Use of the scanline mapping technique in geometric surveys of rock discontinuities can often lead to a bias, in that discontinuities are not always observed when they are at small angles to the scanline. Terzaghi introduced the concept of a blind zone to explain this bias, and developed a widely used procedure to correct for it. Unfortunately, little is known about errors that may occur when the Terzaghi procedure is used outside the blind zone. This paper presents a detailed derivation to show that such errors arise with this application of the Terzaghi procedure. This error was evaluated using simulated orientation data and a case study of the 2008 Wenchuan earthquake (Sichuan, China). The results of these tests yield the optimal values of grid size and sample density for reducing the error.
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This research was supported by the National Natural Science Foundation of China (Grant Nos. 41230637, 41302231, and 41272309). The authors would like to thank our group for the orientation observations.
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Translated from Problemy Prochnosti, No. 6, pp. 111 – 121, November – December, 2016.
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Tang, H.M., Huang, L., Bobet, A. et al. Identification and Mitigation of Error in the Terzaghi Bias Correction for Inhomogeneous Material Discontinuities. Strength Mater 48, 825–833 (2016). https://doi.org/10.1007/s11223-017-9829-9
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DOI: https://doi.org/10.1007/s11223-017-9829-9