ABSTRACT
The Shin-Minatogawa tunnel with a diameter of 14m was excavated in loose hydrated sediments of the Osaka Group in Kobe City in a western part of Japan. The main concern of this construction was that the tunnel had to be excavated under an operating railroad with an overburden of only 13m. Due to the strict guideline on railroad subsidence, a 3-D real-time displacement observation system had to be established. Pore water pressure in sediments was also measured by the single borehole type multi-level piezometer (MP system) to estimate the stability of the cutting face. Use of the measurement results of the pore water pressure and displacement in 3-D, enabled identification of ground behavior achieved by prompt alteration of construction sequence or support measures at each construction stage. It was also possible to determine locations of drainage hole and necessity of rock bolts with no delay. The real-time and continuous monitoring scheme enabled the effective construction method in each step, which lead to safe construction.
