ABSTRACT
The origin of the double circular shield tunnel may be traced to 1981, when a basic patent was applied for in Japan. The patent was registered in 1987, and a horizontal double circular shield tunnel field trial was performed in the same year. In 1988, a vertical double circular shield tunnel trial was conducted in the field. In the construction of the national road No. 54 tunnel in Hiromiosa, a double circular shield, which was designed and manufactured by Ishikawajima-Harima Heavy Industries Co. Ltd, was used to build the first double circular shield tunnel in the world with length of 853.8 m (Moriya, Y., 2000).
