Title screen

[References: p. 86-87 (34 tit.)]

The peculiarities of shear-induced dilatation in block-structured media under nonequiaxial compression are investigated using the movable cellular automaton method. For a characteristic of compression nonequiaxiality (also termed the degree of constraint) a dimensionless parameter representative of the lateral to normal pressure ratio in the deformation plane is used. The main objective of the work is to trace the sequence in which various dilatation mechanisms are involved in deformation depending on the shear stress level and degree of constraint. It is shown that in a block-structured medium as a hierarchically organized system, increasing the degree of constraint changes the dominating dilatation mechanism from slip of discontinuity surfaces to opening and expansion of pores. The dominating dilatation mechanism is changed because the increase in the degree of constraint increases the slip-activating threshold shear stress. Beginning with certain lateral pressures, the slip is impeded giving way to pore space expansion; however, the latter fails to produce the so noticeable volume change as the slip of discontinuity surfaces does, and this lowers the critical dilatation characteristics of the medium, in particular, its volume change and dilatancy coefficient.