Projects : Turbine Foundation and Systems Redesign

D’Appolonia, a Dynamic Power Technologies Group company, was responsible for a geotechnical/structural evaluation of components for Unit 1 of the Decker Creek Power Station in Austin, Texas. The 750 MW power plant had experienced structural problems due to movement of expansive foundation soils. The most significant movements included: tilt of the mat foundation supporting the Turbine-Generator (T-G) pedestal of one of the plant's generating units; distortion of high-energy piping systems in the plant; cracking and offsets in the concrete spillway for the dam impounding plant cooling water; and cracking and heaving of the concrete floor for the cooling water intake canal. The intake canal also suffered from an infestation of Asian clams that caused recurring maintenance and operational problems.

During the plant’s 22-year service life, the 110-foot long by 42-foot wide turbine pedestal had tilted 6 inches due to differential movement of expansive soils supporting the pedestal foundation. To assess the magnitude of pedestal movements since plant construction, historical survey records were reviewed, and survey control and instrumentation was installed to monitor movements in the foundation soils and structure components. Survey control was provided by benchmarks outside the perimeter of the plant. The instrumentation included: standpipe and vibrating wire piezometers, an extensometer, plumb lines, and trams.

The instrumentation data indicated that future foundation movements would be small. Structural analysis of the piping systems indicated that although the piping was locally overstressed, the systems could be repaired by realigning pipes to near their original configuration and installing new hangers/supports to accommodate system movements during plant operation. Therefore, rather than massive pedestal foundation modifications, the repairs in the power plant were limited to realignment of the piping systems supplemented with long-term monitoring of structure and foundation movements.

Projects:

Studies and Development

Site-Civil Development

Structural Engineering

Mechanical Engineering

Electrical Engineering

OEM Analytical Support