Annulus Drill Friction-Reducing Pile Foundation

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Solution Overview

Problem

Existing methods for reducing skin friction at the top of concrete piles near existing underground structures are complex, expensive, and unreliable, particularly when bored piles require casing and concrete penetration into force-decoupling cavities.

Innovation Solution

The method involves using an annulus drill to create a space around the pile shaft, which is then filled with a friction-reducing medium, allowing for effective reduction of skin friction without the need for expensive shut-off measures, as the concrete has hardened by the time the annulus is drilled and filled.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If steel tubes with intermediate cavity are used to replace reinforcement cage in upper area, then skin friction transmission is reduced, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improveskin friction reduction reliabilityVSAvoidpile structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pile shaft is segmented into different friction zones by creating an annular space at the upper portion. This separates the pile into a lower full-contact zone and an upper low-friction zone, allowing differential friction characteristics along the pile length without requiring complex internal structures throughout the entire pile.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A friction-reducing medium is introduced as an intermediary substance between the pile shaft and surrounding soil in the upper area. This medium mediates the interaction by providing low friction while maintaining annular space stability, replacing the need for complex steel tube structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If steel tubes are placed in upper part of pile during construction, then skin friction is reduced, but concrete penetration into cavity occurs and additional barrier techniques are required

Engineering Contradiction:

Improveforce decoupling reliabilityVSAvoidconstruction simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The annular space is created and filled with friction-reducing medium after the pile concrete has hardened. This preliminary hardening of the concrete eliminates the risk of concrete penetrating into the annular space, as the concrete structure is already solid when the friction-reducing measure is applied.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of preventing concrete penetration during pile construction by using complex barrier techniques, the approach is inverted: the friction-reducing annular space is created after the pile has been constructed and the concrete has hardened. This reverses the sequence to eliminate the penetration problem entirely.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If annulus drill is used to create space and fill with friction-reducing medium, then skin friction is reliably reduced with little technical effort, but additional drilling equipment is required

Engineering Contradiction:

Improvemodification effortVSAvoiddrilling equipment

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The annular space drill serves multiple functions: it creates the annular space, removes soil material, and provides a pathway for introducing the friction-reducing medium. This multi-functionality consolidates what would otherwise require separate operations into a single tool, reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The friction-reducing medium is introduced into the annular space using fluid pressure through hoses connected to the annular space drill. This hydraulic method efficiently fills the annular space without requiring complex mechanical filling mechanisms.

Inventive Principle:

Principle #29Pneumatics and hydraulics

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

This approach provides a reliable and cost-effective reduction in skin friction, ensuring minimal transmission of jacket friction forces, thereby reducing stress on neighboring structures without compromising the pile's structure.

Implementation Method 1

the cleared annulus is in turn filled with a friction-reducing medium, which on the one hand supports the annulus in relation to the surrounding soil material, but which on the other hand offers such little resistance to shearing that no appreciable jacket friction forces are transmitted via the annulus

Methodology Applied

Scientific EffectFriction reduction: Lubrication

Data Source

PatentEP2246482B1Method and device for producing a localised low friction foundation element

Publication Date: 2012.06.20 BAUER SPEZIALTIEFBAU GMBH

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AI summary

The method involves drilling a pile i.e. site concrete pile, in a base with an annular space drill bit (50), where inner diameter of the drill bit is large than outer diameter of the pile. An annular space, which is cleared during drilling of the pile, is filled with a friction-reducing medium such as bentonite-cement slurry, polymer suspension and/or a soft gel. A drill is inserted into the base for producing the site concrete pile, and a hollow space produced during insertion of the drill is filled with liquid concrete. An independent claim is also included for a device for producing a localized low friction foundation element.