Abstract:The article expounds and summarizes some experience and lesson achieved in the process of multi-arch tunnel design and construction in Zhejiang Province. Traditional multi-arch tunnel adopts linear middle-wall,which consists of complicated construction steps. In general,as a V-shape rock area up,the middle-wall will be disturbed several times in construction process,and plastic deformation is so obvious as to result in collapsing. Besides,the longitudinal construction joint between the arch part and middle-wall,which always becomes the penetration passage of underground water,as well as incidentally clogging vertical drainage tube in middle-wall greatly affects waterproof performance. Due to the shortcomings mentioned above on structure mechanical and waterproof performance in traditional multi-arch tunnel with linear middle-wall,a novel multi-arch tunnel with curvilinear middle-wall is put forward. It¢s proved by numerical analysis that the new structure has much more excellent mechanical performance. As a result,the plastic deformation in the V-shape rock area up the middle-wall is controled effectively. As for waterproof performance,the second lining of the new structure is separated from the middle-wall. For the unattached second lining has no construction joint,water penetration via construction joint,which is a common quality defect in traditional multi-arch tunnel,is avoided. What is more,the new structure can simplify construction steps and shorten construction period taking advantage of mechanical operation.