Patent Application
20200299917
The present invention is broadly concerned with improved, deformation-compliant rigid soil inclusions, and methods of fabricating such inclusion. More particularly, such inclusions have embedded perforate reinforcements along the lengths thereof, which are structurally significant and maintain the integrity of the inclusions even under seismic ground motion or other loading causing induced bending deformation. Methods of fabricating the inclusions involve driving a tubular mandrel into the soil having a flexible, tubular, perforate reinforcement applied about the exterior surface thereof, and thereafter withdrawing the mandrel while injecting flowable cementitious material into the mandrel, thereby causing the material to form a columnar body, substantially circular in cross-section, with portions of the body exuded through the perforations of the reinforcement.
Traditional cast-in-place piles used as structural supports incorporate steel reinforcing bars within poured concrete or grout structures extending from the supported structure to firm soil or rock at depth. Such piles are essentially elements of the structure extended into the ground. However, another type of support is referred to as a “rigid inclusion,” which is not an extension of the structure, but a reinforcement of the soil below the structure. Thus, in situations where the soil is soft or vulnerable, inclusions serve to transfer vertical loads through the soft soil to competent strata at depth. To this end, a plurality of relatively closely spaced rigid inclusions may be used to collectively strengthen the overall profile of the soil and transmit vertical loads.
Typically, prior art rigid inclusions are constructed by driving a tubular mandrel into the soil to a desired level followed by mandrel withdrawal and simultaneous grout injection through the bore thereof, in order to thereby fill the volume of the withdrawn mandrel.
Unfortunately, these types of inclusions are of little use in soils subject to cycles of shear and flexure due to kinematic and inertial deformation of the surrounding soil, e.g., seismic ground motion or similar vibrations. This is because the inclusions, while initially having significant compressive strength, have virtually no strength to resist shear and flexural deformation, which create tension within the element. Therefore, such prior inclusions are likely to sustain severe cracking, crushing and separation when subjected to shear and flexural deformation due to a seismic event. Thus, following such an event, the inclusions will be unable to support vertical loads, potentially leading to unacceptable settlements and the need to conduct extensive repairs. Stated otherwise, these conventional inclusions are not deformation compliant because, once fractured, the inclusions are no longer capable of operating as intended.
Prior art references include U.S. Pat. Nos. 3,270,469, 3,611,735, 3,726,950, 4,715,203, 5,213,449, and 6,672,015; US Patent Publications Nos. 2004/0016564, 2010/0277290, and 2018/0071949; and foreign references DE 102012004980A1, MX2014015383A, and WO1990015905. Related videos can be found in the You Tube videos found at https://www.youtube.com/watch?v=9R2N13ggXbg and https://www.youtube.com/watch?v=OaltjBxiQY.
There is accordingly a need in the art for improved soil inclusions which are deformation compliant, and corresponding methods of creating such inclusions.
The present invention overcomes the problems described above, and provides deformation-compliant soil inclusions, as well as methods of fabrication thereof. Such inclusions broadly comprise elongated, cast-in-place cured cementitious columnar bodies located within the soil, each having a tubular perforate structural reinforcement embedded within the body in the form of a continuous, non-orthotropic grid, with portions of the body exuded through the perforations of the structural reinforcement. Such reinforcements extend substantially the entire lengths of the bodies and are usually formed of non-metallic composite material (e.g., carbon or glass fiber infused with a synthetic resin, such as epoxy). The cementitious material provides compressive strength and stiffness, while the reinforcement provides flexural strength, shear strength and lateral confinement. These improved capabilities give the inclusions the capability of sustaining repeated cycles of kinematic and inertial deformations in the surrounding soil, while maintaining their original capacity for vertical load transfer. Accordingly, the deformation compatible inclusions provide continued foundation support following a seismic event—a capability not provided by inclusions of the prior art.
Methods of forming the inclusions hereof comprise the steps of first driving a tubular mandrel into the soil with a vibratory hammer or like device, there being a flexible, tubular, perforate reinforcement about the exterior surface of the mandrel. Once fully driven, the mandrel is withdrawn while flowable cementitious material (e.g., grout) is injected into the mandrel during its withdrawal. This causes the cementitious material to form a columnar body, with portions of the body exuded through the perforations of the reinforcement in order to embed the tubular reinforcement within the body.
A sacrificial soil-driving shoe, slightly larger than the mandrel in diameter, is attached to the end of the mandrel prior to the driving step, and the reinforcement is secured to the shoe. The reinforcement may be applied by wrapping around the exterior surface of the mandrel as it is driven, or by initially placing a pre-formed tubular reinforcement about the mandrel before driving thereof.
Typically, the inclusions of the invention have a length of from about 10-50 feet, and the embedded structural reinforcements extend substantially the full lengths of the inclusions.
Turning now to the drawings, a piling rig 20 is illustrated, which broadly includes a tracked vehicle 22, a primary support column 24, a mandrel drive unit 26, and a structural reinforcement application assembly 28. The rig 20 is designed to efficiently create a series of discrete inclusions 30 within the soil 32.
In more detail, the support column 24 is secured to vehicle 22 by means of an articulated coupler 34, allowing the rig to be moved from place to place for creation of inclusions. The support column 24 includes a stabilizing base 36 with an upstanding rigid metallic web 38. A pair of side rails 40 and 42 also form a part of the column 24. As illustrated, the coupler 34 engages the rail 40, allowing the column 24 to be bodily moved during the use of rig 20.
The mandrel drive unit 26 is designed to engage and drive a tubular mandrel 44 having an upper grout inlet 46 and a lower butt end 47 (
Next, the hammer 48 is actuated (
In this embodiment, the material 56a is provided as a flat sheet, with the edges overlapped, as illustrated in
The remaining steps of this embodiment are identical to those described previously, i.e., the material-wrapped mandrel 44 is driven into the soil via hammer 48. Once the wrapped section of the mandrel 44 is fully driven, grout 70 is then injected via inlet 46 to fill the mandrel 44, while the latter is withdrawn, thereby creating the columnar body 72 with grout exuding through the perforations of the material 56b.
The material 56a and 56b serves as a structural element within the body 72. As such, the fiber materials should have a modulus of elasticity in the range of 10,000-30,000 psi and an ultimate strain of 0.01-0.015. Furthermore, the fiber material should have a thickness of from about 0.05-0.1 inches, with perforations having size of from about 0.5-1 square inches. The fibers in the longitudinal and transverse orientations may be of differing diameters.
While the invention has been illustrated and described in typical uses and installations, the invention is not limited in these particulars. For example, while the reinforcing material has been depicted with essentially square perforations 57, these can be of any shape. Further, while the inclusions illustrated in the drawings are in an upright orientation, the inclusions may be installed in a plumb or vertical condition, or in non-vertical orientations, e.g., inclined, battered, or raked. While it is presently contemplated that the reinforcing materials would be in the form of fiber-reinforced epoxy, other types of reinforced or non-reinforced materials could be employed.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/822,221 filed Mar. 22, 2019, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62822221 | Mar 2019 | US |
