Analysis And Prediction Of Surface Settlement In Southern Railway Tunnel Construction

The allowable settlement of bridges,tunnels and other structures is strictly limited to a certain range due to the need of railway line type for safe operation.Especially when tunneling is carried out in geological areas with high surrounding rock grade and poor stability,it is often necessary to evaluate the safety and stability of tunnels during construction by observing the settlement of surface and tunnel vault,stress development of surrounding rock steel arch frame and lining.In this paper,the influencing factors of surface settlement during tunneling construction of a tunnel in southern China are discussed.Based on the engineering practice of tunneling construction,the neural network system and grey relational analysis model for prediction of surface settlement are established.By comparing the prediction results of the two models,it is concluded that the neural network analysis model can comprehensively reflect the joint influence of multiple parameters on the surface subsidence value,and the prediction results are relatively safe and have higher application prospects.In order to explore the possibility of surface settlement prediction during the construction of railway tunnels in mountain areas,a calculation model for the excavation and lining of mountain tunnels is established in ANSYS large-scale finite element calculation platform,and a neural network analysis model and a grey relational analysis model for the prediction of surface settlement during theconstruction are established according to the actual tunnel engineering.By analyzing the results of FEM calculation and settlement prediction,the stress distribution of surrounding rock and the development of surface and vault settlement during tunnel construction are explored,and the safety and reliability of NATM tunneling in mountain area are comprehensively evaluated.The analysis results show that the accuracy of using neural network system to predict the development of vault and ground settlement during tunnel excavation is similar to the measured value.It has the ability of settlement early warning in practical engineering,which provides a reliable guarantee for the safe tunneling construction of tunnel structure.