Prevention of the ground subsidence by using the foot reinforcement side pile during the shallow overburden tunnel excavation in unconsolidated ground

In this paper, three dimensional trapdoor model experiments and the corresponding numerical analyses, and numerical analyses for the actual tunnel excavation are carried out to examine the effect of FRSP on preventing settlements of ground surface and crown and foot of tunnel, and to discuss its mechanism. As a result, it was observed that the FRSP can prevent settlements of the ground surface and tunnel effectively, and these effects of the FRSP are connected with the distance from the tunnel lining to the slip line. When the FRSP is long enough to cross the shear line, it can exert the effect of the shear reinforcement, load redistribution and internal pressure to prevent the settlements of the tunnel and surrounding ground effectively.