Fan-structure shear rupture mechanism as a source of shear rupture rockbursts
BG Tarasov
This paper proposes the further development of a recently identified shear
rupture mechanism (fan mechanism) that elucidates a paradoxical feature
of hard rocks – the possibility of shear rupture propagation through a
highly confined intact rock mass at shear stresses that can be significantly
less than frictional strength. In the fan mechanism, failure is associated
with consecutive creation of small slabs (known as ‘domino blocks’) from
the intact rock in the rupture tip, driven by a fan-shaped domino structure
representing the rupture head. The fan head combines such unique features
as extremely low shear resistance, self-sustaining stress intensification,
and self-unbalancing conditions. Consequently, the failure process caused
by the mechanism is inevitably spontaneous and violent. Physical and
mathematical models explain unique and paradoxical features of the
mechanism, which can be generated in primary ruptures and segmented
faults. The fan mechanism provides a novel point of view for
understanding the nature of spontaneous failure processes, including shear
rupture rockbursts. The process explains, in particular, features of shear
rupture rockbursts such as activation at great depths, generation of new
shear ruptures in intact rock mass, nucleation of hypocentres at significant
distances from the excavation, shear rupture development at low shear
stresses, and abnormal rupture violence.
Keywords: rock strength, failure at confined compression, shear rupture mechanism,
structure of shear rupture, conditions of instability, physical model,
mathematical model, shear rupture rockburst.