27.10.2014 Views

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

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

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

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Damage zones produced using maximum stress and differential stress outline similar areas <strong>of</strong><br />

fracture initiation. Areas <strong>of</strong> active excavation during <strong>the</strong> 2006-2007 time period as well as a zone<br />

<strong>of</strong> high-stress between <strong>the</strong> Return Air Raise Shear Zone and Plum Shear Zone are identified as<br />

areas <strong>of</strong> possible fracture initiation under both maximum stress and differential conditions. This<br />

demonstrates that fracturing <strong>of</strong> intact rock is a possible mechanism for seismicity to <strong>the</strong> south <strong>of</strong><br />

<strong>the</strong> excavation where seismicity is observed, but <strong>the</strong> crack coalescence threshold is not surpassed.<br />

Fracture contours identify <strong>the</strong> area south <strong>of</strong> <strong>the</strong> excavation as a region that is in a state <strong>of</strong> damage<br />

but not yield (Fig. 4.24). This is a lower state <strong>of</strong> degradation than was found in Chapter 3 using<br />

seismic source parameters, where <strong>the</strong> rock mass to <strong>the</strong> south <strong>of</strong> <strong>the</strong> excavation was hypo<strong>the</strong>sized<br />

to be in post-peak conditions.<br />

Figure 4.24 shows that cracking is not possible immediately to <strong>the</strong> north and south <strong>of</strong> <strong>the</strong><br />

excavation, based on <strong>the</strong> final state <strong>of</strong> models produced for Case 1 (Φ=30 o , C=0 MPa). This is<br />

because yielding has already occurred and high stress cannot be accommodated by <strong>the</strong><br />

disintegrated rock mass in this state. UDEC code and routines can be found in Appendix E.<br />

100

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!