Abstract: On the basis of Froude similarity law, model test studies of the anti-explosion ability of tunnels which are reinforced by common anchor bolts, slightly dense anchor bolts, long-dense anchor bolts, short-dense anchor bolts, and long-short alternation anchor bolts are carried out. This article, from five aspects, including stress in surrounding rock, acceleration of tunnel wall, relative displacement between vault and footwall, tangential strain of tunnel wall, and failure mode of tunnels, analyzes the different characteristics of tunnels reinforced by fully grouted anchor bolts which have different lengths and spacings. Furthermore, by using FLAC3D program and parameterized modeling methods, numerical calculations and corresponding model tests are also carried out; and the variation regularity of vault displacement with the change of anchor length and spacing is analyzed. The results show that, as comparing with increasing anchor length, the reinforcement effect of decreasing anchor spacing is better. It just prevents cracks from extending into the reinforced region only when anchor spacing decreases to a certain density. Under the same anchor length, acceleration peak at tunnel vault, peak and residual values of relative displacement between vault and footwall, and peak and residual values of compressive strain at arch springing in the tunnels reinforced by dense anchor bolts reduce greatly. But the reinforcement effect is not evident when the length of dense anchor bolts increases to a certain length; it contrarily arouses the sharp increment of the peak of acceleration at footwall and the peak of tensile strain at vault. The optimum anchor length is one-third of the tunnel span and the optimum anchor spacing is one-fifteenth of the tunnel span.

Key words: similarity theory, model test, anti-explosion ability, failure mode, numerical simulation similarity theory, model test, anti-explosion ability, failure mode, numerical simulation