Abstract: A model for calculating surrounding rock pressure of tunnel with small clear distance under complex unsymmetrical loading is established. The theoretical formulas of surrounding rock pressure are deduced based on roadway tunnel design specifications to investigate the influence of clear distance and ground sloping on surrounding rock pressure of tunnel. The rationality of the theoretical calculation formulas are verified by numerical simulation. The influences of varying clear distance and ground sloping on the surrounding rock pressure of vault, arch waist and arch foot of the first tunnel and the subsequently excavated tunnel are analyzed. Results reveal that when two tunnels are excavated successively, the change of clear distance and ground surface sloping has great influence on the surrounding rock pressure inside the tunnel. The pressure of surrounding rock inside the first-excavated tunnel is positively correlated with clear distance and sloping, while the inner surrounding rock pressure of the subsequently excavated tunnel is negatively correlated with clear distance and sloping.

Key words: clear distance, surrounding rock pressure, ground sloping, complex unsymmetrical loading, theoretical calculation