| With the rapid development of traffic and hydropower engineering, more and more tunnels which are longer and huger will be built. Complex geological problems will be encountered at the tunnel zone. To forecast the geological condition ahead the face with geophysical methods has great significance of reducing accidents during construction and securing the workers from harm. Among these geophysical methods, the Ground Penetrating Radar (GPR) and Tunnel Seismic Prediction System (TSP) are promising methods. GPR prevailed with its simple operation, high resolution, high effective shield, intuitive graph and little interrupt of tunnel construction. The Tunnel Seismic Prediction System (TSP) prevailed with its extensive application, long forecast distance and still, little interrupts of tunnel construction. However, the present elucidative measure lacks uniform criterion and the engineers identify the graph information only by their experience, which affects the forecast accuracy. Therefore, to research the usage of GPR and TSP in tunnel forecast and summarize the universal criterion of elucidative measure are in favor of decreasing the elucidative time of forecast conclusion and increasing the precision.This paper is based on the collection of the research fruits from domestic and international forthgoers on the application and data explanation of GPR and TSP as well as the analysis of forecast results with GPR at Tongluoshan tunnel, Xinzhagou tunnel and Caluo No.2 tunnel, and with TSP at Tongluoshan tunnel, Caluo No.2 tunnel and Pusagang tunnel. The forecast results hav??en contrasted to the geological analysis, the fore drilling bore and real geological condition after excavation, then the graph characters of typical geological problem are abstracted. Numerical simulation of GPR at tunnel forecast has been done by Finite-Difference-Time-Domain which brings the response characteristics of different kinds of geological problems. At last, the rules of the elucidative graph have been summarized and elucidative measure criterions have been obtained. These are conclusions from study as follows:1. Standard usage of GPR which includes geological preparative, disposal of survey lines, parameters setting and attentive problems at tunnel forecast has been summarized by the practical application in Tongluoshan tunnel, Xinzhagou tunnel and Caluo No.2 tunnel. The contrast between forecast results and the real geological condition after excavation proved the forecast effect which shows GPR is suit for tunnel forecast. The response characteristics of fracture zone, water bearing crack and goaf have been gained.2. The propagation of electromagnetic wave was numerical simulated by FDTD method. The geoelectric models with appropriate parameters of integral surrounding rock, fault which consists of conditions with different angle to tunnel and diverse width, empty cave and water cave with different size have been built. The graphs of GPR reflective wave were gained and the response characteristics of these four geological conditions with different types were explored.3. Synthesize numerical simulation results and the successful forecasting examples. Then the elucidative methods of GPR applied in tunnel geological problem forecast were summarized and the elucidative criterions of integral rock, fault and fracture zone, corrosional crack zone, empty cave, water cave and half-filling??e have been explored through the rules of the wave amplitude and phase, the shape of wave, the frequency characters and the changes of transit time.4. The results of forecast graph at Tongluoshan tunnel, Caluo No.2 tunnel and Pusagang tunnel by TSP were collected and the real geological conditions after excavation were recorded in detail. To analyze forecast results by the geological record, typical elucidative graph have been abstracted. Finally, with the elastical wave theory and former analysis, elucidative criterions of TSP have been found.
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