Abstract
The paper deals with the evaluation of tunnel construction subjected to earthquake using a pseudostatic analysis combined with the finite element method. The initial stage of calculation is concerned with the design of computational model and subsequent analysis of the actual excavation process. The case study of the response of a selected construction to earthquake follows next. To that end, the so called 1D free filed dynamic analysis is performed first to generate appropriate loading conditions in terms of a layered-wise constant shear strain. Therein, two particular boundary conditions, termed the fixed and absorbing boundary, are examined. The corresponding loading conditions are finally introduced in a 2D plane strain analysis to yield the internal forces developed in the tunnel lining. The results clearly show inadequacy of the fixed boundary and promote the use of absorbing boundary conditions for the present soil profile.
Highlights
Design of underground structures loaded by earthquake is typically based on analytical solutions utilizing pseudostatic methods
This section reports on the application of simplified pseudostatic analysis to two geometrical models in Fig. 1 being linked two types boundary conditions described in the previous section
To further appreciate the differences in the response provided by the two types of boundary conditions we examine the resulting values of the lining internal forces at the end of the pseudostatic analysis
Summary
Design of underground structures loaded by earthquake is typically based on analytical solutions utilizing pseudostatic methods. Adopting simplified methods generally calls for a number of restrictions such as the assumption of homogeneous elastic medium and a circular or rectangular frame structure representing the tunnel If these assumptions apply, one may follow approaches described, e.g. in [1, 2]. The effect of earthquake is represented by a static load due to shear strain derived from a velocity of the propagating shear wave and the associated maximum velocity of vibrating soil grains This causes, e.g. ovaling or racking of a tunnel cross-section, which in turn serves as a basis for the stress analysis of the tunnel lining [2,3,4].
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