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

Figure 4.17: Model of yielding for Case 3 for (A) elastic model and (B) plastic models. Faults are
assigned a cohesion of 0 MPa and a friction angle of 35 degrees.
4.5 Tectonic Loading Model
In the case of the tectonically loaded model, elements are assigned a hydrostatic stress field with a
value between the far-field maximum and minimum principal stresses, σ 1 and σ 3 . The north, south
and east sides of the model are restrained, preventing movement normal to the boundary. It is
loaded by applying an infinitesimal inward velocity to the free boundary to simulate tectonic
loading, as depicted in Figure 4.5. The advantage of the tectonic model is that there is a continual
source of boundary stress, whereas the model initiated with both boundary and internal stresses
may experience relaxation when the excavation is introduced. The tectonic loading model was
constructed to examine the effect of this type of loading on stress and slip along faults.
This method of loading produces a modified stress distribution from the homogeneous stress field
model (Fig. 4.18). Higher stresses and larger zones of high stress are concentrated to the east and
west of the excavation. Concentration of stresses also occurs to the southeast of the excavation
and aligns with SW-striking shear zones. This effect is less pronounced when examining the
distribution of differential stress values (Fig. 4.19). The difference may be a result of stress
accumulation in the tectonic loading model, as opposed to stress relaxation in the homogeneous
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