mem rock tunnel 050929
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8/15/2019 Mem Rock Tunnel 050929
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Memo
To: Kim Howie From: Heather Anderson
Robinson Consultants Inc. Stantec Consulting Ltd.
File: 1634 00518/63 Date: September 29, 2005
Reference: Lemieux Island Phase 3Proposed Horizontal Rock TunnelTaggart Fax Dated September 21, 2005
We have reviewed the above noted submission from Taggart Constructionregarding the rock tunnel in the aqueduct north of the intersection of PrestonStreet and the West Transitway. The letter from Golder Associates recommends
the installation of 1 metre long rock bolts at 10:30, 12:00 and 1:30 along the lengthof the tunnel to replace the steel liner included in the original design. These rockbolts will be installed following the completion of an initial 1.2 m diameter boreinstalled at the finished obvert elevation. The opening would then be increased tothe required 2.132 m diameter by drilling and blasting.
Several concerns have been identified with this approach. During the drilling andblasting to open the diameter of the tunnel, the bolts installed at 10:30 and 1:30would lose their tension and, therefore, the safety they provide by stabilizing theroof of the tunnel. During the bolt installation, we would recommend that at theselocations, the bolts be recessed into the 1.2 m diameter bore to the finishedlocations required for the 2.132 m opening. In this manner, the drilling and
blasting would have no effect on their integrity. Upon completion of the tunnel andpipe installation, the annular space between the pipe and tunnel should be filledwith grout.
Additionally, Stantec recommends that a representative from Golder Associatesbe required to be on site during the installation of the rock bolts and thesubsequent drilling and blasting to monitor the vibration and the appearance ofadditional fractures in the rock above the tunnel obvert that may pose a risk toworker safety or the structural integrity of the heritage bridge above.
Should you have any questions with respect to this review, please do not hesitateto contact me or Brett.
STANTEC CONSULTING LTD.
Heather AndersonProject [email protected]
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