Patent Application
20230089034
The present technology is generally related to structural piles, pile driving techniques, and more particularly to friction piles and methods of installing friction piles.
Timber piles and standard steel H-piles are well known structural load-bearing piles in the construction industry. These piles are driven into the ground by impacting their head with a falling weight or a driver. The impact vibrates the ground and, through it, the near-by structures, thus creating a potential for adverse effects and/or damage. Therefore, in a crowded metropolitan area, the impact-driven H-piles and timber piles may not be the most suitable pile of choice. Another group of piles is available in the construction industry that are drilled, rather than impact-driven, into the ground thus avoiding and/or reducing the risk of damaging near-by structures. Caisson piles, micro (or mini) piles and helical piles belong to this group of drilled piles. For caisson and micropiles, a cylindrical steel casing with drilling teeth at the tip is inserted into the ground by a rotary drilling machine and the soil inside the casing is removed either by injecting water or by air pressure. Caisson piles transfer load to bedrock by cutting a socket into it. Cement grout may fill in both the steel casing and the socket in the bedrock, and reinforcing steel rods may be inserted in the grout to make the pile stronger. Micropiles, on the other hand, transfer load to competent soil strata through which they pass. This is achieved in conventional micropiles by lifting up the steel casing gradually and filling in the void left by the casing with cement grout thus forming a bond between the grout column and the surrounding soil in the competent layers. Reinforcing steel rods may be inserted into the grout column of a micropile to make the pile stronger. In contrast to caisson piles or micropiles, helical piles use a steel pipe and one or more helical plates near the bottom. The helices facilitate screwing the pipe in the ground by a rotary drive head. The helical plates may also act as load transferring structural elements because they bear on soil. In the construction industry, caisson piles, micropiles and helical piles may be called by different names and may use installation techniques slightly different from those described above. In any event, whereas the larger-diameter steel casing of the caisson piles and micropiles provides a means for drilling and pouring a cement grout column with reinforcing steel that together carries the structural load, the steel pipe of conventional helical piles is relatively narrow and is the sole means for carrying the load down from the structure above - thus limiting the pile load transfer capacity. On the other hand, both caisson piles and conventional micropiles may require heavier machines and more extensive operations making them less economically attractive than helical piles. Accordingly, there is a need for the design of a new pile system that takes advantage of the relative ease of installation of helical piles and, at the same time, delivers the ruggedness of a grout column for effective load transfer by friction. If the body of a conventional helical pile is selected, at least one challenge would be how to fill in the hole created by the helix with grout before soil caves into it. For example, merely letting grout trickle down by gravity subjects the conventional helical pile to risk of formation of an unreliable, nonuniform grout column. What is needed is a system and a method that ensures grout column quality while maintaining low costs.
The techniques of this disclosure generally relate to a new design of the micropile and a novel method of installation.
In one aspect, the new micropile, hereinafter called friction pile system, may include a hollow column having an interior comprising a centrally disposed longitudinal axis extending in a longitudinal direction from a driving end to a closed end, the column having an outside surface, an inside surface, and a first width extending in a lateral direction perpendicular to the longitudinal direction, for example. In various embodiments, an auger portion may be disposed on the outside surface of the column and include a first helical pattern fanning out in the lateral direction. A pressed, bent steel plate mounted near the tip of the pipe column may form the second helical pattern. In various embodiments, a plurality of steel brackets and weld beads are strategically located around the second helical plate. In various embodiments, a plurality of perforations may be selectively disposed along the column and penetrating the outside surface and inside surface respectively. The perforations may be configured to provide a passageway for supplying cementitious material from the interior of the column through the outside surface as excreted cementitious material, for example. In various embodiments, the brackets and the auger portion may be configured to convey the excreted cementitious material towards the top end upon rotation of the column around the longitudinal axis.
In another aspect, the disclosure provides for a method of installing the friction pile system. The method may include screwing down the pipe assembly into the ground by using the bottom helix, for example. In various embodiments, the method may include the step of injecting cementitious material under pressure into an interior of the column through an upper end of the hollow column, for example. In various embodiments, the method may further include the step of excreting the cementitious material from the interior of the column through at least the first perforation, for example. In various embodiments, the method may include the steps of guiding the excreted cementitious material with steel brackets and conveying it upward along the auger portion from the lower elevation of the rotating pipe assembly to the upper elevation, for example.
The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.
The following discussion omits or only briefly describes certain components, features and functionality related to one type of friction piles also called micropiles and related methods of installing these friction piles, which are apparent to those of ordinary skill in the art. It is noted that various embodiments are described in detail with reference to the drawings, in which like reference numerals represent like parts and assemblies throughout the several views, where possible. Reference to various embodiments does not limit the scope of the claims appended hereto because the embodiments are examples of the inventive concepts described herein. Any example(s) set forth in this specification are intended to be non-limiting and set forth some of the many possible embodiments applicable to the appended claims. The particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations unless the context clearly indicates otherwise.
Referring generally to
The interior void space may define a centrally disposed longitudinal axis L-A extending in the longitudinal direction from a top end 101 to a bottom end 102. The top end 101 of body 10 may be configured for connecting to a rotary driver machine configured to rotate the pipe assembly 100, for example. Additionally, the top end 101 may comprise an open end, or at least a partially open end granting access to the interior void space of the body 10. A bottom-most surface of the bottom end 102 may comprise a closed end preventing access to the interior void space of the body 10 (or at least a substantially closed end). The body 10 may have a width that extends in a lateral direction (represented by X direction in the labeled coordinate system) through the body 10 and passing through the longitudinal axis L-A. The width of body 10 may be any size depending on the particular structural load bearing requirements. In various embodiments, the longitudinal direction and lateral direction may be perpendicular to one another.
The bottom end 102 may include a capping portion 16, for example. In various embodiments, the capping portion 16 comprises a steel plate having a planar outside surface that is welded to the bottom-most surface of the body 10, e.g., a continuous fillet weld, etc. that is suitable for the thickness of the steel plate and body 10. Additionally, the capping portion 16 may be flush with the outside surface of the body 10. Furthermore, the capping portion 16 may be angled with respect to the body 10 and/or longitudinal axis L-A at about 25 degrees to about 65 degrees, about 35 degrees to about 55 degrees, or in some embodiments about 45 degrees, terminating in a peak that extends from the body 10 in the direction of the longitudinal dimension. The capping portion 16 may be configured to loosen and/or scratch the ground and push debris laterally to the side while the pipe assembly 100 is being rotated. In some embodiments, (not illustrated) a boring machine may initially drive a relatively narrow pilot hole for guiding the cutting portion 16 into the ground; although, in other embodiments a pilot hole is not necessary.
In various embodiments, a helix portion 12 may be disposed adjacent the capping portion 16 proximate the bottom portion 102. The helix portion 12 may be disposed on the outside surface of the body 10 and have a geometry that is defined by a first helical pattern fanning out from the body 10 in the lateral direction. For example, the first helical pattern may spiral along the outside surface of the body 10 and have about a 4 inch to 8 inch pitch, and in some embodiments about a 6 inch pitch. In the illustrated embodiment, the helix portion 12 makes about one full revolution about the outside surface of body 10 although in other embodiments the helix portion 12 may be repeated with additional plates and/or make additional revolutions around body 10. In various embodiments, the helix portion 12 may be welded to the outside surface of body 10 by, e.g., a thick and continuous fillet weld of about ¼ an inch (quarter of an inch) to about ½ an inch (half of an inch). Additionally, and when viewed as a section cut in plan view (see
Pipe assembly 100 may further include an auger portion 14 disposed on the outside surface of the body 10 that spirals upward along the body 10 between the helix portion 12 and the top end 101. In some embodiments, the auger portion 14 may begin at an elevation that is proximate to the upper most portion of the helix portion 12, for example. In other embodiments, the auger portion 14 may begin at an elevation that is farther away from helix portion 12 and in other embodiments still auger portion 14 may terminate and/or pick up where helix portion 12 terminates. Auger portion 14 may have a geometry that is defined by a second helical pattern fanning out from the body 10 in the lateral direction. The second helical pattern may be different than the first helical pattern. For example, the auger portion 14 may spiral along the outside surface of the body 10 and have about a 8 inch to 16 inch pitch or in some embodiments about a 12 inch pitch. In at least one embodiment, the pitch of the auger portion 14 is about twice that of the helix portion 12. The auger portion 14 may spiral along the outside of the body 10 from an elevation proximate the helix portion 12 to the top end 101. The auger portion 14 may be formed by cutting from a wide steel plate, bending it according to the design criteria, and welding it the outside surface of body 10.
Auger portion 14 may further be functionally supported by a plurality of angles and/or other structural elements 18. Structural elements 18 may comprise a closed L-shaped gusset or flange or a V-shaped gusset or a flange that is disposed on the outside surface of the body 10. For example, both outside surfaces of a 90 degree L-shaped gusset may face away from body 10 and the inside surfaces that form a 90 degree bend face the outside surface of body 10. For example still, the outside notch of the L-shaped gusset may point away from body 10 as illustrated in
Pipe assembly 100 may further include at least one perforation 19. In the example embodiment, pipe assembly 100 may include a plurality of perforations 19 selectively disposed along the body 10 at discrete locations. Each perforation 19 may penetrate the outside surface and inside surface of body 10. In various embodiments, perforations 19 may take any suitable shape, e.g., a circular hole (weep hole), an oblong hole, a slit extending in the longitudinal direction, a slit extending in the lateral direction, and/or an angled slit extending in a direction that is angled with respect to the longitudinal direction. In the embodiment of
In various embodiments, perforations 19 may be configured to provide a passageway for supplying cementitious material from the interior of the body 10 through the outside surface of body 10 as excreted cementitious material. For example, cementitious material may be injected into the interior of body 10 at the top end 101 by any known means such as a swivel system. In some embodiments, cementitious material such as a flowable grout may be injected into the interior of body 10 under pressure, also referred to in the art as pressure injection grouting. The pressure applied may be in the range of 50-200 psi and substantially constant as the pipe assembly 100 is drilled further into the ground. In turn, the interior of the body 10 may become filled with cementitious material and the cementitious material may flow from the interior of the body 10 through the perforations 19 and to the outside of the body 10. The cementitious material may flow to the outside of the body 10 due to gravity forces initially and then being pressure injected.
In some embodiments, the cementitious material may be injected into the interior of the body 10 while the pipe assembly 100 is being inserted into the ground by rotation. For example, at least a portion of the rotation and insertion of the pipe assembly 100 and the pressure injection grouting may be performed simultaneously. In some embodiments, cementitious material may continue to be injected into the interior of body 10 after pipe assembly 100 has reached some or the entirety of the target depth. In other embodiments, the cementitious material may be injected in whole or in part after the pipe assembly 100 has been drilled into the ground and reached its target depth. In various embodiments, a target depth may correspond to an elevation where the depth through the competent soil layer is considered sufficient for the design pile capacity, for example. In some embodiments, the pipe assembly may reach the bedrock.
Consistent with the disclosure herein, the excreted cementitious material will surround the outside of the body 10 due to flowing through penetrations 19, for example. The cementitious material will initially flow through a perforation 19 at the lowest elevation and thereafter will flow through perforations 19 at higher elevations until the cementitious material fills the interior of body 10 and the surrounding space around the pipe assembly 100, i.e. the bore hole and void spaces in the surrounding ground. In various embodiments, perforations 19 may be disposed along the outside of body 10 at regularly spaced elevations from the closed bottom end 102 to the top end 101 or the perforations 19 may be selectively disposed along the outside of body 10 at various elevations configured to facilitate the dispersal of the cementitious material around the body 10. For example,
This arrangement is particularly advantageous because gravity fed grout may be insufficient, on its own, to force the cementitious material through perforations 19 and upwards to fill the whole cavity (bore hole) surrounding the pipe assembly 100. Notably, embodiments in accordance with the pressurization principles of this disclosure provide a plurality of selectively disposed perforations 19 that feed cementitious material to the helix portion 12 and auger portion 14 such that the helical pattern 11, including the helix portion 12 and auger portion 14, conveys the excreted cementitious material upwards and facilitates even dispersal of the cementitious material around the outside of body 10.
In this way, embodiments in accordance with the principles of this disclosure provide for a pipe assembly 100 that is configured to convey cementitious material vertically along the outside of body 10 in the longitudinal direction and force cementitious material into the available pore space in the surrounding soil or strata. The pipe assembly 100 is engineered in a way that the mechanical energy of drilling the pipe downward will be leveraged to guide and push the grout upward along the auger to fill the bore hole. For example, the rotation of pipe assembly 100 may guide and push the grout upward along the auger 14 to fill the bore hole. In addition to assisting upward movement of grout, the external pressure will push the grout laterally outward thereby penetrating soil and improving a bond between the soil and grout column. This configuration facilitates the even dispersal of the cementitious material throughout the inside of body 10 and throughout the outside of body 10. Once the pipe assembly 100 has been drilled to a sufficient depth, and the interior of the body 10 will not receive any more cementitious material, rotation of the pipe assembly 100 may be stopped and the cementitious material may be allowed to cure and/or harden. Because the cementitious material is substantially homogenously dispersed on the outside of body 10, in the interior of body 10, and is forced into the surrounding ground at pressure, the disclosed friction pile system 110 provides for a strong load bearing system in both the vertical direction and in the lateral direction in a cost effective manner.
In some embodiments, it is impractical to provide a single pipe assembly 100 of a length that can reach a target design depth. Accordingly, multiple pipe assemblies 100 that are the same as, substantially the same as, and/or similar to pipe assembly 100 may be connected together at a construction site to provide for a final friction pile system 110 having an appropriate length to reach a target design depth. For example, multiple pipe assemblies 100 may be “spliced” together.
It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. For example, features, functionality, and components from one embodiment may be combined with another embodiment and vice versa unless the context clearly indicates otherwise. Similarly, features, functionality, and components may be omitted unless the context clearly indicates otherwise. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques).
Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified, and that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.
