The M40 Banbury Bypass Contract 4 overlies coal deposits of sufficient size and at a depth that would make mining at a later date possible. The pavement was, therefore, designed with this in mind and a continuously reinforced concrete roadbase was specified as the solution most likely to resist possible future settlement problems.
Continuously reinforced concrete roadbases (CRCR) are not new to the UK but are uncommon. The scale of this project, involving in excess of 100 000 m3 of pavement quality concrete laid over 15.8 km, required the Contractor to review his method of operation carefully.
In addition the earthworks design called for 600 mm of capping. The Contractor chose to construct a capping layer of 250 mm of lime stabilized material overlaid with 350 mm of selected crushed rock over some 40% of the scheme. Elsewhere, where capping was specified, only selected rock was permitted.
Following the completion of the CRCR, heave occurred in the lime stabilized capping layer at various locations along the scheme. The inherent stiffness of the CRCR largely accommodated this though some limited remedial works were necessary which did not delay the opening of the road.
This Paper reviews the processes by which the Contractor planned and undertook his works and identifies the reasons behind the successful and rapid execution of the pavement construction.
