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Geotechnical Stability Exhibit ��� <br /> Engineering Evaluation of Highwall Design for the South Quarry of the Morrison Quarry <br /> observations of the quarry by HDR geologists, subsurface exploration parameters such as <br /> recovery, RQD, and drill rate, and a comprehensive laboratory testing program. <br /> The Hoek-Brown model is a non-linear shear strength model for rock that is well known in the <br /> geotechnical engineering industry for quantifying the factor of safety of simplistic stress-strain <br /> models of rock cuts. The generalized Hoek-Brown model relies on the Geologic Strength Index <br /> (GSI), intact UCS (a,;), disturbance factor (D), and the material constants mb, a, and s, where mb <br /> is reliant on the material constant for intact rock mi modified for GSI. The major and minor <br /> principal stresses (a, and 63) are formulated within the Hoek-Brown (Hoek, et. al. 2002) model <br /> via Equation 1, below. <br /> / 63 <br /> 61 = 63 + 6ci lmb— + S)a <br /> 6ci <br /> Eq. ( 1) <br /> Where the rock mass material constants mb, s, and a are given by Equations 2, 3 and 4, below. <br /> GSI — 100 <br /> mb = miexp <br /> 28 - 14D <br /> Eq. ( 2) <br /> 1 1 GSI zo <br /> a = 2 +6(e-is — e-3) <br /> Eq. ( 3) <br /> GSI — 100 <br /> s = exp <br /> 9 - 3D <br /> Eq. ( 4) <br /> And the disturbance factor D, constant m; for intact rock by rock group, and Geologic Strength <br /> Index are found by interpretation of Figure 4, Figure 5, and Figure 6, below. <br /> May 2023 1 19 <br />