Safety approach for tunnel lining calculations in 3D-contiuum models

Y A B F Liem, J T S Vervoort, M H A Brugman (Arthe Civil & Structure); M Partovi (DIANA FEA)

The state-of-the-art method for calculations on bored tunnel lining is considered to be a 3D-continuum model using Finite Element Software, in which both the soil and concrete lining and their interaction are modelled. According to Eurocode 0 it is preferred to perform a ULS verification using partial factors on individual loads and resistances as described in Eurocode 1, 2 and 7. Eurocode 7 provides 3 design approaches which may be applied. A common approach is to perform SLS calculations and apply an overall safety factor on the resulting forces in order to obtain ULS results. This is similar to Design Approach 2 in Eurocode 7 (EC7-DA2). However, a more economic design may be reached by applying partial factors on the loads and soil parameters rather than the calculation results. In this paper an approach is presented for ULS tunnel lining calculations in a finite element environment, following Design Approach 3 as described in EN-1997 and applying partial factors within the finite element model to achieve the desired safety level (EC7-DA3). Furthermore, a case study is presented, illustrating the difference between the results for EC7-DA2 and EC7-DA3.

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