Study On Comprehensive Advanced Geological Prediction Method For Underground Caverns Under Complex Geological Conditions

With the continuous development and utilization of mineral resources in China,the construction of underground chambers such as traffic tunnels,hydraulic tunnels and mine roadways is also accelerating.Geological disasters occur from time to time,which not only affects the progress of construction,but also causes casualties.Therefore,in the process of underground chamber construction,it is necessary to carry out advanced geological prediction and Prevention Research on the geological hazards that may occur during excavation.In this paper,the tunnel of Meng-hua section of North-South Coal Transport is taken as the research object.The unknown geological conditions in front of the tunnel during excavation are decomposed by EMD using ground penetrating radar data.At the same time,combined with TST and transient electromagnetic method,the comprehensive advanced geological prediction has achieved good results.The main research work is as follows:(1)On the basis of summarizing the research status of advanced geological prediction methods for underground chambers at home and abroad,the advantages and limitations of several commonly used advanced geological prediction methods are evaluated.Aiming at the low accuracy of single advance geological prediction method for underground caverns,based on the theory of underground cavern system and the idea of weighted integration,the advantages of TST,TEM and GPR are weighted and integrated to form a comprehensive advanced geological recognition model,which combines long-medium-short distance with space-plane-line mutual verification.(2)In order to solve the problem that the detection results are susceptible to other noise interference in underground caverns when the ground penetrating radar is used for advanced detection.Based on the data processing of the instrument’s own software,the application of EMD decomposition to optimize the denoising of the original GPR data signal is proposed.The results show that EMD decomposition can separate the noise contained in the original GPR signal from high frequency to low frequency in turn,and has the effect of filtering and noise reduction.(3)Aiming at the subjectivity and multi-solution of interpretation of geophysical detection results of geological hazards,the analytic hierarchy process(AHP)is introduced.Taking the prediction of faults by three detection methods as an example,the specific process of determining the weight of each method in the comprehensive advanced geological prediction system by using the analytic hierarchy process(AHP)is given.(4)Taking a tunnel in Meng-hua section of coal transportation from north to South as an example,the above comprehensive advanced geological prediction method is applied to detect the geological conditions in front of the work.Firstly,EMD decomposition is applied to optimize the filtering and noise reduction of GPR signals,and the results are compared with those of software processing.Then,combined with the geological structure image of rock mass and wave velocity image of rock mass given by TST,the apparent resistivity profile of rock mass given by TEM are comprehensively analyzed.Finally,the advanced geology in the comprehensive advanced geological prediction system is determined by analytic hierarchy process.The weight of the forecasting method is analyzed statistically for the comprehensive forecasting results of multiple mileage sections.The results show that the comprehensive advanced geological prediction results are basically consistent with the actual excavation situation,and the accuracy of the prediction results is obviously better than that of the single advanced geological prediction method.