It is generally considered recently that the mechanical model which describes the rheological behaviour of matter consists of three elements, i.e. spring, dash-pot and slider combined. But there are some complex mechanical behaviours of rocks that the combination of these three elements can not account for such as a cresent shaped hysteresis loop, a stress-strain diagram which opens upwards, the difference between Young's moduli for tensile and compressive stress, etc.
In order to account for these characteristics of the mechanical behaviour of rocks, the author presents a concept of new element of the mechanical model which is named as the “stopper”. This new element behaves as a rigid body over or under the designated stress level. Some effects of the properties of this new element are discussed in the present paper, and it is revealed that
(1) the “stopper” presents a non-linearity of the mechanical behaviour like the slider,
(2) the “stopper” does not present any residual strains, therefore has nothing to do with the hysteresis loss.
Finally, using the “stopper” and other conventional elements of mechanical model, the mechanical behaviour of some rocks are described.
