This project site is just west of the levee from the Sacramento River and north of Raley Field in West Sacramento. The site has deep alluvium soil consisting of loose silt and sand to depths of 65 feet. Because of the loose soil and high groundwater, static settlement and liquefaction related settlements posed considerable design challenges for the project. Farrell collaborated with the developer and the engineers to evaluate deep liquefaction mitigation OR a shallow structural mat supported with an improved, uniform “soil mat” solution. The improved, uniform “soil mat” solution was selected by the developer to save considerable money and time.
Farrell used Rapid Impact Compaction (RIC) on this project to improve the upper 10 to 12 feet of soil to form an improved, uniform “soil-mat” for settlement control. This improved soil-mat then supports an 18 inch thick structural mat. This RIC work provides a uniform improved soil layer above the soft and loose layers at depth to control static settlements and to provide uniform support to the 2 and 3 story apartments above. The RIC ground improvement showed increased density with post test results of the silty sand, sandy silt, and clayey silt soil to depths of 10 feet. The native soil N-values of 8 to 10 increased to N-values of 25 to 30 in the upper 10 feet as a result of the RIC compaction and ground improvement.