1993-04-27_REVISION - M1977378 ‎(2)‎

• Permit No: M1977378
• IBM Index Class Name: REVISION
• Doc Date: 4/27/1993
• Doc Name: Response
• From: John F. Abel, Jr.
• To: Sunnyside Gold Corp
• Type & Sequence: TR14
• Media Type: D
• Archive: No

L:•R. Perino Page 10 Dril 27, 1993
coarse aggregate concrete bulkheads initially bypassed brine
through multiple pipes, flowing at a rate that increased from 700
to 6000 gpm under a constant 250 psi of hydraulic back pressure.
Neither bulkhead was notched into the ribs, despite the fact the
cross section of the boring machine cut entry was smooth and
planar, the salt compression strength was probably less than the
concrete strength and neither bulkhead was grouted. The 6-foot
thick bulkhead was constructed over a period of nine days and
failed by leakage and solutioning of the salt around one side, but
not by thrust. The final, successful, 50-foot thick bulkhead, was
built in three parts, a first 10-foot thickness, a second 15-foot
thickness and a final 25-foot thickness over a total period of
twelve days. Twelve days later the 50-foot thick bulkhead was
converted to a permanent bulkhead, able to withstand the potential
3000 feet of head (1300 psi) by extending its length 37 feet with
unreinforced concrete to a total of 87 feet, notching that section
into the ribs, pressure grouting the salt-concrete contact for the
37-foot long section through 110 two-inch diameter grout pipes and
bulk grouting over 11040 tons of cement to fill the entire room
behind the 87-foot long bulkhead. The continued operation of the
Rocanville Mine necessitated protection from any possible leakage
and solutioning of the soluble salt.
Scaling of the Sunnyside Mine bulkhead locations will remove
any loose pieces of latite present on the roof, walls and floor.
In addition, the uniaxial compression strength testing samples
included apparently weaker natural joints coated and cemented with
a white mineral. Blast induced fractures in the rock immediately
adjacent to the tunnel will probably permit loosened rock to be
barred out of the tunnel walls but will not produce a smooth
sliding surface for bulkhead movement parallel to the tunnel axis.
Figure 1 presents the blast damage zones adjacent to a
fully-coupled blasthole in massive rock (Morhard et al, 1987, p
175) . At the Sunnyside Mine the exposed ribsides appear to be in
the least fractured zone, Zone 4 on Figure 1. The perimeter
blastholes in each tunnel round are, of necessity angled outward
in the direction of advance in order to maintain the required
clearance envelope and to permit the holes to be drilled. The
result is an irregular saw-toothed tunnel wall profile which
increases the wall irregularity.
Blast fractures are radial to the individual blastholes and
are limited in extent. Calder (1977, p 6) reported the radius of
rupture around blastholes in various rocks using different
explosives. He reported that the blast damage zone (radius of
rupture) around fully-coupled, ANFO loaded, 2-in. diameter
blastholes in Lithonia granite extended a maximum distance of
approximately 2 feet, 12 diameters, from the center of the hole.
Morhard, et al (1987, p 177) presented a compilation of blast
damage zones. For hard rock, such as the latite at the Sunnyside
Mine, the rupture radius ranged from 7 to 15 diameters of the
blasthole from the center of the blasthole. Blasting probably
produces a zone of increased permeability adjacent to the tunnel
but not a path for bulkhead failure under thrust.