Hollow Rebar Tubes for Post-Grouting Drilled Shafts

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Solution Overview

Problem

Post-grouting of drilled shafts requires additional pipes for grout delivery, which adds expense and congestion to the steel reinforcement cage, and these pipes do not contribute structurally to the foundation, making them inefficient.

Innovation Solution

Using hollow rebar tubes with central longitudinal openings for both structural reinforcement and as access tubes for grout delivery, eliminating debonding issues with threads or ridges, and integrating them with a grout delivery mechanism like a perforated pipe or gravel basket for efficient post-grouting and ultrasonic inspection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional pipes are used for grout delivery, then post-grouting can be performed, but device complexity and congestion of steel reinforcement cage increase

Engineering Contradiction:

Improvepost-grouting capabilityVSAvoidcongestion of steel reinforcement cage

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the grout delivery function with the structural reinforcement function by using hollow rebar tubes that serve dual purposes: providing structural support and delivering grout to the shaft base. This merging eliminates the need for separate dedicated grout delivery pipes, reducing congestion in the reinforcement cage while maintaining post-grouting capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The hollow rebar tubes are designed to perform multiple functions simultaneously: they provide structural reinforcement to the drilled shaft and serve as conduits for grout delivery. This multi-functionality resolves the contradiction by eliminating the need for separate specialized components, thereby reducing device complexity while maintaining the required post-grouting function

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If additional pipes are used for grout delivery, then post-grouting can be performed, but material and labor costs increase

Engineering Contradiction:

Improvepost-grouting capabilityVSAvoidmaterial and labor costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

By merging the grout delivery function into the structural rebar itself, the patent eliminates the need for additional materials (separate pipes) and reduces labor costs associated with installing and removing dedicated grout delivery systems. The hollow rebar tubes are installed as part of the standard reinforcement process, streamlining construction

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The multi-functional hollow rebar tubes reduce overall material requirements since they replace both structural rebar and dedicated grout delivery pipes. This reduces material costs and simplifies the construction process, making post-grouting more cost-effective

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If additional pipes are used for grout delivery, then post-grouting can be performed, but structural efficiency decreases

Engineering Contradiction:

Improvepost-grouting capabilityVSAvoidstructural contribution of components

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent merges the grout delivery function with structural reinforcement by using hollow rebar tubes that provide both functions. This eliminates the need for non-structural dedicated grout pipes, ensuring that all components in the reinforcement cage contribute to the structural strength of the drilled shaft

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The hollow rebar tubes are designed to provide both structural support and grout delivery functionality. This multi-functionality resolves the contradiction by ensuring that every component serves a structural purpose while also enabling post-grouting, thereby maintaining structural efficiency

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces material and labor costs, provides structural reinforcement, and eliminates debonding, making the process more efficient and cost-effective while allowing for dual use in post-grouting and ultrasonic inspection.

Implementation Method 1

Each of the at least one pair of hollow rebar tubes may include threads or ridges that eliminate debonding of the hollow rebar tubes from concrete of the drilled shaft

Methodology Applied

Scientific EffectMechanical interlocking: Mechanical Fastener

Data Source

PatentUS10774493B2Hollow rebar for post-grouting the base of reinforced concrete drilled shafts

Publication Date: 2020.09.15 ASCHENBROICH HORST K

AI summary

Performing post-grouting of a drilled shaft includes forming the drilled shaft using a plurality of hollow rebar tubes, where each of at least one pair of hollow rebar tubes has a central longitudinal opening, coupling the at least one pair of hollow rebar tubes to a grout delivery mechanism disposed below the shaft, and providing grout to the grout delivery system through the at least one pair of hollow rebar tubes. Each of the at least one pair of hollow rebar tubes may include threads or ridges that eliminate debonding of the hollow rebar tubes from concrete of the drilled shaft. The hollow rebar tubes may be TITAN 52/26, TITAN 73/53 and/or TITAN 73/56 hollow threaded rebar. Each of the at least one pair of hollow rebar tubes may further provide structural reinforcement of the drilled shaft. The grout delivery mechanism may include a perforated pipe.