The time-dependent transmissivity of joints.

Demonstrates that 2 nominally flat rock surfaces in contact subject to a cycle of applied normal stress exhibit all the properties of crack opening, closing, and hysteresis exhibited by a dilatant rock and that in this case the mechanism must be friction. It is concluded that an axial crack in dilatant rock will exhibit frictional interactions on opening or closing if the crack walls are not in perfect registration, and that there is no justification for accepting the reversible Griffith crack concept.-from STAR, 21(11) , 1983