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Title: Design Considerations for Raising the Hinze Dam Mass Concrete Spillway

Author(s): Scott Jones, David Hughes, and Orville R. Werner II

Publication: Symposium Paper

Volume: 325


Appears on pages(s): 4.1-4.30

Keywords: mass concrete; temperature control; cracking; mix design, construction

DOI: 10.14359/51710945

Date: 7/25/2018

As a part of the 15 m [49 ft] raise of Hinze Dam, the existing 33 m [108 ft] high mass concrete spillway structure was raised an additional 12.5 m [41 ft] by using conventional mass concrete placed on the top and downstream side of the existing spillway to form a new monolithic structure. Heat generated by the hydration of the cement and fly ash would raise the peak temperature in the body of the new concrete relative to the stable and relatively uniform temperature within the existing concrete, resulting in a potential for tensile strains to develop along the interface that are large enough to cause cracking through the body of the composite dam and potentially compromise the interface bond. Two-dimensional transient coupled thermal-structural finite element (FE) analyses were used to predict thermal deformations and stresses within the body of the spillway in the weeks and months following placement. These analyses formed part of the basis for establishing pre-cooling placement requirements for the mass concrete. The concrete mix was designed to greatly minimize the evolution of heat by using a higher than usual percentage of fly ash. Laboratory measured mechanical and thermal properties of the concrete and local boundary climatic data were input to the analyses. This paper presents the assumptions, methods, and criteria used in the finite element method (FEM) analyses; the results of the mix selection process and laboratory thermal testing program; and the results and conclusions drawn from the analyses. A discussion on the concrete mix design trials recently completed on site is also included.