Filter tests on gravelly soil and a filter material under different stress states are conducted using a new large permeameter. The results show that: (1) In the case of confined compression

the permeability of the gravelly soil exhibits a negative exponential relationship with the increasing of compressive stress

which is consistent with a commonly used empirical relation. The critical hydraulic gradient of the gravelly soils increases nonlinearly with the increasing of compressive stress. (2) In the case of horizontal compression and free vertical deformation

the permeability of the soil sample decreases and reaches a minimum

then increases with increasing stress. The critical hydraulic gradient increases and reaches a maximum

then decreases with increasing stress. Before the peak

the critical hydraulic gradient of the soil sample with looser or finer filter increases more significantly with the increasing horizontal stress. After the peak

the critical hydraulic gradient of the soil sample with denser or finer filter decreases more quickly with the increasing horizontal stress.