Relaxation of shear stress along rock discontinuity

Although several fundamental aspects of rock discontinuities have been resolved and widely accepted, most of them are based on either geologically-oriented research or mechanically-oriented research without paying proper attention to the time-dependent behaviour. These researches up to date are insufficient to describe the rheological properties of rock discontinuities. This paper presents some results from an ongoing experimental research aiming at a fundamental rheological or time-dependent behaviour of rock discontinuities. In order to investigate rheological aspect in the shear behaviour of rock discontinuities, relaxation tests in a direct shear testing machine were carried out on artificial rock discontinuity. It was found that shear behaviour of rock discontinuity is a kind of time-dependent behaviour and similar to the time-dependent behaviour of rock in uniaxial compression.