Abstract:

This paper proposes a new modified crosssection racking deformation (MCSRD) method to assess tunnel seismic capacity. It is a quasistatic approach that imposes a prescribed seismic shear strain to the boundaries of a ground domain where an underground structure has been constructed. The modified method simulates seismic action on the underground structures, and the seismic interaction between the underground structure and surrounding ground can be automatically taken into account by numerical program. Based on the method, we can quickly assess the seismic capacities of the underground structures as compared to the complicated dynamic time history analysis. However, although the method is relatively simple and efficient, there are several numerical points that have to be addressed. These points include: (1) how far is the suitable boundary distance to the structure, (2) the types of imposed shear strain on boundary and the shear strain rate, (3) the effect of interface between ground and tunnel lining, and (4) the influence of plastic behavior of ground. To this end, the research performed a series of numerical studies to clarify the effects of the above numerical points. At the beginning of this paper, the approach for assessing seismic capacity of underground structure based on the MCSRD method is introduced. Then, a comparison between the analytical results of a circular tunnel and the numerical solutions is made to validate the used numerical program. Subsequently, numerical studies aimed to the above numerical points are performed to find out some suggestions so as to help engineers more correctly use the MCSRD method in their design work.

Key words: seismic capacity, racking deformation method, numerical analysis