Horizontal Directional Drilling In Southern Ontario – A Case Study of Feasibility Through To Construction

K Refahi

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: INFRASTRUCTURE - IV Pipelines & Tunnels

ABSTRACT: diameter gas pipeline across the north boundary of the Greater Toronto Area (GTA) required crossings at numerous highways and roads, railways, and watercourses. Horizontal Directional Drilling (HDD) was used for installation at a number of these crossing locations. The geotechnical investigations for the crossings confirmed that the alignments for the HDDs would penetrate a combination of glacial tills (often containing cobbles and boulders) and shale bedrock. The geotechnical reports outlined the limitations and constraints associated with the HDD approach and assessed the feasibility of the installations. Detailed numerical studies were carried using FLAC for three crossings where it was deemed that the existing infrastructure could be adversely affected by the HDDs. The numerical studies assessed conditions for potential disturbance that could occur at various down-hole mud pressures. The results of the analysis indicated that the existing infrastructure would not be significantly impacted. The construction monitoring during the HDD installations indicated that where a sufficient mud pressure could not be provided, ground loss and sinkholes developed. Significant difficulties were also encountered due to the presence of boulders in the glacial till soil. Notwithstanding the construction difficulties encountered all the HDDs were subsequently successfully completed.

RÉSUMÉ: Grand Toronto complétée par forage directionnel horizontal (FDH) à plusieurs de ces traverses. Les études géotechniques réalisées pour ces emplacements de traverse ont présence de blocs et cailloux) et un socle rocheux de shale. Les rapports géotechniques ont dressé les limites et les contraintes associées à la méthode du FDH et évalué la faisabilité des installations proposées. Des études numériques alué les conditions de perturbations potentielles qui pourraient survenir en réponse à diverses pressions de boue de forage. Les résultats des analyses ont démontré que les infrastructures existantes ne seraient pas affectées de façon significative. Le monitorage effectué durant les des gouffres se développaient. Des difficultés importantes ont également été rencontrées en présence de blocs au sein du till glaciaire. Nonobstant des difficultés de construction rencontrées, toutes les installations de FDH furent complétées avec succès.

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