Using GeoFBA

a load-structure method tensile-compressional model is established for analyzing and calculating the tunnel which is 30 m depth embedment in surrounding rock Ⅳ

and is eroded by combined effect of chloride and freezing and thawing cycles. The load-structure model is installed tensile spring in the range of 152° of the arch crown; and the left part is set by compressional spring. The calculation indicates that first of all

the tunnel safety falls down gradually with the increase of circumferential crack width (the corrosion degree of reinforcement) as well as longitudinal crack depth; furthermore

when lining suffers the same corrosion degree of reinforcement and the same depth of longitudinal crack

the problem occurs on the arch crown which would bring up bigger effect on the tunnel safety than that occurs in the haunch; in addition

the change of circumferential crack width

which is smaller than 0.2 mm

would make less influence on the tunnel lining safety