Research on Advanced Cutting Control Blasting of Complex Lithologic Tunnel

In response to the poor excavation effect of traditional blasting in complex lithology tunnels, a method called advanced cutting control blasting is proposed based on the research of traditional smooth blasting and pre-splitting blasting. This method involves conducting the blasting around weak surrounding rock areas after tunnel contouring hole blasting. A quasi-three-dimensional model was established, and numerical simulations were conducted using the fluid-structure interaction(ALE) algorithm and ANSYS/LS-DYNA finite element analysis software to compare the advanced cutting control blasting method with traditional pre-splitting and smooth blasting methods. The results show that compared to smooth blasting and pre-splitting, advanced cutting control blasting reduced the depth of damage around the tunnel contour by 6.85% and 10.08%, respectively. Based on simulation results, field blast test plans were designed, and comparative tests between smooth surface blasting and advanced cutting control blasting methods were carried out. The blast results demonstrated that after adopting the advanced cutting control method, the tunnel contour had good shaping effects without block falling or collapse in weak surrounding rock areas, while over-excavation was effectively controlled. Three-dimensional cross-sectional scanning data and statistical results of post-blast sections indicated that compared to well-performing smooth surface blasting, maximum over-excavation decreased by 35.98%, average over-excavation decreased by 25.60%, concrete consumption decreased by 26.3%, and flatness standard deviation increased by 24.29%. This method has been verified through field practice as it reduces over-excavation while mitigating blast damage in complex lithology areas, thereby improving tunnel retaining rock flatness.