Riddolls, B.W.; Perrin, N.D. 1973 Engineering geological reports for construction of Terrace Tunnels, Wellington urban motorway. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 217 2 v.
Abstract: This document contains engineering geological data obtained by NZ Geological Survey from various subsurface investigations carried out over the last three years for the design and construction of the Terrace Tunnels. Apart from some brief explanatory notes to accompany logs of the stream diversion drive in the North Portal area, all the information has previously been made available to the Ministry of Works. Some minor amendments have been made, but otherwise the reports are identical to those issued originally. Volume I contains the two principal reports (Nos.108 and 123) on the test drive and north portals investigations, recent observations in the Kumutoto Stream diversion drive, and a description of a drill hole near the southern portal. The relevant geological maps, site investigation plans and Terrace Tunnels test drive logs are in volume II. Two engineering geological aspects of the rock have been classified. The weathering classification differentiates the various intensities of weathering into grades that were based mainly on appearance and field strength. The classification of rock condition refers to the characteristics of the rock mass in place, combining the degree of weathering with other important rock defects such as joints and faults. It cannot be overemphasized that abrupt changes in rock condition aver short distances are characteristic of the site. The various observations of rock condition or type recorded in this document apply to the localities or investigation holes where they were recorded. No attempt should be made to extrapolate or correlate any observations in places where subsurface investigations have not been made. Although the geological cross-sections have been constructed on the basis of all the available data, they should not be interpreted as giving an exact indication of subsurface conditions, but rather as the most detailed representation possible. (auth)