In IUCM, the elastic modulus of the intact rock is the only elastic property that can be provided as input. If Ei is available, the Hoek and Diederichs (2006) equation below assigns the models’ elastic modulus.
If not available from testing, Ei can be estimated from the equation below that uses the modulus ratio (MR), introduced by Deere (1968) and updated by Hoek and Diederichs (2006).
Brown (2008) also suggested that in addition to demonstrating a better fit to known data that Equation [20] provides, this method has the great advantage that because of the shape of the sigmoidal curve used, it avoids the unrealistically high elastic modulus values given by other methods.
For the calculation of Poisson’s ratio, the following equation proposed by Hoek et al. (2000) is used in the IUCM to assign the Poisson’s ratio in the models:
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