Long Term Performance of Raft and Footing Foundations Above Clayey Silt

by A. O. Landva, Univ of New Brunswick, Fredericton, Canada,
A. J. Valsangkar, Univ of New Brunswick, Fredericton, Canada,
Z. Wroblewicz, Univ of New Brunswick, Fredericton, Canada,



Document Type: Proceeding Paper

Part of: Vertical and Horizontal Deformations of Foundations and Embankments

Abstract: Two multistorey buildings have recently been constructed on a 30-m thick layer of clayey silt in downtown Fredericton, New Brunswick. The Bank of Montreal building is ten storeys high with a basement and is supported on a partially compensated structural raft immediately above the clayey silt. The Carleton Place structure is an eight-storey building without basement and is supported on spread footings on a compacted sand and gravel raft and a 3 metres thick layer of loose sand above the clayey silt. The clayey silt is extremely sensitive to disturbance, and this makes undisturbed sampling impractical, if not impossible. Conventional borings are therefore of limited use for settlement predictions. The investigations of the Carleton Place foundations were supplemented with a 5 m high test fill instrumented with settlement points and piezometers. The Bank of Montreal investigations were supplemented with self-boring pressuremeter tests and flat dilatometer tests. The settlement performance of both structures has been monitored over a period of more than ten years. Both foundations have performed in a completely satisfactory manner. This paper presents settlement data for both structures over a period of 10 years.

Subject Headings: Clays | Silt | Soil settlement | Foundation settlement | Footings | Raft foundations | Compacted soils | Soil-structure interaction | Soil pressure | Soil dilatancy | North America | Canada | Montreal | Quebec | New Brunswick | Fredericton

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