<p><p><div><h2>Project Summary/Scope:</h2>A ground improvement method combing vacuum consolidation, prefabricated wick drains, and hydraulic fill was used on the Pier 300, 42-acres located at Port of Los Angeles. The project was used to assess the technology for a future hydraulic fill site at the Port of Los Angeles.</p><p>Subsurface Conditions: The subsurface conditions of the 30-meter square site vary, consisting of intermittent layers of clayey and sandy soils. Below the test pad surface the granular layer was extended about 1.5 meters to 2.5 meters and was underlain by 4.5 to 6 meters of cohesive hydraulic fill. The groundwater table was about 3.4 meters below the test pad surface.</p><p>The wick drains, spaced 1.5 meters at-center, were inserted into the soil and terminated at 0.6 meters above the bottom sand. A 10-horsepower pump was initially selected, followed by a ½-horsepower pump to sustain the vacuum. A PVC membrane of 0.05 cm thick was used for sealing.</p><p>A trench was constructed to a depth of about 3.3 meters. The impermeable membrane was installed on the ground surface and sealed along the peripheral trenches. An embankment was constructed next to the vacuum test pad for comparison purpose. The total settlement of the ground surface was between 7.5 and 9 cm, compared to the settlement of 15 cm in the control embankment.</p><p>The project lasted less than 2 months.<br><h2>Performance Monitoring:</h2>Three pore pressure transducers and three deep settlement points were installed at the vacuum test pad for each of two instrumentation stations.</p><p>The total settlement of the ground surface was between 7.5 and 9 cm, compared to the 15 cm of settlement in the control embankment. The designed vacuum efficiency was 70%. However, the average efficiency of vacuum was 40 to 50%. Seepage and the size of the test area influenced the efficiency of vacuum consolidation.<br><h2>Project Technical Paper:<strong> </strong></h2>Jacob, A., Thevanayagam, S., and Kavazanjian, E. (1994). “Vacuum-Assisted Consolidation of a Hydraulic Landfill.” Proceedings of Settlement ’94, ASCE, June 16-18, College Station, Texas, 1249-126.<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div><div class="grayed-title"></div></p></p>