In order to provide reference for the seismic design of the portal in the bridge-tunnel connected system

the failure process of the portal was studied through the large-scale shaking table tests

and obtained the acceleration signals which were quantitatively analyzed by wavelet packet transform. It is found that the failure of the portal is marked with the appearance of the crack in the vault slope. The unsafety degree of tunnel portal in the bridge-tunnel connected system ranks as the vault

the abutment

the slope and the invert in turns under the action of ground motion. The strength and stiffness of the bridge and tunnel are relatively high and therefore

the failure often starts from the slope

then the vault and abutment

while the damage of the invert is generally slight. The seismic wave with a low-frequency (0.1?12.51 Hz) plays a leading role in the failure process of the portal-slope system. Due to the complex refraction and reflection effect between the different material interfaces

the low-frequency waves will change drastically before propagating from soil into concrete structures. By analyzing the changes in the percentage of the energy of the low-frequency waves

the failure of portal-slope system can be divided into three stages

i.e.

the elastic deformation stage under the small-shake

the small elastic-plastic deformation stage under the medium-shake

and the large failure deformation stage under strong-shake.