ABSTRACT
The objective of this chapter is to analyze the different factors affecting tunnel construction. The great complexity of forces to which the tunnel lining rings are subjected, due to the EPB machine advance, as well as other actions, such as the backfilling pressure due to mortar injection, make the development of a detailed study regarding the implications they have mainly in the quality of the finished tunnel, to be of great interest. This implies the need to study the ring behaviour during construction, by the definition of the acting forces, and by the study of test results that were carried out.
