Case Studies

WEB-BASED REAL-TIME MONITORING AT PERRIS DAM

Perris Dam is an earthen dam 125 feet high and 2.2 miles long, in Riverside County, California. Thin sandy layers in its foundation could liquefy during a large earthquake, potentially causing dam failure and flooding the residential neighborhood immediately below the dam. The remediation plan worked out by California Department of Water Resources and the Division of Safety of Dams includes a test construction phase, with excavation and dewatering at the dam toe. DWR requested rigorous monitoring of groundwater and subsurface movements to ensure public safety.

REAL-TIME MONITORING FOR HIGHWAY 12 WIDENING PROJECT

Highway 12 is currently a two-lane roadway with average daily traffic volume of about 31,000 vehicles. It winds through the steep and landslide-prone hills of the California Coast Ranges. The $139 million widening project through Jameson Canyon between Fairfield and Napa runs across a hillside that is traversed by a large water pipeline. Excavation at the bottom of the hillside could cause landslides and damage or rupture the pipeline.

UC BERKELEY SOIL-NAIL WALL MONITORING

The Stanley Biosciences and Bioengineering Facility is the largest research building on the campus of University of California Berkeley, with three basement levels and eight above-ground levels. Construction required an excavation up to 83 feet deep through clayey shale, greywacke, and a groundwater table about 10 feet below ground. The Hayward fault runs about 600 feet away. MACTEC, the geotechnical engineer, designed a soil-nail wall earth-retention system to accomplish the excavation. They needed to monitor forces in the soil nails during construction.

DYNAMIC STRUCTURAL MONITORING OF WIND TURBINE TOWERS

Geodaq teamed with Lymon C. Reese and Associates (LCRA) to monitor and evaluate the dynamic behavior of five wind turbines with an overall height of nearly 500 feet. These were among the tallest in the world at the time, with correspondingly high stresses. Turbines are in constant motion, and tower loading and vibration change with wind speed. So monitoring needs to sample every sensor frequently, while maintaining records over months or years that can be analyzed with respect to weather conditions.

KEY-BLOCK CELL EXCAVATION MONITORING AT MORMON ISLAND AUXILIARY DAM

The Mormon Island Auxiliary Dam is an earthen dam at Folsom Lake, 4,820 feet long and 110 feet high. To improve seismic safety in the dam and its foundation, the U.S Bureau of Reclamation is adding seven adjacent key-block cells to the dam. Shimmick Construction needed comprehensive, reliable real-time monitoring of forces and displacements in the walls and bracing for the 80 foot deep cell excavations.

HIGHWAY 299 REMOTE LANDSLIDE MONITORING

Highway 299 in Northern California is a heavily traveled two-lane highway that runs over an active earthflow that may slide at more than one location below the ground surface. Movement and resulting repaving is so frequent that a test bore revealed asphalt going 33 feet down. Caltrans's initial attempt to monitor earth movement by taking measurements in the field was thwarted within months because earth movements bent the inclinometer casings so much that surveys using a conventional inclinometer probe were impossible at deeper levels.