Abstract: Due to the construction of more doubletrack projects, limitation of geological conditions and existing buildings and the demand of comprehensive development of urban underground space, there will inevitably be many close or overlapped tunnels. In this paper, the seismic dynamic response characteristics and interaction law of the overlapped tunnel structure are discussed. The vibration platform tests on three seismic intensities and five working conditions are completed under the action of seismic waves. The peak strain values of the circumferential and axial strains of the upper and lower tunnels under different loading conditions are analyzed and studied. The test results show that: (1) The higher the seismic intensity, the greater the seismic hoop strain. (2) The circumferential strain peak value of the underpass tunnel is larger than that of the overpass tunnel; the circumferential strain peak value of the underpass tunnel sidewall is the largest, and the part of the underpass tunnel inverted arch is the second large, followed by the part of the overpass tunnel inverted arch and sidewall. (3) When the seismic intensity is small, the peak value of circumferential strain of the two cross tunnels is basically the same. (4) When the seismic intensity is large, the peak value of the circumferential strain of the underpass tunnel is much larger than that of the overpass tunnel. (5) The peak value of axial strain in the underpass tunnel is larger than that in the overcross tunnel, and the peak value of axial strain in the inverted arch of the overcross tunnel is the largest, followed by the inverted of the overcross tunnel, and the peak value of axial strain in the crown of the overcross tunnel and the underpass tunnel is the smallest. Finally, the dynamic response laws of the overcross tunnel and undercross tunnel are compared and analyzed. 

Key words: overlapped tunnel, largescale vibration platform test, dynamic response