Effect of soil-rock interface position on seismic response of subway station structure

Abstract

For subway stations in a site with thin soil layers on the engineering rock, the lower part of the subway station is embedded in the hard rock mass and the upper part is buried in the soil layers. The presence of the soil-rock interface may lead to significant increase to the seismic responses of the adjacent soil masses and underground structures. In this paper, the effect of the soil-rock interface position on the seismic response of a two-story and three-span subway station structure is investigated by numerical analyses. It is found from the numerical analyses that a most detrimental soil-rock interface position exists and makes the underground structure have maximum responses under a given artificial earthquake motion. For the upper floor, the most detrimental soil-rock interface position is near the middle slab. For the lower floor, the most unfavorable soil-rock interface position is near the bottom slab. Softer site generally leads to greater structural responses under the same intensity of ground motion excitation. On the basis of the above findings, three earthquake motions included above an artificial earthquake motion and other two real earthquake motions and three burial depths of structure are further studied. Same conclusions can be obtained for the structure with different burial depths or subjected to different input earthquake motions. The conclusions drawn from the numerical examples of this paper may be useful for seismic design of subway station structure buried in shallow soil layers on rock.