Resin Injection Forepoling or Spile

Instead of using heavy support system such as umbrella pipe roofing, the alternative choice is to use the shorter high strength hollow steel tube or self-drilling spile but injected with poly-urethane or silicate resin which is applied widely in Japan as the so-called "PUIF method". Generally, a 3m or 4m length injection spile will be drilled through the lattice girder profiles and inserted as very small angle roof-bolting. The injection of the resin serves to greatly improve the self-supporting capacity of tunnel crown because of foaming and adhesive length between the bolts and the ground itself. The tunneling excavation is suggested to excavate a 1 m shift under 3m PUIF and continuously 2 shifts excavation under the 4m PUIF.

Safety/Quality Approval
PU Injection bolt's diameter: 27.2mm; 5.0mm
Steel grade: tensile load> 250kN
Self-drilling injection bolt: R32N
Steel grade: tensile load> 280kN