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title of the thesis - Department of Geology - Queen's University

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zones are planar in geometry, are <strong>of</strong> uniform strength and are laterally continuous beyond <strong>the</strong><br />

limits <strong>of</strong> <strong>the</strong> mine, though in reality shears may be discontinuous and have variable orientations<br />

and properties.<br />

Table 4.1: Rock mass and discontinuity model properties<br />

Rock mass Properties<br />

Discontinuity Properties<br />

Property Value Property Value Range<br />

Cohesion (C) 10 MPa Cohesion (C) 0-10 MPa<br />

Friction Angle (Φ) 35° Friction Angle (Φ) 10-35°<br />

Density † (ρ) 2965 kg/m 3 Normal Stiffness †† 700,000 MPa/m<br />

Young’s Modulus (E) 35 GPa Shear Stiffness †† 99,400 MPa/m<br />

Poisson Ratio (υ) 0.263 Tensile Strength 0-10 MPa<br />

Bulk Modulus * (K) 24,613 MPa<br />

Shear Modulus * (G) 13,856 MPa σ 1 (E-W) ††† –102.7 MPa<br />

σ 3 (N-S) †††<br />

–73.4 MPa<br />

*<br />

Calculated<br />

†<br />

Density from Tulk (2001)<br />

††<br />

Stiffness values increased to prevent contact overlap in UDEC<br />

†††<br />

Maximum and minimum stresses (in plane) calculated from overcoring measurements<br />

Two different approaches are used to load <strong>the</strong> model once <strong>the</strong> geometry, properties <strong>of</strong> <strong>the</strong> material<br />

and discontinuities are specified<br />

1. A homogeneous stress field was initiated within <strong>the</strong> model and at <strong>the</strong> boundaries<br />

2. Incremental displacements were used to syn<strong>the</strong>size tectonic loading<br />

Methods and results for both loading methods are discussed in <strong>the</strong> following sections. Boundary<br />

conditions for both models are depicted in Figure 4.5.<br />

Staged models were also created to better understand <strong>the</strong> effect <strong>of</strong> mining on <strong>the</strong> stress field and<br />

induced fault slip. This allowed <strong>the</strong> rock mass and faults to come to equilibrium without an<br />

excavation. UDEC code for <strong>the</strong> models used in this research can be found in Appendix E.<br />

84

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