Patent Application
20200354914
The presently disclosed subject matter relates generally to concrete support columns and more particularly to a method and apparatus (e.g., driving mandrels) for forming cemented ground support columns.
Deep foundations have been used for centuries to support bridges, buildings, and other heavy structures on soft ground. Historically, deep foundations consisted of timber pilings driven into the ground using drop hammers. In more modern times, timber piles have been replaced with driven precast concrete pilings or steel pilings that offer a longer useable life and higher support capacities. Cast-in-drilled-hole concrete piers (also known as “drilled piers”, “drilled caissons,” or “drilled shafts”) have been used for over a hundred years to provide support for heavy loads with application for highway bridge supports. These piers may be constructed in dry holes or may be constructed in holes drilled below the ground water level provided that temporary stabilization measures such as casings or drilling fluids are used in construction. Cast-in-drilled hole pilings are advantageous because they have high support capacities but have the drawback that they are difficult to construct particularly when the designer wishes to have a higher-end bearing surface than afforded by the drilling tool.
Although auger belling tools, that rake outward and expand the bottom of the pier to a cross sectional area larger than the shaft of the pier, are implemented at many sites with dry soil conditions or with stiff low-permeability cohesive soils, the construction of such piers in soft ground conditions or in granular and collapsible materials is difficult and may lead to construction deficiencies. At dry soil sites or at sites with subsurface materials consisting mainly of stiff low-permeability clay soils, belling tools are used within cast-in-drilled-hole installations to expand the cross-sectional area at the bottom of the pier. In soft ground conditions or in granular soils, however, these tools can lead to ground loss and failure unless the subsurface materials are stabilized with drilling fluids that require extensive skill to employ. What is needed is a method that robustly allows for the construction of piers with differing diameters in many applicable soil conditions.
Auger-cast piles have been used in the United States since the 1950's and are installed by drilling continuous-flight augers into the ground and extracting the augers while backfilling the cavities with fluid grout. Auger cast piles may be constructed relatively quickly but have the disadvantage that the piles may have quality control issues with “necking” (reduced pile cross section) during auger extraction. Further, auger-cast pilings can be constructed with one nearly-uniform diameter only. What is needed is a method that robustly allows for the construction of cast-in-place inclusions with increased quality control relative to pier necking and the ability to create expanded diameters at selected depths.
Controlled modulus columns are a method described in U.S. Pat. No. 6,672,015, entitled “Concrete Pile Made of Such a Concrete and Method for Drilling a Hole Adapted for Receiving the Improved Concrete Pile in a Weak Ground,” and consist of inserting a reverse-rotation displacement auger into the ground, which has the advantage that it produces little cuttings, while backfilling the cavities with cementitious ground during extraction. These elements develop little cuttings at the ground surface because of the reverse auger rotation but have the same disadvantages as described above for auger-cast pilings. Like auger-cast piles, controlled modulus columns may be constructed with one uniform diameter only and with little potential for creating piers of incrementally varying diameters.
Other ground improvement methods currently exist in the field including the tamper head driven mandrel with restrictor elements (e.g., U.S. Pat. No. 7,604,437, entitled “Method and Apparatus for Creating Support Columns Using a Hollow Mandrel with Upward Flow Restrictors”) that is used primarily for the placement of aggregate in the ground for ground improvement applications. This method offers the advantage that the restrictor elements may be used to prevent upward flow of the aggregate in the mandrel, a feature that facilitates the construction of compacted bulbs of aggregate during downward driving through the placed stone. As further described in U.S. Pat. No. 9,637,882, entitled “Method and Apparatus for Making an Expanded Base Pier,” the restrictor elements may further be applied to the construction of below-grade low-slump concrete elements whereby the restrictor elements are used to create a bottom bulb. The restrictor elements used in this art is effective for preventing the upward flow of stone or low-slump concrete but is ineffective in high slump concrete or cementitious grout because more fluid infill materials easily move past the restrictor elements.
Similarly, concrete ground improvement elements may also be constructed below grade and the bottom bulb may be expanded using the system described in the '882 patent provided that the concrete infill materials contain sufficient amounts of coarse aggregate and are applied at using a sufficiently low slump to allow the restrictor elements to engage the concrete. This system cannot be effectively used, however, with fluid-like infill materials such as high-slump concrete, sand-cement grout and sand-polymer grout mixtures that are much easier to pump but do not contain sufficient coarse aggregate or a low enough slump for the restrictor elements to bind with the material. What is needed is a method that can be used to create below-grade expanded diameters within piers constructed from fluid cemented infill materials with or without strengthening fiber additives. What is further needed is a means of constructing high-capacity cast-in-situ concrete pilings with high confidence quality control and the ability of constructing piers with differing diameters at varying depths to enhance load transfer to competent soils.
The present subject matter relates to systems, apparatuses, and methods for constructing a support column. A driving mandrel has a top portion, a feed tube, and an expansion head portion that are operatively connected. The expansion head portion comprises an expansion chamber and a tubular egress port within the expansion chamber, the tubular egress port is configured to crimp or compress radially inwards to prevent backflow of infill material upward into the tubular egress port.
The top portion may have an open upper end to the feed tube or an upper end that is closed, such as by a lid, and the expansion chamber has an open lower surface. Optionally, the top portion includes an inlet injection port, a pressure gauge, and a pressure relief valve.
The expansion head portion may include an internal connection ring to which the tubular egress port is affixed such that the tubular egress port extends into the expansion chamber. The tubular egress port may be made of a material selected to be sufficiently flexible for crimping, including with limitation, concrete hose, Kevlar tubing, or aramid fiber tubing.
The invention may comprise a feed tube that is cylindrical, or that has different geometric cross-sections. The feed tube has an inside diameter and an outside diameter, and the expansion chamber has an inside diameter and an outside diameter, such that the expansion chamber inside diameter may be greater than the feed tube outside diameter.
A method for constructing a support column may comprise the steps of: providing a mandrel assembly having a feed tube operatively connected to an expansion head, wherein the expansion head comprises an expansion chamber and an egress port within the expansion chamber, the egress port being adapted for crimping; driving the mandrel assembly into a ground surface to a prescribed initial depth with respect to the ground surface level; adding infill material to the feed tube, wherein the infill material has sufficient mobility for advancing within the feed tube and through the egress port; driving the mandrel assembly further into the ground surface to a prescribed driving termination depth with respect to the ground surface level; raising the mandrel assemble above the prescribed driving termination depth; forming a space at the bottom of the mandrel assembly; allowing a first portion of the infill material to exit through the egress port by gravity into the expansion chamber and into the space; and forming a first placed infill material at the prescribed driving termination depth.
The method adding step may be done by pumping the infill material into the feed tube. The method may further comprise the step of constructing an expanded diameter of the first placed infill material. The constructing step may include the steps of: re-driving the raised mandrel assembly downwards into the first placed infill material; crimping and constricting by the egress port to prevent upward movement into the egress port by the first placed infill material; and allowing the expansion chamber to push the first placed infill material downward and outward at a prescribed expanded diameter ground depth with respect to the ground surface level.
The method may further comprise the step of raising the mandrel assembly above the expanded diameter of the first placed infill material, and allowing a second portion of the infill material to exit through the egress port by gravity into the expansion chamber. The method may further comprise the steps of constructing a shaft above the expanded diameter of the first placed infill material.
A method may comprise the steps of providing a mandrel assembly having a feed tube operatively connected to an expansion head, wherein the expansion head comprises an expansion chamber and an egress port within the expansion chamber, the egress port being adapted for crimping; driving the mandrel assembly into a ground surface to a prescribed initial depth with respect to the ground surface level; adding infill material to the feed tube, wherein the infill material has sufficient mobility for advancing within the feed tube and through the egress port; driving the mandrel assembly further into the ground surface to a prescribed driving termination depth with respect to the ground surface level; raising the mandrel assembly above the prescribed driving termination depth; forming a space at the bottom of the mandrel assembly; allowing a first portion of the infill material to exit through the egress port by gravity into the expansion chamber and into the space; forming a first placed infill material at the prescribed driving termination depth; forming a second placed infill material at a different depth than the prescribed driving termination depth; forming a second placed infill material having a different diameter than the first placed infill material and at a different depth than the prescribed driving termination depth.
The method may further comprise the step of compacting the first placed infill material to have a diameter a larger than the diameter of the expansion chamber.
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. 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.
The presently disclosed subject matter relates to the efficient construction of ground support columns used to provide support for and control settlements below building foundations, retaining walls, floor slabs, industrial facilities and the like. In some embodiments, the presently disclosed subject matter provides methods and apparatus for forming cemented ground support columns. Namely, driving mandrels are provided for the efficient construction of incrementally enlarged diameter piers. Further, construction methods are provided of using the driving mandrels for the efficient construction of incrementally enlarged diameter piers.
The presently disclosed methods and driving mandrels may be used to efficiently construct cemented piers with low and high mobility infill materials in soft ground conditions while allowing for the construction of incremental expanded diameters at selected depths. The presently disclosed methods and driving mandrels allow for the effective placement and compaction of infill materials strengthened by fibers.
The presently disclosed methods and driving mandrels provide for the efficient construction of cementitious ground reinforcement elements that may be installed with a high degree of construction confidence to provide variable diameters at various depths within the constructed elements. This method is particularly effective because it allows engineers and contractors with a means to optimize the shaft bearing capacity and the geotechnical support capacity for the same element, an advantage not shared by piers or shafts with uniform cross-sections.
The present subject matter provides an improved method and apparatus for constructing cementitious piers. In one embodiment, the driving mandrel contains a specially designed flexible tubular egress port connecting the main body (feed tube) of the driving mandrel with the mandrel bottom-expansion head. The flexible tubular egress port has the advantage that it allows for smooth flow of mobile (fluid) cementitious aggregate materials downward as the tube is filled and then as the tube is lifted upwards. The smooth flow of material is advantageous because it allows for rapid pier construction by facilitating immediate filling of the cavity made by the driving mandrel. The flexible tubular egress port is configured to be sufficiently flexible such that the tube compresses radially inwards and “crimps” as the mandrel is re-driven downwards during pier expansion operations. The crimping that is uniquely allowed by the flexible tubular egress port prevents the backflow of cementitious infill materials upward into the feed tube, thus allowing for pier diameter expansion.
In conventional methods and driving mandrels that do not include upward flow restrictors, placed cementitious materials are compressed within the compaction head. This causes the infill materials to compress and results in upward movement of the infill materials in the compaction head resulting in a decrease in the effectiveness of the expansion of the infill materials to form an expanded bottom bulb. The use of the flexible tubular egress tube of the presently disclosed driving mandrels uniquely retards and restrains upward movements of the cementitious materials because the flexible feed tube bends and crimps, thus preventing upward flow. The prevention of the upward flow of the cementitious infill material allows the expansion chamber to push the cementitious materials downward into the cavity below, thereby effectively resulting in an expanded pier diameter at any depth so selected by the constructor. The expanded pier diameter may be constructed at any elevation along the pier, allowing for the construction of larger piers in soft ground conditions and allowing for the efficient construction of bottom bases using materials with variable mobilities. The purpose of the presently disclosed methods and driving mandrels is to provide a pier construction method that allows high slump concrete and sand-cement/polymer grout mixtures to be placed and expanded below grade with a high degree of precision and confidence.
The expansion head portion 118 contains an internal connection ring 128 and the flexible tubular egress port 122 that is affixed to the internal connection ring 128. The flexible tubular egress port 122 may consist of flexible cylindrical tubular material, such as concrete hose, Kevlar tubing, aramid fiber tubing, or other flexible tubular materials. The flexible tubular egress port materials are selected to be sufficiently flexible to allow for crimping during downward driving and sufficiently durable to allow for construction on harsh subsurface environments. The flexible tubular egress port 122 is affixed at the top to the internal connection ring 128 and is configured to extend into the expansion (or compaction) chamber 120. The expansion (or compaction) chamber 120 has an inside diameter (ID) 136 and an outside diameter (OD) 138. The expansion (or compaction) chamber 120 has an open lower surface 134 for placement of cementitious material in the created cavity.
First, STEP A of
Next, STEP B of
Continuing STEP B, when the driving mandrel 100 is driven to the initial driving depth 210, infill material 230, such as high slump concrete or cementitious grout, is then pumped into the driving mandrel 100 through the optional inlet injection port 116 or through the open upper end 114. Cementitious infill materials that are placed within the feed tube 112 are designed with sufficient mobility (fluidity) so that they are easier to mix and pump and flow unimpeded downward through the feed tube 112 and through the bottom flexible tubular egress port 122. Typical cementitious infill materials designed for this purpose may include mobile (medium to high slump) concrete, sand-cement grout, or neat cement grout.
Next, STEP C of
Next, STEP D of
Next, STEP E of
Next, STEP F of
First, STEP A of
Next, STEP B of
Continuing STEP B of
Next, STEP C of
Next, STEP D of
Next, STEP E of
Next, STEP F of
It is well known by those skilled in the art that the formation of cementitious elements below grade is fraught with difficulty and that the formation of support piers with different cross-sectional dimensions is difficult at best. As shown in
The flexible tubular egress port 122 (e.g., a flexible tube or hose) should be large enough in area to provide for efficient through-flow but small enough in cross-sectional area to facilitate crimping and bending of the flexible tube during downward mandrel movements. The upper end of the flexible tubular egress port 122 is connected to the feed tube 112 using a variety of different connection details. The flexible tubular egress port 122 extends downward into the expansion (or compaction) chamber 120 to a sufficient length to allow for hose crimping and bending during downward mandrel movements. The tubular egress port materials may consist of many differing grades, strengths, and thicknesses, each containing its own advantages and disadvantages with respect to flowability, crimpability, mobility, bendability, durability, and longevity.
The flexible tubular egress port 122 can be oriented vertically at the center of the feed tube 112 or positioned at one side (i.e., offset from center) of the feed tube 112. The flexible tubular egress port 122 can be positioned vertical or horizontally. The flexible tubular egress port 122 may vary in diameter from about 1 inch (2.5 cm) up to about the inside dimension of the feed tube 112 and generally less than about 36 inches (91 cm). The required length of the flexible tubular egress port 122 as it extends into the expansion (or compaction) chamber 120 depends on the characteristics of the infill material placed, requirements for flow, the diameter of the egress port and other factors. The port length (L) to port diameter (d) ratio (L/d) generally ranges from 1 to 20 with most applications ranging between 2 and 3.
In summary,
Further,
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, 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.
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.
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.
The presently disclosed subject matter is related to and claims priority to U.S. Provisional Patent Application No. 62/568,948 entitled “Methods and Apparatus for Building Cemented Ground Support Columns” filed on Oct. 6, 2017; the entire disclosure of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2018/054384 | 10/4/2018 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62568948 | Oct 2017 | US |
