Time-frequency Analysis Based On MATLAB Geological Radar Data Interpretation

With the rapid development of China's transportation infrastructure,it is very common to build tunnels in karst development areas.The geological conditions in the karst area are extremely complicated.It is easy to encounter bad geological bodies such as caves,faults and fracture zones during the construction process,causing geological disasters such as water inrush(sludge)and collapse,seriously endangering the safety of construction workers and restricting tunnel construction.schedule.Therefore,advanced geological prediction during tunnel excavation is an important and indispensable task,and geological radar method is currently the most accurate and widely used method for short-distance forecasting.However,in terms of data interpretation analysis,the way in which Chinese interpreters acquire geological information depends on amplitude information,and the accuracy of forecasting does not meet the actual engineering needs.Relying on the 14 tunnels under construction in the Dongda Expressway in Guizhou Province(ie Bijiehuan Expressway),based on the powerful numerical processing of MATLAB software to analyze the mapping function,the data structure of the US SIR geological radar is analyzed,and the S-transformation time-frequency analysis method is used.In the geological radar data analysis,according to the time-frequency variation characteristics of single medium and typical bad geological body,a new method of radar data interpretation and real-time analysis interpretation method is proposed.The specific content includes:1)Analyze the data structure of SIR geological radar,and supplement the parsing of the variable part in the data header.It is found that this part mainly contains information such as time zero,gain setting,filtering setting and post-processing.The data collected by the SIR-4000 host is different from the old SIR host data,which is mainly reflected in the starting position of the data block and the difference in the number of data bits.As a result,the data block of the SIR-4000 data needs to be interpreted using long characters.2)Using MATLAB software to read the radar data of SIR-4000 and SIR old models,and successfully generate single wave map,waveform stacking map,energy map and Fourier transform spectrum map,and expand the geological radar dataprocessing method.The S-transform time-frequency analysis method is used in radar data analysis,and a time-frequency map and a maximum specific gravity frequency change map for time-frequency analysis of geological radar data are generated.3)Exploring the effect of gain and filtering on data frequency information.Using the Fourier transform global spectrum analysis and time-frequency analysis to view the frequency domain information respectively,it is found that the gain has an effect on the overall frequency analysis,which also indicates that the Fourier transform quantitative analysis without considering the gain is not rigorous;At the moment of frequency analysis,the maximum specific frequency value has almost no influence.If the maximum specific frequency value is used for data interpretation,the influence of gain can be avoided.The selection of the filtering method has no effect on the overall frequency analysis and time-frequency analysis.4)Time-frequency analysis of single medium and typical bad geological geological radar data,and obtain time-frequency variation characteristics of single medium and typical bad geological geological radar data.The geologic radar data of rock,water and air have a maximum specific gravity ridge on the time-frequency diagram.The time-frequency diagram of the soil medium has poor stability over the entire time domain,and there is no maximum specific gravity.Parallel ridges.For the typical bad geological body geological radar data also has its various time-frequency variation characteristics,mainly in the parallel time axis maximum proportion of the ridge value and its duration.5)Based on the time-frequency variation characteristics of single medium and typical bad geological bodies,the time-frequency interpretation method of geological radar data is proposed as a new method for interpretation of geological radar data.And applied to the actual project,the effect is good.Compared with the conventional analysis,since it does not depend on the amplitude information,it has certain advantages in analyzing data with unsatisfactory acquisition results.To some extent,the professional requirements of the collectors are reduced,which is conducive to the improvement of the accuracy of geological radar prediction.