Piecewise nonlinear fitting method of tunnel surrounding rock displacement and its application

The displacement prediction of tunnel surrounding rock is an important part in New Austrian Tunnel Method, which is the safety measure during construction and also an important means of reducing material consumption. In recent years, with the construction of road tunnel and railway tunnel developing fast, the large section tunnel projects increase day by day, and the divisional tunneling is constantly applied to the tunnel engineering. The piecewise nonlinear fitting method of surrounding rock displacement is put forward on the basis of the deformation law of surrounding rock of large section tunnel. The study shows that the deformation time-history curves of surrounding rock of the divisional excavation are stepped up and the fitting precision of traditional one function fitting method is lower, the regression curves can´t fully reflect the development trend of the data. So the piecewise nonlinear fitting function is created in this paper. Through the application, the prediction accuracy and correlation coefficient is proved higher by using piecewise nonlinear fitting function for surrounding rock displacement prediction, this method can more accurately predict the final value of the deformation of tunnel surrounding rock.