Numerical analysis of site deformation and formation stress characteristics of Jingyang–Weinan active fault zone

The Jingyang–Weinan Fault that Xi’an Metro Line 10 crosses is a Holocene active fault, and its future stick-slip earthquakes and coseismic dislocations pose a potential threat to the metro line. To reveal the deformation and stratum stress characteristics of the site caused by the stick-slip seismic and coseismic dislocations of the Jingyang–Weinan Fault zone, based on the Jingyang–Weinan fault zone crossed by Xi’an Metro Line 10, the geomechanical model of the fault zone site coseismic dislocations and stick-slip seismic was established, and the numerical simulation analysis of the stratum deformation and stress field characteristics of fault zone site was carried out considering different dislocation amounts and seismic intensity. The results show that under the coseismic dislocation, the stress reduction and strengthening zones appear in the hanging wall and footwall near the fault zone, and the site presents an inverse “S” shaped differential settlement failure. The differential displacement peaks at the fault zone, and the plastic zone is concentrated here. The deformation range and plastic zone of the hanging wall are 1.67 times and 2.50 times more than that of the footwall, respectively. The displacement and differential deformation of the site near the fault zone reach the peak value under the stick-slip earthquake. The influence range of the site displacement during the large earthquake is approximately 6.50 times more than that during the medium earthquake. It has a typical magnification effect on the hanging wall, and the displacement decreases linearly far away from the fault zone. The amplification factor of peak surface acceleration (PGA) in the large earthquake is 1.14 times more than that in the medium earthquake. The site shows “V” shear failure; the plastic zones of hanging wall and footwall in the large earthquake is about 1.40 times and 1.00 times larger than that in the medium earthquake, respectively. This study can provide a scientific basis for the seismic fortification of Xi’an Metro Line lines crossing the Jingyang–Weinan fault zone.