Feet-Lock Bolt Application in Cracked Surrounding Rock Tunnels

In constructing cracked surrounding rock tunnels, installing systematic bolts is difficult, and construction cost is high. To solve these problems, feet-lock bolts have become a new potential substitute. Therefore, the safety and support effect of feet-lock bolts must be studied. A programme in which feet-lock bolts replace systematic bolts is adopted in the Fulushan Tunnel. A numerical simulation and a field test for preliminary support structure and surrounding rock have been conducted in this research. Results show that, (1) in the numerical simulation, the deformation and stress errors of the preliminary support structure are relatively minimal when systematic bolts are replaced by feet-lock bolts. (2) In the field test, the deformation and stress of the preliminary support structure satisfy the specification requirement after systematic bolts are replaced by feet-lock bolts. Therefore, installing feet-lock bolts, rather than systematic bolts, is reasonable and feasible in constructing cracked surrounding rock tunnels.