Pipe Twisting for Buried Pipeline Extraction Under High Skin Friction
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Solution Overview
Problem
Existing methods for extracting underground utility pipelines require high forces to break the initial skin friction between the pipe and soil, often leading to tensile failure before the pipe can be effectively extracted, especially due to high shear stress induced by soil conditions.
Innovation Solution
A system and method utilizing a pipe twisting device to apply torsional force to the pipe, breaking the skin friction in a progressive and localized manner, reducing the force required to extract the pipe by deforming it circumferentially rather than axially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If axial force is applied to break skin friction between pipe and soil, then pipe extraction is achieved, but the required force magnitude exceeds pipe tensile strength causing failure
Solution Approach 1:
The patent transitions from applying axial extraction force to applying torsional moment to the pipe. By twisting the pipe in a third dimension (rotational axis perpendicular to extraction axis), the skin friction is broken through circumferential deformation rather than direct axial pulling, allowing extraction without exceeding tensile strength limits
Solution Approach 2:
The torsional extraction process breaks skin friction progressively along the pipe length rather than simultaneously across the entire embedded portion. As rotation proceeds, different segments of the pipe break free from soil friction at different positions and times, distributing the force requirement over the extraction duration
2Ease of operation
If high magnitude axial force is applied to break initial skin friction, then pipe can be extracted, but pipe experiences tensile failure
Solution Approach 1:
The method applies torsional moment around the pipe's longitudinal axis rather than axial force along the extraction direction. This dimensional change in force application allows breaking soil adhesion through rotational deformation, maintaining pipe integrity while achieving extraction
Solution Approach 2:
The patent changes the type of mechanical parameter applied to the pipe from axial tensile force to torsional moment. This parameter transformation enables skin friction breaking through a different mechanical mechanism that does not directly stress the pipe's tensile strength
3Productivity
If axial pulling is used to break skin friction along entire pipe length, then extraction is achieved, but significant force magnitude is required simultaneously
Solution Approach 1:
The torsional extraction method breaks skin friction segmentally along the pipe length embedded in soil. As the pipe rotates, different longitudinal segments break free from soil friction at different times rather than simultaneously, reducing the peak force magnitude required compared to axial pulling
Solution Approach 2:
The extraction process uses periodic torsional oscillation or continuous rotation to progressively break skin friction along the pipe length. This time-dependent periodic action allows the system to overcome frictional resistance in stages rather than requiring all friction bonds to break simultaneously
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 allows for the extraction of underground pipes using significantly lower forces, reducing the risk of tensile failure and making the process more feasible by breaking skin friction progressively along the pipe length, with minimal torque required to twist and dislodge the pipe from the soil.
Implementation Method 1
a pipe twisting device supported at the first end of the product pipeline and configured to apply a torsional force to the product pipeline such that at least a portion of the product pipeline is torsionally deformed
Implementation Method 2
The ability of an apparatus to pull an existing pipe section out of the ground is limited by the pipe's tensile yield strength and the friction between the pipe section and the surrounding soil
Data Source
AI summary
A system for breaking the skin friction between an underground pipe section and the surrounding soil. The system uses a pipe twisting device attached to one end of the pipe section. The pipe twisting device applies a torsional force to the pipe section so as to torsionally deform the pipe section. Such deformation breaks the skin friction between the pipe section and the surrounding soil. After the skin friction is broken along the entire length of the pipe section, an apparatus configured to apply an axial force to the pipe section pulls the pipe section out of the soil.