3D simulation of mechanized tunnel excavation Dimitris Litsas 1 , Petros Fortsakis 2 , Michael Kavvadas 3 1 National Technical University of Athens, Civil Engineer, MSc, PhD Candidate 2 Deutsche Bahn International, Civil Engineer, MSc, PhD, Tunnel Expert at Qatar Rail 3 National Technical University of Athens, Civil Engineer, Associate Professor Abstract EPBs and slurry machines are commonly used in urban tunnelling projects, since they decrease the displacements induced by tunnel excavation, ensuring high performance in a wide range of ground conditions, low cover depths and high ground water pressures. The calculations related with mechanized tunnelling (settlements, dimensioning of the tunnel lining etc.) are usually carried out by using simplified approaches, such as 2D numerical analyses, empirical methods etc. However, the simulation of the actual construction procedure includes high complexity due to the multiple interfaces, the role of the 3D geometry, the different phases of the grout and the structural system of the segmental lining (radial and longitudinal joints). This paper presents a realistic full 3D simulation of a shield tunnelling process (EPB or slurry machine) with the finite element code ABAQUS. The objective of this paper is to demonstrate the main modeling techniques employed for the simulation of several key characteristics of the excavation and construction. Indicatively, the main components of the machine (shield, excavation chamber, cutterhead) are simulated using solid elements and the gaps due to overcut and tapered shield are also included in the model via interface elements. The tail void grout is modeled with 3-dimensional finite elements simulating in detail the grout injection pressure and the time-dependent hardening. The segmental lining is modeled with shell elements, considering the coupling behaviour of the joints between the segments, resulting to a more realistic distribution of the internal forces and consequently the dimensioning of the concrete shell.