Research on the Dynamic Response of Tunnel Primary-Lining Structures under Explosion

The primary lining structure plays a key role in blasting tunnel construction, and its intensity change and dynamic response directly affect the security of tunnel structures. To investigate the dynamic response of the primary lining structure under blasting loads, a field test combined with numerical simulation was conducted on the new passenger line railway that traverses from Beijing to the Shenyang TJ-1 (Liaoning) Sanlengshan tunnel. The peak particle vibration velocity data were recorded by conducting eight monitoring tests at three measuring points by using TC-4850. The Sadaovsk formula for the propagation law of peak particle vibration velocity was fitted by using the least squares method. The numerical simulation software LS-DYNA was used to obtain the material and equation parameters, and the reliability of the numerical model was verified by using the propagation law of peak particle vibration velocity to determine the variations in the stress and displacements in key locations (i.e., skew, haunch, spandrel, and vault) while considering the strength of the primary lining. Results show that the maximum stress of the tunnel primary-lining structure at the skew and vault in the X direction is greater than at the haunch and spandrel. The maximum stress values in the Y and Z directions are 0.1181 MPa and 0.2391 MPa at the skew, respectively. The maximum stress value in theZ direction is larger than that in the X and Y directions. The maximum displacement value of the tunnel primary-lining structure is 3.61 mm at the haunch and appears in the Z direction much earlier than in the X and Y directions. By increasing the primary lining strength of C25 and C35, the stress becomes positive, whereas the displacement shows a negative relationship.