Masoud Oulapour - Assistant Professor, Faculty of Civil Engineering, Shahid Chamran University of Ahvaz
Hossein Mohmedi kartalaei - M.Sc. student of geotechnics, Shahid Chamran University of Ahvaz

During earthquakes the ground excitations may cause a loss of stability of the soil resulting in excessive settlements of structures, landslides, etc. The process leading to the loss of strength is called soil liquefaction. This phenomenon has been observed in most the of large earthquakes such as the 1964 earthquake of Niiggata Japan, the Alaska earthquake of 1964 and the San Fernando earthquake of 1971. This paper deals with numerical modelling of the behaviour of soils Saturated under liquefaction. The main objectives are to study the effect of liquefaction Changes to Depth Using Finite Element Method under earthquake excitation. This simulation is based on the using a two-surface constitutive model developed by Poorooshasb and Pietruszczak (1985).Based on the results of this simulation, it is concluded that the effect of the reduction of effective stress and consequently liquefaction with the depth as well as the time of earthquakes is different, and the major drop in effective stress occurs at Near the Earth s surface.

liquefaction, numerical modeling, Finite Element, two-surface model