STRESS-STRAIN FIELDS AT THE TUNNELING FACE - 3-DIMENSIONAL ANALYSIS FOR 2-DIMENSIONAL TECHNICAL APPROACH

For tunnelling in rock, the original stress field in the ground is changed considerably before a first lining is participating in stabilizing the opening. Depending on this stress release at the tunnel face, only a small portion of the primary stresses is acting on the lining. Only a three-dimensional approach is able to determine the stresses and the deformations of the ground and the lining realistically. The paper presents some results of elastic three-dimensional finite-element-analyses in consecutive steps of the sectional excavation of circular and non-circular tunnels. From these results an equivalent two-dimensional approach is derived for technical applications, given in diagrams.