By summing up the field monitoring during tunnel construction of some highways in Henan Province of China, the monitoring data combine with finite element model are employed to analyze the predisplacement of the surrounding rock during the tunneling. The formula for calculating the pre-displacement of the surrounding rock is obtained from the elastic mechanics and integral creep model. Numerical results indicate that the pre-displacement appear at 1~1.5D away from the tunnel face in the beginning, and turn to a stable state at 2~3D away from the tunnel face; the pre-displacement of the surrounding rock accounting for 30% of the total displacement. Thereby, sufficient attention must be paid to the pre-displacement of the surrounding rock in design and construction of the tunnel.
Along with the development of national economy and the pace of highway construction, the quantities of the highway tunnels are increasing. The stability and deformation of tunnel become prominent issues in engineering construction. Field monitoring is an important part of NATM principles, however, the monitoring data of the surrounding rock of the tunnel are gotten after the tunnel face cross.[1] In fact, the deformation is generate long away before tunnel face, and these pre-deformation have an important impact on the stability of the tunnel construction.
Non-linear numerical methods have become a key tool in modeling geotechnical or transportation engineering for the analysis of stresses and deformations in the structures such as tunnel, highway, slopes and foundations. Based on observations, pre-displacement and total displacement behavior models can be constructed. The models can be either analytical or numerical. The numerical model leads to correct answers within the framework of axioms underlying the mathematics. Vlachopoulos and Diederichs use a series of numerical analyses to develop a newseries of functions defining robust longitudinal displacement profiles, as a function of maximum normalized plastic radius.
A reasonable numerical model and 3D finite element model for the tunnel should be used to calculate the pre-displacement and total displacement of the tunnel, which results in non-linear behavior. In this paper, a new approach to modeling pre-displacement in tunnel is reported.
