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Drilled Displacement Columns at Emerald Bay

Updated: Jan 22, 2023



GMU is the Geotechnical Engineer for the Emerald Bay Entrance Widening Project, located in the Laguna Beach area of Orange County. In order to widen the entrance area, a new slope must be constructed descending from the entrance road to the park area below. The park area is underlain by alluvium that was found to be soft and susceptible to seismic deformation. To reduce seismic slope safety factors and deformation to an acceptable level, ground improvement was needed for the project. Improvements in the form of installation of displacement grout columns into the soft alluvium below the toe of the planned slope was designed.




These displacement grout columns are currently being installed by D.J. Scheffler, Inc. As shown in the photo, the column is drilled with a piling drill rig that uses a displacement tool to laterally displace the soil into adjacent ground. This drilling method creates relatively low noise and minimal spoil soils.




The image above shows the displacement tool beginning a new column. The tool used for this project is 18 inches in diameter. Standard tool sizes range from 14 inches to 24 inches in diameter. The piling drill rig is equipped with electronic monitoring systems to track values including torque, depth, time duration, concrete pump pressure and pumping speed.



As the drill stem is extracted, a small door opens at the base of the displacement tool, and concrete is pumped into the column. Once the displacement column is completed, a strand of #10 rebar is installed in the center of the column using a crane to center the strand.




The finished product (above) may not look exciting, but the effect the grout column improvements have on the soil, and the planned roadway project is significant. For more information on how GMU can use solutions like displacement grout columns on various projects, check out our web page here.

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