Drill Tooth Geometry for Granular Stone Column Formation
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Solution Overview
Problem
Existing drill units for forming granular stone columns face issues with granular material moving inwardly against the flow direction, leading to reduced feed rate and quality of the column, especially in soils susceptible to liquefaction, and increased bridging risks.
Innovation Solution
A drill tooth design with specific geometric features, including planar or convex first and concave or convex second faces, and strategically angled alignment lines, is integrated into the drill unit to guide material radially outward and reduce pressure, enhancing material flow and column formation quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drill units are used without special tooth design, then the structure is simpler, but granular material moves inwardly against the flow direction reducing feed rate and column quality
Solution Approach 1:
The drill tooth is designed with non-uniform geometric properties: the first face is planar or convex while the second face is planar or concave, creating localized flow guidance zones. This local differentiation directs granular material radially outward along the first face while the second face manages material flow from the opposite direction, preventing inward movement and bridging without requiring complete structural redesign of the drill unit
Solution Approach 2:
The invention specifies precise angular parameters for the tooth geometry: the angle between the first face alignment line and second face alignment line is constrained to 0°-74°, with optimal ranges of 10°-30° for the first face and 0°-20° for the second face. These parameter optimizations control material flow dynamics, ensuring outward radial movement while maintaining manufacturable tooth geometries
2Reliability
If conventional drill units are used, then the device is simpler, but bridging occurs more frequently reducing column formation quality
Solution Approach 1:
The asymmetric tooth geometry creates localized flow control zones where the first face (planar or convex) actively guides material outward to prevent bridging, while the second face (planar or concave) manages material from the opposite direction. This local functional differentiation reliably prevents bridging occurrences without requiring complex overall drill unit redesign
Solution Approach 2:
The drill tooth geometry is designed to preemptively guide material flow in the correct outward radial direction before bridging can occur. The angled faces create flow paths that prevent material accumulation and bridging formation in advance, ensuring reliable column formation quality
3Productivity
If drill units operate in liquefiable soils without specialized teeth, then the drill design is simpler, but material feed rate reduces due to ground pressurisation
Solution Approach 1:
The tooth geometry parameters (angles between 0°-74°, with optimal ranges of 10°-30° for the first face and 0°-20° for the second face) are optimized to reduce resistance to material flow. This geometric parameter optimization counteracts the pressurisation effect in liquefiable soils, maintaining material feed rate by facilitating smoother outward radial flow
Solution Approach 2:
The specialized tooth faces create localized flow acceleration zones that overcome ground pressurisation effects. The first face (planar or convex) and second face (planar or concave) work together to maintain material flow velocity despite external soil pressure, ensuring consistent feed rate in challenging ground conditions
Data Source
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AI summary
A drill unit for forming a column in ground which includes an outer drill and a concentric inner drill, where attached to the outer drill there is at least one drill tooth which includes a first face, a second face and a base face wherein: - the first face and the second face are immediately adjacent one another and are coterminous at a first edge and a second edge; - the base face is the face closest to, or coterminous with, the first terminal end; - all faces, except the base face, are independently coterminous with the base face; and extend away from the base face in the same direction; - at least part of the at least one drill tooth extends away from the first terminal end to terminate at the second edge; - the second edge is the edge of the at least one tooth that is most longitudinally distant from the first terminal end; - the first face further includes a first alpha edge, where the first alpha edge is an edge of the first face opposite the first edge; - a line joining the first edge and the first alpha edge, where the first face and the base face are coterminous, a first face alignment line, is at an angle of ɸ to a perpendicular extending from the first outside surface; - the second face further includes a second alpha edge which is an edge of the second face opposite the first edge; and - a line joining the first edge and the second alpha edge, where the second face and the base face are coterminous, a second face alignment line, is at an angle of θ to a tangent on the first outside surface; such that, when in use forming the column, the first edge is configured to be a leading edge.