To restrain the tunnel settlement in soft ground, the reinforcement method of tunnel supports legs with jet-grouting before excavation were adapted. The uniaxial compressive strength of ground which the tunnel was excavated are about 0.2-2.OMpa. The effect of reinforcement was as follows.
1) The settlement of tunnel supports legs were reduced to approximately 50 % compared with no reinforcement pattern at the same ground condition.
2) The settlement were increased as the rock strength was more soft, but the velocity of the settlement were lower. So the next reinforcement method was adapted, before the rock condition was very bad.
