Numerical and experimental study on optimal design of rock bolts in single-lining support of expressway tunnel

This study presents comprehensive numerical and experimental investigation into the optimal design of rock bolts in single-lining tunnel support for expressway tunnels. Focusing on key design parameters, including anchorage length, bolt diameter, spacing, surrounding rock grade, and bolt type, the research explores their influence on tunnel stability. The study employs finite element simulations to analyze the distribution of axial force (Pu), surrounding rock stress (su), and displacement (du). Experimental testing under varying conditions is used to validate the numerical results. The findings reveal that an anchorage length of approximately 2.5 m, a bolt diameter of 28 mm, and an anchorage spacing of 1.0 m offer the best performance for grade III rock conditions. Moreover, self-drilling hollow grouting bolts (SHGB) outperform expansion shell bolts (ESB) in terms of axial force capacity and deformation control. The study concludes by providing practical recommendations for the design of rock bolts in single-lining expressway tunnels, aiming to enhance both safety and cost-effectiveness in tunnel construction.