ABSTRACT
In Japan, maintenance is carried out with great care on a daily basis to prevent accidents due to the spalling of tunnel concrete linings. Repairs are planned and carried out in areas where spalling may occur in the future. The authors have developed a “polyurea resin spraying method” that prevents spalling of the tunnel concrete lining by spraying polyurea resin onto the surface of the tunnel concrete lining. This repair method has both non-transparent and transparent types. This method relies on the bond strength between the resin and the tunnel concrete lining, similar to a fiber-sheet bonding method. In many mountain railway tunnels, the lining is uneven and seepage can be seen on the surface of the lining. Therefore, we needed to confirm the load resistance and durability of this method when applied under such conditions. Thus, the authors carried out a push-out test on a specimen and a durability test on a actual tunnel. The result confirmed that there were no problems in applying this method to seepage and uneven areas. Then, this method was applied to two tunnels in service under severe conditions. In the first tunnel, there were 104 seepages on the surface of the tunnel concrete lining in the repair area. By temporarily stopping the water with mortar and drainage, we were able to spray the resin without any problems. In the second tunnel, the tunnel concrete lining in the repair area had irregularities of 10-20 mm. By increasing the amount of resin sprayed than usual, we were able to spray the resin without any problems. This study has confirmed that the developed method can be applied to seepage and uneven areas, which are weak points of bonding methods.
