Numerical investigation on the three-dimensional isolation of a subway station intersecting a ground fissure

Under the coupling action of horizontal and vertical deformation of a ground fissure site caused by earthquakes, the column of a subway station intersecting a ground fissure (SSIF) is susceptible to compression-shear damage, resulting in structural collapse. This study proposed installing three-dimensional (3D) isolation bearings at the top of columns to upgrade the seismic performance of the SSIF. After numerical models were built and validated with the shaking table test, the 3D isolation effect and mechanism of the SSIF were studied. The results show that: (1) Relative vertical settlement of a ground fissure site weakens the horizontal damping effect of isolation bearings, and far-field long-period and near-fault pulse-type ground motions both cause the large settlement; (2) solitary horizontal isolation can hardly meet the seismic control demand of the column, but the 3D isolation can attenuate adverse effects of the settlement on the damping effect and seismic capacity of the column to maintain the high damping level; (3) after the 3D isolation, the weak member of the SSIF is altered from the column to the top slab, which yield without severely damaging columns and side walls, avoiding structural collapse, similar to the ductile structural form of the “strong column-weak beam”.