Trenchless Sewer Pipe Replacement Using Slurry Damping
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Solution Overview
Problem
Existing methods for removing and replacing gravity flow sewer pipes, such as pipe bursting and reaming, fail to accurately control the grade and often result in dips and sags due to lack of effective lubrication and support, limiting the size and type of pipes that can be installed and causing significant disruption.
Innovation Solution
The method involves drilling vertical sight relief holes and filling the existing pipe with a soil slurry to support and lubricate a pilot stem, allowing for precise installation of a new pipe by breaking up the old pipe with a back reaming tool, while the slurry acts as a damping agent to prevent tool movement and friction issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pipe bursting or reaming is used to replace existing sewer pipes, then the installation process is less disruptive, but the grade control is poor resulting in dips and sags
Solution Approach 1:
A slurry mixture is introduced as an intermediary medium to fill the existing pipe and provide continuous support to the pilot stem during installation. This slurry acts as a mediator that transmits support forces uniformly along the pilot stem, preventing grade deviations while enabling trenchless installation methods.
Solution Approach 2:
The method utilizes hydraulic principles by introducing a fluid slurry mixture into the existing pipe. The slurry flows and settles to provide hydrostatic support to the pilot stem, using fluid pressure and buoyancy forces to maintain proper grade control during the pipe replacement process.
2Ease of operation
If larger tools are used to reduce friction during pipe installation, then lubrication is improved, but the pipe floats out of grade causing more dips and sags
Solution Approach 1:
The slurry changes the physical parameters of the installation environment by providing both lubrication (reducing friction coefficient) and buoyant support (reducing effective weight). This dual parameter change allows smaller, more precise tools to be used while maintaining ease of installation and grade control simultaneously.
Solution Approach 2:
The slurry serves as an intermediary that provides both lubrication and support functions. Instead of relying solely on tool size for lubrication, the slurry medium delivers lubrication and grade control through its physical properties, eliminating the need for oversized tools.
3Device complexity
If the pilot stem is unsupported during installation, then the installation process is simpler, but the pilot stem experiences flopping, whipping, or jumping off the support member
Solution Approach 1:
The slurry provides self-service support to the pilot stem through buoyancy and friction forces. The pilot stem automatically receives support from the slurry medium without requiring complex external support structures, maintaining stability while keeping the installation process relatively simple.
Solution Approach 2:
The slurry creates an equipotential environment around the pilot stem by providing uniform buoyant support along its length. This equalizes the gravitational forces acting on the pilot stem, preventing unstable movements while maintaining installation simplicity.
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 enables accurate, trenchless installation of new pipes with close tolerance, reducing disruption and ensuring proper flow, allowing for larger pipe sizes and various types to be installed without reoccurring dips and sags, and is cost-effective.
Implementation Method 1
filling the existing sewer pipe with soil slurry material so as to provide a damping effect on the pilot stem
Implementation Method 2
lack of good methods of lubricating the pipe for installation
Data Source
AI summary
An improved method for replacing existing underground sewer pipe is accomplished without excavation, pipe bursting, or pipe reaming. First, vertical sight holes are drilled into the ground and through the existing pipe. Slurry material from the vertical hole drilling fills the old pipe. Then, a pilot hole is drilled in a first direction through the old pipe. Then, a reaming tool is pulled in the opposite direction so as to enlarge the pilot hole and grind out the old pipe, while simultaneously pulling the new pipe into position behind the reaming tool. The broken old pipe and slurry are vacuumed out of the vertical relief holes.