Irregular-Shaped Shield

Abstract

Systems of excavation, thrust, muck removal, and erection of lining segments are key processes of conventional boring using shield tunneling machines. For an irregular-shaped (noncircular) shield, the process is principally the same except that the systems of excavation and erection of lining segments have to be changed to cater for the irregular shape of the eventual tunnel. The rectangular shield (also known as the box shield) is more often adopted in industry practice and is considered the most common shape for an irregular-shaped shield.