Determination of In Situ Stresses in Concrete Dams

by Merlin D. Copen, (F.ASCE), Head; Concrete Dams Section, Div. of Design, U.S. Bureau of Reclamation, Denver, CO,
George B. Wallace, (M.ASCE), Head; Struct. and Rock Mech. Sec., Div. of Res., U.S. Bureau of Reclamation, Denver, CO,

Serial Information: Journal of the Power Division, 1971, Vol. 97, Issue 2, Pg. 455-473

Document Type: Journal Paper


The in situ stresses within three concrete dams on the Salt River above Phoenix were determined by application of a three-directional borehole deformation gage. Two of the dams showed some signs of deterioration and structural cracking due to alkali aggregate reaction, thus requiring stress determinations for safety evaluation. Information on in situ stresses in the other dam was needed for design of expanded power facilities. The stress relief method, its verification tests and applications are examined. Best results for three-dimensional stress analyses are obtained if the drill holes are orthogonal, however, a technique is presented for evaluating reliability of results obtained from having various orientations. The resulting stresses from the stress relief tests are compared with those computed by the trial load method. Maximum water surface and minimum concrete temperatures were the loading criteria for both methods. The 6-in. overcores were tested in the laboratory to determine the ability of the concrete to resist the in situ stresses.

Subject Headings: Concrete dams | Field tests | Structural safety | Three-dimensional analysis | Stress analysis | Load tests | Load factors | Concrete | Phoenix | Arizona | United States

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