Abstract:

During tunnel construction, determining which advanced geological prediction method is most accurate and applicable under varying engineering geological conditions could be quite challenging. Single methods often lack sufficient accuracy and applicability. To address these issues, this paper introduces the principles and characteristics of advanced geological prediction technologies for long-distance tunnels using seismic wave methods and for medium- and short-distance tunnels using electromagnetic methods. We discuss the advantages and disadvantages of different advanced geological prediction methods based on their working principles, methods, and prediction ranges, and outline their most suitable scenarios. We propose a practical, comprehensive advanced geological prediction process, demonstrated through engineering examples from the Dali II section of the Central Yunnan Water Diversion Project. This process combines long-distance TSP method, medium- and short-distance TEM, and GPR to predict adverse geological features such as fault fracture zones and fissure water. Initially, we use long-distance prediction methods to classify the risk levels of geological disasters and identify high-risk sections. Subsequently, short-distance prediction methods more accurately identify and locate adverse geological features. By analyzing the geophysical response characteristics obtained from the three prediction methods, we evaluate the types and spatial distributions of adverse geological bodies. We also present a case study using GPR to detect dissolution, analyzing its wave-field characteristics to infer the physical properties, scale, and spatial distribution of dissolution features. The prediction results align closely with findings from tunnel excavation, validating the reliability of the three advanced geological prediction methods and confirming the practicality of the proposed comprehensive prediction process. This approach provides valuable guidance for geophysical exploration, enhancing the accuracy of geological predictions and ensuring tunnel construction safety.

Key words: advanced geological prediction, Tunnel Seismic Prediction(TSP), Ground-penetrating radar(GPR), Transient Electromagnetic Method(TEM), adverse geological body