The design and construction of a shield tunnel which have a non-excavating extension part in the middle by the Japan longest distance class

摘要

This shield tunnel, referred to as Kasugai Public Utility Conduit, was ordered by the Chubu Regional Bureau of the Ministry of Land, Infrastructure and Transport and, upon completion, will have an inner diameter of 4.2 m and total tunnel length of 6.82 km. Further, three underground sections will be cut and widened 2.5 m in diameter and 10～17 m in length from inside the path of the tunnel. The ground consists of hard, cobblestone-mixed, diluvial gravel layer. Boring is to be performed by use of one shield machine. With the aim of proper execution of construction, the following equipment and methods were utilized to carry out the highly difficult work successfully. 1. High-durability shield machine constructed by the relay bit construction method. 2. New quick block (QB) segments for high-speed automatic assembly and wedge block (WB) segments. 3. Construction method of underground widening in which a shield machine for widening the tunnel.