The middle wall of an expressway multi-arch tunnel is calculated by using finite element numerical method aiming at its strength deficiency. The result indicates that the safety factors of the middle wall cannot satisfy Code’s requirements. The treatment projects of chiseling away the middle wall partly and wholly are researched; the result indicates that when the middle wall is repaired by the chiseling away partly method

the treatment of middle wall will have a small impact on the preliminary lining; the inner force of the original middle wall will increase slightly which exerts a small effect on the whole tunnel structure. However

when the middle wall is repaired by the chiseling away wholly method

the treatment of middle wall will have a marked impact on the preliminary lining. The study on the length of construction indicates that when the once length equals respectively to 12 m and 9 m on the three and four grade rock mass is reasonable. The safety of the repaired multi-arch tunnel middle wall can satisfy the Code’s requirements.