First and second lining vibration design of urban tunnels in Tehran ABAQUS software

Abstract

Nowadays, a great portion of transportation is being accomplished through underground structures. As such structures are embedded into the ground and there is a remarkable interaction between them and the surrounding soil, very little attention has been paid to the impact of earthquake on these structures. With respect to the increase in rate of transportation as well as decrease in depth to the ground surface, the safety of these structures against earthquake need to be taken into account much more carefully. Due to the importance and diversity of this issue, design of tunnel linings has been widely investigated so far. In this respect, one of the questions that arises in engineers’ minds is regarding the time duration of stresses release after excavation until execution of the concrete lining. Accounting for the stiffness of the permanent lining, in the beginning of the analyses, is so conservative such that in case of soil or rock mass with high overburden, irrational results will be obtained. The main objectives of this research is to obtain seismic and dynamic results of metro tunnels supported by concrete linings and specify the significant and effective parameters on seismic design of such underground structures. By means of applying two types of vibration including periodic loads as well as base excitation using accelerograms, the impact of surcharge on seismic response of the lining was studied. Among the results, the maximum displacement was related to the KN60 surcharge. Regarding the effect of soil elasticity modulus on displacements, it can be concluded that increase in this modulus, reduces the displacements and the considerable reduction takes place when the increase is in the range of 20 to 40 MPa. Moreover, increasing the Poisson ratio led to a little increase in dynamic response of the lining