Slide resistance of the artificial reef was studied according to a channel-type model, see figure1, and the
characteristics of passive earth pressure and frictional force were examined in a small tractive tunk filled with
sand and water.
The results obtained from this experiment are as follow ;
(1) Moving directional component of passive earth pressure that acts on a flat plate accepting slide resistance
obliquely is equal to passive earth pressure that acts on moving directional projective plane of the plate.
(2) Frictional angle ( δ) between artifial reef and sand, which is used to calculate the passive earth pressure
coefficient, is always negative, i. e. 'δ‹0', see equation (5), In this case, frictional angle can be
'δ= tan-1 μ', where μ is frictional coefficient between artificial reef and sand.