The Parameter Back-analysis Of Surrounding Rocks And Dynamic Simulation Of The Construction Of Leimao Mountain Tunnel

The parameter of rocks surrounding the tunnel is one of the important parameters on highway tunnel construction, an important basis for tunnel design and construction as well. How to define the parameter of rocks and constitutive model has been one of the focuses of Geotechnical Engineers’study. With the popularity of NATM, the dynamic feedback of information has garnered particular attention. Therefore, it is bound to be necessary and deserving to study the back analysis of geotechnical field parameters of Leimao Mountain tunnel, and its dynamic simulation of construction to achieve information feedback.Using field investigation, monitoring and measurement, theoretical analysis and numerical simulation methods, this paper analyzed and studied Leimao Mountain tunnel project of Guangxi Qinzhou to Chongzuo highway. Based on MATLAB NNTool and the actual measured data of Leimao Mountain tunnel, this research adopted BP neural network model and FLAC3D numerical simulation together, establishing training samples and testing samples by orthogonal design method and uniform design method. Through studying and training these samples, this paper established a nonlinear mapping relationship of the parameters of tunnel surrounding rocks, tunnel level convergence displacement and headroom convergence displacement.With the established nonlinear mapping relationship and back analysis for elastic modulus and lateral pressure coefficient of two parameters of Leimao Mountain tunnel, we can calculate that the elastic modulus is9.73GPa and the lateral pressure coefficient is0.42. Conducting the analog simulation, we can find that simulation results meet the accuracy requirements of this project. With the three-dimensional model of Leimao Mountain tunnel based on FLAC3D, this paper simulated the dynamic excavation, predicted rock displacement of the unexcavated section, and reach a conclusion that the influence distance between excavations section and heading that is2D～3D.(D is the span of excavation section)The research about back-analysis of this paper has significant technical and economic benefits for tunnel construction, design and monitoring, providing suggested values and feedback information on the design, construction and monitoring of the follow-up tunnel excavation for similar tunnel projects.