Centrifuge Testing of Prefabricated Vertical Drains for Liquefaction Remediation

One potential method for soil improvement against soil liquefaction is accelerated drainage through in situ vertical drains. Vertical drains are utilized to expedite the dissipation of excess pore water pressures by reducing the length of the pore water drainage path. For more than thirty years, gravel drains have been employed to ensure the excess pore water pressure ratio (rU = Δu/σ'v) remains below a prescribed maximum value. Recently, interest in the use of prefabricated vertical drains has increased because these elements can be installed with less site disruption than with other soil improvement methods. This paper presents the results from initial centrifuge experiments intended to evaluate the effectiveness of prefabricated vertical drains for liquefaction remediation. The centrifuge model includes sloping ground towards a central channel. Prefabricated vertical drains were installed in the soil upslope of one side of the central channel, while the other side was left untreated. Based on the results of the experiment, the prefabricated vertical drains were effective at draining and dissipating the excess pore water pressures, as well as significantly reducing the horizontal and vertical deformations.