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• Review of the geologic column showed five distinct groups of material properties in the region encompassed by the models. Table 1 lists the zones and related geomechanics properties derived from NaTec 26-88-1 where appropriate. In general, the elastic modulus values obtained from core hole 26-88-1 were relatively low, and no additional reduction factor was applied to these values to account for the rock mass inhomogeneides. Poisson's ratio values were likewise taken from the NaTec 26-88-1 core testing results. The rock strength data taken from the NaTec 26-88-1 core testing data (where available) is lower than the strength values used in our earlier stability study. The core from 26-88-1 in and azound the Boies Bed was inhomogeneous and broken when removed from the core barrel, making test sample selection difficul[. Nonetheless, no specific physical reason is available for the difference between previous and most recent results. Strength data for the B-Groove R6 and lower LS zones not cored or tested in NaTec 26-88-1 were taken from regional sources. The Rock Qtiality Designation (RQD) listed in Table 1 is the percentage of core over 4 in. in length and is used as ati index of rock quality. It forms a pan of the Rock Mass Rating (RMR) listed in Table 1 foreach rockcategory. With the RMR and the intact rock strength, 6~ (uniaxial strength), the rock mass strength, 6~ can be estimated from Equation 1. 6,=YS 6, , (1) where s = e~"10°t'~. Tht; RMR was developed by Bieniawski (1979) and Equation 1 developed by Hcek and Brown (1988). The Hcek-Brown strength envelope is given by 6,=6~+ m,6~6~+s 6,2 , (2) where m, = m;epe'He.raone and m; is determined from laboratory a-iaxial strength data for the nahcolitic oil shale. Froth test data from NaTec 26-88-1, m; = 6.33. The rock mass strength can be used to calculate the cohesion, c, of the rock mass from • 6 c = 2 tan 45 - 2 (3) J. F. T. Agapito & Associates, Inc. 11