Research On Directional Seismic Wave Formation Method And Wave Field Simulation For Tunnel Reflection Interface

The rapid development of transportation industry is inseparable from the construction of tunnels.In order to avoid or reduce the occurrence of geological disasters in tunnel construction,it is necessary to detect the reflection interface in front of the tunnel face in advance,so as to take corresponding measures in advance to prevent the occurrence in advance.In advance geological forecast method of tunnel,based on the reflection seismic exploration method of "Tunnel Seismic Prediction(Tunnel Seismic Prediction,TSP)" has been more widely used,the technology can detect the front for the majority of strata within 100 m of geology,and it has the advantages of relatively simple data collection,little impact on tunneling work and low cost.However,the traditional TSP method has disadvantages such as strong interference noise and energy cannot be concentrated in the direction of the working face,which makes it powerless in the increasing demand of tunnel detection and the increasingly strict requirement of detection accuracy.According to the above problem,this thesis uses directional seismic wave method to study on the wave field simulation,the main work of this thesis has the following 3 points:(1)The 3-dimensional tunnel geological model was constructed,in which the selection of model boundary conditions was strictly designed based on the theory of the perfectly matching layer,and the model was reasonably divided based on the finite element method,so that the model was closer to the actual situation and the numerical simulation results were more accurate;(2)Using the directional seismic wave method to carry out the wave field simulation of tunnel advanced geological prediction,concluded that the directional seismic wave method can not only enhance the energy intensity of the signal in the direction of the hand face,but also reduce the clutter interference.The effectiveness of the directional seismic wave method is proved by statistical method.The signal strength can be increased by about 35.4%;(3)The tunnel model with reflection interface is studied specifically,and the influence of interface angle,distance and curvature is mainly discussed.The directional seismic wave method can complete the prediction,but the prediction effect will be weakened with the decrease of angle.In order to improve the accuracy of prediction,the multibeam-forming directional seismic wave method is proposed for the situation that the interface angle is small.The signal strength can be increased by about 43.3%.Above all,this thesis constructed a 3-dimensional tunnel geological model,with numerical calculation,to verify the effectiveness of the model and method,explores the interface angle,distance,curvature on the detecting effect,especially for small angle of the interface,the multibeam-forming directional seismic wave method is proposed to be used for prediction,which puts forward the feasibility of solving the problem of reflection interface exploration in the tunnel from a theoretical perspective to a certain extent.It has a certain scientific significance and practical application value,and provides a theoretical basis for further research on the advanced geological prediction technology of the tunnel with the directional seismic wave method.