3D NUMERICAL INVESTIGATIONS ON BEHAVIOUR OF NATM PRIMARY SUPPORT COMPONENTS.

Zaharia, M.1, Iftimie, T.2

1. Bridges and Tunnels Department, Arcadis – Eurometudes Bucharest, Calea Grivitei 136, Sect. 1, Romania, zahariamihai2003@yahoo.com 2. Railways, Roads and Bridges Faculty, Technical University of Civil Engineering Bucharest, B-dul Lacul Tei 124, Sect.2, R-72302, Bucharest, Romania, tiftimie@cfdp.utcb.ro

The paper presents some of the design and research efforts made for the carrying out of a

competitive and optimal primary support for the road and railway tunnels executed with New Austrian Tunneling Method (NATM) in soft rock.Firstly is done a critical overview on classical calculation methods of the NATM primary support components (anchors, shotcrete, steel profile or lattice girders) putting in evidence of limits and difficulties. A series of systematic, three-dimensional finite element analyses and parametric studies was carried out to investigate the behaviour of NATM primary support components, independents or coupled. The influence of various caracteristic parameters for each type of primary support components on some control parameters was analisedFor anchors system was investigated the influence of length, distribution and moment of installation on the displacements and stresses in rock ring and the influence of plate on axial force in anchors. For shotcrete lining was investigated the influence of rigidity, hardening of shotcrete in time and moment of installation on the displacements and stresses in rock ring and the influence of irregular shape of excavation contour on the axial force and bending moments. For steel arches was investigated the influence of distance between arches, rigidity and moment of installation on the displacements, stresses in rock ring, axial forces and bending moments.Combinations between anchors and shotcrete, anchors and arches, shotcrete and arches and between all three components and final internal lining were made.Comparisons between behaviour of anchors, shotcrete, arches and all combinations are represented. Conclusions for each step of analysis and general conclusions are useful for an optimum design of the NATM primary support anf final lining.

Conventional tunnelling