Testing, analysis and performance of new and existing buried pipes installed using conventional and trenchless technologies

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The installation, repair and replacement of buried sewer, water and energy pipes involves huge expenditures. For example, the 2012 Canadian Infrastructure Report card states "the replacement cost for the wastewater infrastructure in “fair” to “very poor” condition is $39 billion". Sinkholes from leaking sewers and water pipes endanger traffic and infrastructure at the ground surface. Risks from lifeline failures include loss of water or flooding from damaged water mains, and the costs resulting from explosions or environmental contamination from leaking oil and gas pipelines can be very substantial (>$700M was spent on cleanup after the Enbridge pipeline rupture in Michigan in 2010). The two dimensional strength limits of new buried pipes under overburden pressures have been studied extensively by the applicant and others. However, rigid sewer pipe stability at the end of service life is controlled by fracture of the pipe structure, likely caused by erosion of the soil beside the pipe through leaking joints, and guidance is needed if these erosion voids require repair before the sewer is rehabilitated with a liner, and how to do so. Information is also needed on the impact of corrosion of steel in reinforced concrete sewers. Furthermore, the loading that results from nonuniform ground movements along continuous and jointed pipelines can induce failure, and trenchless methods of pipe replacement or installation now used widely in congested urban areas can damage adjacent pipe infrastructure. This Discovery Grant will support a program of research investigating the factors controlling ‘how much pipe and/or soil deterioration is too much deterioration?’, the changes to soil-pipe interaction that occur with that deterioration, both before and after repair of the soil or pipe, the impact of differential ground movements on water, oil and gas transmission pipelines, and pipeline damage issues associated with trenchless construction. The goal is to develop new and extend existing guidance for design and construction of new or replacement pipes, the assessment of deteriorated pipes, and their repair. 1. A seminal investigation into soil voids due to erosion into leaking sewers will be the first to measure void impacts on pipe strength and the influence of the void once filled with grout or polymer foam. Test data on void geometry and pipe response will support computer modeling of soil voids before and after pipe repair using liners. Soil voids likely produce the most catastrophic municipal pipe failures (sinkholes under pavements or other structures place the public and other infrastructure at risk). Also, the long term failure of clay and concrete sewers likely results from such erosion through joints, and confirmation of these processes will strengthen efforts to develop pipes with improved longevity. 2. Pressure pipe response in moving ground will be examined using buried pipe tests and analyses. Pipeline bending and failure will be examined where pipes pass across unstable slopes or earthquake faults, or where deformations are induced by trenchless construction methods such as static pipe bursting and directional drilling. The new testing, analysis and design procedures can improve both pipeline safety and economy. Thirteen graduate student projects in the two theme areas are being proposed over the 5 years of DG funding. Four MASc and nine PhD students will work on projects obtaining seminal test results, developing new methods of computer analysis, producing new or improved procedures for pipe and culvert installation, assessment, and design, and acquiring specialised expertise in geotechnical and/or structural engineering, and leading-edge analysis, testing and design capabilities of great value to industry.