The Numerical Simulation Research Of Wave Field Characteristics Of Typical Poor Geological In Tunnel Seismic Prediction(TSP)

In recent years, our country’s domestic infrastructure development has made significant achievements in the background of sustainable economic development.The number of tunnel projects in the construction of high-speed railway and highway increased significantly compared to the previous, and the tunnel length is increased significantly too.Tunnel project is underground construction, the geological conditions of surrounding rock are often very complex. For example, weak stratum, Karst, high stress, faults are frequently encountered during the construction of tunnel. If there is no reliable geological prediction, these potential geological hazards may become a disaster. In the early1990s, the Swiss Amberg Measuring Technology Co., Ltd. had developed a set of forecasting equipment-TSP (Tunnel Seismic Prediction).This equipment is based on seismic reflection and has features of far detection distance (up to front of Face100-200m), high resolution, fast data interpretation and little impact on construction. However, there are still some difficult in the TSP data interpretation because the complex tunnel seismic wave field,which is caused by the actual complex geological and engineering conditions. In addition, in the detection of complex non-layered geologic targets,karst, for example, the forecasting accuracy rate of TSP usually decreased because these targets do not meet the condition of layered reflection which is the basis of TSP system.Therefore, the research and cognition of tunnel seismic wave field characteristics under typical adverse geological conditions can provide a theoretical basis for TSP data processing and interpretation. In addition, it have important scientific significance for the promotion of tunnel prediction theories and methods.This paper have studied finite-element modeling of elastic wave field and used ANSYS software to simulate the Tunnel Seismic Prediction (TSP)2D seismic wave field.20tunnel numerical models under different geological situations (8model are fault fracture zone in front of the tunnel, the remaining12are tunnel hole in front of the tunnel) have be established to provide Seismic data. These data will be processed in several steps such as format Conversion, frequency filtering, FK filtering, τp transform. Then we can use these processed data to research and understand Tunnel Seismic wave field characteristics under typical adverse geological conditions, to provide a solid theoretical foundation for the TSP tunnel prediction data processing and interpretation, to promote the theory and methods of Tunnel Seismic Prediction.The main conclusions are the following:When there is a fault in front of the tunnel and the fault is perpendicular to the tunnel axis, the imaging position is accuracy. And when the fault is tilted, we have to do migration imaging, In the tilted fault model, there are some reflected wave whose apparent velocity is Much larger than the direct wave.For the cavity in front of the tunnel, the greater of the cavity,the stronger of the reflected wave. Besides, we can effectively distinguish the air, water and soft soil filled in the cavity based on the strength of P-wave, s-wave reflected wave.If the type of the bad geological in front of the tunnel is unknown, we can use the characteristics of s-wave reflection to identify cavity filled with water or air.