A 2-Dimentional Approach for Numerical Modeling of Seismic Gravel Drains in Liquefiable Grounds

Liquefaction of water saturated granular soils is one of the major risks thai affect the safety and earthquake pcrfonnancc of infraSlmC\urc such as bridges, dams, ports, and lifelines in various parts of Ihe world. The seismically-induced ground deformations arc often Ihe main concern when liquCr:1cl ion occurs in significant zones of an earth Sinlcturc or soil foundat ion. Recent studies ineluding field data, centrifuge model testing and numerical investigations suggest that one of the promising measures 10 alleviate large earthqu.ake-induced deformat ions and ground failures is by installing stone columns and/or gravel drains. Design of such treatment scheme needs to account for a number of facto rs involved in a project through a parametric study. Such analysis should be carried out by using numerical model ing in a cost and time-effective nL1nner. To do that, commonly a twodimensional (2-D) numerical approice; however the materials properties (i.e. mech,Ulical ,Uld hydmulic properties) should be modified to reflect the three-dimensional (3-D) conditions. The equivalent 2-D analyses should provide compamblc results especially in tenns of displacements which COll\rolthe design. This paper describes the results of a coupled mechanical-hydraulic dynamic analysis carried out for a port stmcture founded on liquefiable ground treated with stone colunms. An effective stress-based procedure was employed to analyze the excess pore water pressure generation, dissipation, and redistribution in the soil layers. Two sets of2-D analyses using two approaches for equivalent soils parameters were carried out and the results are presented and compared