Jet Grouting to Provide Scour Protection

The San Juan Creek Bridge near Antonio Parkway in Orange County, California, was slated for improvement as part of the widening of Ortega Highway (SR-74) into four lanes to relieve traffic congestion and accommodate planned growth in the region. To provide scour protection for the existing and new bridge piles, soilcrete (soil–cement) columns were constructed around the pile locations by using jet grouting, an in situ ground modification system. The Super Jet system of jet grouting was used. Headroom under the existing bridge was 10 ft. One hundred fifty-eight overlapping soilcrete columns were constructed around the planned piles. These columns were installed to the top of the San Juan Capistrano formation or to the designed scour depth. The specified minimum unconfined compressive strength (UCS) was 600 psi, and the required average strength was 750 psi. A test section was used to confirm the geometry and strength of the soilcrete columns. UCS tests were performed on wet grab samples and core samples. State-of-the-art quality control measures were implemented throughout the project. The design, construction, and quality control measures undertaken by the geotechnical contractor are discussed.