| Tunnel construction in muddy strata can easily cause instability of the face and excessive settlement of the ground surface.There is no criterion to support the support method and support parameters for the shallow VI tunnel with silt grade.Based on the tunnel project of Fuzhou Lake East East Road,the finite element method is used to study the influence of different support modes and parameters on the deformation of tunnel excavation.Through numerical orthogonal test,the sensitivity of various factors to tunnel excavation is analyzed,and the deformation and stress law of the tunnel are tested and analyzed,and the analytical design and dynamic monitoring are carried out.Combined with analytical design and dynamic monitoring method,the early warning value of deformation of muddy tunnel is given,and hopes to accumulate experience for analogy design of shallow buried tunnel in muddy city.(1)based on the East Hudong Road Tunnel project,the numerical analysis model is established.The influence factors of the diameter of the pipe shed,the circumferential distance between the pipe shed and the surface of the surface rotary jet pile are selected as the influencing factors.In the case of single factor,the influence of different levels on the safety of the tunnel construction is analyzed.(2)the "CRD+ pipe shed + surface swirling spray" is taken as the analysis object,and the orthogonal test principle is adopted to analyze the sensitivity of three factors,the diameter of pipe shed,the distance of the circumferential direction and the diameter of the surface of the surface rotary jet pile,by using the orthogonal test principle.The results show that the diameter of the pipe shed > circumferential distance > the diameter of the surface rotary jet pile,the diameter of the pipe shed and the distance between the circumferential direction have a significant influence on the influence of the tunnel excavation,and the influence of the surface rotary jet pile diameter on the tunnel excavation is in general influence level.(3)a more systematic field test is carried out on the strengthening measures of "CRD+ large pipe shed + surface rotary jet".The results show that the closer the vertical displacement of the surface is,the greater the displacement is.With the advance of the mileage pile number,the settlement and convergence of the vault settlement will increase with the increasing of the mileage pile number.And the final settlement exceeds the reserved deformation,which results in the initial invasion limit.The pressure values between surrounding rock and initial support are distributed asymmetrically around the tunnel,which is considered to be related to the distribution of surrounding rock on both sides of the excavation face.(4)based on the two dimensional calculation model and field test,the recommended value of deformation warning value of shallow buried tunnel in silt grade VI surrounding rock is recommended. |
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