ALBERT

Description: Hydro-Quebec's Toulnustouc hydroelectric complex is located approximately 120 km north of Baie-Comeau on the Quebec North Shore region. The project involved the construction of a 77-m-high dam and a 45-m-high dike that allowed the expansion of an existing 235 km (super 2) reservoir by some 22 km (super 2) . When completely filled, the new part of the reservoir has a maximum depth of 75 m. Starting on 10 February 2005 and over a period of four days, the water of the original reservoir was used to start filling the new part. The water level of the entire reservoir increased by another 10 m after the spring snowmelt. The project also included a 9.8-km-long headrace tunnel constructed in Precambrian bedrock that creates a 170-m water head between the reservoir and the powerhouse. Electricity production started in May 2005. The complex is located in an area of low-level earthquake activity on the Canadian Shield. Four stations of the Canada National Seismograph Network (CNSN) located within 100 km of the reservoir provide a location threshold with a magnitude of about 1.2 (m (sub N) ). To complement the CNSN, two portable seismographs were installed near the flooded area and the headrace tunnel about one week before flooding started. Between February and mid-May 2005, a total of four triggered earthquakes were recorded by the field instruments and the CNSN stations. The first event, a magnitude 1.4 (m (sub N) ), occurred 16 days after flooding of the extension of the reservoir started. Three events were located beneath the reservoir and one was near the tunnel between the reservoir and the powerhouse where the water pressure is most intense. Numerous smaller but unlocatable events (m (sub N) 〈1.0) were detected by one of the field stations. About two years later, two events separated by one minute and recognized as multiplets occurred near the reservoir. The small stress perturbations that led to the reservoir-triggered seismicity at Toulnustouc support the hypothesis that the mid to upper crust of intraplate areas is in a state of stress close to failure.

Description: The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness resulting in substantial deformations. The intent of this paper is to compare, interpret, and summarize the large amount of field and laboratory data obtained for six sites in Western Canada as part of the CANLEX project. The sites are compared in terms of both flow-liquefaction and cyclic-softening considerations. The paper presents a number of conclusions drawn from the project as a whole, in terms of both fundamental and practical significance.Key words: sand, flow liquefaction, cyclic softening, CANLEX.

Description: The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness resulting in substantial deformations. In many areas of Canada, large structures are constructed on or comprise sandy soils, e.g., some major hydroelectricity earth dams and many tailings impoundments in the mining industry. The behaviour of loose sandy soils can be difficult to predict, but can have a significant financial impact on these types of engineering structures. Consequently, the intent of the CANLEX project was to improve the overall understanding of soil liquefaction. This paper provides an overview of the CANLEX project, outlining the project objectives, major achievements, and conclusions. Four companion papers describe different aspects of the project; thus, together, the five papers provide a summary of the CANLEX project.Key words: geotechnical, liquefaction, CANLEX, collaborative project.