Patent Description:
The presently disclosed subject matter relates generally to the compaction and densification of granular subsurface materials and more particularly to methods and apparatuses for 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.

Heavy or settlement sensitive facilities that are located in areas containing soft, loose, or weak 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.

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.

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 <CIT>. 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.

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 <CIT> and <CIT>; the tamper head driven mandrel method described in <CIT>; the tamper head driven mandrel with restrictor elements method described in <CIT>; and the driven tapered mandrel method described in <CIT>; the entire disclosures of which are incorporated by reference in their entirety.

The short aggregate column method (<CIT> and <CIT>), 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 <NUM> inches); b) compacting the soil at the bottom of the cavity; c) installing a relatively thin lift of aggregate into the cavity (typically around <NUM>-<NUM> 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 build up 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 tamper head driven mandrel method (<CIT>) 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 (<CIT>) uses a plurality of restrictor elements installed within the tamper head <NUM> to restrict the backflow of aggregate into the tamper head during compaction.

The driven tapered mandrel method (<CIT>) 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 <NUM> to about <NUM> 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. <CIT> discloses a system and method for installing aggregate piers. A cylindrical hollow mandrel is driven to a desired depth. Aggregate is fed through the mandrel in steps. <CIT> discloses a system for constructing a support column including a mandrel with an upper portion and a tamper head.

The present disclosure relates generally to an apparatus for densifying and compacting granular materials. The apparatus according to the invention is disclosed in independent claim <NUM>. The diametric expansion elements, in their expanded state, may form compaction surfaces having a diameter greater that he diameter of the drive shaft. The diametric expansion elements may be attached to a bottom surface of the drive shaft, or attached to a base plate attached to the bottom end of the drive shaft. The base plate may be changeable.

The diametric expansion elements may include any one or more of chains, cables, wire rope, and/or a lattice of vertically and/or horizontally connected chains, cables, or wire rope. The diametric expansion elements may be configured and sized accordingly to achieve desired lift thickness, compaction surface area, and/or soil flow based on material type and/or project requirements. Additionally, the diametric expansion elements may be housed within a sacrificial tip that may be releasably connected to a bottom portion of the drive shaft. The apparatus may also include one or more wing structures attached to the drive shaft that are configured to loosen free-field soils around the drive shaft.

In certain other embodiments, the apparatus may include a drive shaft, a compaction chamber at a lower end of the drive shaft, and one or more diametric expansion elements, wherein the apparatus further includes an opening in an upper surface of the compaction chamber forming a flow-through passage exterior of the drive shaft and configured for accepting granular materials from outside of the drive shaft. The drive shaft may be the same size and/or diameter, a larger size and/or diameter, or a smaller size and/or diameter than the compaction chamber. Additionally, the compaction chamber may be connected to the drive shaft through a load transfer plate, and may further incorporate one or more stiffener plates connected to the drive shaft and the load transfer plate.

Certain embodiments of the apparatus may include one or more diametric expansion and restriction elements attached to one or both of an interior or exterior of the compaction chamber. The one or more diametric expansion and restriction elements may also be attached to the load transfer plate. The apparatus may include both interior diametric restriction elements and exterior diametric expansion elements. Moreover, the interior diametric restriction elements and exterior diametric expansion elements may or may not be connected to one another. The drive shaft may include a hollow tube, a substantially I-beam configuration that may further include an opening in the I-beam configuration, or a solid cylindrical shaft configuration. The apparatus may further be configured to be inserted in a pre-drilled cavity.

In certain other aspects of the present disclosure, an apparatus for densifying and compacting granular materials is presented according to other embodiments. The apparatus includes a drive shaft, a compaction chamber, and one or more diametric restriction elements, wherein the compaction chamber comprises a pipe and the drive shaft is fitted into one end of the pipe. The apparatus may be configured to be inserted in a pre-drilled cavity. The drive shaft includes an I-Beam configuration, and may further include an opening in the I-Beam configuration wherein at least a portion of the opening in the drive shaft may extend into the pipe. Certain embodiments may also include a reinforcing ring fitted around a bottom end of the compaction chamber, and may further include a substantially ring-shaped wearing pad abutting the reinforcement ring.

Embodiments of the apparatus may also include a ring that may be secured to the compaction chamber and positioned near the end of the drive shaft that includes an arrangement of the diametric restriction elements. A second arrangement of diametric restriction elements may be secured to the drive shaft. The ring may be optionally removable.

In certain other embodiments, the apparatus may include a drive pipe affixed to a lower end of the drive shaft, wherein a bottom end of the drive pipe may extend into the compaction chamber, and further wherein the drive pipe may secured to the compaction chamber by one or more struts or plates extending from sides of the compaction chamber radially inward to the drive pipe. The one or more struts or plates may extend along the drive pipe above the compaction chamber to a termination point, tapering from the sides of the compaction chamber to the termination point. Additionally, a bottom end of the drive pipe may be closed using a plate or cap and the plate or cap extends below a lower end of the one or more struts or plates.

Other embodiments of the apparatus may also include a perimeter ring inside the compaction chamber, the ring including an arrangement of the diametric restriction elements and being disposed along the inner perimeter of the compaction chamber at substantially the lower end of the one or more struts or plates. The ring may be removable. The apparatus may also include diametric restriction elements that are coupled to the lower end of the one or more struts or plates and the perimeter of the plate or cap.

Certain other aspects of the present disclosure include a method of densifying and compacting granular materials, the method including the steps of (a) providing a compaction apparatus comprising a closed end drive shaft having a first diameter and one or more diametric expansion elements, wherein the one or more diametric expansion elements expand when the apparatus is driven downward forming compaction surfaces having a second diameter greater than the first diameter of the drive shaft, (b) driving the compaction apparatus into free-field soils to a specified depth, (c) lifting the compaction apparatus a specified distance, and (d) repeating the driving and lifting of the compaction apparatus. The method may also include repeating the driving and lifting steps incrementally until the compaction apparatus has been lifted to or near an original ground elevation. In such embodiments, each of the repeated driving of the compaction apparatus may be to a distance generally less than a distance the compaction apparatus was previously lifted.

Driving of the compaction apparatus may be effectuated using one of an impact or vibratory hammer. In certain embodiments, the lifting of the compaction apparatus allows for surrounding materials to flow around the compaction apparatus to fill a void created by lifting the compaction apparatus. In some embodiments, the one or more diametric expansion elements may be placed within a sacrificial tip and upon the initial lifting of the compaction apparatus the one or more diametric expansion elements are removed from the sacrificial tip and move downward relative to the compaction apparatus so as to hang from a bottom portion of the compaction apparatus. The method may, in some embodiments, create a well compacted column of densified soil below and around the one or more diametric expansion elements.

Certain other embodiments of methods of densifying and compacting granular materials include the steps of (a) providing a compaction apparatus comprising a drive shaft, a compaction chamber at a lower end of the drive shaft, and one or more diametric expansion elements, wherein the apparatus further comprises an opening in an upper surface of the compaction chamber comprising a flow-through passage exterior of the drive shaft and configured for accepting granular materials from outside of the drive shaft, (b) driving the compaction apparatus into free-field soils to a specified depth, (c) lifting the compaction apparatus a specified distance such that the one or more diametric restriction elements move downward relative to the compaction apparatus to hang from connections to the compaction apparatus thereby allowing granular materials located above a top portion of the compaction chamber to flow through the flow-through passage, (d) re-driving the apparatus downwardly into the free-field soils causing the one or more diametric restriction elements to bunch-up forming compaction surfaces, and (e) repeating the driving and lifting of the compaction apparatus. Moreover, other methods of densifying and compacting granular materials include the steps of (a) providing a compaction apparatus comprising a drive shaft, a compaction chamber, and one or more diametric restriction elements, wherein the compaction chamber comprises a pipe and the drive shaft is fitted into one end of the pipe, (b) driving the compaction apparatus into free-field soils to a specified depth, (c) lifting the compaction apparatus a specified distance such that the one or more diametric restriction elements move downward relative to the compaction apparatus to hang from connections to the compaction apparatus thereby allowing granular materials located above a top portion of the compaction chamber to flow around the outside of the drive shaft and into the compaction chamber, (c) re-driving the apparatus downwardly into the free-field soils causing the one or more diametric restriction elements to bunch-up forming compaction surfaces; and (d) repeating the driving and lifting of the compaction apparatus.

Having thus described the presently disclosed subject matter in general terms, reference will now be made to the accompanying Drawings, which are not necessarily drawn to scale, and wherein:.

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. 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 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 compaction apparatuses in which each soil compaction apparatus includes an arrangement of diametric expansion/restriction elements. The diametric expansion/restriction elements can be fabricated from, for example, individual chains, cables, or wire rope, or a lattice of vertically and horizontally connected chains, cables, or wire rope. In a specific example, the diametric expansion/restriction elements can be formed of half-inch (<NUM>,<NUM>), grade <NUM> alloy chains.

Embodiments of the soil compaction apparatus include, but are not limited to, closed-ended driving shafts, open-ended driving shafts, flow-through passages, no flow-through passages, removable rings for holding the diametric expansion/restriction elements, and any combinations thereof.

In an example method of using the presently disclosed soil compaction apparatus, after initial driving, the soil compaction apparatus is raised and the diametric expansion elements hang freely by gravity from the bottom of the driving shaft. As the driving shaft is raised the free-field soils flow into the cavity left by the driving shaft. After raising the driving shaft the prescribed distance, the driving shaft is then re-driven downwardly to a depth preferably less than the initial driving depth into the underlying materials. This allows the diametric expansion elements the opportunity to expand radially, forming a compaction surface that has a diameter larger than the driving shaft. This process creates a well compacted column of densified soil below and around the diametric expansion 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.

Referring now to <FIG>, a soil compaction apparatus <NUM> according to one embodiment is illustrated, wherein the soil compaction apparatus <NUM> is used to compact granular materials. Namely, <FIG> are side views of the presently disclosed soil compaction apparatus <NUM> in the raised and lowered positions, respectively, and comprising an arrangement of diametric expansion elements <NUM>. The soil compaction apparatus <NUM> shown in <FIG> may be inserted or driven into free-field soils (i.e., soil that exists in its natural or placed state below grade). The soil compaction apparatus <NUM> comprises a driving shaft <NUM>. In this example, the driving shaft <NUM> is a closed-top and closed-end driving shaft. Namely, a base plate <NUM> is provided at the end of the driving shaft <NUM> that is driven into the soil, thereby forming the closed-end or closed-bottom driving shaft.

Further, an arrangement of diametric expansion elements <NUM> are attached to the bottom of the driving shaft <NUM> via, for example, a mounting plate <NUM>. For example, the diametric expansion elements <NUM> can be fastened to the mounting plate <NUM>. Then, the mounting plate <NUM> can be bolted to the base plate <NUM>. In this example, the diametric expansion elements <NUM> are located at the closed bottom of the driving shaft <NUM> that is used to compact granular materials.

The diametric expansion elements <NUM> can be fabricated from individual chains, 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 diametric expansion elements <NUM> are half-inch (<NUM>,<NUM>), grade <NUM> alloy chains. In the embodiment shown in <FIG>, when the soil compaction apparatus <NUM> is initially driven downward into free-field soil, the diametric expansion elements <NUM> may be placed within a sacrificial tip <NUM>, as shown in <FIG>. The sacrificial tip <NUM> may have a depth enough, such as <NUM> inches (<NUM>), to house the diametric expansion elements <NUM>.

After initial driving (see <FIG>), the soil compaction apparatus <NUM> is raised and the diametric expansion elements <NUM> hang freely by gravity from the bottom of the driving shaft <NUM> (see <FIG>). As the driving shaft <NUM> is raised the free-field soils (or additionally added aggregate) flow into the cavity left by the driving shaft <NUM>. Optionally, one or more wings <NUM> are attached to the outer sides of the driving shaft <NUM>. The wings <NUM> can act to loosen the free-field soils around the driving shaft <NUM>.

After raising the driving shaft <NUM> the prescribed distance, the driving shaft <NUM> is then re-driven downwardly to a depth preferably less than the initial driving depth into the underlying materials. This allows the diametric expansion elements <NUM> the opportunity to expand radially (see <FIG>) forming a compaction surface CS that has a diameter larger than the base plate <NUM>. In one example, the diameter Di1 of the driving shaft <NUM> and base plate <NUM> is about <NUM> inches (<NUM>), while the diameter Di2 of the expanded compaction surface is about <NUM> inches (<NUM>). The process creates a well-compacted column of densified soil below and around the diametric expansion elements <NUM>. This process of lifting the driving shaft <NUM> upward and driving back down is repeated incrementally until the driving shaft <NUM> has been lifted to or near an original ground elevation.

The diametric expansion elements <NUM> are configured and sized accordingly to achieve the desired lift thickness, compaction surface area, and soil flow based on the material type and project requirements. The base plate <NUM> and the diametric expansion elements <NUM> (with mounting plate <NUM>) are typically changeable. The configuration of the changeable base plate <NUM> with the attached diametric expansion elements <NUM> can be adapted to project requirements, which eliminates having to make separate drive shaft mandrels and is therefore a low cost and effective method. The soil compaction apparatus <NUM> shown in <FIG> has the advantage of being simple to fabricate, construct, and maintain.

Referring now to <FIG>, a side view and a plan view, respectively, of yet another example of the presently disclosed soil compaction apparatus <NUM> is illustrated comprising yet another arrangement of diametric expansion/restriction elements <NUM>. In this example, a flow-through passage <NUM> around the driving shaft <NUM> and within a compaction chamber <NUM> facilitates aggregate flow into the compaction chamber <NUM> from an exterior of the driving shaft <NUM>. In one example, the driving shaft <NUM> is an I-beam or H-beam that provides the "flow-through" arrangement, wherein soil can flow through the driving shaft <NUM> and into the flow-through passages <NUM> of the I-beam or H-beam (and compaction chamber <NUM>). In the case of an H-beam being used as the driving shaft <NUM>, the outer two flanges on the H-beam can also help case the soil cavity walls while the mandrel is being lowered and raised in the cavity. It is also contemplated that the driving shaft <NUM> can be a solid cylindrical shaft (with struts or similar connections to the compaction chamber) or the like.

The soil compaction apparatus <NUM> shown in <FIG> further comprises a compaction chamber <NUM>. Namely, the compaction chamber <NUM> is mechanically connected to the bottom end of the driving shaft <NUM>. The compaction chamber <NUM> is, for example, cylinder-shaped. The compaction chamber <NUM> may be the same size or diameter as the driving shaft <NUM> or the compaction chamber <NUM> may be larger or smaller than the driving shaft <NUM>. In <FIG>, the compaction chamber <NUM> is larger in cross-sectional area than the driving shaft <NUM>. In one example, the length of the compaction chamber <NUM> is about <NUM> inches (<NUM>).

The compaction chamber <NUM> may be connected to the driving shaft <NUM> with a load transfer plate <NUM> with the optional use of one or more stiffener plates <NUM>. The compaction chamber <NUM> may be open at its lower surface allowing for the intrusion of granular materials into the compaction chamber <NUM> when the soil compaction apparatus <NUM> is driven downwards. In the embodiment shown in <FIG>, the compaction chamber <NUM> may also be generally open at its upper surface facilitating the flow-through passage(s) <NUM>. Namely, the load transfer plate <NUM> can be a ring-shape plate with an opening in the center portion thereof.

Further, in the embodiment shown in <FIG>, both interior diametric restriction elements 114I and exterior diametric expansion elements 114E are attached to the load transfer plate <NUM>. In this example, interior diametric "restriction" elements 114I means interior to the compaction chamber <NUM> and exterior diametric "expansion" elements 114E means exterior to the compaction chamber <NUM>. The interior diametric restriction elements 114I and exterior diametric expansion elements 114E may or may not be connected to one another. The diametric expansion/restriction elements <NUM> (generally including interior diametric restriction elements 114I and exterior diametric expansion elements 114E) typically may consist of individual chain links, cable, or of wire rope or a lattice of connected elements that hang downward from the load transfer plate <NUM>. In a specific example, the diametric expansion/restriction elements <NUM> are of half-inch (<NUM>,<NUM>), grade <NUM> alloy chains.

In the embodiment shown in <FIG>, the soil compaction apparatus <NUM> can be used to compact and densify granular soils in the free field or within a predrilled cavity. When the soil compaction apparatus <NUM> is extracted upwards through the free field soil or within a preformed cavity, the diametric expansion/restriction elements <NUM> hang vertically downward and offer little resistance to the upward movement of the soil compaction apparatus <NUM>. When the soil compaction apparatus <NUM> is driven downward, the diametric expansion/restriction elements <NUM> engage the materials that the soil compaction apparatus <NUM> is being driven into because these materials (i.e., free field soil or aggregate placed in a predrilled hole) are moving upwards relative to the downwardly driven soil compaction apparatus <NUM>.

The engaged materials cause the diametric expansion/restriction elements <NUM> to "expand" or "bunch" together, thereby substantially inhibiting any further upward movement of the soil or aggregate materials. The interior diametric restriction elements 114I thus "bunch" in the interior of the compaction chamber <NUM> causing the compaction chamber <NUM> to "plug" with the upwardly moving soil material during downward movements of the mandrel. This creates an effective compaction surface CS that is then used to compact the materials directly below the bottom of the soil compaction apparatus <NUM>. The exterior diametric expansion elements 114E likewise "expand" exterior of the compaction chamber <NUM> thus inhibiting the upward movement of the soil or aggregate materials exterior to the compaction chamber. This mechanism thus effectively increases the cross-sectional area of the compaction surface CS during downward compaction strokes. The increase in cross-sectional area allows for the use of the soil compaction apparatus <NUM> with an effective cross-sectional area that is larger during compaction than during extraction, offering great efficiency and machinery and tooling cost savings during construction.

Referring now to <FIG>, a side view and a plan view, respectively, are illustrated of yet another example of the presently disclosed soil compaction apparatus <NUM> comprising yet another arrangement of diametric restriction elements <NUM>. The soil compaction apparatus <NUM> shown in <FIG> is substantially the same as the soil compaction apparatus <NUM> shown in <FIG>, except that it does not include the exterior diametric expansion elements 114E. In this example, the load transfer plate <NUM> does not extend beyond the diameter of the compaction chamber <NUM> and only the interior diametric restriction elements 114I are attached thereto. Both of the soil compaction apparatuses <NUM> shown in <FIG>, <FIG> provide an efficient flow-through passage <NUM> in an arrangement exterior of the driving shaft <NUM> that allows for improved granular material flow into the compaction chamber <NUM>.

In the soil compaction apparatus <NUM> shown in <FIG>, when the soil compaction apparatus <NUM> is raised, granular materials that are located above the top of the compaction chamber <NUM> may flow around the outside of the compaction chamber <NUM> and/or through or exterior of the driving shaft <NUM> and into flow-through passage <NUM> to enter the compaction chamber <NUM> from above. The ability of the granular materials to flow through the flow-through passage <NUM> allows the soil compaction apparatus <NUM> to be raised upwards with less extraction force and thus with greater efficiency (as opposed to a more generally "closed" upper portion of the compaction chamber as seen in the prior art). After the soil compaction apparatus <NUM> is raised, it is then re-driven back downwards. The downward action allows the interior diametric restriction elements 114I to "bunch" together thereby forming an effective plug that is then used to compact the materials below the bottom of the soil compaction apparatus <NUM>.

The soil compaction apparatus <NUM> shown in <FIG> is especially effective at densifying and compacting aggregates within preformed cavities. By way of example, <FIG> shows the soil compaction apparatus <NUM> shown in <FIG> in a cavity <NUM>, wherein the soil compaction apparatus <NUM> is used to compact granular materials within a preformed cavity. In this example, the soil compaction apparatus compaction chamber <NUM> has a height H of approximately <NUM> inches (<NUM>).

In an exemplary method, the cavity <NUM> is formed by drilling or other means and the soil compaction apparatus <NUM> is lowered into the cavity <NUM>. Aggregate may then be poured from the ground surface to form a mound on top of the compaction chamber <NUM> within the cavity <NUM>. When the soil compaction apparatus <NUM> is raised, the aggregate may then flow through and around the flow-through passage <NUM> and into the interior of the compaction chamber <NUM>. Further raising the soil compaction apparatus <NUM> allows aggregate to flow below the bottom of the compaction chamber <NUM>. When the soil compaction apparatus <NUM> is driven downwards into the placed aggregate, the interior diametric restriction elements 114I move inwardly to "bunch" together to form a compaction surface. This mechanism facilitates the compaction of the aggregate materials below the compaction chamber <NUM>. The soil compaction apparatus <NUM> and method described above for this embodiment allows the soil compaction apparatus <NUM> to remain in the cavity <NUM> during the upward and downward movements required for the compaction cycle and eliminates the need to "trip" the mandrel out of the cavity <NUM> as is required for previous art. The soil compaction apparatus <NUM> and method further eliminate the need for a hollow feed tube and hopper that is typically required for displacement methods used in the field and described above. Another advantage of the open flow-through passage <NUM> in the upper portion of the compaction chamber <NUM> is the ability to develop a head of stone above the compaction chamber to temporarily case the caving cavity soils during pier construction, while being able to leave the mandrel in the cavity while aggregate is added.

The soil compaction apparatuses <NUM> shown in <FIG> may also be used in conjunction with the method for compacting and densifying aggregate in predrilled holes as described above in <FIG>, and <FIG>. When the soil compaction apparatuses <NUM> shown in <FIG> are used, the exterior diametric expansion elements <NUM> hang downwards during upward extraction and expand/bunch together during the downward compaction stroke. This prevents the aggregate below from moving upwards relative to the exterior of the driving shaft <NUM> and/or the compaction chamber <NUM>. The prevention of upward movements allows a tamper head to effectively enlarge during the compaction of the aggregate. A larger sized tamper head provides greater confinement to the lift of aggregate placed and effectively densifies a greater depth of aggregate within the lift that is placed. This mechanism allows for the use of thicker lifts of aggregate during compaction, making the process less costly and more efficient.

Referring now to <FIG>, a side view of another soil compaction apparatus <NUM> is illustrated comprising a removable ring of diametric restriction elements (defined in further detail hereinbelow), according to another embodiment. <FIG> illustrate a top view and a bottom view, respectively, of the soil compaction apparatus <NUM> of <FIG>.

The soil compaction apparatus <NUM> includes a driving shaft <NUM>. The driving shaft <NUM> is typically an I-beam or H-beam that provides a "flow-through" arrangement, wherein soil/aggregate can flow through or exterior of the driving shaft <NUM> and into the flow-through passages <NUM> of the I-beam or H-beam (see <FIG>). In one example, the I-beam or H-beam has a height of about <NUM> inches (<NUM>), a width of about <NUM> inches (<NUM>), and a length of about <NUM> inches (<NUM>). An opening <NUM> may be provided in the web of the I-beam or H-beam that forms the driving shaft <NUM> to allow aggregate or other materials in the cavity above the bottom end of the drive shaft to pass from one half of the cavity to the other. The opening <NUM> may be near the bottom end of the driving shaft <NUM>. In one example, the opening <NUM> has rounded ends and is about <NUM> inches (<NUM>) long and about <NUM> inches (<NUM>) wide. To overcome any loss of strength in the driving shaft <NUM> due to the presence of the opening <NUM>, a pair of reinforcing plates <NUM> can be, for example, welded to the driving shaft <NUM>, i.e., one reinforcing plate <NUM> on one side and another reinforcing plate <NUM> on the other side near the opening <NUM>. In one example, each reinforcing plate <NUM> is about <NUM> inches (<NUM>) wide and about <NUM> inch (<NUM>) thick.

In soil compaction apparatus <NUM>, the bottom end of the driving shaft <NUM> is fitted into one end of a pipe <NUM> such that a portion of the opening <NUM> is inside the pipe <NUM>. Namely, the driving shaft <NUM> is fitted into the pipe <NUM> to a depth d1. In one example, the depth d1 is about <NUM> inches (<NUM>). Once fitted into the pipe <NUM>, the driving shaft <NUM> can be secured therein by, for example, welding. In one example, the pipe <NUM> has a length L1 of about <NUM> inches (<NUM>), an outside diameter (OD) of about <NUM> inches (<NUM>), an inside diameter (ID) of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inch (<NUM>).

Fitted around the bottom end of the pipe <NUM> can be a reinforcing ring <NUM>. In one example, the reinforcing ring <NUM> has a height h1 of about <NUM> inches (<NUM>), an OD of about <NUM> inches (<NUM>), an ID of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inch (<NUM>). In one example, the reinforcing ring <NUM> can be secured to the pipe <NUM> by welding. Further, a ring-shaped wearing pad <NUM> can abut the end of the pipe <NUM> and the reinforcing ring <NUM>. In one example, the wearing pad <NUM> has a thickness t1 of about <NUM> inch (<NUM>). The wearing pad <NUM> may be replaced as needed.

The soil compaction apparatus <NUM> also typically comprises a removable ring <NUM> to which an arrangement of the diametric restriction elements <NUM> is attached. In one example, the removable ring <NUM> has a height of from about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>), an OD of about <NUM> inches (<NUM>), an ID of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inches (<NUM>). By attaching the diametric restriction elements <NUM> to the removable ring <NUM>, a removable ring of the diametric restriction elements <NUM> is formed. The removable ring <NUM> with the diametric restriction elements <NUM> may be fitted inside of the pipe <NUM> and positioned near the end of the driving shaft <NUM> such that the diametric restriction elements <NUM> hang down toward the bottom end of the pipe <NUM>. The removable ring <NUM> can be secured inside the pipe <NUM> by, for example, bolts <NUM>.

Another set of diametric restriction elements <NUM> can be secured to the web of the I-beam or H-beam that forms the driving shaft <NUM>. Hereafter, the diametric restriction elements <NUM> attached to the removable ring <NUM> are called the diametric restriction elements 114A. Hereafter, the diametric restriction elements <NUM> attached to the web of the driving shaft <NUM> are called the diametric restriction elements 114B.

In one example, the removable ring <NUM> can be a single-piece continuous ring. In this example, the diametric restriction elements 114A are formed, for example, by welding twenty-six (<NUM>), <NUM>-inch (<NUM>) long, half-inch (<NUM>), grade <NUM> alloy chains to the removable ring <NUM>. In another example, the removable ring <NUM> can consist of two half-rings that are positioned together inside of the pipe <NUM>. In this example, the diametric restriction elements 114A are formed, for example, by welding thirteen (<NUM>), <NUM>-inch (<NUM>) long, half-inch (<NUM>), grade <NUM> alloy chains to each half of the removable ring <NUM>.

In one example, the diametric restriction elements 114B attached to the web of driving shaft <NUM> are formed by welding five (<NUM>), <NUM>-inch (<NUM>) long, half-inch (<NUM>), grade <NUM> alloy chains to the web of the I-beam or H-beam that forms the driving shaft <NUM>. When the mandrel is driven into the aggregate, the chains bunch-up, thereby substantially restricting the flow of aggregate upward and allowing the mandrel to compact the aggregate. When the mandrel is extracted, the chains fall, allowing aggregate to flow downward relative to the mandrel.

Referring now to <FIG>, a side view of a soil compaction apparatus <NUM> is illustrated comprising the diametric restriction elements <NUM>, according to another embodiment. <FIG> illustrate a top view and a bottom view, respectively, of the soil compaction apparatus <NUM> of <FIG>. In this example, the soil compaction apparatus <NUM> can comprise a pipe <NUM>. The bottom end of the pipe <NUM> may be closed using a plate or cap <NUM>, thereby rendering the pipe <NUM> a closed-end pipe. The top end of the pipe <NUM> typically has a flange <NUM> for connecting to the tip of the driving shaft <NUM>. In one example, the pipe <NUM> is about <NUM> inches (<NUM>) long and has an OD of about <NUM> inches (<NUM>), an ID of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inch (<NUM>). The pipe <NUM>, the plate or cap <NUM>, and the flange <NUM> can be fastened together by, for example, welding.

The bottom end of the closed-end pipe <NUM> is fitted into one end of a compaction chamber <NUM>. In one example, the compaction chamber <NUM> is a pipe that has a length L1 of about <NUM> inches (<NUM>), an OD of about <NUM> inches (<NUM>), an ID of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inch (<NUM>). In one example, the pipe <NUM> is fitted into the compaction chamber <NUM> a distance of about <NUM> inches (<NUM>).

The pipe <NUM> may be supported within the compaction chamber <NUM> by, for example, four struts or plates <NUM> arranged radially around the pipe <NUM> (e.g., one at <NUM> o'clock, one at <NUM> o'clock, one at <NUM> o'clock, and one at <NUM> o'clock). In one example, the struts or plates <NUM> are about <NUM> inch (<NUM>) thick. The struts or plates <NUM> typically extend into the compaction chamber <NUM> a distance d1, or for example, about <NUM> inches (<NUM>). The top end of the struts or plates <NUM> can be tapered toward the pipe <NUM> as shown, whereas the lower ends of the struts or plates <NUM> are typically squared off. Alternatively, the struts or plates <NUM> may be squared off at the top similar to the lower end. The plate or cap <NUM> at the end of the pipe <NUM> may extend slightly below the lower end of the struts or plates <NUM>. The pipe <NUM>, the compaction chamber <NUM>, and the struts or plates <NUM> can be fastened together by, for example, welding.

Further, a ring <NUM> may be provided inside of the compaction chamber <NUM> and near the lower end of the struts or plates <NUM>. In one example, the ring <NUM> has a height of about <NUM> inches (<NUM>), an OD of about <NUM> inches (<NUM>), an ID of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inch (<NUM>). The ring <NUM> can be fastened inside of the compaction chamber <NUM> by, for example, welding or bolting.

As shown in <FIG>, the diametric restriction elements <NUM> may be attached to and hang down from the lower surface of the ring <NUM>, the lower edges of the four struts or plates <NUM>, and around the perimeter of the plate or cap <NUM>. The diametric restriction elements <NUM> can be fabricated from individual chains, cables, or wire rope, or a lattice of vertically and horizontally connected chains, cables, or wire rope. In a specific example, the diametric restriction elements <NUM> are <NUM>-inches (<NUM>) long, half-inch (<NUM>), grade <NUM> alloy chains that are welded to the ring <NUM>, the struts or plates <NUM>, and the plate or cap <NUM>.

Referring now to <FIG>, a side view of a soil compaction apparatus <NUM> is illustrated comprising the diametric restriction elements <NUM>, according to another embodiment. <FIG> illustrate a top view and a bottom view, respectively, of the soil compaction apparatus <NUM> of <FIG>.

In this example, the soil compaction apparatus <NUM> typically comprises a drive pipe <NUM>. The bottom end of the drive pipe <NUM> may be closed using a plate or cap <NUM>, thereby rendering the drive pipe <NUM> a closed-end pipe. The top end of the drive pipe <NUM> typically has a flange <NUM> for connecting to the tip of the driving shaft <NUM>. In one example, the drive pipe <NUM> is about <NUM> inches (<NUM>) long and has an OD of about <NUM> inches (<NUM>), an ID of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inch (<NUM>). The drive pipe <NUM>, the plate or cap <NUM>, and the flange <NUM> can be fastened together by, for example, welding.

The bottom end of the closed-end drive pipe <NUM> is fitted into one end of a compaction chamber <NUM>. In one example, the compaction chamber <NUM> is a pipe that has a length L1 of about <NUM> inches (<NUM>), an OD of about <NUM> inches (<NUM>), an ID of about <NUM> inches (<NUM>), and thus a wall thickness of about <NUM> inch (<NUM>). In one example, the drive pipe <NUM> is extended into the compaction chamber <NUM> a distance of about <NUM> inches (<NUM>).

The drive pipe <NUM> may be supported within the compaction chamber <NUM> by, for example, three struts or plates <NUM> arranged radially around the drive pipe <NUM> (e.g., one at <NUM> o'clock, one at <NUM> o'clock, and one at <NUM> o'clock). In one example, the struts or plates <NUM> are about <NUM> inch (<NUM>) thick. The struts or plates <NUM> can extend into the compaction chamber <NUM> a distance d1, or for example, about <NUM> inches (<NUM>). The top end of the struts or plates <NUM> can be squared off at about the top edge of the drive pipe <NUM> as shown. The lower end of the struts or plates <NUM> can be also be squared off. The plate or cap <NUM> at the end of the drive pipe <NUM> may extend slightly below the lower end of the struts or plates <NUM>. The drive pipe <NUM>, the compaction chamber <NUM>, and the struts or plates <NUM> can be fastened together by, for example, welding.

The diametric restriction elements <NUM> are typically attached to and hang down from the lower surface of the ring <NUM>, around the perimeter of the plate or cap <NUM>, and from the bottom of the struts <NUM>. The diametric restriction elements <NUM> can be fabricated from individual chains, cables, or wire rope, or a lattice of vertically and horizontally connected chains, cables, or wire rope. In one example, there are thirty two (<NUM>), <NUM>-inch (<NUM>) long, half-inch (<NUM>), grade <NUM> alloy chains welded to the ring <NUM> and fourteen (<NUM>), <NUM>-inch (<NUM>) long, half-inch (<NUM>), grade <NUM> alloy chains welded to the plate or cap <NUM>.

Having generally described the invention, various embodiments are more specifically described by illustration in the following specific EXAMPLES, which further describe different embodiments of the soil compaction apparatus.

In one example, a method of compacting aggregate using an embodiment of the subject matter disclosed herein in a pre-drilled cavity was demonstrated in full-scale field tests. The compaction mandrel was comprised of an "I-beam" drive shaft with a <NUM>-inch (<NUM>) diameter flow-through compaction chamber at the bottom, similar to the soil compaction apparatus <NUM> shown in <FIG>, <FIG>.

Test piers with a diameter of <NUM>-inches (<NUM>) were installed to a depth of <NUM> feet (<NUM>). The piers were constructed by drilling a cylindrical cavity to the specified depth. After drilling, stone aggregate was poured into the cavity until there was an approximate <NUM>-foot thick lift of uncompacted stone at the bottom of the cavity. The mandrel was then lowered into the cavity until it reached the top of the stone. The hammer was started and the mandrel was lowered into the stone until the diametric restrictor elements on the bottom were engaged. The mandrel was then driven into the stone, both compacting the stone and driving the stone downward and laterally into the surrounding soil.

While the mandrel was in the cavity and compacting the bottom lift of stone, additional aggregate was poured into the cavity until the aggregate was approximately <NUM> feet (<NUM>) above the compaction head. The mandrel was then raised <NUM> feet (<NUM>), causing the diametric restrictor elements to unfurl and allowing the aggregate to pass through the compaction head (via the flow-through passages). The mandrel was then driven down into the aggregate <NUM> feet (<NUM>), causing the diametric restrictor elements to bind up and both compact the aggregate between the initial lift and compaction head and drive the aggregate laterally into the surrounding stone. The mandrel was then subsequently raised <NUM> feet (<NUM>) and lowered <NUM> feet (<NUM>) compacting each lift of aggregate in <NUM>-foot (<NUM>) increments, until reaching the ground surface. The level of stone was maintained above the top of the compaction head throughout construction of the pier.

Modulus tests were performed on two of the constructed piers, one for a pier constructed to a depth of <NUM> feet (<NUM>) using clean, crushed stone and one to a depth of <NUM> feet (<NUM>) with the bottom <NUM> feet (<NUM>) of compacted aggregate consisting of clean, crushed stone and the upper <NUM> feet (<NUM>) of compacted aggregate consisting of concrete sand. The results shown in plot <NUM> of <FIG> indicate that the constructed piers confirmed the design and were sufficient to support the structure.

More than <NUM>,<NUM> piers were installed at this site with the technique described above. Traditional replacement methods such as those described in <CIT> and <CIT> were not feasible at this site because the drilled cavities were unstable below a depth of <NUM> feet (<NUM>). The installation method described herein allowed for the head of stone above the compaction chamber to temporarily case the caving soils during pier construction. The advantage of being able to leave the mandrel in the cavity as aggregate was added allowed for an average installation rate of approximately <NUM> feet (<NUM>) of pier per hour, a rate estimated to be approximately <NUM> percent faster than is typically observed for traditional replacement methods. Further, the present invention was advantageous over the displacement method described in <CIT> because it allowed for higher capacities to develop in the upper cohesive soils relative to displacement methods.

In another example of an embodiment of the subject matter disclosed herein, a method of compacting aggregate in a pre-drilled cavity with a mandrel having a <NUM>-inch (<NUM>) diameter flow-through compaction chamber similar to <FIG> was demonstrated in full scale field tests. A modulus test pier was constructed to verify the performance of the construction method.

The cavity for the test pier was drilled to a depth of <NUM> feet (<NUM>). After drilling, the mandrel was lowered into the cavity until the compaction chamber reached the bottom. Clean stone aggregate was poured into the cavity until there was enough uncompacted stone to create a <NUM>-foot (<NUM>) thick compacted lift. The mandrel was raised <NUM> feet (<NUM>) and lowered <NUM> feet (<NUM>) to drive the stone into the underlying soil. The mandrel was then removed and a telltale assembly was placed into the cavity, on top of the initial compacted lift.

The mandrel was lowered back into the cavity and crushed stone aggregate was poured into the cavity until it reached the ground surface. The mandrel was raised <NUM> feet (<NUM>), allowing the aggregate to pass through the compaction head (via the flow-through passage), and then driven down into the aggregate <NUM> feet (<NUM>), causing the diametric restrictor elements to bind up and both compact the aggregate and to drive the aggregate laterally into the surrounding soil. The mandrel was then subsequently raised <NUM> feet (<NUM>) and lowered <NUM> feet (<NUM>) until reaching the ground surface. The level of stone was maintained above the compaction chamber throughout construction of the pier.

The modulus test results are shown in plot <NUM> of <FIG>. The test was conducted using a test set up and sequence used for a "quick pile load test" described in ASTM D1493. The test results show a plot of applied top of pier stress on the x-axis and top of pier deflection on the y-axis. The results indicate that the constructed piers confirmed the design and were sufficient to support the structure.

Several hundred piers were installed at this site with the technique described above to depths of up to <NUM> feet (<NUM>). The advantage of being able to leave the mandrel in the cavity as aggregate was added allowed for an installation time that is faster than is typically observed for traditional replacement methods. Further, the present invention was advantageous over the displacement method described in <CIT> because it allowed for higher capacities to develop in the upper cohesive soils relative to displacement methods.

Following long-standing patent law convention, the terms "a," "an," and "the" refer to "one or more" when used in this application, including the claims. Thus, for example, reference to "a subject" includes a plurality of subjects, unless the context clearly is to the contrary (e.g., a plurality of subjects), and so forth.

Throughout this specification and the claims, the terms "comprise," "comprises," and "comprising" are used in a non-exclusive sense, except where the context requires otherwise. Likewise, the term "include" and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

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, ± <NUM>% in some embodiments ± <NUM>%, in some embodiments ± <NUM>%, in some embodiments ± <NUM>%, in some embodiments ± <NUM>%, in some embodiments ±<NUM>%, in some embodiments ± <NUM>%, and in some embodiments ± <NUM>% from the specified amount, as such variations are appropriate to perform the disclosed methods or employ the disclosed compositions.

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 <NUM> to <NUM> includes <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, as well as fractions thereof, e.g., <NUM>, <NUM>, <NUM>, <NUM>, and the like) and any range within that range.

Claim 1:
An apparatus (<NUM>) for densifying and compacting soil and granular materials wherein the apparatus comprises:
a drive shaft (<NUM>);
a compaction chamber (<NUM>) at a lower end of the drive shaft (<NUM>); and,
one or more diametric restriction elements (<NUM>) attached to one or both of an interior or exterior of the compaction chamber (<NUM>), the diametric restriction elements (<NUM>) being fabricated from individual chains, cables, or wire rope, or a lattice of vertically and horizontally connected chains, cables, or wire rope;
wherein the compaction chamber (<NUM>) comprises a pipe, and the drive shaft (<NUM>) is fitted into one end of this pipe;
characterized in that the drive shaft (<NUM>) comprises an I-beam or H-beam configuration that provides a "flow-through" arrangement, wherein soil can flow through the drive shaft (<NUM>) and into flow-through passages (<NUM>) of the I-beam or H-beam configuration.