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Rock Mechanics.pdf - Mining and Blasting

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Figure 16.14 Chart developed to estimate<br />

the lateral extent of the zone<br />

of influence of the cave, highwall<br />

side, Ten 4 – Regimiento Sector,<br />

El Teniente Mine, Chile (after<br />

Karzulovic et al., 1999).<br />

MINING-INDUCED SURFACE SUBSIDENCE<br />

Horizontal displacements predicted using a FLAC numerical model were calibrated<br />

against observations made in drifts that had suffered subsidence-induced damage in<br />

locations such as that illustrated schematically in Figure 16.12. In this way, it was<br />

possible to determine the threshold horizontal displacements likely to be associated<br />

with defined levels of damage. The chart developed in this way to estimate the extent<br />

the zone of influence of the cave on the highwall side of three production sectors on<br />

the El Teniente Ten 4 level is shown in Figure 16.14. It will be noted that for heights<br />

above the crater floor of 500 m or more, the lateral extents of the zones of influence,<br />

ti(z), for the three sectors referred to in Figure 16.14 are in the range 50–70 m.<br />

Brown (2003) gives further examples of the development of surface subsidence<br />

associated with block <strong>and</strong> panel caving at the Miami Mine, Arizona, USA (Fletcher,<br />

1960), the San Manuel Mine, Arizona (Hatheway, 1968) <strong>and</strong> the Henderson Mine,<br />

Colorado, USA (Stewart et al., 1984). Together these examples illustrate many of<br />

the factors influencing caving subsidence. In all three cases, the surface expression of<br />

subsidence was influenced by the presence of faulting. At the Miami Mine, toppling of<br />

blocks isolated by successive cracks occurred in some areas. As at El Teniente, surface<br />

topography had an influence on the primarily up- <strong>and</strong> down-slope growth of the crater<br />

at the Henderson Mine. Interestingly, during a shut-down of approximately 16 months<br />

500

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