hs2 tunnelling boring florence tbm phase moment tbms chilterns tunnels dig tunneling meet chiltern beneath groundbreaking vl dji volkerwessels underneath
hs2 viaduct longest begins rail work bridge will supported structure low set
piling hs2 euston underway alignment
hs2 piling euston underway alignment 225km birmingham
viaduct hs2 colne rail longest casts segments chilterns largest
hs2 viaduct longest work rail colne valley begins london north west ground starts infrastructure 2021 will foundations engineers railway sinking