VERSATILE GROUND ANCHOR FOR EXPEDIENT SURFACING APPLICATIONS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]The applications claims the benefit of U.S. Provisional Application No. 63/705,764, filed Oct. 10, 2024, entitled “Versatile Ground Anchor For Expedient Surfacing Applications”, and is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002]Not applicable.

REFERENCE TO APPENDIX

[0003]Not applicable.

BACKGROUND OF THE INVENTION

Field of the Invention

[0004]The disclosure generally relates to devices and methods of creating ground surfaces. More specifically, the disclosure relates to devices and methods for supporting ground surfaces against lateral and vertical loads that enable expedient deployment from ground surfaces while supporting durable use.

Description of the Related Art

[0005]Expeditionary airfield (EAF) matting systems are lightweight, modular structures that enable the rapid deployment of aircraft operating surfaces in the absence of traditional construction materials. An array is assembled from multiple mats to form vertical take-off and landing (VTOL) pads, runways, taxiways, parking aprons, and hangar floors. Contrary to traditional pavement systems where lateral movement is restricted largely by the dead weight of the structure, matting arrays are relatively unconstrained, and significant vertical and lateral movement can develop during aircraft and ground vehicle operations. Consequently, anchoring at the boundary of these arrays is crucial. The close proximity of these systems to aircraft induces both aerodynamic and mechanical loads that must be sustained by the ground anchor's vertical pullout and lateral load bearing capacity.

[0009]There is general agreement in the literature that the lateral bearing capacity of a pile is sensitive to numerous factors: pile shape, pile/soil interface conditions, the properties of the soil, batter angle, pile rigidity, and soil evolution during installation, which influence the response of the pile. For example, on weak, compressible soils, axial loads are generally supported by interfacial friction or bearing pressure at the pile tip, and lateral loads are supported through the bending stiffness of the pile and earth pressure developed with the surrounding soil. These factors may be coupled in varying capacities; no all-encompassing design methodology has been universally accepted, and much of the recent literature suggests that modification of the pile shaft, and the resulting shape and rigidity, is a viable pathway for improving lateral bearing capacity. Many commercially available ground anchors that possess the necessary capacity for vertical loads lack the necessary capacity for lateral loads; however, ground anchors that possess both the necessary vertical and lateral load capacity are cumbersome to install, often requiring excessive man-hours and heavy equipment to install the anchor to the required depth. Studies have shown that tapered helical piles and step-tapered piles in sand and step-tapered piles in clay improve lateral bearing capacity by a significant amount.

[0010]FIG. 1A illustrates a schematic side view of an installed, known cruciform stake. FIG. 1B is a schematic cross-sectional view of the stake of FIG. 1A. FIG. 1C is a schematic perspective view of the stake, locking pin, and edge clamp installed at a boundary of a support surface. The current preferred ground anchor used by the United States Marine Corp to anchor airfield matting is the cruciform stake 2. The cruciform stake 2 consists of a solid, single, 4″ effective diameter, aluminum extrusion 4 that is tapered at one end to improve installation. A hole 6 drilled through one of the cruciform walls near the top of the anchor facilitates installation of a steel locking pin 8 that vertically constrains an edge plate clamp 10, which transmits the constraint to a boundary mat 12 in the array of mats (not shown). The term “mat” is used broadly and can include a variety of portable support surfaces. The length of the stake varies depending on the application. The cruciform stake 2 resembles a slender finned pile, and exhibits a large lateral load-bearing capacity due to the large area moment of inertia of its cross-section as well as a large vertical load-bearing capacity due to friction generated at the interfacial area between the stake and ground 14.

[0011]While the cruciform is currently accepted as a standard for a robust EAF ground anchor, installation of the anchor is labor and material-intensive, particularly when longer anchors are installed in higher strength soils. A propensity for buckling is also a concern and often necessitates auguring a pilot hole prior to driving the cruciform, escalating both labor and equipment requirements. Installation typically requires at least three personnel: one operating a forklift/front-end loader platform, one driving the stake with a hydraulic drive hammer from the platform, and one keeping the anchor properly aligned as its driven. Consequently, this process compromises expediency and force-projection capabilities.

[0012]FIG. 2A illustrates a schematic side view of an installed, known screw-type ground anchor. FIG. 2B is a schematic cross-sectional view of the anchor of FIG. 2A. FIG. 2C is a schematic perspective view of the anchor and a plate clamp installed at a boundary of a mat. The mat 12 is secured by a plate clamp 10 overlapping a portion of a mat 12 with the anchor 16 inserted through a washer and a locking plate 18 and screwed into the ground 14 until sufficient compressive force from the anchor head bearing on the washer and locking plate is produced on the mat to the ground. Installation of the illustrated ground anchor can forego the traditionally needed hydraulic tools, front-end loader/forklift, and three-man team needed for the cruciform stake. However, despite the limited tests suggesting the use of these anchors may be appropriate in a strictly VTOL application, analysis indicates that the anchor's ability to sustain lateral loads is substantially lower than that of the cruciform stake. As long as loading remains vertical, lateral bearing capacity need not be considered; however, any deviation, whether due to strong cross-winds during landing on a VTOL pad or a high-angle turn during taxiing, can introduce lateral loads that must be sustained without inducing anchor or ground failure.

[0013]Therefore, there remains a need for an improved ground anchor and related method that can withstand the vertical and lateral loads for anchoring surfaces, especially temporary surfaces such as EAF mats.

BRIEF SUMMARY OF THE INVENTION

[0014]The disclosure provides a method and device for supporting both vertical and lateral loads on expedient ground surfaces. The disclosure provides a screw-type ground anchor with an external hollow stiffening cage to increase the ground anchor's lateral load bearing capacity and an anchor screw to provide vertical load bearing capacity without compromising its ease of installation. The anchor screw installs the stiffening cage concurrently while being installed by pressing down the stiffening cage while the anchor screw is rotated into the ground. By combining the stiffening cage with the anchor screw, rapid installation can be achieved while retaining lateral and vertical load bearing capacity.

[0015]The disclosure provides a ground anchor, comprising: a stiffening cage comprising a plurality of beams and at least one collar gusset configured to couple the beams to form a frame with a cage length with a hollow longitudinal cavity internal to the frame; and an anchor screw having a head coupled with a longitudinal screw portion and configured to fit inside the hollow longitudinal cavity and extend below the stiffening cage.

[0016]The disclosure further provides a method of installing a ground anchor into a ground, the ground anchor comprising a stiffening cage of coupled beams having an upper end and a lower end and an anchor screw having a head coupled with a longitudinal screw portion, the method comprising: placing the lower end of the stiffening cage onto the ground with the upper end extending upward from the ground; inserting the stiffening cage at least partially into the ground; inserting the anchor screw in a hollow longitudinal cavity of the stiffening cage and into the ground; rotating the anchor screw to cause the anchor screw to descend into the ground; contacting the upper portion of the stiffening cage with the anchor screw head; and continuing rotating the anchor screw to further descend into the ground while pressing down the stiffening cage into the ground surrounding the anchor screw to a finish depth.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0017]FIG. 1A illustrates a schematic side view of an installed, known cruciform stake.

[0018]FIG. 1B is a schematic cross-sectional view of the stake of FIG. 1A.

[0019]FIG. 1C is a schematic perspective view of the stake, locking pin, and edge clamp installed at a boundary of a support surface.

[0020]FIG. 2A illustrates a schematic side view of an installed, known screw-type ground anchor.

[0021]FIG. 2B is a schematic cross-sectional view of the anchor of FIG. 2A.

[0022]FIG. 2C is a schematic perspective view of the anchor and a locking plate clamp installed at a boundary of a mat.

[0023]FIG. 3A is a schematic side view of an exemplary embodiment of a hollow stiffening cage as a portion of an improved ground anchor according to the invention.

[0024]FIG. 3B is a schematic top perspective view of the ground anchor of FIG. 3A with an anchor screw installed in the hollow stiffening cage to form the illustrated embodiment of the ground anchor of the invention.

[0025]FIG. 3C is a schematic side view of an installed ground anchor according to the invention.

[0026]FIG. 4A is a schematic top view of a diagram of the stiffening cage of the ground anchor with the load-bearing beams and the upper collar gusset.

[0027]FIG. 4B is a schematic top view of an edge base plate.

[0028]FIG. 5A is a schematic perspective top view of the ground anchor with the anchor screw turning in the stiffening cage during installation.

[0029]FIG. 5B is a schematic perspective top view of the ground anchor with a friction-reducing washer between the anchor screw and the stiffening cage.

[0030]FIG. 6 is a schematic perspective top view of the stiffening cage of the ground anchor with a strike plate.

[0031]FIG. 7A is a schematic side view of placement of a stiffening cage of the ground anchor in alignment with an edge base plate for insertion into the ground with a strike plate.

[0032]FIG. 7B is a schematic view of driving the stiffening cage through a surface-located edge base plate partially into the ground using the strike plate.

[0033]FIG. 7C is a schematic side view of inserting the anchor screw into the hollow cavity of the stiffening cage and partially into the ground.

[0034]FIG. 7D is a schematic side view of turning the anchor screw into the ground while pulling the stiffening cage through the edge base plate into the ground.

[0035]FIG. 7E is a schematic side view of the installed ground anchor with the stiffening cage firmly installed into the ground.

DETAILED DESCRIPTION

[0036]The Figures described above, and the written description of specific aspects and functions below are not presented to limit the scope of what Applicant has invented or the scope of the appended claims. Rather, the Figures and written description are provided to teach any person skilled in the art to make and use the inventions for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the inventions are described or shown for the sake of clarity and understanding. Persons of skill in this art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present disclosure will require numerous implementation-specific decisions to achieve the developer's ultimate goal for the commercial embodiment. Such implementation-specific decisions may include, and likely are not limited to, compliance with system-related, business-related, government-related, and other constraints, which may vary by specific implementation or location, or with time. While a developer's efforts might be complex and time-consuming in an absolute sense, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill in this art having benefit of this disclosure. It must be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. The use of a singular term, such as, but not limited to, “a,” is not intended as limiting of the number of items. Further, the various methods and embodiments of the system can be included in combination with each other to produce variations of the disclosed methods and embodiments. Discussion of singular elements can include plural elements and vice-versa. References to at least one item may include one or more items. Also, various aspects of any embodiments could be used in conjunction with each other to accomplish the understood goals of the disclosure. Unless the context requires otherwise, the term “comprise” or variations such as “comprises” or “comprising,” should be understood to imply the inclusion of at least the stated element or step or group of elements or steps or equivalents thereof, and not the exclusion of a greater numerical quantity or any other element or step or group of elements or steps or equivalents thereof. The order of steps can occur in a variety of sequences unless otherwise specifically limited. The various steps described herein can be combined with other steps, interlineated with the stated steps, and/or split into multiple steps. Some elements are nominated by a device name for simplicity and would be understood to include a system or a section, such as a controller would encompass a processor and a system of related components that are known to those with ordinary skill in the art and may not be specifically described. Various examples are provided in the description and figures that perform various functions and are non-limiting in shape, size, description, but serve as illustrative structures that can be varied as would be known to one with ordinary skill in the art given the teachings contained herein.

[0037]The disclosure provides a method and device for supporting the vertical and lateral loads on expedient ground surfaces. The disclosure provides a screw-type ground anchor with an external hollow stiffening cage to increase the ground anchor's lateral load bearing capacity and an anchor screw to provide vertical load bearing capacity without compromising its ease of installation. The anchor screw installs the stiffening cage concurrently while being installed by pressing down the stiffening cage while the anchor screw is rotated into the ground. By combining the stiffening cage with the anchor screw, rapid installation can be achieved while retaining lateral and vertical load bearing capacity.

[0038]FIG. 3A is a schematic side view of an exemplary embodiment of a hollow stiffening cage as a portion of an improved ground anchor according to the invention. FIG. 3B is a schematic top perspective view of the ground anchor of FIG. 3A with an anchor screw installed in the hollow stiffening cage to form the illustrated embodiment of the ground anchor of the invention. FIG. 3C is a schematic side view of an installed ground anchor according to the invention. Generally, the improved ground anchor 30 uniquely integrates a hollow stiffening cage 32 with an anchor screw 34 to provide both lateral and vertical anchoring with an ease of installation, the combination of which has not been known.

[0039]The hollow stiffening cage 32 with a cage length has an upper portion 36 and a lower portion 38. The stiffening cage 32 can include an upper collar gusset 40 forming a flange coupled at the upper portion 36 to a plurality of tapered load-bearing beams 42 and a lower collar gusset 44 coupled at the lower portion 38 to the plurality of beams to support the stiffening cage shape. The collar gussets 40, 44 and beams 42 form a frame with a hollow longitudinal cavity 46 formed by an inner projected radius from the center point 66 to the inner surfaces of the load-bearing beams 42. The collar gussets 40, 44 increase flexural rigidity of the cross section of the stiffening cage 32 and therefore flexural rigidity of the ground anchor 30. A lower portion 48 of the load-bearing beams 42 can be tapered to facilitate entering into the ground 14 and generating a compressive load with the ground to maximize shear during installation.

[0040]The ground anchor 30 also includes an anchor screw 34. The anchor screw includes a head 50 and a longitudinal screw portion 52 and can be sized to be inserted into and through the hollow longitudinal cavity 46 of the stiffening cage 32. The diameter of the screw portion 52 can be sized to fit snugly into the longitudinal cavity 46 without causing a significant torque on the stiffening cage 32 that would twist the stiffening cage in the ground 14 during installation.

[0041]The anchor screw 34 is advantageously longer than the hollow stiffening cage 32 to allow the anchor screw to enter into the ground 14 to a depth sufficient to sustain enough compressive force on the hollow stiffening cage to pull the stiffening cage into the ground as the anchor screw is installed into the ground. The hollow stiffening cage 32 can be, for example, 40%-60% of the length of the anchor screw 34, although other percentages are possible depending on ground conditions and other factors. As a nonlimiting example, it is believed that setting the stiffening cage 32 to a depth of at least six inches in stiff clay to 15 inches in loose sand soil is a minimum depth to reach a maximum bending stress for the ground anchor. Advantageously, the installation is relatively simple, can be done by a single person without specialized tools, and can be done with or without power tools on site.

[0042]The assembly for installation can include an edge base plate 54 disposed beneath the upper collar gusset and partially around the stiffening cage as described in more detail in FIGS. 4B and 6. During installation, the anchor screw 34 can be inserted into the hollow longitudinal cavity 46 of the hollow stiffening cage 32 through the base plate 54 and into the ground 14. When installed, the head 50 can exert compressive force against the base plate by compressive forces through the upper collar gusset. The base plate 54 can overlap a portion of a mat, similar to FIG. 2C, so that when installed the mat is secured in position and supported against lateral and vertical forces. Alternatively, the anchor screw 34 can be inserted through an opening in the mat (not shown) and into the stiffening cage 32, so that when installed the head 50 of the anchor screw can exert a compressive force more directly on the mat to maintain the lateral and vertical support.

[0043]FIG. 4A is a schematic top view of a diagram of the stiffening cage of the ground anchor with the load-bearing beams and the upper collar gusset. The orientation of the improved ground anchor stiffening cage 32 can be important. Advantageously, an installer could align an expected load vector 64 at a radial orientation from a center line 66 of the longitudinal cavity 46 with at least one of a strong bending axis 68 to minimize deflection under load conditions and maximize holding capacity of the installed ground anchor. For symmetrical structures of the stiffening cage, such as shown, strong bending axes 68A, 68B (generally “68”) will be radially aligned from the center line 66 through a middle of a load-bearing beam 42. In this embodiment, there are two strong bending axes due to the symmetry of the load-bearing beams in opposite pairs. A strong bending axis 68 contrasts with a weak bending axis 70 that would generally be in a radial orientation midway between the radial directions of two strong bending axes, when the load-bearing beams are circumferentially aligned evenly and the load-bearing beams are symmetrical.

[0044]Further, FIG. 4A also illustrates the inner projected radius R1 of the longitudinal cavity 46, and a radius R2 diameter of an opening 72 in the upper collar gusset 40, and an outer radius R3 of a perimeter of the upper collar gusset. The radii R1-R3 can be relevant to openings on the base plate described below.

[0045]FIG. 4B is a schematic top view of an edge base plate. The base plate 64 can formed with an opening 56 for the stiffening cage 32 to be inserted therethrough. A radius R4 of the opening 56 measured from a centerline 60 can be sized to be at least as large as the radius R1 of the longitudinal cavity 46 of the stiffening cage, yet the radius R4 would generally not be greater than the radius R3 of the outer perimeter of the upper collar gusset 40. Further, the opening 56 can be formed with radially extended slots 58 oriented and sized to allow the load-bearing beams to be inserted therethrough. A projected outer radius R5 of the plurality of slots are sufficiently sized for such load-bearing beam insertion. A difference between radius R4 of the base plate opening and the radius R3 of the upper collar gusset perimeter provides a support area for the anchor screw to create a force through the upper collar gusset on the bearing plate that can in turn create a force of the mat to hold in place.

[0046]FIG. 5A is a schematic perspective top view of the ground anchor with the anchor screw turning in the stiffening cage during installation. FIG. 5B is a schematic perspective top view of the ground anchor with a friction reducing washer between the anchor screw and the stiffening cage. During installation, friction generated at the interface between the anchor screw 34 with the stiffening cage 32 will tend to rotate the stiffening cage from its intended orientation, when orientation can be a factor in performance of the ground anchor 30 as described above. Seating the stiffening cage a sufficient depth prior to the anchor screw actuation to finish the installation of the ground anchor will provide resistance against rotation. Alternatively, to reduce torque on the stiffening cage, a thin self-lubricating washer 74, such as made with an acetal plastic, including Delrin®, can be installed between the anchor screw and the stiffening cage. Such a washer lowers frictional force between anchor flange and stiffener flange and provides some protection from abrasion for the anchor and cage.

[0047]FIG. 6 is a schematic perspective top view of the stiffening cage of the ground anchor with a strike plate. As described above, a base plate 54 with an opening 56 having slots 58 can be used to help orient the ground anchor through guiding the load-bearing beams 40 being placed into the ground, in addition to being a contact surface for applying force to secure a mat from the vertical and horizontal loads during use. In at least one embodiment, to assist the stiffening cage 32 in an oriented ground engagement, a strike plate 76 can engage the top of the stiffening cage to contact the upper collar gusset 40 for driving the stiffening cage at least partially into the ground. The strike plate 76 can be formed with an upper strike portion 78 of about the size of the upper collar gusset 40 and a guide portion 80 having a size to be inserted into the opening 72 of the upper collar gusset to help maintain lateral engagement of the strike plate with the stiffening cage during installation.

[0048]FIGS. 7A through 7E illustrate an exemplary method of installing the ground anchor. FIG. 7A is a schematic side view of placement of a stiffening cage of the ground anchor in alignment with a base plate for insertion into the ground with a strike plate. FIG. 7B is a schematic view of driving the stiffening cage through a surface-located base plate partially into the ground using the strike plate. FIG. 7C is a schematic side view of inserting the anchor screw into the hollow cavity of the stiffening cage and partially into the ground. FIG. 7D is a schematic side view of turning the anchor screw into the ground while pulling the stiffening cage through the edge base plate into the ground. FIG. 7E is a schematic side view of the installed ground anchor with the stiffening cage firmly installed into the ground. The stiffening cage 32 can be set at a proper location on the ground 14 generally using a base plate 54. As described above, the base plate can be configured to align the load-bearing beams 34 in a desired orientation generally along a strong bending axis to an expected load condition. The stiffening cage 32 can be driven into the ground 14 using the strike plate 76 engaging the upper collar gusset 40 for an initial depth for stability, which can be the length of the taper of the load-bearing beams. The anchor screw 34 can be inserted into the longitudinal cavity 46 of the stiffening cage 32 and rotated to initially screw into the ground before engaging the top of the stiffening cage. The anchor screw 34 can continue to be rotated to bring the head 50 of the anchor screw in contact with the top of the stiffening cage 32 generally on the upper collar gusset 40. Continued rotation of the anchor screw 34 pulls the anchor screw with the stiffening cage 32 into the ground 14 until the upper collar gusset 40 forces the base plate 54 firmly to the ground generally contacting a mat, such as shown in FIG. 2C to seat the ground anchor 30 and secure the mat. In other embodiments, the base plate may not be used, if for example, an equivalent opening was formed directly into the mat to be secured to the ground.

[0049]Other and further embodiments utilizing one or more aspects of the inventions described above can be devised without departing from the disclosed invention as defined in the claims. For example, shapes of the components such as the base plate, stiffening cage, load-bearing beams, and other components can vary. Further variations include the number of load-bearing beams and absolute and relative sizes of the components can vary. Other variations than those specifically disclosed herein are within the scope of the claims.

[0050]The invention has been described in the context of preferred and other embodiments and not every embodiment of the invention has been described. Obvious modifications and alterations to the described embodiments are available to those of ordinary skill in the art. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the invention conceived of by the Applicant, but rather, in conformity with the patent laws, Applicant intends to protect fully all such modifications and improvements that come within the scope of the following claims.