STUDY ON THE METHOD OF SURROUNDING ROCK RAPID CLASSIFICATION DURING CONSTRUCTION PERIOD OF MOUNTAIN TUNNEL

The rapid classification of surrounding rock during construction period is an important task of "dynamic design and dynamic construction" of mountain tunnels. Based on the long-term geological cooperation of a highway tunnel construction in Beijing, we have selected the rock strength, the number of joints, the structural plane state, the relationship between the dominant structural plane and the tunnel axis, and the groundwater as the surrounding rock quality grading index, and studied the rapid acquisition methods of each grading index, and then established a table scoring method that combines qualitative and quantitative grading indicators. The TRT advanced geological prediction system can better reflect the geological conditions in front of the tunnel face. And we have systematically summarized cluster anomalies, single anomalies, fault anomalies, and interbed anomalies in the TRT forecasting system. The authors proposed a dynamic fast grading method for surrounding rock during construction period, which is combining table scoring method with TRT advanced geological prediction. This method can predict the "invisible" geological information in front of the tunnel face based on the "visible" geological information of the excavated tunnel face. And this method has strong operability and high coincidence rate with actual geological conditions and has important guiding significance for tunnel construction.