Modeling Uplift and Fluid Flow in Fractures to Determine the Failure Probability of Concrete Gravity Dams

Jensen, Erik

Graduate Thesis Or Dissertation

Modeling Uplift and Fluid Flow in Fractures to Determine the Failure Probability of Concrete Gravity Dams Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/08612n87f

Abstract

The United States Army Corps of Engineers (USACE) currently operates many large concrete gravity dams that outright fail or narrowly meet design criteria. This is particularly true when elevated reservoir levels cause tensile stresses along a dam's upstream face resulting in cracks along the dam-foundation contact, within the dam or within the dam's foundation. Water pressures are then able to develop within these cracks increasing the uplift pressure on the dam potentially further destabilizing the system. Certain crack locations and orientations can also render drainage systems within the dam ineffective further increasing water pressures. To study the effects of fractures and uplift pressures on concrete gravity dams, a series of finite element models were developed to couple dam and foundation deformations to water flow through a dam, its foundation, or any fractures within the system. The finite element models were verified by providing similar factors of safety to the classical gravity dam design methods. Also, a blueprint for implementing the finite element models inside a probabilistic framework in order to determine a dam's failure probability was outlined. Ultimately, the goal of this research was to provide the USACE an arsenal of tools and analyses to study the stability of their existing concrete gravity dams, while accounting for flow through fractures or jointed rock foundations. These analyses offer engineers methods to study numerous different fracture geometries, material properties, or drain locations while accounting for water flow through the entire dam system.

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