Challenges with tunnelling in saturated cohesionless soils

Laifa Cao, Scott Peaker

In the proceedings of: GeoEdmonton 2018: 71st Canadian Geotechnical Conference; 13th joint with IAH-CNC

Session: Tunnelling in Urban Environments

ABSTRACT: This paper presents two case studies involving tunnelling in saturated cohesionless soils in the Greater Toronto Area. The first case discusses the installation of the 3.2 m diameter Langstaff Road trunk sewer using an earth pressure balance tunnel boring machine (EPB TBM). While tunnelling in saturated sand to silt, a significant amount of soil and water entered into the tunnel through the tailbrush seals between the tunnel segments and the tail can of the TBM. The TBM was flooded and had to be abandoned. The second case study examines the installation of a 1.5 m diameter feedermain in saturated sandy silt to gravel and sand crossing the Credit River by means of pipe ramming. During piping ramming, erosion of the leading edge soil plug in the pipe occurred, causing inundation of the launching shaft. The possible reasons for soil loss for the two cases are investigated and recommendations for tunnelling within saturated cohesionless soils are provided.

RÉSUMÉ: Toronto. Le pression équilibre tunnelier (EPB TBM). Alors que les tunnels en saturé sable, de limon, une quantité importante de sol et ns le tunnel à travers les joints de tailbrush entre les segments de tunnel et de la queue peut du conduite de diamètre de 1,5 m en limon saturé à gravier et le sable traversant la rivière Credit par tuyau de refoulement. et des recommandations pour le creusement de tunnels dans les sols pulvérulents saturés sont fournies.

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