Hollow Mandrel Flow Restrictors for Aggregate Pier Compaction
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Solution Overview
Problem
Existing methods for installing aggregate piers in soft soils face challenges in preventing the upward flow of aggregate into the mandrel during compaction, which can reduce the efficiency and effectiveness of the construction process.
Innovation Solution
A mandrel equipped with flow restrictors, either mechanical or passive, that restrict the upward movement of aggregate during compaction, allowing for efficient delivery and compaction of aggregate without material being pushed up into the mandrel, using a combination of steel chains or static structures to prevent upward flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a mandrel is used to deliver and compact aggregate during pier construction, then construction efficiency is improved, but aggregate may flow upward into the mandrel during compaction reducing effectiveness
Solution Approach 1:
The mandrel is segmented into multiple sections that can be extended or collapsed independently. The flow restrictors are integrated as separate collapsible sections that can be deployed during compaction and retracted during aggregate delivery, allowing the mandrel to perform different functions in different operational phases without compromising either productivity or reliability.
Solution Approach 2:
The mandrel incorporates dynamically adjustable flow restrictors that can change their configuration based on operational needs. During compaction, the restrictors collapse to block upward aggregate flow; during aggregate delivery, they extend to allow free flow. This dynamic adaptation resolves the contradiction by making the mandrel structure responsive to real-time operational requirements.
2Loss of substance
If the mandrel allows free upward movement of aggregate during extraction, then material loss is reduced, but compaction effectiveness decreases due to upward flow into the mandrel
Solution Approach 1:
The flow restrictors are pre-positioned within the mandrel structure to automatically activate during compaction operations. Before upward aggregate flow can occur during compaction, the restrictors are in place to block it, preventing the harmful effect before it can compromise compaction density. During extraction, the restrictors are retracted to allow free movement and minimize material loss.
Solution Approach 2:
The mandrel system changes the flow parameters of aggregate by adjusting the restrictor configuration. During compaction, the restrictors reduce the effective flow area to prevent upward movement, ensuring proper densification. During extraction and filling operations, the restrictors are retracted to maximize flow area and minimize material loss, thus adapting the flow parameters to match operational requirements.
Data Source
AI summary
A system and method for installing aggregate piers is provided. A cylindrical hollow mandrel is driven to a desired depth. Aggregate is fed through the mandrel in steps. The mandrel is raised and driven to tamp the aggregate. Physical members in a tamping head of the mandrel allow aggregate to remain in a cavity formed by the mandrel, and prevent aggregate from entering the mandrel during driving.