ABSTRACT
Tunnel forcpiling reinforced with steel tube triggered by TREVI in Reinforced Protective Umbrella Method (hereinafter RPUM), with relevancy to NATM, is expanding in its applications in Japan not only for narrowly spaced mountain tunnels but also for city area tunnel executions in non-cohesive sandy soil.
The RPUM developed by Trevi SpA in Italy and executed with the specialized machines has been introduced into Japan in 1993 made it possible to proceed the large diameter tunneling on safety job conditions.
Aim of the RPUM are; Minimization of ground settlement considering the existing architectures above tunneling. Preventive consolidation of soil in face area and surrounding section to secure stability and to avoid deformation of the tunnel.
The forepiling with RPUM will make it possible to study the very complicated and varied soil formation in Japan as a consecutive or fomogenised geological conditions to analyze and foresee the preceding soil behaviours to be excavated, eventually lead to most safety and adequate tunneling job.
The execution of RPUM in Japan till now after its introduction becomes 45,000 meter in total by the forepile length, reinforced with steel tube Dia. 114.3mm - 136.2mm, Thickness 4.6mm -12.0mm, Length 12m - 16m per piece, by Italian brand Soilmec model SM505DT & SM605DT specialized machines.
Such execution includes tunnelings at Reclaimed extreamly lose land, Sedimentary soil mixed with pebble and boulder, and Shallow earth covering with school buildings on the ground among other places.
The advanced method in RPUM, Jet Grouting with steel tube for reinforcement with continuous 350kgf/cm2 high pressure pump, two nozzles of 2.8mm dia. and special jetting devices installed in the tube for production of conic continuous wall surrounding the section to consolidated with rock mass has been increasingly executed, involving use of silica resin etc for quick treatment in some cases.
Thanks to these developments, safety and assured tunneling execution including face stability and settlement restraint are realizing.
It will be a good refernce for future tunneling technologies and techniques.
