A tunnelling shield can be used as a temporary support structure. It is usually in place for the short term from when the tunnel section is excavated until it can be lined with a permanent support structure.OverviewA tunnelling shield is a protective structure used during the excavation of large, human-made. When excavating through ground that is soft, liquid, or otherwise unstable, there is a potential The first successful rectangular tunnelling shield was developed by and patented with in January 1818. Brunel and his son used it to excavate the.