Dynamic response characteristics of adjacent tunnel lining under blasting impact in subway connecting passage

The connecting passage between two adjacent tunnels is conducive to the rescue and evacuation of subway tunnels when disasters occur. The blasting method is usually used in the construction of connecting passage. The vibration caused by blasting construction may endanger the safety of subway tunnel structure. As a result, the influence of blasting pressure on the stability of subway tunnel lining structure during the excavation of connecting passage is studied, and the safe blasting construction distance is proposed, which is crucial to the safety of adjacent subway tunnel lining. This study takes the connecting passage of Wuhan Metro Line 8 as an example. Using Finite element software ANSYS/LS-DYNA, an accurate numerical calculation model of construction site is established. The nonlinear elastoplastic mechanical characteristics of soil, rock, and tunnel lining are simulated by Drucker Prager, Plastic Kinematic, and Johnson Holmquist Concrete constitutive material models, respectively. The credibility of the three-dimensional numerical calculation model and material constitutive model was proved by contrasting the field measured data of the connecting passage with the numerical calculated results. Analysis of numerical results, the axial and radial PPV, frequency, and Von Mises stress of subway tunnel lining are obtained. The influence of subway tunnel lining under adjacent blasting can be obtained by analyzing the distribution law of PPV and Von Mises stress. Non-static tensile strength is needed considering the high pressure and high strain rate process of concrete during blasting. By fitting the relationship between PPV and dynamic tensile stress, and referring to DIF parameters, the safety range of PPV in subway tunnel lining blasting is determined. The critical safety distance between blasting construction and tunnel lining is obtained by Sadovsky vibration velocity attenuation formula, which is used to guide the subsequent blasting excavation of continuous tunnels.