The Contract is for the provision of a Phase 3 Ground Investigation for the A31 Magherafelt Bypass.
The proposed A31 Magherafelt Bypass will be located to the east of Magherafelt. It will entail the construction of a new road that and extends in a south west to north east direction between the A31 Moneymore Road and the A31 Castledawson Road. This investigation aims to provide additional information at structure locations following the updating of structure locations and to gain information in areas where access was not agreed as part of the Phase 1 and Phase 2 investigations undertaken in 2007 and 2008.
Phase 3 will comprise the following:
•40 cable percussion boreholes
•Rotary coring in 17 of the proposed boreholes
The following investigation techniques are proposed:
•Cable percussion boreholes to allow visual assessment and taking of undisturbed samples of soft alluvial / glacial soils, to establish the thickness of compressible drift soils where these are anticipated to be beyond the depth of trial pits in embankment areas, provide information on ground conditions at structure locations and to establish the ground profile in deep cutting areas. Continuous alternate SPT/U100 sampling and possibly piston sampling will be required in soft alluvial ground. Core drilling will be required in alternate holes to prove the nature and weathering profile of the first 2-3m of rock encountered within selected boreholes and establish rock head. One borehole is proposed at the location of each structure foundation. Geobore S drilling is also required in selected boreholes
•Visual inspection of slope height, angle, geology and stability of existing cuttings, embankment and natural slopes.
•Soils testing shall be carried out by a laboratory that holds UKAS accreditation for testing soils for civil engineering purposes.