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Investigations of high uplift pressures beneath a concrete dam

1993; NRC Research Press; Volume: 30; Issue: 6 Linguagem: Inglês

10.1139/t93-095

1208-6010

Alfred W. Hanna, H D Plewes, Raymond K. Wong, William C. Seyers,

Rock Mechanics and Modeling

Deficiency investigations were undertaken at Hugh Keenleyside Dam, near Castlegar, British Columbia, to identify the nature and sources of foundation defects responsible for high uplift pressures under a section of the concrete dam. Several techniques employed in the investigations proved particularly useful in delineating the defects. These were temperature surveys and chemical analysis of flows from pressure instruments and foundation drains, air-injection tests, foundation coring and installation of additional piezometers. A comprehensive program of pressure response testing of cells, piezometers, and drains was also carried out to establish the interconnections within the rock foundation. Detailed assessments of construction records to assemble relevant geological and foundation conditions, foundation excavation, preparation, and treatment aspects, and particular structural foundations were vital in discerning the cause for the high uplift pressures. Piping of a relatively thin, upstream, impervious till blanket (required for the earthfill dam) on blast-induced, highly fractured rock extending under the structure was found to be the defect responsible for reservoir leakage and high uplift pressures. Key words : uplift pressures, concrete dam, foundation drains, piezometers, uplift cells, temperature survey.