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.