Mandrel and methods for compacting soil and granular materials

Abstract

Methods and apparatuses for densifying the ground and creating ground improvement elements are disclosed. In some embodiments, the ground improvement densification apparatuses include a driving mandrel. The driving mandrel includes a mandrel web, at least one flange disposed on a side of the mandrel web; and an array of ground densification elements attached at a first end to the mandrel web and extend freely beyond a bottom of the mandrel web.

Description

[0001] MANDREL AND METHODS FOR COMPACTING SOIL AND GRANULAR MATERIALS

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The present application claims the benefit and priority of U.S. Provisional Patent Application No. 63 / 660,842, filed on June 17, 2024, entitled “ MANDREL AND METHODS FOR COMPACTING SOIL AND GRANULAR MATERIALS”, the contents of which are hereby incorporated in their entirety.

[0004] TECHNICAL FIELD

[0005] The presently disclosed subject matter relates generally to the efficient compaction and densification of granular subsurface materials and more particularly to methods and apparatuses for densifying and compacting soil and granular materials, that are either naturally deposited or consist of man-placed fill materials, using lightweight, easily extractable apparatuses of substantially unitary cross-section for the subsequent support of structures, such as buildings, foundations, floor slabs, walls, embankments, pavements, and other improvements.

[0006] BACKGROUND

[0007] Heavy or settlement sensitive facilities that are located in areas containing soft, loose, weak, or potentially liquefiable soils are often supported on deep foundations. Such deep foundations are typically made from driven pilings or concrete piers installed after drilling. The deep foundations are designed to transfer structural loads through the soft soils to more competent soil strata. Deep foundations are often relatively expensive when compared to other construction methods. Deep foundations also exhibit a relatively high carbon footprint that, because of the materials used for construction, are thus environmentally insensitive.

[0008] Another way to support such structures is to excavate out the soft, loose, or weak soils and then fill the excavation with more competent material. The entire area under the building foundation is normally excavated and replaced to the depth of the soft, loose, or weak soil. This method is advantageous because it is performed with conventional earthwork methods, but has the disadvantages of being costly when performed in urban areas and may require that costly dewatering or shoring be performed to stabilize the excavation.

[0009] Yet another way to support such structures is to treat the soil with "deep dynamic compaction" consisting of dropping a heavy weight on the ground surface. The weight is dropped from a sufficient height to cause a large compression wave to develop in the soil. The compression wave compacts the soil, provided the soil is of a sufficient gradation to be treatable. A variety of weight shapes are available to achieve compaction by this method, such as those described in U.S. Patent No. 6,505,998. While deep dynamic compaction may be economical for certain sites, it has the disadvantage that it induces large waves as a result of the weight hitting the ground. These waves may be damaging to structures. The technique is deficient because it is only applicable to a small band of soil gradations (particle sizes) and is not suitable for materials with appreciable fine-sized particles.

[0010] In recent years, aggregate columns have been increasingly used to support structures located in areas containing soft soils. The columns are designed to reinforce and strengthen the soft layer and minimize resulting settlements. The columns are constructed using a variety of methods including the drilling and tamping method described in U.S. Patent Nos. 5,249,892 and 6,354,766; the tamper head driven mandrel method described in U.S. Patent No. 7,226,246; the tamper head driven mandrel with restrictor elements method described in U.S. Patent No. 7,604,437; and the driven tapered mandrel method described in U.S. Patent No. 7,326,004; the entire disclosures of which are incorporated by reference in their entirety.

[0011] The short aggregate column method (U.S. Patent Nos. 5,249,892 and 6,354,766), which includes drilling or excavating a cavity, is an effective foundation solution when installed in cohesive soils where the sidewall stability of the hole is easily maintained. The method generally consists of: a) drilling a generally cylindrical cavity or hole in the foundation soil (typically around 30 inches); b) compacting the soil at the bottom of the cavity; c) installing a relatively thin lift of aggregate into the cavity (typically around 12- 18 inches); d) tamping the aggregate lift with a specially designed beveled tamper head; and e) repeating the process to form an aggregate column generally extending to the ground surface. Fundamental to the process is the application of sufficient energy to the beveled tamper head such that the process builds up lateral stresses within the matrix soil up along the sides of the cavity during the sequential tamping. This lateral stress buildup is important because it decreases the compressibility of the matrix soils and allows applied loads to be efficiently transferred to the matrix soils during column loading. The short aggregate column method relies on the utilization of placed aggregate typically consisting of gravel- to sand-sized particles that may require relatively long hauling distances depending on the proximity of project sites to construction quarries.

[0012] The tamper head driven mandrel method (U.S. Patent No. 7,226,246) is a displacement form of the short aggregate column method. This method generally consists of driving a hollow pipe (mandrel) into the ground without the need for drilling. The pipe is fitted with a tamper head at the bottom which has a greater diameter than the pipe and which has a flat bottom and beveled sides. The mandrel is driven to the design bottom of column elevation, filled with aggregate and then lifted, allowing the aggregate to flow out of the pipe and into the cavity created by withdrawing the mandrel. The tamper head is then driven back down into the aggregate to compact the aggregate. The flat bottom shape of the tamper head compacts the aggregate; the beveled sides force the aggregate into the sidewalls of the hole thereby increasing the lateral stresses in the surrounding ground. The tamper head driven mandrel with restrictor elements method (U.S. Patent No. 7,604,437) uses a plurality of restrictor elements installed within the tamper head to restrict the backflow of aggregate into the tamper head during compaction. The tamper head driven mandrel with restrictor elements method typically requires the use of open-graded sand or gravel sized aggregates that exhibit a relatively narrow bandwidth of particle sizes sometimes requiring relatively long hauling distances depending on the proximity of the project site to suitable quarries.

[0013] The driven tapered mandrel method (U.S. Patent No. 7,326,004) is another means of creating an aggregate column with a displacement mandrel. In this case, the shape of the mandrel is a truncated cone, larger at the top than at the bottom, with a taper angle of about 1 to about 5 degrees from vertical. The mandrel is driven into the ground, causing the matrix soil to displace downwardly and laterally during driving. After reaching the design bottom of the column elevation, the mandrel is withdrawn, leaving a cone shaped cavity in the ground. The conical shape of the mandrel allows for temporarily stabilizing of the sidewalls of the hole such that aggregate may be introduced into the cavity from the ground surface. After placing a lift of aggregate, the mandrel is re-driven downward into the aggregate to compact the aggregate and force it sideways into the sidewalls of the hole. Sometimes, a larger mandrel is used to compact the aggregate near the top of the column.

[0014] Another more recent method used for the compaction of granular materials is disclosed in U.S. Patent No. 9,702,107 which describes uniquely configured mandrels equipped with compaction chambers for the efficient construction of densified aggregate columns and the densification of soil. This method includes the provision of a compaction chamber comprised of a generally cylindrical tube that contains diametric expansion elements. This method is efficient because it allows for the rapid compaction of granular materials within the compaction chamber. The method generally allows for a larger bandwidth of backfill gradations, which is advantageous in comparison to fully-encased flow through mandrels. The compaction chamber typically consists of a tubular steel section that is attached to the mandrel shaft. During mandrel upward extraction, the tubular section sometimes grazes the sidewalls of the cavity, which scrapes a portion of the matrix soil that then falls into the compaction chamber potentially contaminating the backfill materials. Further, the compaction chamber may be difficult to remove from the cavity because of its weight and because of the increased resistance that may occur during upward scraping.

[0015] What is needed is an efficient method of compacting the ground with depth and for compacting densified granular columns with a low-weight mandrel that may be easily extracted after driving and may be used with a large variety of backfill materials. What is further needed is a method for rapidly and efficiently compacting and densifying loose potentially liquefiable ground to increase site resiliency during seismic events.

[0016] SUMMARY

[0017] The present disclosure relates generally to an apparatus for densifying and compacting granular materials. In some aspects, the techniques described herein relate to a ground densification apparatus, including: a driving mandrel including: a mandrel web; at least one flange disposed on a side of the mandrel web; and an array of ground densification elements attached at a first end to the mandrel web and extend freely beyond a bottom of the mandrel web.

[0018] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the array of ground densification elements is unrestrained by any compaction chamber and configured and sized to achieve a desired lift thickness, compaction surface area, and backfill flow based on backfill material type and project requirements.

[0019] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the array of ground densification elements is at least one of a chain, a chain link, a cable, a wire rope, or a lattice of vertically and / or horizontally connected chains, cables, or wire rope.

[0020] In some aspects, the techniques described herein relate to a ground densification apparatus, further including at least one compaction shutter attached to the driving mandrel.

[0021] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the at least one compaction shutter is rotatably attached to the driving mandrel.

[0022] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the at least one compaction shutter is rotatably attached using a hinge.

[0023] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the at least one compaction shutter is attached to the mandrel web near the bottom of the driving mandrel.

[0024] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein at least one compaction shutter is attached to a front side and a back side of the driving mandrel.

[0025] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the at least one compaction shutter is rotatable from a substantially vertical position parallel to a major axis of the driving mandrel to a substantially horizontal position transverse to the major axis of the driving mandrel.

[0026] In some aspects, the techniques described herein relate to a ground densification apparatus, further including at least one rotation stop disposed on the driving mandrel above the at least one compaction shutter to limit rotation to a horizontal position of the at least one compaction shutter.

[0027] In some aspects, the techniques described herein relate to a ground densification apparatus, further including at least one enhancing window disposed within the mandrel web to permit passage of backfdl material therethrough during operation.

[0028] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the driving mandrel is shaped as an I-beam, H-beam, W-beam, HP- beam, S-beam, or M-beam.

[0029] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the at least one flange disposed on the side of the mandrel web forms at least a part of the I-beam, H-beam, W-beam, HP -beam, S-beam, or M-beam shape.

[0030] In some aspects, the techniques described herein relate to a ground densification apparatus, further including a geosynthetic swatch to minimize an inclusion of ground into an area subtended by the mandrel web and the at least one flange.

[0031] In some aspects, the techniques described herein relate to a ground densification apparatus, wherein the driving mandrel is substantially unitary in cross-sectional area throughout an entire length of the driving mandrel.

[0032] In some aspects, the techniques described herein relate to a method of using a ground densification apparatus, including: driving the ground densification apparatus into a ground to form a cavity; raising the ground densification apparatus; applying backfill material into the cavity during a raising, the backfill material flowing downwardly and freely along and through an area formed by a mandrel web of the ground densification apparatus, at least one flange, and at least one flow through enhancing window; re-driving the ground densification apparatus downwardly to a depth preferably less than an initial driving depth, wherein during re-driving an array of ground densification elements expands horizontally to engage with the backfill material to densify the backfill material in the cavity, wherein the array of ground densification elements and a sidewall of the cavity form a compaction area for backfill material densification; and repeating the re-driving until the ground densification apparatus has been lifted to or near an original ground elevation and a densified and well-compacted column of backfill material has been formed in the cavity. In some aspects, the techniques described herein relate to a method, further including using an at least one movable compaction shutter rotatably attached to the driving mandrel above the array of ground densification elements to engage with the array of ground densification elements and the backfill material to densify the backfill material in the cavity, such that the at least one moveable compaction shutter exhibits a substantially vertical configuration during raising and a substantially horizontal configuration during driving.

[0033] In some aspects, the techniques described herein relate to a method, further including driving the driving mandrel through stone at a desired cavity location, whereby the driving mandrel with an array of ground densification elements the stone forms a driving plug that prevents ground from entering into a bottom of the ground densification apparatus.

[0034] In some aspects, the techniques described herein relate to a method, wherein the ground densification apparatus includes a driving mandrel, the driving mandrel including: the mandrel web; the at least one flange disposed on a side of the mandrel web; and the array of ground densification elements attached at a first end to the mandrel web and extend freely beyond a bottom of the mandrel web.

[0035] In some aspects, the techniques described herein relate to a method, wherein the array of ground densification elements is unrestrained by any compaction chamber and configured and sized to achieve a desired lift thickness, compaction surface area, and backfill flow based on backfill material type and project requirements.

[0036] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings and images. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example, are not necessarily to scale and are for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

[0038] In the drawings:

[0039] FIG. 1 illustrates an isometric view of an example of the presently disclosed soil compaction apparatus in the raised and lowered positions, respectively, and comprising an arrangement of compaction enhancement elements, in accordance with various embodiments;

[0040] FIG. 2 illustrates another view of the soil densification and compaction apparatus of FIG. 1, in accordance with various embodiments of the present disclosure;

[0041] FIGS. 3 A and 3B illustrate a further view of the soil densification and compaction elements of FIG. 1, in accordance with various embodiments of the present disclosure;

[0042] FIG. 4 is an illustration of the soil densification and compaction apparatus of FIG. 1 on the ground surface, in accordance with various embodiments of the present disclosure;

[0043] FIG. 5 is an illustration of the soil densification and compaction apparatus of FIG. 1 creating an open hole during driving, in accordance with various embodiments of the present disclosure;

[0044] FIG. 6 is an illustration of aggregate compaction using the soil densification and compaction apparatus of FIG. 1, in accordance with various embodiments of the present disclosure;

[0045] FIG. 7A shows an illustration of the side view of a ground improvement element

[0046] 201 completed using the present subject matter including the ground densification elements, in accordance with various embodiments of the present disclosure;

[0047] FIG. 7B shows an illustration of the side view of a ground improvement element

[0048] 202 completed using the present subject matter including the ground densification elements, in accordance with various embodiments of the present disclosure; FIG. 8 illustrates a graph of stress based on pier stress, in accordance with various embodiments of the present disclosure;

[0049] FIG. 9 illustrates a zoomed in portion of a driving mandrel 100, in accordance with various embodiments of the present disclosure;

[0050] FIG. 10 illustrates the driving mandrel of FIG. 9 with an elongated enhancing window, in accordance with various embodiments of the present disclosure;

[0051] FIG. 11 illustrates a driving mandrel with two compaction shutters, in accordance with various embodiments of the present disclosure;

[0052] FIG. 12 illustrates a driving mandrel being driving into the ground, in accordance with various embodiments of the present disclosure;

[0053] FIGs. 13 A and 13B illustrate example driving mandrels with different sizes of enhancing windows, in accordance with various embodiments of the present disclosure; and

[0054] FIGs. 14A and 14B illustrate various views of a driving mandrel, in accordance with various embodiments of the present disclosure.

[0055] DETAILED DESCRIPTION

[0056] The presently disclosed subject matter now will be described more fully hereinafter with reference to the accompanying Drawings, in which some, but not all embodiments of the presently disclosed subject matter are shown. Like numbers refer to like elements throughout. The presently disclosed subject matter may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Indeed, many modifications and other embodiments of the presently disclosed subject matter set forth herein will come to mind to one skilled in the art to which the presently disclosed subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated Drawings. Therefore, it is to be understood that the presently disclosed subject matter is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. In some embodiments, the presently disclosed subject matter provides methods and apparatuses for densifying and compacting soil and granular materials that are either naturally deposited or consist of man-placed fill materials for the subsequent support of structures, such as buildings, foundations, floor slabs, walls, embankments, pavements, and other improvements. Namely, the presently disclosed subject matter provides various embodiments of soil densification and compaction apparatuses in which an open-ended mandrel that provides partial sidewall restraint, may be rapidly and efficiently inserted, provide compaction and densification, and extracted efficiently, while utilizing the backfill materials to assist in maintaining the stability of the soil exposed to the open sides of the apparatus.

[0057] In one embodiment, the mandrel contains a relatively uniform cross-sectional area that partially restrains the matrix materials from entering into the cavity while utilizing a broad range of backfill materials that maintains sidewall stability in the areas not directly restrained by the driving mandrels.

[0058] In another embodiment, the lightweight mandrel may be used efficiently with lightweight pile driving equipment to provide cost efficiency and environmental benefits.

[0059] In another embodiment, the relatively unitary cross-sectional geometry facilitates smooth and rapid extraction without further engaging the sidewalls of the matrix materials.

[0060] In another embodiment, relatively low-profile compaction enhancement elements are used to create the cavity and enhance densification.

[0061] In yet another embodiment, installation and compaction is enhanced with moveable shutters that uniquely form an open and a closed position that allows for smooth and rapid extraction while enhancing densification.

[0062] In another embodiment, the unique mandrel design provides greater flow and greater aggregate backfill density than the prior art.

[0063] In another embodiment, a large variety of backfill materials are utilized with the apparatus to provide cost effectiveness and a smaller environmental footprint resulting from locally available aggregate sources.

[0064] In still another embodiment, the sidewall stability of the portions of the cavity that are not restrained directly by the mandrel are provided by utilizing flow-through features that allow backfill materials to flow from one to the other side of the mandrel during driving and extraction operations.

[0065] In yet another embodiment, the drivability of the mandrel into soft, loose, saturated, or weak ground is enhanced using a geosynthetic driving swatch that uniquely and efficiently provides a temporary seal against the entrance of external materials.

[0066] In an example method of using the presently disclosed soil compaction apparatus, after initial driving, the soil compaction apparatus is raised and the compaction elements are configured to allow unimpeded passage of granular or cementitious material from the bottom of the piling element. As the piling element is raised, the backfilled aggregate flows freely and unimpeded downward along the piling passageway thus maintaining sidewall stability. After raising the piling element the prescribed distance, the piling element is then re-driven downwardly to a depth preferably less than the initial driving depth into the underlying materials. This allows the compaction elements the opportunity to engage with the backfilled materials, thus providing downward compaction of these materials as they are engaged in the downwardly moving piling element. The process of the present subject matter creates a well compacted column of densified soil below and around the compaction elements. This process of lifting the driving shaft upward and driving back down is repeated incrementally until the driving shaft has been lifted to or near an original ground elevation.

[0067] Referring now to FIG. 1, a ground densification apparatus according to one embodiment is illustrated, wherein a substantially uniform cross-sectional area ground densification apparatus is used to compact backfill placed or allowed to flow in the annular spaced created by driving. Namely, FIG. 1 is an isometric view of the presently disclosed ground densification apparatus including a driving mandrel 100. The driving mandrel 100 may include a web 101, flanges 102, ground densification elements 103, compaction shutter(s) 104, and enhancing window(s) 105. The ground densification elements 103 may be low cross-sectional area bi-directional ground densification elements. The ground densification apparatus shown in FIG. 1 may be inserted or driven into free-field soils (i.e., soil that exists in its natural or placed state below grade). In this example, the ground densification apparatus exhibits a substantially uniform cross-sectional area device equipped with ground densification elements 103. When used to create a cavity by driving, the device shown in FIG. 1 may be optionally equipped with a geosynthetic swatch to minimize the inclusion of ground into the area subtended by the web 101 and the two flanges 102.

[0068] The web 101 (also referred to as a mandrel web) may be a generally flat surface that defines one or more enhancing windows 105. Various other components, such as the flanges 102, the 103, the compaction shutter(s) 104, and / or the like may be part or attached to the web 101. The term “web” means that there is at least one gap or space (also referred to herein as a “window” or “enhancing window”) disposed between structural elements of the mandrel. Optionally, a plurality of gaps or spaces are interspersed between a plurality of structural elements. The web 101 (and associated flanges 102) may be made out of any number of materials, such as steel.

[0069] The flanges 102 extend generally perpendicularly from the web 101. Each of the flanges 102 are parallel to one another, such that the web 101 and flanges 102 create three sides of a rectangular shape. As discussed herein, the web 101 and flanges 102 may create a rectangular cavity in the ground during insertion. The flanges 102 may be unitary to the web 101. Alternatively, the flanges 102 may be otherwise secured to the web 101 (e.g., via welding and / or fasteners). The flanges 102 may be part of an I-beam, H-beam, W-beam, HP -beam, S-beam, or M-beam in which the web 101 is the center part of the beam.

[0070] The ground densification elements 103 may be defined along in the direction of a bottom of the web 101. The ground densification elements 103 may also be defined as an array of ground densification elements 103. The ground densification elements 103 may be attached to the web 101 (e.g., via a bolt or other fastener). The ground densification elements 103 may extend downwardly in the direction of the bottom of the web 101 (as defined by the orientation of FIG. 1). The ground densification elements 103 (which may be chain links, cables, and / or other flexible and durable materials) may extend beyond the bottom of the web 101, such that upon lowering of the driving mandrel 100, the ground densification elements 103 engages the ground before the web 101 (or flanges 102). The ground densification elements 103 may be a low cross-sectional area bi-directional ground densification elements. The ground densification elements 103 is bi-directional, such that the ground densification elements 103 provide compacting support during downward movement without restricting upward movement. The compaction shutter(s) 104 may be provided assist with flow and compaction enhancement. The compaction shutter(s) 104 may be one or more movable compaction shutters that extend outward during downward apparatus movements as shown in FIG. 3 A and retracts to a position adjacent to the web 101 as shown in FIG. 3B during upward apparatus movements (e.g., during removal of the driving mandrel 100). The movement of the compaction shutter(s) 104 may be facilitated by a hinge 106 that allows rotation, and rotation stops 107 that prevents the compaction shutter(s) 104 from rotating to a position more than approximately horizontally relative to the vertically oriented ground densification apparatus. During densifi cation operations, the driving mandrel 100 moves upwardly and downwardly. As the ground densification apparatus moves upwardly, the compaction shutter(s) 104 rotate downward thus providing very little resistance to the downward flow of the backfill materials. As the apparatus is driven back downwardly, the compaction shutter(s) 104 engages with the backfill materials and rotates to a position that is essentially horizontal and orthogonal to the direction of apparatus movement. The compaction shutter(s) 104 described in this embodiment is used to assist in achieving the downward flow and the greater stiffness created by columns created with this ground densification apparatus relative to other devices that partially restrict or constrain flow.

[0071] In various embodiments, the driving mandrel 100 may include at least one of the ground densification elements 103 or the compaction shutter(s) 104. For example, some embodiments may include both the ground densification elements 103 and the compaction shutter(s) 104, while other embodiments

[0072] The enhancing window(s) 105 may be one or more apertures defined along the web 101. The enhancing window(s) 105 may be flow through enhancing windows. The enhancing window(s) 105 are used to balance the volume of placed backfill from one side of the apparatus to the other. This allows the backfill materials to efficiently flow to the areas where there are the greatest aggregate “takes” and serves as yet another means to achieve efficient backfill flow and greater volume of backfill placed. In various embodiments, the driving mandrel 100 may be an I-beam, H-beam, W-beam, HP-beam, S- beam, or M-beam that provides the “flow-through opening” arrangement to allow the backfill to flow through the web 101 and into the enhancing window(s) 105 defined in the I-beam, H-beam, W-beam, HP-beam, S-beam, or M-beam. Referring now to FIG. 2, the ground densifi cation elements 103 are attached to the driving mandrel 100 towards the bottom leading edge of the device 100. Any number of different sizes of driving mandrels may be contemplated based on the use case and / or desired size of cavity. In an example embodiment, the web 101 and the flanges 102 may have the same or similar widths, such that the cavity created by the driving mandrel may have a square cross-section. For example, the web width may be 15 inches and the flange width for each flange 102 may be 15 inches. The length of the ground densifi cation elements 103 may be based on various factors, such as type of ground being densified. For example, each of the array of ground densification elements 103 may be 8 inches in length.

[0073] As shown in FIG. 2, the ground densification elements 103 rest neatly against the interior surfaces of the driving mandrel 100 (e.g., against the interior surface of the web 101 and / or the flanges 102). In various embodiments, the functional purpose of the ground densification elements 103 may be to “bunch” or otherwise “flatten” to form a compaction surface to provide for and assist with compaction of backfill materials in an instance in which the driving mandrel 100 is driven in a downward direction, and to “straighten” against the interior surfaces of the device 100 (thus not providing compaction or interfering with withdrawal) in an instance in which the driving mandrel 100 is withdrawn in an upward direction. As the driving mandrel 100 is moved downward, the non-attached end of each ground densification element rotates away from the driving mandrel 100 creating an angle between the ground densification elements 103 and the rest of the driving mandrel 100 (e.g., the web 101 and / or the flange(s) 102).

[0074] The ground densification elements 103 may be comprised of chain links, cables, or other flexible and durable materials. For example, the ground densification elements 103 may include multiple chain links that are each attached at a first end and freely hanging therefrom. The chain links (or other materials) may be attached in a generally straight line across the driving mandrel 100. In various embodiments, each of the ground densification elements 103 may be the same length, such that each of the ground densification elements 103 engages the ground at the same or near the same time during movement of the driving mandrel 100.

[0075] The ground densification elements 103 shown in FIG. 1 and FIG 2 are not constrained by any “compaction chamber” and rely on interaction with the placed backfill materials and the sidewalls of the constructed cavity for this purpose. It is understood that a compaction chamber is generally defined as a structural element that is of an enclosed design so that aggregate is functionally enclosed during mandrel driving for a compaction purpose. As contemplated by the disclosure of the present subject matter, the ability of the ground densification elements 103 to provide superior ground and backfill densification even functioning unconstrained by any compaction chamber was a surprising result indicated by testing related thereto.

[0076] The ground densification elements 103 can be fabricated from individual chain links, cables, wire rope, or the like, or a lattice of vertically and horizontally connected chains, cables, wire rope, or the like. In a specific example, the ground densification elements 103 are half-inch, grade 100 alloy chains.

[0077] In various embodiments, such as the embodiment shown in FIG. 2, the ground densification elements 103 are used in conjunction with the driving mandrel 100 to keep the ground material below and adjacent to the driving mandrel 100 from intruding into the cavity. The ground material below and adjacent to the driving mandrel 100 is prevented from intruding into the cavity by driving the driving mandrel 100 through a mound of stone at the column location. The interaction of the driving mandrel 100 with the ground densification elements 103 and the placed stone forms a driving plug that prevents native ground from entering into the bottom of the ground densification apparatus.

[0078] As the ground densification apparatus is driven into the ground, backfill materials are added from the ground surface to fill the void created during driving. The backfill materials stabilize the sidewalls of the hole in the area of the ground densification apparatus 100 not otherwise stabilized by the flanges 102. The backfill materials may consist of aggregate, crushed stone, sand, mixed granular materials, concrete, aggregate-dry cement mixes, and other materials. Because the driving mandrel 100 is substantially unitary in cross-sectional area throughout the entire length of the ground densification apparatus, the downward flow of the backfilled materials is not impeded by bridging around changes in section. The design of the driving mandrel allows the usage of a wide variety of materials, providing cost effectiveness and reducing the environmental footprint in comparison with devices that require a more specific gradation to achieve material flow. After initial driving of the driving mandrel 100 into the ground, the driving mandrel 100 may be raised and the ground densification elements 103 hang freely by gravity from the bottom of the driving mandrel 100. As the ground densification apparatus is raised backfill materials flow downwardly along the cross-sectional area defined by the web 101 and flanges 102. The efficiency of backfill downward flow results in a great volume of material placed and densified as the driving mandrel 100 is moved upwardly and downwardly through the backfill materials. Upward movements result in the ground densification elements 103 offering little resistance and downward movements engage the ground densification elements 103 to achieve the densification and compaction of the backfill.

[0079] After raising the ground densification apparatus the prescribed distance, the ground densification apparatus is then re-driven downwardly to a depth preferably less than the initial driving depth into the underlying materials. The repeated downward drive allows the ground densification elements 103 to engage with the backfill forming a compaction surface that has an area defined by in one direction by the apparatus web 101 and in the other direction by the full length of the flanges 102.

[0080] The process of moving the driving mandrel 100 upward and downward multiple times creates a densified and well-compacted column of backfill material below and around the ground densification elements 103. The process of lifting the ground densification apparatus upward and driving back down is repeated incrementally until the ground densification apparatus has been lifted to or near an original ground elevation.

[0081] The ground densification elements 103 are configured and sized accordingly to achieve the desired lift thickness, compaction surface area, and backfill flow based on the material type and project requirements. The ground densification elements 103 are typically changeable. The ground densification apparatus shown in FIGs. 1 and 2 has the advantage of being simple to fabricate, construct, and maintain. A further advantage is that the unimpeded downward flow that allows the use of a wider range of backfill materials and greater volume of material placed during construction than observed for other devices with substantially non-uniform cross-sectional areas.

[0082] Referring now to FIGs. 3A and FIG. 3B, top views of the operation of a ground densification apparatus are illustrated. The ground densification apparatus of FIGs. 3A and 3B include a flow and compaction enhancement feature. In this example, the flow and compaction enhancement element includes a compaction shutter 104 that extends outward during downward apparatus movements as shown in FIG. 3 A and retracts to a position adjacent to the web 101 as shown in FIG. 3B during upward apparatus movements. The movement of the shutter may be facilitated by a hinge 106 that allows rotation, and rotation stops 107 that prevents the compaction shutter 104 from rotating to a position more than approximately horizontally relative to the vertically oriented ground densification apparatus.

[0083] During densification operations, the apparatus moves upwardly and downwardly. As the ground densification apparatus moves upwardly, the compaction shutter 104 rotates downward thus providing very little resistance to the downward flow of the backfill materials. As the apparatus is driven back downwardly, the compaction shutter 104 engages with the backfill materials and rotates to a position that is essentially horizontal and orthogonal to the direction of apparatus movement. The compaction shutter 104 described in this embodiment is used to assist in achieving the downward flow and the greater stiffness created by columns created with this ground densification apparatus relative to other devices that partially restrict or restrain flow.

[0084] Referring now to FIG. 4, a side view of yet another embodiment of the subject invention is illustrated by providing flow through enhancing windows 105 in the web 101 of the ground densification apparatus. The flow through enhancing windows 105 are used to balance the volume of placed backfill from one side of the apparatus to the other. This allows the backfill materials to efficiently flow to the areas where there are the greatest aggregate “takes” and serves as yet another means to achieve efficient backfill flow and greater volume of backfill placed.

[0085] In one example, the ground densification apparatus is an I-beam, H-beam, W-beam, HP-beam, S-beam, or M-beam that provides the “flow-through opening” arrangement, wherein backfill can flow through the web 101 and into the flow through enhancing windows 105 of the I-beam, H-beam, W-beam, HP-beam, S-beam, or M-beam.

[0086] FIG. 5 shows a view looking down into an open cavity in subsurface materials created using the embodiment shown in FIG. 4 after the apparatus is driven into the ground. The open cavity is formed by placing a mound of crushed stone aggregate or other suitable material at the ground surface and driving the ground densification apparatus through the mound of stone to engage the ground densification elements 103 installed at the bottom of the driving mandrel 100 and the flow through enhancing window 105 also placed near the bottom of the apparatus. The engagement of the ground densification elements 103 and the compaction shutter 104 elements causes the placed aggregate to compact and “bunch” at the bottom of the apparatus in the annular space defined by the web 101 and the flange 102. The formation of the bottom plug, when combined with the lateral restraints provided by the flanges 102 restrains the soil materials at the bottom and two sides of the driving mandrel 100 from entering the created cavity. The remaining two sides of the cavity are formed by the natural ground arching around the cavity to the ends of the flanges 102. Arching occurs readily in unsaturated ground and less readily in soft or loose ground particularly below the ground water table. For these conditions, aggregate, recycled concrete, sand, concrete, grout, or other suitable and flowable materials are added to the cavity from the ground surface to fill the cavity as the mandrel is advanced below grade. In this way, all of the surfaces of the cavity are restrained so that the natural ground does not enter the created cavity during initial driving.

[0087] Referring now to FIG. 6, the light weight ground densification apparatus is used to engage and densify the placed backfill materials to create ground improvement elements. After the cavity is created as shown in FIG. 5 and backfill is placed within the cavity, the ground densification apparatus is raised and partially extracted from the cavity as shown in FIG. 6. During this operation, the ground densification elements 103 and the movable compaction shutters 104 disengage from the aggregate allowing substantially unimpeded downward flow of the aggregate or other placed backfill materials relative to the ground densification apparatus. Because the ground densification apparatus has a substantially unitary cross-section, the aggregate or other placed backfill materials does not have the opportunity to bridge or otherwise “hang up” and thus may flow downward rapidly without obstruction or restriction. This allows the placed backfill to continue to impede sidewall interior flow in the non-flange-restricted portions of the cavity. Unlike apparatuses with substantially non-uniform cross-sectional areas, downward flow results in noncontamination of the backfill that then allows for compaction and densification to proceed without risk of clogging from sidewall intrusions. Because the ground densification apparatus is substantially lighter than other forms of compaction devices, upward retraction results in very little resistance allowing the work to proceed with lighter hammers and smaller more environmentally-friendly equipment.

[0088] Referring now to FIGs. 7A and FIG. 7B, there are illustrations of ground improvement elements completed with different processes. FIG. 7A shows an illustration of the side view of a ground improvement element 201 completed using the present subject matter including the ground densification elements 103 and compaction shutter 104 and the flow through enhancing windows 105 shown in FIG. 1 and FIG. 4. The ground improvement element 201 shown in FIG. 7A was installed by driving the ground densification apparatus to the design depth while backfilling with crushed stone aggregate and compacted by raising the driving mandrel 100 up a distance of 3 feet and then back down a distance of 2 feet repeatedly to complete the element. As shown in FIG. 7A, the density of the compacted stone is evidenced by the lack of spalling into the excavation, which results from the high degree of compaction that develops relative cohesion of the aggregate stone. The element is of uniform cross section created by the consistent densification process and the availability of backfill materials that results from the high degree of downward flow created by the ground densification apparatus, which includes flow-through enhancing windows 105 and a substantially uniform cross-section that offers almost no restriction to backfill downward flow.

[0089] FIG. 7B alternatively shows a picture of a side view of another ground improvement element 202 that was installed with a device that included the full complement of ground densification elements 103, did not include movable compaction shutters 104, and did not include flow through enhancing windows 105, all of which are shown in FIG. 1 and FIG. 4. As shown in FIG. 7B, the soil around one side of the ground improvement element 201 was then then excavated on one side to show the installed element. Here, the illustration shows poorly densified stone as evidenced by the spalling of the stone into the side excavation and shows the “necking” or narrowing of the element towards the bottom where the element encounters softer ground. The absence of the ground densification elements 103 in combination with the movable compaction shutters 104 and / or the flow through enhancing windows 105 seems to indicate a ground improvement element that is inferior to that created using the present subject matter described herein with the results of the method of installation shown in FIG. 7A.

[0090] Referring now to FIG. 9, a zoomed in portion of a driving mandrel 100 is shown. The driving mandrel 100 includes a compaction shutter 104 and an array of ground densification elements 103. The compaction shutter 104 may include the operability of the compaction shutters discussed herein. The compaction shutter 104 may include one or more attachment mechanisms 900. The attachment mechanisms 900 may constrain the downward rotation of the compaction shutter 104 (e.g., in order to resist sudden rotation of the compaction shutter 104. The attachment mechanism(s) 900 may be a chain, cable, rope, and / or other material to connect the compaction shutter 104 to the driving mandrel 100 (e.g., attach the compaction shutter 104 to the web 101). The attachment mechanism(s) 900 may be connected to the compaction shutter to allow for the compaction shutter to exhibit a substantially vertical configuration during raising (e.g., generally parallel to the web 101 during upward movement of the driving mandrel 100) and a substantially horizontal configuration during driving (e.g., generally perpendicular to the web 101 during downward movement of the driving mandrel 100).

[0091] Referring now to FIG. 10, more of the driving mandrel 100 of FIG. 9 is shown. The enhancing window 105 of the web 101 is elongated. As such, less enhancing windows may be provided, but the enhancing window(s) that are provided may have a higher area, such that one enhancing window operates similarly multiple of the enhancing windows shown in FIGs. 1, 4, and 6. Any number of different enhancing window(s) may be provided.

[0092] Referring now to FIG. 11, multiple compaction shutters 104 may be provided. The compaction shutters may be the same design or alternatively, as shown, the compaction shutters may have different designs. For example, the compaction shutter may be designed as shown in FIGs. 1-4 (labelled as compaction shutter 104B in FIG. 11 to distinguish) and / or the compaction shutter may be designed as shown in FIGs. 9-10 (labelled as compaction shutter 104A in FIG. 11 to distinguish). As shown, the compaction shutter 104B may include the pinned-hinge design of FIGs. 1-4 and the compaction shutter 104A may include the attachment mechanism(s) 900 shown in FIGs. 9 and 10. Any number of different compaction shutters may be used. In various embodiments, the compaction shutters may be the same (as shown in FIG. 14B). Alternatively, only a single compaction shutter may be provided.

[0093] Referring now to FIG. 12, a driving mandrel 100 is shown being driving into the ground in accordance with various embodiments. While the driving mandrel 100 shown in FIG. 12 corresponds to the driving mandrel 100 discussed in reference to FIGs. 9-11, any number of embodiments discussed herein may be used in the same fashion. Namely, the driving mandrel 100 is attached to a driver mechanism 1200. The driver mechanism 1200 may be a pile driving rig, a hydraulic press and / or other mechanism that moves upward and downward along an axis. The motion of the driver mechanism 1200 causes the driving mandrel 100 to move upward and downward as discussed herein.

[0094] In various embodiments, the driver mechanism 1200 may be a lightweight pile driving equipment. Various types of pile driving equipment may be contemplated based on the size of the driving mandrel 100. For example, an excavator mounted vibratory hammer may be used as a driving mandrel 100 for one or more embodiments. An example driver mechanism 1200 may include an excavator mounted sheet pile driver.

[0095] Referring now to FIGs. 13A and 13B, example driving mandrels are shown with different sizes and shapes of enhancing windows. The enhancing window(s) 105 may be any number of shapes and / or sizes. As shown in FIG. 13 A, the enhancing windows may be different shapes or sizes (e.g., the lower enhancing window is more elongated than the upper enhancing window). Alternatively, the enhancing windows 105 of FIG. 13B are the same size and shape. Any number of enhancing windows may also be contemplated (e.g., FIGs. 13 A and 13B illustrate two enhancing windows, while other embodiments show more or less enhancing windows). As such, any number of different number, size, and / or shapes of enhancing window(s) 105 may be contemplated.

[0096] Referring now to FIG. 14A and 14B, an example driving mandrel 100 is shown in accordance with various embodiments. The driving mandrel 100 of FIGs. 14A and 14B is an H-beam. As shown, the web 101 connects in the flanges 102 in the middle to create an H cross-section (as shown in FIG. 14A). The driving mandrel 100 may include two sets of the compaction shutter(s) 104 and / or the array of ground densification elements 103 defined on each side of the web 101. The compaction shutter(s) 104 are shown using the pinned-hinge design of FIGs. 1-4. In such a design, the compaction shutter may rotate about the hinge point 1400. A spring and / or other resistance mechanism may be provided to resist unintended rotation of the compaction shutter.

[0097] Having generally described the present subject matter, various embodiments are more specifically described by illustration in the following specific EXAMPLES, which further describe different embodiments of the soil compaction apparatus.

[0098] EXAMPLE I

[0099] In one example, a method of compacting aggregate using an embodiment of the subject matter disclosed herein without pre-drilling was demonstrated in full-scale field tests. The ground densification apparatus was comprised of a wide-flanged beam “W- beam” driving mandrel 100 with a web 101 width of 15 inches and a flange 102 length of 15 inches and eight flow through enhancing windows 105 provided within the web 101. The bottom ground densification elements 103 consisted of 22 strands of chain linked elements each attached to the driving mandrel 100 at the top of each of the 8-inch long chain link strands. Two movable compaction shutters 104 were provided in the driving mandrel 100, one on either side of the apparatus and each located approximately 13 inches above the bottom of the driving mandrel 100. The movable compaction shutters 104 were 12 inches wide and 4 inches long and connected to the flanges 102 via 7 / 8-inch diameter hinges. The movable compaction shutters 104 were allowed to hang substantially downward in the driving mandrel 100 “resting” state that occurred prior to driving and during driving mandrel 100 extraction. During downward driving, the movable compaction shutters 104 were allowed to rotate upward until they were substantially horizontal, a position that was held by the inclusion of a rotation stop 107 placed over the shutter to prevent further rotation. In this example, the driving mandrel 100 was driven into the ground in a displacement operation. Crushed stone backfdl was added at to the cavity formed by the driving mandrel 100 as it advanced to stabilize the sidewalls of the cavity. After driving the driving mandrel 100 to 11 feet below the ground surface, the ground densification apparatus was then raised approximately 3 -feet then driven back down approximately 2-feet repeatedly to form a densified ground improvement element.

[0100] FIG. 8 shows the results 800 of two load tests performed on two ground improvement elements installed at the project site. The plot shown in FIG. 8 indicates applied top-of-pier stress on the x-axis and top of pier deformation on the y-axis. The top of pier stress is computed as the quotient of the applied top of pier load and the pier area that was computed to be 4.9 square feet. The relatively flat response of the tests shows that a high pier stiffness was achieved by this test. The results of this example show that the ground densifi cation apparatus of the present subject matter is effective at creating stiff and strong ground improvement elements without the need for pre-drilling.

[0101] EXAMPLE II

[0102] In yet another example of an embodiment of the subject matter disclosed herein, a method of compacting aggregate without pre-drilling was demonstrated in full-scale field tests. The ground densification apparatus was comprised of a wide-flanged beam “W- beam” driving mandrel 100 with a web 101 width of 15 inches and a flange 102 length of 15 inches and eight flow-through enhancing windows 105 provided within the web 101. The bottom ground densification elements 103 consisted of 22 strands of chain linked elements each attached to the driving mandrel 100 at the top of each of the 8-inch long chain link strands. Two movable compaction shutters 104 were provided in the driving mandrel 100, one on either side of the apparatus and each located approximately 13 inches above the bottom of the driving mandrel 100. The movable shutters 104 were 12 inches wide and 4 inches long and connected to the flanges 102 via 7 / 8-inch diameter hinges. The movable compaction shutters 104 were allowed to hang substantially downward in the driving mandrel 100 “resting” state that occurred prior to driving and during driving mandrel 100 extraction. During downward driving, the movable compaction shutters 104 were allowed to rotate upward until they were substantially horizontal, a position that was held by the inclusion of a rotation stop 107 placed over the shutter to prevent further rotation. In this example, the driving mandrel 100 was driven into the ground in a displacement operation. Crushed stone backfill was added at to the cavity formed by the driving mandrel 100 as it advanced to stabilize the sidewalls of the cavity. This operation was performed at the same site as chosen for Examples 1. The driving mandrel described above was then backfilled with crushed stone aggregate. The densification apparatus was then raised approximately 3-feet then driven back down approximately 2-feet repeatedly to form a densified ground improvement element FIG. 7A shows an excavated aggregate pier constructed in the manner described above. The aggregate pier shows uniform cross-section and compaction as evident by the cohesion exhibited by the ability of the stone to stay together even after the confining soil around has been removed. These results show that the ground densification apparatus of the present subject matter is effective at creating stiff and strong ground improvement elements without the need for pre-drilling.

[0103] For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing amounts, sizes, dimensions, proportions, shapes, formulations, parameters, percentages, parameters, quantities, characteristics, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about” even though the term “about” may not expressly appear with the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are not and need not be exact, but may be approximate and / or larger or smaller as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art depending on the desired properties sought to be obtained by the presently disclosed subject matter. For example, the term “about,” when referring to a value can be meant to encompass variations of, in some embodiments, ± 100% in some embodiments ± 50%, in some embodiments ± 20%, in some embodiments ± 10%, in some embodiments ± 5%, in some embodiments ±1%, in some embodiments ± 0.5%, and in some embodiments ± 0.1% from the specified amount, as such variations are appropriate to perform the disclosed methods or employ the disclosed compositions.

[0104] Further, the term “about” when used in connection with one or more numbers or numerical ranges, should be understood to refer to all such numbers, including all numbers in a range and modifies that range by extending the boundaries above and below the numerical values set forth. The recitation of numerical ranges by endpoints includes all numbers, e.g., whole integers, including fractions thereof, subsumed within that range (for example, the recitation of 1 to 5 includes 1, 2, 3, 4, and 5, as well as fractions thereof, e.g., 1.5, 2.25, 3.75, 4.1, and the like) and any range within that range. The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

[0105] The term “consisting of’ means “including and limited to”.

[0106] The term "consisting essentially of means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0107] The term “plurality” means “two or more”.

[0108] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

[0109] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0110] Although the foregoing subject matter has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be understood by those skilled in the art that certain changes and modifications can be practiced within the scope of the appended claims.

[0111] All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

[0112] Claim Clauses Clause 1. A ground densification apparatus, comprising: a driving mandrel comprising: a mandrel web; at least one flange disposed on a side of the mandrel web; and an array of ground densification elements attached at a first end to the mandrel web and extend freely beyond a bottom of the mandrel web.

[0113] Clause 2. The ground densification apparatus of Clause 1, wherein the array of ground densification elements is unrestrained by any compaction chamber and configured and sized to achieve a desired lift thickness, compaction surface area, and backfill flow based on backfill material type and project requirements.

[0114] Clause 3. The ground densification apparatus of Clause 2, wherein the array of ground densification elements is at least one of a chain, a chain link, a cable, a wire rope, or a lattice of vertically and / or horizontally connected chains, cables, or wire rope.

[0115] Clause 4. The ground densification apparatus of Clause 1, further comprising at least one compaction shutter attached to the driving mandrel.

[0116] Clause 5. The ground densification apparatus of Clause 4, wherein the at least one compaction shutter is rotatably attached to the driving mandrel.

[0117] Clause 6. The ground densification apparatus of Clause 5, wherein the at least one compaction shutter is rotatably attached using a hinge.

[0118] Clause 7. The ground densification apparatus of Clause 4, wherein the at least one compaction shutter is attached to the mandrel web near the bottom of the driving mandrel.

[0119] Clause 8. The ground densification apparatus of Clause 4, wherein at least one compaction shutter is attached to a front side and a back side of the driving mandrel.

[0120] Clause 9. The ground densification apparatus of Clause 5, wherein the at least one compaction shutter is rotatable from a substantially vertical position parallel to a major axis of the driving mandrel to a substantially horizontal position transverse to the major axis of the driving mandrel.

[0121] Clause 10. The ground densification apparatus of Clause 9, further comprising at least one rotation stop disposed on the driving mandrel above the at least one compaction shutter to limit rotation to a horizontal position of the at least one compaction shutter.

[0122] Clause 11. The ground densification apparatus of Clause 1, further comprising at least one enhancing window disposed within the mandrel web to permit passage of backfill material therethrough during operation. Clause 12. The ground densification apparatus of Clause 1, wherein the driving mandrel is shaped as an I-beam, H-beam, W-beam, HP -beam, S-beam, or M-beam.

[0123] Clause 13. The ground densification apparatus of Clause 12, wherein the at least one flange disposed on the side of the mandrel web forms at least a part of the I-beam, H- beam, W-beam, HP -beam, S-beam, or M-beam shape.

[0124] Clause 14. The ground densification apparatus of Clause 1, further comprising a geosynthetic swatch to minimize an inclusion of ground into an area subtended by the mandrel web and the at least one flange.

[0125] Clause 15. The ground densification apparatus of Clause 1, wherein the driving mandrel is substantially unitary in cross-sectional area throughout an entire length of the driving mandrel.

[0126] Clause 16. A method of using a ground densification apparatus, comprising: driving the ground densification apparatus into a ground to form a cavity; raising the ground densification apparatus; applying backfill material into the cavity during a raising, the backfill material flowing downwardly and freely along and through an area formed by a mandrel web of the ground densification apparatus, at least one flange, and at least one flow through enhancing window; re-driving the ground densification apparatus downwardly to a depth preferably less than an initial driving depth, wherein during redriving an array of ground densification elements expands horizontally to engage with the backfill material to densify the backfill material in the cavity, wherein the array of ground densification elements and a sidewall of the cavity form a compaction area for backfill material densification; and repeating the re-driving until the ground densification apparatus has been lifted to or near an original ground elevation and a densified and well -compacted column of backfill material has been formed in the cavity.

[0127] Clause 17. The method of Clause 16, further comprising using an at least one movable compaction shutter rotatably attached to the driving mandrel above the array of ground densification elements to engage with the array of ground densification elements and the backfill material to densify the backfill material in the cavity, such that the at least one moveable compaction shutter exhibits a substantially vertical configuration during raising and a substantially horizontal configuration during driving. Clause 18. The method of Clause 16, further comprising driving the driving mandrel through stone at a desired cavity location, whereby the driving mandrel with an array of ground densification elements the stone forms a driving plug that prevents ground from entering into a bottom of the ground densification apparatus. Clause 19. The method of Clause 16, wherein the ground densification apparatus comprises a driving mandrel, the driving mandrel comprising: the mandrel web; the at least one flange disposed on a side of the mandrel web; and the array of ground densification elements attached at a first end to the mandrel web and extend freely beyond a bottom of the mandrel web. Clause 20. The method of Clause 19, wherein the array of ground densification elements is unrestrained by any compaction chamber and configured and sized to achieve a desired lift thickness, compaction surface area, and backfill flow based on backfill material type and project requirements.

Claims

CLAIMSTHAT WHICH IS CLAIMED:

1. A ground densification apparatus, comprising: a driving mandrel comprising: a mandrel web; at least one flange disposed on a side of the mandrel web; and an array of ground densification elements attached at a first end to the mandrel web and extend freely beyond a bottom of the mandrel web.

2. The ground densification apparatus of Claim 1, wherein the array of ground densification elements is unrestrained by any compaction chamber and configured and sized to achieve a desired lift thickness, compaction surface area, and backfill flow based on backfill material type and project requirements.

3. The ground densification apparatus of Claim 2, wherein the array of ground densification elements is at least one of a chain, a chain link, a cable, a wire rope, or a lattice of vertically and / or horizontally connected chains, cables, or wire rope.

4. The ground densification apparatus of Claim 1, further comprising at least one compaction shutter attached to the driving mandrel.

5. The ground densification apparatus of Claim 4, wherein the at least one compaction shutter is rotatably attached to the driving mandrel.

6. The ground densification apparatus of Claim 5, wherein the at least one compaction shutter is rotatably attached using a hinge.

7. The ground densification apparatus of Claim 4, wherein the at least one compaction shutter is attached to the mandrel web near the bottom of the driving mandrel.

8. The ground densification apparatus of Claim 4, wherein at least one compaction shutter is attached to a front side and a back side of the driving mandrel.

9. The ground densification apparatus of Claim 5, wherein the at least one compaction shutter is rotatable from a substantially vertical position parallel to a major axis of the driving mandrel to a substantially horizontal position transverse to the major axis of the driving mandrel.

10. The ground densification apparatus of Claim 9, further comprising at least one rotation stop disposed on the driving mandrel above the at least one compaction shutter to limit rotation to a horizontal position of the at least one compaction shutter.

11. The ground densification apparatus of Claim 1, further comprising at least one enhancing window disposed within the mandrel web to permit passage of backfill material therethrough during operation.

12. The ground densification apparatus of Claim 1, wherein the driving mandrel is shaped as an I-beam, H-beam, W-beam, HP-beam, S-beam, or M-beam.

13. The ground densification apparatus of Claim 12, wherein the at least one flange disposed on the side of the mandrel web forms at least a part of the I-beam, H-beam, W- beam, HP-beam, S-beam, or M-beam shape.

14. The ground densification apparatus of Claim 1, further comprising a geosynthetic swatch to minimize an inclusion of ground into an area subtended by the mandrel web and the at least one flange.

15. The ground densification apparatus of Claim 1, wherein the driving mandrel is substantially unitary in cross-sectional area throughout an entire length of the driving mandrel.

16. A method of using a ground densification apparatus, comprising: driving the ground densification apparatus into a ground to form a cavity; raising the ground densification apparatus; applying backfill material into the cavity during a raising, the backfill material flowing downwardly and freely along and through an area formed by a mandrel web of the ground densification apparatus, at least one flange, and at least one flow through enhancing window; re-driving the ground densification apparatus downwardly to a depth preferably less than an initial driving depth, wherein during re-driving an array of ground densification elements expands horizontally to engage with the backfill material to densify the backfill material in the cavity, wherein the array of ground densification elements and a sidewall of the cavity form a compaction area for backfill material densification; and repeating the re-driving until the ground densification apparatus has been lifted to or near an original ground elevation and a densified and well-compacted column of backfill material has been formed in the cavity.

17. The method of Claim 16, further comprising using an at least one movable compaction shutter rotatably attached to the driving mandrel above the array of ground densification elements to engage with the array of ground densification elements and the backfill material to densify the backfill material in the cavity, such that the at least one moveable compaction shutter exhibits a substantially vertical configuration during raising and a substantially horizontal configuration during driving.

18. The method of Claim 16, further comprising driving the driving mandrel through stone at a desired cavity location, whereby the driving mandrel with an array of ground densification elements the stone forms a driving plug that prevents ground from entering into a bottom of the ground densification apparatus.

19. The method of Claim 16, wherein the ground densification apparatus comprises a driving mandrel, the driving mandrel comprising:the mandrel web; the at least one flange disposed on a side of the mandrel web; and the array of ground densification elements attached at a first end to the mandrel web and extend freely beyond a bottom of the mandrel web.

20. The method of Claim 19, wherein the array of ground densification elements is unrestrained by any compaction chamber and configured and sized to achieve a desired lift thickness, compaction surface area, and backfill flow based on backfill material type and project requirements.

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