Floor Heave in Mountain Tunnels and the Effects of Countermeasures
In mountain tunnels, the ground pressure on the tunnel lining increases during service, in some cases leading to the problems such as cracking of the tunnel lining and reduction of the inner space. Often deformation due to ground pressure develops very slowly over time and its development does not stop unless countermeasures are taken (Matsunaga et al., 2009). The problems include not only sidewall compression but also ground (tunnel floor) heaving, especially in the case of tunnels under unfavorable geological conditions, as has been reported in various examples. In a railroad tunnel, since trains run at high speed, ground heaving affects the stability of train running and must be given special attention, because the tunnel track clearance is tight and the allowable displacement is small.