College of Construction Engineering��Jilin University��Changchun��130026��China

Experiments were conducted in large scale sand tank to simulate the two- dimensional seepage process through large sand grain in dam foundation to analyze the variations of the seepage situation�� Soil samples in different location were taken out to analyze their particles’composition after seepage failure�� Based on the parame- ters obtained from the experiments��numerical analysis is conducted to simulate the seepage field using the software of GeoStudio 2007 whose results of the spatial distribution of the seepage field agreed well with those from experi- ments��indicating the reasonable of the experimental model�� ��esults showed that seepage deformation mainly oc- curred in dam foundation where the seepage path was short while there were no clear deformation along the upstream and downstream of the dam foundation�� The seepage path changed greatly after seepage failure leading to the great increase of the volume of seepage flow��thus accelerating the damage process��