A theoretical model to predict blast-induced vibration and its zoning characteristics in surrounding rock of a tunnel

In this paper, a theoretical model for the vibration response of surrounding rock induced by a tunnel blasting is developed based on stress-wave theory and explosion characteristics of cylindrical charges. The theoretical results are validated through comparisons with simulations conducted using dynamic finite element software. Using the theoretical model, the particle vibration response of surrounding rock during the blasting excavation of a typical long and large high-speed railway tunnel is analyzed. The peak particle velocity (PPV) generated by P-, S- and R-waves is determined through the polarization analysis, a widely adopted method for wavefield separation. The findings highlight the distinctive PPV characteristics of surrounding rock across three regions along the axis of the tunnel’s excavated free surface: 1) Near-field (r < 3r_e, where r and r_e represent standoff distance and equivalent tunnel radius, respectively): the maximum PPV is induced by P- and S-waves. 2) Middle-field (3r_e < r < 11 ∼ 14r_e): the maximum PPV is induced by P-wave. 3) Far-field (r > 11 ∼ 14r_e): the maximum PPV is induced by R-wave. Both the amplitude of PPV and its rate of attenuation with r progressively decrease from the near-field to the middle- and far-fields. Along the tunnel axis, the maximum tensile stress (σ_tmax) and the maximum shear stress (τ_max) show a pattern of rapid increase followed by a sharp decline as r increases. In the near-field, P-wave are more likely to cause tensile failure in surrounding rock. In the middle- and far-fields, R-wave play a more significant role in affecting the stability of tunnel support structures on the surface of the surrounding rock.