Page 132 - Rock Mechanics For Underground Mining

ROCK STRENGTH AND DEFORMABILITY

Table 4.2 Variation of the constant m i for intact rock by rock group (after Hoek, 2003).

Porphyries

∗ Conglomerates and breccias may present a wide range of m i values depending on the nature of the cementing material and the
degree of cementation, so they may range from values similar to sandstone, to values used for fine grained sediments (even under
10).
∗∗ These values are for intact rock specimens tested normal to bedding or foliation. The value of m i will be significantly different
if failure occurs along a weakness plane.

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