The motion and soil pressure of air dried sands are studied based on field observations and investigations. First

the driving and resisting forces for movement of dry sands

which is regarded as a continuous medium that can flow

are analysed thoroughly. Then the equations for velocity distribution along vertical direction of the dry sand flow and that for velocity of sand mass sliding along the subface and top surface are derived. Finally

a calculation model for the horizontal earth pressure of granular flowing class or sands on the retaining wall is derived in connection with practical retaining works

in which the dry sands are treated as a triangular body.