containers 10 a-10 c, more or less containers 10 may be used depending on the height of the individual containers 10 and the roof height, which tends to vary in underground mines. For example, a support may be comprised of two containers 10 in lower mine seams, with one of the pair of containers serving as the height adjustment container that is filled after the other container is full. Also, it should be noted that with the exception of the top-most container 10, the height adjustment container 10 may be one or more of the remaining containers in the stack, and is not necessarily the bottom-most container.
In order to facilitate the flow of pumpable material 24 into the containers, each container may be provided with conduits, ports, tubes 25, pipes, openings or other facilities for conducting flowable material into the adjacent containers, such as those described above with respect to FIGS. 6-8. For clarity the conduit and related interconnections are not shown in FIG. 9.
Referring to FIG. 10, in another embodiment, nested containers 10 may be used to construct or assemble a custom-height support member 100. The bottom-most container 10 c is inverted, such that the open top end 13 is positioned adjacent to the mine floor 22. A pipe segment 30 is positioned between the bottom-most container 10 c and the top-most container 10 a, with the bottom end 12 of each container 10 a, 10 c positioned adjacent to and partially within the interior opening of pipe segment 30. The pipe segment 30 includes, for example, a straight piece of pipe cut to a desired length, or any other conduit material that is capable of being cut to a length that may provide a desired height 21 of the top-most container 10 a. After positioning the pipe segment 30 between the top-most container 10 a and the bottom-most container 10 c, the pipe segment 30 is at least partially filled with the flowable load-bearing material 24 to raise the top-most container 10 a to the desired height 21. The desired height 21 may be a height that allows positioning the top end 13 of the top-most container 10 a in direct contact with the mine roof, or alternatively, positioning the top end 13 adjacent to the mine roof with a desired spacing to allow for placement of yield rings or other material for loading the support 100 when the mine roof settles onto the support member 100. In one embodiment, the top-most container 10 a and the bottom-most container 10 c contain solid fill, which is not shown in FIG. 10 for clarity.
Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of this specification.

Claims

1. A method of transporting a mine roof support for efficient use of the capacity of a transportation vehicle comprising:

assembling a plurality of hollow individual containers, by placing individual open top containers together such that each individual container fits inside of an adjacent container;

placing the plurality of individual containers on a vehicle for transportation from a manufacturing site of the containers to an underground mine site;

transporting the plurality of containers via the transportation vehicle to the underground mine site; and

separating the plurality of containers at the mine site to provide individual hollow containers.

2. The method of claim 1, further comprising filling the hollow containers with a load-bearing material at the mine site.

3. The method of claim 2, further comprising positioning the filled individual containers between the mine roof and the mine floor.

4. The method of claim 2, wherein the containers are nestable one within another prior to filling the containers with the load-bearing material.

5. The method of claim 4, further comprising:

cutting a straight piece of pipe to a predetermined length;

positioning the straight piece of pipe between two of the individual hollow containers, the individual hollow containers including at least a top-most container and a bottom-most container; and

filling the straight piece of pipe with the load-bearing material to raise the top-most container to a predetermined height below a mine roof.

6. A transportable mine roof support comprising: a container member having a bottom portion and a side portion upwardly extending from the bottom portion; a support member movably received within the container member; and a bore defined within the support member.

7. The transportable mine roof support of claim 5, wherein the container member is substantially cylindrical in shape with a tapering outer wall to permit ease of nesting the container member.

8. The transportable mine roof support of claim 6, wherein the support member defines an enclosure receiving a filler therein.

9. The transportable mine roof support of claim 7, wherein the filler is foam cement, concrete, or crushed mine tailings.

10. The transportable mine roof support of claim 5, wherein the bore includes: a first opening defined along a side portion of the support member; and a second opening defined along a bottom portion of the support member.

11. The transportable mine roof support of claim 9, wherein the bore is sized to receive material therethrough.

12. The transportable mine roof support of claim 10, wherein the material is sand, polyurethane foam, or pea gravel.

13. The transportable mine roof support according to claim 11, wherein at least two containers of the plurality of containers are filled in series by flowing the load-bearing material into said containers, beginning with a top-most container and progressing in sequence to the bottom-most container.