12.07.2015 Views

Technical Manual: Conduits through Embankment Dams (FEMA 484)

Technical Manual: Conduits through Embankment Dams (FEMA 484)

Technical Manual: Conduits through Embankment Dams (FEMA 484)

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Chapter 9—Inspection and Assessment of Conduit-Related Problemsan example of a how a crack survey was used within a conduit, see theBeltzville Dam case history in appendix B.• Joint separations between conduit sections and at connections to entrance andterminal structures. In accessible conduits, joint meters have been used tomonitor the opening and closing of joints in conduits. For additional guidanceon crack and joint measuring devices, see USACE’s Instrumentation for ConcreteStructures (1987, pp. 5-1 to 5-24).• Metallic corrosion of pipe or exposed reinforcement.• Discoloration or staining of concrete surfaces.• Damaged protective coatings.• Deformation of the conduit circumference.• Chemical deterioration of concrete.• Leakage into or out of the conduit.• Misalignment of conduit sections.• Plugged drain holes.• Voids behind the concrete near any observed cracks, joint separations, ormisalignments. The ideal time to look for seepage <strong>through</strong> these areas is whenthe conduit has been recently unwatered and water may be draining into theconduit from the surrounding embankment.• Spalled concrete from compression or reinforcement corrosion.• Drummy or hollow-sounding concrete. The extent of deterioration may bedifficult to determine. Sampling (coring) and testing of the material may berequired. Samples taken from areas of deterioration are often compared withsamples taken from good quality concrete. Testing may include determiningthe strength properties and use of petrographic examination.• Erosion, abrasion, or damage in concrete downstream of gates/valves, offsets,and/or changes in slope.• Cavitation damage.• Binding of mechanical equipment.211

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