Expanded Base Pier Construction Using Tamper Head Compaction
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Solution Overview
Problem
Existing methods for constructing support columns in areas with weak soils often rely on deep foundations or aggregate columns, which may not efficiently transfer loads to underlying strong soils, especially when stability and load distribution are critical.
Innovation Solution
A mandrel system with a tamper head and feed tube is used to form an expanded base pier by driving the mandrel into the ground, compacting aggregate or concrete, and introducing cementitious materials to create a stiff and strong base that can efficiently transfer loads to underlying strong soils, utilizing a valve mechanism and flow restrictors to manage material flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If deep foundations (driven piles or drilled concrete columns) are used to transfer loads through soft soils, then load transfer capability is improved, but construction complexity and cost increase
Solution Approach 1:
The patent changes the physical parameters of the foundation by creating an expanded base at the bottom of the borehole through controlled concrete placement and vibration. This expands the bearing area from the original drill hole diameter to a larger expanded base diameter, improving load transfer capability while using a simpler construction process compared to traditional deep foundations
Solution Approach 2:
The invention adds a dimensional aspect by creating an expanded base that extends laterally beyond the drill hole boundaries. This three-dimensional expansion of the foundation base increases the contact area with competent soil strata, enhancing load transfer without requiring deeper or more complex foundation elements
2Stability of the object's composition
If aggregate columns are used to reinforce soft soil layers, then settlement is minimized, but load transfer efficiency to underlying strong soils is reduced
Solution Approach 1:
The patent applies preliminary compaction to the soil at the bottom of the borehole before placing the expanded base concrete. This pre-compaction stabilizes the soil foundation, preventing future settlement, while the subsequent expanded base provides efficient load transfer to the stabilized soil layer
3Ease of manufacture
If a simple drill and fill method is used for pier construction, then construction ease is improved, but pier strength and stability are reduced
Solution Approach 1:
The construction method employs periodic vibration during concrete placement to densely pack the concrete and eliminate voids. This rhythmic vibration action ensures the concrete achieves maximum density and strength while maintaining the simplicity of the drill-and-fill construction approach
Solution Approach 2:
The patent uses mechanical vibration applied to the concrete during placement to increase particle density and eliminate air voids. This vibration process significantly enhances the strength and stability of the pier while requiring only simple construction equipment and procedures
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 system effectively forms a strong expanded base pier that significantly improves load transfer capabilities, demonstrating a 2.5 to 3-fold improvement in load carrying capacity compared to traditional aggregate columns and a 1.4 to 1.5-fold improvement compared to grouted piers, as shown in load tests.
Implementation Method 1
compact the aggregate or concrete, and introducing cementitious materials to create a stiff and strong base
Implementation Method 2
an air pressure source is connected to the feed tube for evacuating concrete from the feed tube through air pressure supplied thereto
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5E
AI summary
A system for constructing a support column includes a mandrel with an upper portion and a tamper head. A feed tube extends through the mandrel for feeding flowable material to the head. The tamper head includes a lower enlarged chamber with a reducing surface at an upper portion for compacting material and restricting upward flow of aggregate. The tamper head is of a size providing an enclosed region for allowing cementitious materials to be placed therein. The system allows a support column including a cementitious inclusion on top of an expanded base to be built.