The Port of Los Angeles sought a field test of vacuum-assisted preconsolidation of hydraulic fill to assess the feasibility of this technology as an alternative or supplement to conventional surcharge techniques for ground improvement of future hydraulic fill sites at the Port.
Geosyntec's Scope of Services
As part of the Pier 30 42-acre site ground modification project, Geosyntec, in association with personnel from the Port of Los Angeles and the Polyethnic University (Brooklyn), performed the field test. The test section was approximately 160 ft. x 160 ft. and consisted of prefabricated wick drains capped with a geomembrane, a slotted pipe collector system embedded in a sand blanket beneath the geomembrane, and a vacuum pump. Instrumentation for the test included high air-entrainment piezometers to measure negative pore pressures, monitoring of the ground surface settlement, and multi-point borehole extensometers for deep settlement measurements.
The Geosyntec team completed the test and collected their findings; the results showed that a vacuum equivalent to about 3 meter of surcharge fill was obtained at the test site. This measurement equates to a vacuum efficiency of approximately 50 percent. Geosyntec analyzed the test results and concluded that performing the test under full-scale prototype conditions with a more effective membrane seal would achieve higher efficiency and greater equivalent surcharge heights.
The test program's results demonstrated that vacuum consolidation is an economically viable alternative/supplement to mechanical surcharge.