کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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810242 | 1468742 | 2009 | 13 صفحه PDF | دانلود رایگان |
We present and test a new technique for determining the far-field virgin state of stress near the TauTona gold mine. The technique we used to constrain the far-field stress state follows an iterative forward modelling approach that combines observations of drilling-induced borehole failures in borehole images, boundary element modelling of the mining-induced stress perturbations, and forward modelling of borehole failures based on the results of the boundary element modelling. Using this approach, we constrained a range of principal stress orientations and magnitudes that are consistent with all the observed failures and other stress indicators. We found that the state of stress is a normal faulting regime (Sv*⩾SHmax*⩾Shmin*)(Sv*⩾SHmax*⩾Shmin*) with principal stress orientations that are slightly deviated from vertical and horizontal and, therefore, denoted with a (*). The maximum principal stress, Sv*Sv*, is deviated ∼10° from vertical plunging towards the NNW with a magnitude gradient of ∼27 MPa/km. The intermediate principal stress, SHmax*SHmax*, is inclined ∼10° from horizontal plunging towards an azimuth of ∼156° and has a magnitude gradient of ∼24 MPa/km. The least principal stress, Shmin*Shmin*, is inclined ∼5° from horizontal plunging towards an azimuth of 247° and has a magnitude gradient of ∼14 MPa/km. This stress state indicates that the crust is in a state of frictional faulting equilibrium, such that normal faulting is likely to occur on cohesionless pre-existing fault planes that are optimally oriented to the stress field. Modelling of breakout rotations and gaps in breakout occurrence associated with recent fault slip on critically stressed faults located >100 m from the mine further confirmed this stress state.
Journal: International Journal of Rock Mechanics and Mining Sciences - Volume 46, Issue 3, April 2009, Pages 555–567