This study was designed to evaluate the ability of vertical drains to prevent liquefaction and limit associated settlement. Drain performance was investigated using full-scale tests with vertical drains in liquefiable sand using a laminar shear box with acceleration time histories applied at the base. Performance of the sand box with drains in these tests was compared with performance of the sane box without drains in previous tests. The test data was also used to create case histories which can be used for further research and calibration of computer models. Although some investigations regarding vertical drains have been performed with centrifuge tests, no full-scale drain installation had been tested previously. Two drain geometries were investigated, first with drains spaced at 4 feet and second with drains spaced at 3 feet, to determine the effect of spacing on drain effectiveness.Sand was hydraulically placed at a relative density of about 40%. Sensors to monitor pore water pressure, settlement, lateral displacement, and acceleration were placed in the laminar shear box. Three rounds of testing were performed with each drain configuration. Each round consisted of three tests, with peak sinusoidal acceleration levels of 0.05g, 0.1g, and 0.2g respectively, with 15 sinusoidal cycles in each case. A cone penetration test sounding was performed between each round as well as before and after testing to characterize the soil properties for each round.Prefabricated drains were effective at reducing excess pore pressure generation during shaking and increasing the rate of dissipation immediately following the shaking. Liquefaction induced settlement was typically reduced by about 50% relative to tests without drains. These results are in good agreement with results from previous centrifuge testing. Drains spaced closer together reduced the excess pore pressure that generated during shaking and increased the rate of pore pressure dissipation relative to tests with drains spaced further apart, but post-liquefaction settlements were similar. As the soil became denser, settlement decreased significantly, as did the time for pore pressures to dissipate.
College and Department
Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering
BYU ScholarsArchive Citation
Oakes, Caleb Robert, "Shaking Table Testing to Evaluate Effectiveness of Prefabricated Vertical Drains for Liquefaction Mitigation" (2015). Theses and Dissertations. 6152.
Caleb Oakes, Kyle Rollins, liquefaction, liquefaction mitigation, drains