By next February two full face earth pressure balance tunnelling machines will have completed a near three year battle through difficult ground beneath Copenhagen's main streets to achieve all 16.6km of tunnelling for the £600M metro. The twin machines - christened Betty and Liva after local music hall stars - have linked all six city centre underground station boxes and nine deep ventilation shafts, several of which were initially used for construction access.
A slow start, through ground conditions ranging from limestone with bands of hard flint to abrasive glacial sands containing large boulders, led to both machines being strengthened and their heads, each with 40 cutter discs, being modified. Recent drive rates of 248m of completed 5.2m diameter tunnel a week are claimed as world records for this type of machine and the metro's first city centre phase should open in autumn 2002.
Strict environmental controls have led to fume-free tunnel locomotives; spoil being barged direct to create offshore reclamation and muffled surface plant forming secant piled station boxes tight against city centre buildings. To meet the required zero settlement beneath these timber piled structures, a world leading £10M computerised ground water monitoring regime was set up to ensure the oak piles did not dry out during dewatering of adjacent station boxes.