Prestressed Diaphragm Wall Cable Anchoring

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Solution Overview

Problem

Diaphragm walls are prone to cracking under tensile forces, which can lead to structural deformation and integrity issues, especially when the underlying ground conditions are not favorable, and increasing the structure's dimensions to enhance resistance is resource-intensive and space-consuming.

Innovation Solution

A method for producing a prestressed diaphragm wall by excavating a profile in the ground, placing an anchoring tube, pouring concrete outside it, and tensioning a cable anchored within the tube to compress the concrete, thereby reducing the likelihood of cracking and enhancing structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the dimensions of the diaphragm wall are increased to enhance resistance to cracking, then the structural strength is improved, but the resources and space necessary for its realization increase

Engineering Contradiction:
Improveresistance to crackingVSAvoidresources
Core Design Contradiction:
StrengthVSQuantity of substance

Solution Approach 1:

The invention changes the stress state parameter of the concrete from unstressed to prestressed by introducing tensioned cables. This parameter change allows the concrete to resist tensile forces without increasing its dimensions, thereby improving cracking resistance while maintaining resource efficiency.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The prestressing cables are tensioned before the concrete is fully subjected to service loads. This preliminary application of compressive stress counteracts the tensile stresses that will occur during service, preventing cracking before it occurs and eliminating the need for larger dimensions.

Inventive Principle:
Principle #10Preliminary action

2Strength

If the dimensions of the diaphragm wall are increased to enhance resistance to cracking, then the structural strength is improved, but the space necessary for its realization increases

Engineering Contradiction:
Improveresistance to crackingVSAvoidspace
Core Design Contradiction:
StrengthVSLength of stationary object

Solution Approach 1:

By changing the stress state parameter through prestressing, the concrete gains tensile resistance without requiring increased dimensions. The prestress parameter transforms the concrete's mechanical behavior, allowing it to withstand tensile loads within the same spatial footprint.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If prestressing cables are anchored directly in the concrete panel, then the nature of the underlying ground has no influence on the implementation of the prestressing, but the anchoring process becomes more complex

Engineering Contradiction:
Improveindependence from ground conditionsVSAvoidanchoring process
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Anchoring tubes are installed in the excavation before concreting takes place. This preliminary placement ensures that the tubes will be embedded in the concrete panel, providing reliable anchor points for the prestressing cables regardless of the underlying ground conditions. The ground conditions become irrelevant to the prestressing implementation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The anchoring tubes serve as intermediaries between the prestressing cables and the concrete panel. These tubes are embedded in the concrete and provide a controlled interface for cable anchoring, isolating the prestressing system from the variability of ground conditions and simplifying the overall anchoring process.

Inventive Principle:
Principle #24Intermediary (Mediator)

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 prestressing method significantly reduces deformations and maintains the integrity of adjoining structures by distributing compressive forces effectively, regardless of the ground conditions, and allows for targeted prestressing of the structure's sides subjected to tensile stresses.

Implementation Method 1

after fixing, traction is exerted on the cable so as to put the cable under tension, and the cable is locked under tension with respect to the panel of concrete. When the cable is tensioned and then locked in this position, generally after the concrete has hardened, the concrete located between the lower portion of the cable and the upper face of the wall is compressed.

Methodology Applied
Scientific EffectPrestressing: Compression

Data Source

PatentEP2964837B1Method of making a diaphragm wall in a soil and wall produced by this method
Publication Date: 2018.04.04 SOLETANCHE FREYSSINET SAS
  • EP2964837B1 patent drawingFigure 1
  • EP2964837B1 patent drawingFigure 2~3
  • EP2964837B1 patent drawingFigure 4

AI summary

The invention relates to a prestressed diaphragm wall in the ground (10) including a concrete panel (52), at least one anchor tube open at its upper end (38) and closed at its lower end (36) and, embedded at least partially in the concrete panel, at least one cable (60) extending inside the anchor tube (30), a lower portion of the cable (60) being fixed to said tube (30), and a cable anchoring system (90), configured to hold the cable in tension (60) and secure its upper portion (68) to the upper portion of the concrete panel (52). It also relates to a method for making a prestressed diaphragm wall.