Damage characteristics of grouted tunnel rock mass in fault zones induced by blasting

When a tunnel crosses a fault fracture zone, in order to avoid the occurrence of water inrush, collapse and other disasters, the construction plan of pre-grouting and then blasting excavation is often used. It is of great significance to clarify the blasting damage characteristics of grouting rock mass for the safe construction of the tunnels through faulted fracture zones. This paper takes the construction of Longnan tunnel of Ganzhou-Shenzhenhigh speed railway through fault8 as an example. The distribution law of acoustic wave velocity with depth in the surrounding rock after tunnel blasting was obtained using the two-hole acoustic method test. Based on the stress criterion and the elastoplastic constitutive model, a statistical damage model of the rock mass was established, and a new LS-DYNA solver was generated by Fortran compilation. The cumulative damage evolution and distribution law of grouting reinforced surrounding rock of the tunnel under the effect of 10 cycles of blasting excavation was calculated by using the complete restart algorithm, which basically matched with the field acoustic testing results. Numerical analysis results show that the maximum damage depth of the surrounding rock is located at the bottom of the inverted arch after blasting, and the average damage depth does not exceed 2.5m at the vault, the shoulder and the waist of the arch, which need anchor anchoring. The degree of damage to the surrounding rock in the arch foot of the upper and middle steps of the tunnel is the most serious, but the depth of damage to the surrounding rock is small. However, the degree of damage to the surrounding rock in other key areas besides the arch foot is small but the depth of damage is large. © 2021, Science Press. All right reserved.