Stone Column Drill Differential Rotation Bridging
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Solution Overview
Problem
Existing drill technologies for forming in-ground granular stone columns face issues such as bridging of aggregate materials, difficulty in compaction, and potential sticking during extraction, leading to increased time and potential damage to equipment.
Innovation Solution
A granular stone column drill design featuring a first drill with a second drill co-axially positioned, a displacement device with a guide channel following a sinusoidal wave-like path, and a gearbox with an epicyclic gear set, which minimizes bridging and facilitates efficient compaction and extraction by allowing differential motion between the drills.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the auger is driven in the opposite direction to the hollow tube to minimise bridging, then the drill can be more easily extracted from the ground, but the sun gear needs to be properly aligned and engaged with the planetary gears before the granular column can be formed, which can be time consuming and may damage or break the teeth or gears if misaligned
Solution Approach 1:
The system performs its own alignment and engagement automatically during operation. The sun gear is initially disengaged during insertion, then automatically engages with the planetary gears when the drills reach the target depth and the direction reversal is initiated, eliminating the need for manual alignment operations
Solution Approach 2:
The sun gear is pre-configured in a disengaged position before drilling begins, allowing the drills to be inserted without engagement. The engagement action is prepared in advance but executed automatically at the appropriate moment, separating the insertion phase from the formation phase
2Manufacturing precision
If the feed rate of aggregate, rpm of the drills and extraction rate are varied to compact the aggregate, then compaction can be improved, but it can be difficult to achieve the required compaction and mechanical vibration of the completed stone column is needed as an additional step
Solution Approach 1:
The compaction function is merged with the drilling and extraction operations. The differential rotation of the two drills creates a compaction action during the formation process itself, combining compaction with column formation in a single integrated operation rather than requiring separate compaction steps
3Reliability
If manual clearing of bridging is performed to overcome the bridging problem, then the flow of aggregate into the stone column can be maintained, but this can be time consuming and can affect the quality of the granular stone column formed
Solution Approach 1:
Instead of rotating both drills in the same direction, the system inverts the approach by rotating the drills in opposite directions. The second drill rotates counter-clockwise while the first drill rotates clockwise, creating a shearing action that prevents aggregate bridging and maintains continuous flow without manual intervention
Data Source
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AI summary
A granular stone column drill which includes a first drill, a second drill and a displacement device, where - the first drill includes a tube within which the second drill at least partially, co- axially, lies; - the second drill includes a drill flight and first terminal end; - the displacement device includes a displacement unit and at least one guidance means; - the displacement unit includes a guide channel and an exposed wall such that the guide channel extends into the exposed wall; - the exposed wall lies approximately parallel to a centreline of the second drill; and - the at least one guidance means are located within the guide channel; such that the guide channel is a continuous circumferential channel that follows a wave like path, and either the at least one guidance means or the displacement unit is releasably or permanently attached to the second drill.