Evaluation of Gravel Drains Performance in Mitigating Liquefaction Hazards

Soil liquefaction is a phenomenon resulting from reduction in soil stiffness and strength after an earthquake or other rapid loading. In loose sandy soils, compressibility tendency in grains leads to build up of excess pore water pressure and reduction of effective stress. During liquefaction the soil ability to assure the building stability is declined which causes settlement and overturning of structure. In the current study, the performance of gravel drains in mitigating liquefaction induced settlements is evaluated based on input motion level and drains arrangement. A series of shaking table 1g one dimensional model tests are carried out in Urmia University soil dynamics lab including 2 input motion levels and 3 drain arrangements. Firoozkouh No. 161 sand is used in the test and wet tamping method is utilized in model preparation. A complete set of acceleration, pore water pressure and displacement transducers are instrumented in the tests. A foundation is set at the top of liquefiable sands. The results show that the evaluation of gravel drains performance in liquefaction resistance can be determined based on the foundation settlement and effective stress values. On the other, hand it is highly dependent on the input acceleration level and drains arrangement.