Reversible Displacement Auger Tool for Pile Stability
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Solution Overview
Problem
Existing auger pressure grouting techniques face challenges when forming piles in sites with loose or low-density overburden, such as landfill sites, as the grout spreads laterally and piles tend to uproot or turn during operations, especially with lower-cost materials like corrugated metallic casings, which are not cost-effective.
Innovation Solution
An auger assembly with an elongated shaft and helical flighting, featuring an arcuate rake above the working end to compress loose overburden material during rotation, creating a self-sustaining annulus, and then engaging solid earth to form a bore, allowing for efficient delivery of grout through the hollow shaft to create cast-in-place piles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auger pressure grouting is used in loose overburden, then pile formation is attempted, but grout spreads laterally and piles uproot or turn
Solution Approach 1:
The patent applies preliminary action by compacting the loose overburden material before grout injection. The auger assembly compacts the soil in a first direction to create a dense annular region, then reverses to a second direction to form the bore. This pre-compaction prevents grout from spreading laterally during injection, solving the grout dispersion problem while maintaining pile stability.
2Reliability
If corrugated metallic casings are used to confine grout, then grout containment is improved, but cost increases and piles still uproot during operations
Solution Approach 1:
The patent applies self-service by using the auger assembly itself to create the confining structure through soil compaction, rather than requiring external casings. The auger compactsthe loose overburden to form a self-sustaining annular region that naturally contains the grout. This eliminates the need for complex corrugated metallic casings while achieving both grout containment and pile stability.
3Manufacturing precision
If auger rotates in first direction through loose overburden, then compaction occurs, but bore formation in solid earth is prevented
Solution Approach 1:
The patent applies dynamics by changing the rotation direction of the auger assembly. The auger rotates in a first direction to compact the loose overburden, then reverses to a second direction to engage and bore into the solid earth. This dynamic direction change allows the same auger assembly to perform both compaction and bore formation functions, achieving both overburden compaction and bore creation capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively compacts loose overburden, forming a stable bore that prevents grout dispersion and maintains pile integrity, enabling efficient and cost-effective pile formation even in challenging soil conditions.
Implementation Method 1
apparatus proximal to the working end and operable to compress the loose material, such apparatus comprising a rake extending outwardly toward the periphery of the flighting and positioned above the working end of the auger assembly. The rake is oriented to engage the loose material during rotation of the auger shaft in a first direction, and to compact the loose material in the region adjacent the flighting periphery.
Implementation Method 2
an elongated, flighted auger having a hollow central shaft, as well as an upper auger motor. During pile-forming operations, the auger is first shifted downwardly during rotation thereof, so as to screw the auger into the earth.
Data Source
AI summary
An auger assembly designed for creation of bores at sites where solid earth has a layer of loose overburden comprising an elongated auger shaft presenting a working end, with outwardly extending, helical fighting along at least a portion of the length of the shaft. Apparatus proximal to the working end is operable to compress the loose material as the auger assembly is rotated in a first direction, and preferably is in the form of arcuate rake structure above the working end; the auger serves to compress the loose material during rotation in the first direction until the solid earth is encountered, whereupon the auger assembly is rotated in the opposite direction to form the bore within the solid earth. The auger assembly preferably includes an upper auger section and a detachably secured lower auger bit assembly. The auger assembly is particularly useful in the formation of cast-in-place cementious piles.