Perrin, N.D. 1976 The Terrace tunnel project. Settlement resulting from east and west side drive excavation. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 249 9 p.
Abstract: Up to 1.5 inches (38 mm) of settlement has occurred at the surface above the Terrace Tunnel as a result of excavation of the two foundation drives. It has been monitored by weakly levelling of surface points, and magnetic settlement gauge readings. It appears likely that a maximum of 3 inches (76 mm) of additional settlement can be expected with the excavation of the top heading. (auth)
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