This paper describes the design and construction of an excavation made for a new subway station in Toronto. Overburden soils at the station site consist of nearly normally consolidated silty clay, glacial till, and dense sand. A wing of a college building that abuts the excavation edge is supported by shallow spread footings. Design assessments predicted that porewater pressure losses in the clay soils, both through the excavation wall and through the underlying fissured till, could result in damaging building settlement. The design assessments included empirical and numerical modelling of various shoring systems. Underpinning of the structure was judged to be too costly and disruptive to the tenants compared to other means of protection. As a result of the design-stage work, the retaining system type, a minimum wall stiffness, and a porewater pressure replenishment system were made part of the minimum contract requirements. A detailed monitoring program was undertaken on behalf of the transit authority; it included multiple piezometer arrays, inclinometers, and measurements of both ground and building settlement. Construction data are presented in relation to the design predictions and the system performance is discussed in this paper.
Shoring for Leslie Station: design assessment and construction performance
1999
14 Seiten, 5 Quellen
Conference paper
English
SAE Technical Papers | 2012