Ontario Power Generation's Response to the Joint Review

(H-a) = 4.25 m
Figure 5: Return air tunnel geometry.
5.0 RECOMMENDATIONS
CLOSURE WALL CAPACITY
Calculations based on average stresses over the length of the closure wall (with conservative assumptions) and
further checking with boundary element stress analyses, suggests that a factored shear strength capable of
resisting a pressure of 10.2 MPa is achievable. Using a load factor of 1.6 (ACI 318M), the allowable gas
pressure acting on the face of the closure wall is 6.3 MPa.
This allowable pressure is based on the ‘no dilation’ mechanism (and, therefore no normal stress on the
interface), which is a reasonable lower bound strength for the closure wall. Should the loaded end of the closure
wall slip due to excess shear stress; or due to expansion of the walls (as a result of the gas pressure); or even
due to some pressure penetrating the interface near the end of the closure wall, compression and ‘bulging’ of the
closure wall would occur and generate a normal stress across the interface resulting in increased shear capacity.
6.0 REFERENCES
q = 69.416
[1] L&ILW DGR – Geotechnical Interpretative Report, Golder Document No. 1011170042-REP-G2050-
0001-00, March 2011
August 27, 2012
Report No. 1011170042-TM-G2170-0001-00 8
a = 0.75 m
W = 4.8 m
H = 5.00 m