Abstract: To investigate the mechanical properties of inclined and advance rockbolts on the Chongqing-Kunming high-speed railway, a field test is conducted in the Leye tunnel. Utilizing the support stress field concept, finite difference numerical simulations provide a quantitative description of the effective support range for these rockbolts. A multi-index method-considering tunnel displacement differences, surrounding rock plastic zones, and minimum principal stress in the surrounding rock-is employed to quantitatively evaluate the support effectiveness of the rockbolts. By analyzing the axial force distribution in the rockbolts and steel arch, the bearing pattern of the inclined and advance support system is determined and validated through field test results. The results reveal that: (1) After tunnel excavation, the rockbolt support creates a stress field with increased maximum principal stress near the excavation face, enhancing the anti-deformation ability of rock mass. (2) As the spatial effect of the tunnel face weakens, the load on the surrounding rock supported by the rockbolts increases, resulting in a larger effective support range. (3) Near the tunnel face, inclined and advance support improves the self-bearing capacity of the surrounding rock, reduces axial forces in the steel arch at the crown, shoulder, and haunch, and improves the stress characteristics of the steel arch.

Key words: tunnel, inclined and advance rockbolt, support stress field, effective support range, support effect, bearing pattern of support system