Study On Deformation Law Of Surrounding Rock In The Double-Arch Tunnel

The construction of highway in China is in a fast development period recently. Because of being limited by topographical and geological condition, a lot of double-arch tunnels are elected to pass through the mountains in the Mid-west. The stability of double-arch tunnel is a hotspot issue now because of its big span and complicated structure. Especially the law and allowable range of surrounding rock displacement remain to be studied deeply on.This paper adopts experiments simulated by equivalent materials, field monitoring measurement and finite element analysis method to study on deformation law of horizontal displacement and subsidence at top of double-arch tunnel caused by excavating. Some predicting models and calculating formulas on the displacement of surrounding rock are obtained, and then applied to design and construct projects, keep safe, monitor deformation, administer construction of similar double-arch tunnel and direct practical engineering.Though similar material imitating experiment, field monitoring measurement and finite element numerical analysis, the law of deformation of surrounding rock is got. With equal tunnel width, the type of surrounding rock is the important factoy changing deformation. Distancement in typeâ…¡rock is much more than typeâ…¢rock; different methods of tunnel construction make values and distribution of displacement differently. The displacement caused by middle-pilot method construction is less while the displacement caused by three-pilot method is more; the biggest radial displacement is at the top of arch in construction process, next came at the waist and the sidewall, the smallest is at the middlewall. Therefore, the monitoring and prevention of displacement at the top of arch should be strengthened in the construction.Based on the numerical analysis and statistical analysis through massive monitor data of double-arch tunnel and the laboratory test data, and combined with finite element theory dynamic analysis, the critical deformation values of the arch top subsidence and horizontal displacement are obtained under the typeâ…¡and typeâ…¢surrounding rock condition. At the same time, the displacement forecast is carried on to the similar tunnel construction process and obtains good results.The similar material imitating experiment has successfully simulated the changing displacement which caused by methods of three-pilot holes, double-pilot hole and middle-hole excavation in the typeâ…¡and typeâ…¢surrounding rock. The sizes and distribution rules of displacement are compared and conclusion is obtained: the method of middle-hole construction is simple and the surrounding rock displacement caused by it is small, therefore it is a kind of new method which is worth recommending. Thus a new method is added for construction of double-arch tunnel in the type II surrounding rock.According to the analysis of finite element method and to data of deformation monitoring measure, four concentration areas of deformation appear in the construction of double-arch tunnel ,which are at bottom of side-wall, at bottom of middle-wall, at top of middle-wall and at side of side-wall of two holes. The rock deformation is important for stability of double-arch tunnel, so the monitoring, measurement and adopts steps of it must be strenthened to control deformation of surrounding rock.This paper desigs and develops Bi-Tunnel Deformation Monitor Computer System(BTDMCS) which has been applied actually in some bi-tunnel engineering to monitor deformation. Dynamic predicting managment is carried out. The correctness and serviceability of the soft are tested and verified.