Instrumentation & Monitoring
Instrumentation and monitoring to measure displacement, pore water pressure, and settlement
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The Challenge
- Intentionally flooded the site to prevent damage to the structure
- Measure the floor elevation level, pore water pressure, and lateral displacement to assess for optimal performance
A hydroelectric facility valued at $450 million, generates an annual output of 379 million kWh using three 24-MW bulb-type turbine and generating units. The project construction diverted water from the Smithland Lock and Dam on the Ohio River through the new powerhouse in order to create clean, renewable energy for the region. The entire site was intentionally flooded in May 2011 in order to prevent serious damage to the structure of the cofferdam due to high river levels.
The elevation of the Ohio River near the Smithland Dam crested above the 100 Year Flood elevation, a level not reached since 1937. Fortunately, little damage was caused to either the structure or the side walls and slopes.
The Solution
Geocomp installed nine in-place inclinometer strings to measure lateral displacements within the vertical profile of the embankment surrounding the 110-ft deep excavation. Thirty-four piezometers were installed around the excavation both inside and outside the slurry wall, cofferdam, and excavation for measurement of pore water pressure to evaluate the effectiveness of the seepage cutoff wall. Thirteen iSite® data loggers, powered by seven solar panel systems, were installed for storage and transmission of instrumentation data. Robotic total stations monitored twenty-nine prisms at the top of the earth embankment surrounding the excavation to measure settlement and lateral movement.
Real-time data were collected from all instruments. Downloadable charts, tables, and reports were provided and used for performance monitoring during ongoing construction of the powerhouse to demonstrate stable slopes, effectiveness of the seepage barrier, and functioning dewatering system.
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