Keller drilled, installed and post-tensioned arrays of rock anchors required to anchor mooring points deep into rock for the Hebron Deep Sea project.
Bull Arm is a picturesque cove on the east coast of Newfoundland where Exxon Mobil’s Hebron deep sea project is being constructed ahead of its launch into open waters. Keller was subcontracted by Kiewit-Kvaerner Contractors to drill, install and post-tension arrays of rock anchors required to anchor mooring points deep into rock.
Rock anchors were constructed for 6 mooring points at the dry dock site and 3 new mooring points at the deep sea site 0.5 km away in the cove. During the several months between the launch of the gravity based structure from dry dock and being towed to its eventual open sea location, the structure will reside in the cove at the deep sea site, where the combination of the 3 new mooring points and the existing 6 mooring points (leftover from the Hibernia project of the 1990’s) will have to withstand tremendous forces induced by tides, wind, and storm wave action.
The two sizes of double-corrosion-protected solid bar tendons employed included 36 mm diameter/1030 MPa and 75 mm diameter/1030 MPa. All of the 36 mm anchors were constructed on dry land while drilling of the 75 mm anchor holes took place from a barge. The typical conditions encountered at the barge drilling locations coupled with the fact that the mooring points are cast steel imported from Norway (necessitating all anchors within the same grouping to be arrayed on divergent inclinations and azimuths to fit the inherited anchor pattern), required the installation of permanent 245 mm steel casings in the upper 3 m of every rock anchor hole. The largest rock anchors are embedded 21 m and were post-tensioned to test load 3650 kN.
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