Finite element modeling of laminar shear box testing that consisted of loose sand treated with large diameter prefabricated vertical drains (PVDs), was performed. The objective of the modeling was to evaluate the reliability of the computer program FEQDrain for predicting excess pore pressure ratios (Ru) at sites treated with prefabricated drains. FEQDrain was found to be capable of successfully modeling measured excess pore pressure ratio time histories from the laminar shear box experiment, as long as an appropriate combination of €˜number of equivalent cycles<'> and €˜shaking duration<'> was chosen, and sensitive parameters were in the range of measured values. Hydraulic conductivity, soil compressibility, and cycles to liquefaction are sensitive parameters and govern the computed Ru values.Modeling shows that the loading rate in the laminar shear box (15 cycles at 2 Hz) likely induced higher Ru values than would be expected in a typical earthquake event with a longer duration. The longer duration allows the drains to dissipate pore pressures and prevent liquefaction. The number of equivalent cycles and duration of shaking combinations recommended for various moment magnitudes in the FEQDrain user manual predict lower, but similar Ru versus time curves. Thus, suggesting that PVDs would be equally effective for any size earthquake. However, drains are most effective at preventing liquefaction when earthquake ground motions are long and uniform, rather than short and intense.Results from models in this study compare favorably with those from computer modeling performed by Howell et al. (2014). The individual hydraulic conductivity and compressibility values were different they were somewhat compensating. Similar Ru values can be modeled with different combinations of these parameters.Based on computer analyses, wick drains and 2€ diameter PVDs were found to be relatively ineffective for preventing liquefaction. However, 3€ diameter PVDs are fairly effective but can be overwhelmed during intense shaking. In contrast, 4€ diameter and larger PVDs are significantly more effective.
College and Department
Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering
BYU ScholarsArchive Citation
Meservy, Travis Hatch, "Reliability of FEQDrain for Modeling Performance of Sand Treated with Large-Diameter Prefabricated Drains for Liquefaction Mitigation" (2017). Theses and Dissertations. 7234.
Travis Meservy, Kyle Rollins, FEQDrain, liquefaction, large diameter drains, earthquake drains