Helical Aggregate Pier Installation With In-Place Soil Compaction
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Solution Overview
Problem
Existing methods for installing aggregate piers require multiple steps and equipment changes, soil matrix removal, and cause site disturbance, making them costly and time-consuming, especially in urban areas.
Innovation Solution
A system and method using a pipe with a helix and compacting device that rotates into the soil to form aggregate piers, allowing for continuous installation without soil removal, using a torque driver to advance and withdraw the pipe, and a compacting device to densify aggregate lifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional cavity formation methods are used to install aggregate piers, then the aggregate pier can be formed, but multiple equipment changes and steps are required increasing installation time and cost
Solution Approach 1:
The patent combines multiple functions (cavity formation, aggregate delivery, and compaction) into a single integrated apparatus. The auger both forms the cavity by displacing soil and delivers aggregate through its hollow center, eliminating the need for separate drilling and filling operations. The tamper head provides compaction during the same continuous operation, merging what were previously distinct steps into one continuous process.
Solution Approach 2:
The auger serves multiple functions simultaneously: it acts as a drilling tool to form the cavity, a conveyor to deliver aggregate material, and a guide for the tamper head. This multi-functionality eliminates the need for multiple specialized equipment pieces, directly addressing the contradiction between productivity and device complexity.
2Productivity
If cavity formation by material removal is used, then the aggregate pier can be installed, but the soil matrix must be removed from the site increasing cost and time
Solution Approach 1:
Instead of removing soil to create the cavity, the patent uses the auger to displace and compact the existing soil matrix around the pier location. The soil that would have been removed as waste is now beneficially compacted to provide lateral confinement and support for the aggregate pier, converting a harmful waste removal process into a beneficial soil improvement action.
Solution Approach 2:
Rather than discarding the excavated soil, the system recovers it by compacting it in place around the aggregate pier using the tamper head. This recovered soil provides structural support and eliminates the need for disposal, directly addressing the loss of substance issue while maintaining installation efficiency.
3Strength
If impact ramming method is used to densify aggregate, then the aggregate pier can be compacted, but site disturbance and material sound nuisance occur especially in urban areas
Solution Approach 1:
The patent replaces the traditional impact-based mechanical ramming system with a rotational compaction system. The tamper head rotates and applies continuous friction-based compaction forces to the aggregate, eliminating the loud impact sounds and violent ground vibrations characteristic of traditional ramming methods while achieving equivalent or superior compaction density.
Solution Approach 2:
The compaction mechanism changes from impact loading (high force, short duration) to friction-based rotational loading (moderate force, continuous duration). This parameter change in the compaction approach significantly reduces noise and vibration while maintaining the required aggregate density for structural support.
4Productivity
If axial ramming is used to form aggregate lifts, then the aggregate pier can be constructed, but precise control of pier diameter and depth is difficult
Solution Approach 1:
The patent uses the rotational movement of the auger and tamper head to create consistent, uniform aggregate lifts with precise dimensional control. The rotation provides a natural reference for diameter control, while the controlled depth of auger penetration and tamper head travel provide precise depth control, achieving manufacturing precision that was difficult with axial ramming methods.
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
Reduces installation costs and time by eliminating the need for soil removal and multiple equipment changes, while precisely controlling pier diameter and depth, suitable for urban construction sites.
Implementation Method 1
A helix is disposed on the pipe between the second opening and the distal end. The helix extends along at least a portion of an outer surface of the pipe. The helix is configured such that when the helix is received in a soil matrix and the pipe is rotated in the first direction the helix imparts an axial force on the pipe in the direction of the distal end of the pipe thereby advancing the pipe into the soil matrix
Implementation Method 2
The helix is further configured such that when the helix is received in a soil matrix and the pipe is rotated in the second direction the helix imparts an axial force on the pipe in the direction of the proximal end of the pipe thereby withdrawing the pipe from the soil matrix
Implementation Method 3
The compacting device is configured to densify the aggregate material to form lifts
Data Source
AI summary
A system and method for installing an aggregate pier in a soil matrix includes a pipe configured to interface with a torque driver for rotating the pipe. A helix is disposed on the pipe and configured to advance/withdraw the pipe based on direction of rotation. A compacting device is disposed between the distal end of the pipe and the helix. It extends radially outward and upward. In some embodiments, the compacting device is configured as a frustum. A lift in an aggregate pier is formed by rotating the pipe in a second direction to withdraw a portion of the pipe from the soil matrix thereby creating a void; (b) filling the void with aggregate; (c) rotating the pipe in the first direction to advance the pipe. The compacting device contacts the aggregate disposed in the void and imparts an axial and radial force.