Corrugated Pipe Outer Layer Deformation Resistance

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Solution Overview

Problem

Corrugated pipes used for soil drainage and surface water transportation often fail due to excessive deformation or fracturing, and their non-linear exterior surface makes it difficult for backfill material to fill trench haunches properly, leading to sagging and increased deformation under load.

Innovation Solution

A corrugated pipe design featuring a smooth inner wall and a corrugated outer wall with an additional outer layer having convex and concave sections aligned with the corrugation crests, which increases the moment of inertia and stiffness while reducing deformation and promoting better backfilling by distributing loads more uniformly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If stiffer material is used to reduce deformation, then deformation resistance is improved, but fracture risk increases under stress

Engineering Contradiction:

Improvedeformation resistanceVSAvoidfracture resistance

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The pipe combines a flexible inner layer with a stiffer outer layer to create a composite structure. The inner layer maintains elasticity to prevent brittle failure, while the outer layer provides enhanced deformation resistance. This composite approach allows the pipe to achieve both flexibility and stiffness without the trade-off present in single-material designs.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The pipe structure transitions from uniform material properties to localized differentiation, with the outer layer having different stiffness characteristics than the inner layer. This allows different regions of the pipe wall to perform different functions: the inner layer handles elastic deformation while the outer layer resists bending.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If pipe walls are thickened to reduce deformation, then deformation resistance is improved, but material cost and weight increase

Engineering Contradiction:

Improvedeformation resistanceVSAvoidpipe weight

Core Design Contradiction:

Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

Instead of uniformly thickening the entire pipe wall, the invention applies a thinner outer layer with higher stiffness properties. This composite construction achieves the required moment of inertia and deformation resistance with less total material, reducing both weight and material cost while maintaining structural performance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the material parameter (stiffness) of the outer layer rather than changing the geometric parameter (thickness) of the entire wall. By selecting a material with higher modulus for the outer layer, the pipe achieves increased moment of inertia without proportionally increasing wall thickness, thereby reducing weight compared to uniform thickening.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If corrugation height to width ratio is reduced to increase deflection capability, then deformation flexibility is improved, but structural stiffness decreases

Engineering Contradiction:

Improvedeflection capabilityVSAvoidstructural stiffness

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The composite structure allows the corrugated inner layer to provide high deflection capability with its flexible material properties, while the outer layer compensates for reduced structural stiffness by providing additional bending resistance. This enables the pipe to achieve greater than 30% deflection without structural failure while maintaining adequate stiffness.

Inventive Principle:

Principle #40Composite materials

4Stability of the object's composition

If outer wall corrugation is used to increase moment of inertia, then deformation resistance is improved, but backfilling difficulty increases due to non-linear surface

Engineering Contradiction:

Improvedeformation resistanceVSAvoidbackfilling ease

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The invention differentiates the surface characteristics of different layers: the outer layer has a smoother surface optimized for backfilling, while the inner corrugated layer provides structural benefits. This localized quality assignment allows the pipe to achieve deformation resistance through the corrugated inner structure without suffering the backfilling difficulties associated with a corrugated outer surface.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7484535B2Corrugated pipe with outer layer

Publication Date: 2009.02.03 ADVANCED DRAINAGE SYSTEMS INC

AI summary

A pipe having an axially extending bore is defined by a pipe wall including a corrugated outer wall having axially adjacent annular outwardly-extending crests separated by valleys. The pipe wall also includes a non-linear outer layer having adjacent concave portions and convex portions. The concave portions are aligned with the corrugation crests of the outer wall so that the convex portion of the outer layer extends outwardly between at least two corrugation crests to provide improved resistance to deformation.