![]() Methods and guidelines for resolving these problems are presented. Suggestions are then provided on how to prescriptively address the problems created by incorrectly utilizing tensile strength test data in defining the compressional envelope. The concept of this envelope being valid only in the compressional range and being transitional to a hybrid sigmoidal tensile envelope at lower stress ranges is discussed. Equations for properly correcting BTS results to calculate theoretically equivalent DTS and Hoek-Brown (H-B) pseudo tensile strength values are presented, along with a suggested iterative approach for utilizing derived H-B strength estimates for better refining a representative failure envelope. These differences in curve fit regression estimates can become even more pronounced if inappropriate corrections are made to adjust indirect (Brazilian) tensile test (BTS) results to equivalence with direct tensile strength (DTS) values. It has long been known that significantly different estimates of the Hoek-Brown m i constant occur if curve fitting regressions are made including or ignoring tensile strength data.
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