Filling the Void – Contractor Employs Grouting to Stop Infiltration Ahead of Relining
As a trenchless rehabilitation contractor, it’s important to have more than one technology in the toolbox. This was highlighted in 2018, when Le Groupe ADE was called in as a subcontractor to reline a portion of a 600-mm diameter armed concrete sewer pipe.
The project took place in the Bordeaux neighbourhood, in the borough of Ahuntsic-Cartierville, at the north end of Montreal. Located near the Rivière des Prairies and the Bordeaux Prison, the pipe is below the main entrance to the prison making trenchless the preferred approach. An open-cut project would greatly impact the traffic at the prison, require moving a gatehouse, a fence and closing the entrance for a few days.
The original plan called for the cured-in-place pipe (CIPP) relining of a 6-m long portion of the pipe. When the Groupe ADE team inspected the pipe prior to relining, it was noted that relining alone was not possible due to the presence of roots and heavy infiltration.
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The Groupe ADE team cleaned the pipe to remove the roots and determined that the pipe was suffering from severe infiltration. As the project was near the river, the ground was always saturated with water and stopping the infiltration was necessary before any relining could commence.
By eliminating infiltration before lining pipes, you achieve an infiltration-free environment and maximum liner performance. Groupe ADE determined that injection grouting with Avanti’s AV-100 Chemical Grout was the best solution to the problem, and the contractor worked with Specroc Technologies Inc. to source the grout.
The goal of injection grouting in municipal sewer systems is to seal leaks and stop infiltration through joints and defects in structurally sound pipes. Groundwater infiltration brings soil fines into the system which reduces the pipe’s sewerage capacity, erodes supporting soils, and creates voids outside the pipe structure. If not addressed, the collection system could become structurally incapable and what could have been a simple repair can become a costly rehabilitation project, a complete replacement.
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AV-100 Chemical Grout is specifically designed to eliminate infiltration into manholes, mainlines, manholes, laterals, lateral connections, and before/after lining by creating an effective, long-lasting water barrier on the exterior of structures or in CIPP annular space. AV-100 is an ultra-low viscosity, chemically reactive gel that travels anywhere water can travel and cures in controllable set times from seconds to several hours. Once cured, it creates an effective, long-lasting water barrier while providing superb soil stabilization.
Over the course of two days, the Groupe ADE team sealed five leaking mainline joints using remote packer equipment from Logiball Inc., filling a void of approximately 1m3 outside the pipe and eliminating the incoming infiltration.
Using their years of trenchless experience, Groupe ADE knew, had they only cleaned the roots and relined the pipe, the external void and active infiltration would still be present, leading to the eventual collapse of the road. By grouting first, Groupe ADE was able to follow with the originally planned relining. This provides the system a long-lasting solution and protection from future root intrusion.
This article was compiled by Trenchless Technology Canada Staff with information provided by Avanti International and Specroc Technologies Inc.