Abstract:
A physical modelling approach was adopted to simulate the process of cave mining propagation at
various horizontal to vertical stress state ratios, and image data was captured and used to characterize
the resulting failure mechanisms. Image processing was integrated into the study to determine minor
principal strains in models to identify where critical extensional strains had been exceeded relative
to crack propagation. The study exhibited a scale factor magnitude of 119 using a calculated critical
extensional strain value of 0.014% for the modelling material used. It was perceived that cave propagation
occurred through successive parallel extensional ‘fracture bands’ in all cases, as noticed in models of
prior studies, deviating from that described by the Duplancic model. Cracks tended to bisect regions
of minor principal strain equal to the critical extensional strain, which suggests ‘fracture banding’ is an
acceptable failure mode for brittle, rock-like materials. Moreover, it was found that models with lower
horizontal to vertical stress ratios (K ratios) showed a greater degree of vertical development of the
caving mechanism (at similar vertical stresses), while the vertical extent of the cave was suppressed
in models with higher K ratios. Models subjected to larger vertical stresses experienced slower cave
formation in latter time-steps. These models exhibited larger two-dimensional caved perimeters and
areas, respectively.
