Most shallow landslides occur from the middle and upper parts of slopes, although slope stability analyses for shallow landslides show landslides occur from the lower parts of slopes. Flume experiments were carried out on the movement of collapsed mass, preparing soil mass at the upper part of the flume. The movement was different by the water content of the soil mass. The soil mass with higher water content traveled longer. The dry soil was wholly transformed and the soil containing water moved keeping original shape in some cases as shown in many actual examples of shallow landslides. In order to develop simulation method applicable to the moving and transforming process of shallow landslides, which occurred from the middle and upper parts of slopes and moved incompletely fluidized, a distinct element methodiDEMjwas applied to the movement of the soil mass aiming at moving process of keeping original shape. Combined particles were introduced when applying DEM. Pore]springs were considered in addition to rebounding]springs. This is called an extended distinct element methodiEDEMj. The method explained well the transforming process of the soil mass observed in the experiment.

Key wordsFshallow landslide, collapsed soil mass movement, fluidization, extended distinct element method (EDEM)