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Frictional Resistance in the Post-critical Failure of Rock Samples Caused by Triaxial Compression |
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Frictional Resistance in the Post-critical Failure of Rock Samples Caused by Triaxial Compression Author: D. Krzysztoń
Triaxial compression tests in a stiff testing machine at a confi ning pressure of 0–70 MPa were performed
on Carboniferous rock samples collected from the Upper Silesian Coal Basin. The results showed
that the post- critical failures of waste rocks were congruent with smooth curves; post-failure behaviour
of coal, however, were characterised by a stick-slip (Fig. 1).
The normal and shear stresses at the sample slip plane of a known slope were calculated for the
determined values of critical stress and residual stress in a uniaxial state of stress, and for a given confi ning
pressure. The coeffi cients of maximum and residual frictions were also calculated (Tables 1–5). The
obtained results, shown in Figs. 6 and 7, were compared with the Byerlee law, which describes the frictional
shear strength. At high values of confi ning pressure the frictional shear strength can reach the value of the
fracture strength. Then the transition from brittle fracture to ductile fl ow takes place.
A knowledge of the conditions in which stick-slip occurs has a practical meaning with regard to the
prediction of mining tremors. |
2011