Study On Characteristics And Detecting Technology Of Infrasonic Signal Produced By Rock Fracture

With constant progress of human society and further development of engineeringand construction, the geo-environment has been increasingly affected. In addition,with the extreme climate change in the globe, the geo-disasters keep occurring moreand more frequently, which has posed a great threat and caused huge loss to humanlife and possessions. Especially in recent years, several serious earthquakes, such asthe WenChuan earthquake in2008and the LuShan earthquake in2013, causedcollapse of mountains and diversion of rivers, thus further leading to deterioration ofthe current geo-environment, including frequent avalanches and debris flow. Due tothe fragility of rocks, the macro deformation of rocks is usually a temporary process.Therefore, the debris flows or avalanches are usually sudden, hidden and disastrous.The rocky avalanche is the accumulated effect of the active process of rock fracture. Itis therefore highly worthwhile to study and explore the method of detecting theaccompanying physical features of rock fracture and to obtain information of thedisastrous process for the sake of disaster monitoring and warning.Based on cross-disciplinary theories and supported by the National BasicResearch Program“973”Project“Research on Early Recognition, Precursor Obtainingand Warning Methods of Large Landslides in the Western Part of China”(No.:2013CB733200), this study has solved the key technical problems of detecting ananalyzing infra-sound, and has conducted a series of study on detecting, identifyingand analyzing the infra-sound produced during the processes of rock fracture,earthquake and avalanche. The following results are generated in this paper:(1) A digital system for detecting infra-sound had been developed, and a technicalsystem for analyzing the infra-sound information has been established. Based onthe theories of multi-disciplines including Electronics, Imbedded System andFramework, Software, and Engineering Geology, this paper demonstrates indetails the framework of developing this system and specific steps, providessupportive research equipment for indoor and field infra-sound auto-detection.Considering the characteristics of infra-sound, this paper also explains the methodof processing and analyzing the infra-sound information, develops the GUI processing and analyzing software based on MATLAB, and has successfullyanalyzed, identified and retrieved some infra-sound data detected by the digitaldetector.(2) The infra-sound produced by indoor rock fracture is detected, and thecharacteristics is studied. This paper has conducted basic experiments on six kindsof typical rock samples, and has automatically detected the phenomenon of rockfracture during uni-axial loading through digital infra-sound detector. Byprocessing, identifying and analyzing the infra-sound data, this study hasdiscovered the physical phenomenon of infra-sound emission produced by rockfracture, revealed the frequency range of infrasound, and analyzed the fixedrelationship between infrasound production and the rocky nature.(3) The infrasound produced by earthquake is detected, and its characteristics arestudied. In this study, the infrasound produced by LuShan earthquake and itsaftershocks was detected and recorded by a digital infrasound detector. This paperhas identified and retrieved the infrasound signals, studied the time range andfrequency range of the earthquake infrasound and local infrasound, and exploredthe generation mechanism of earthquake infrasound. In this study, a mathematicalrelationship model between earthquake scale and infrasound signals has beenestablished through statistical method, and finally it is proved that infrasound isproduced when the earthquake power is transmitted through the air.(4) The infrasound produced by rock avalanches is produced, and its characteristicsare examined. In this study, long-time monitoring and experimentation on thesmall-scale avalanches which occurred near Daguangbao Slide located in AnxianCounty in Sichuan Province have been conducted, and we also conductedon-the-spot observation and analysis. Our results are: First, infrasound can beproduced by avalanches. Second, the interaction (like collision, friction) betweenlarge rocks and the ground can generate infrasound signals which possess a certainfrequency range. Third, natural phenomena like thunder and wind can alsogenerate massive infrasound signals. Our study can provide some theoreticalknowledge and technical support for the monitoring and early warning ofgeo-disasters.Our study has conducted detailed exploratory research on the infrasound signalproduced by rock fracture both indoors and outdoors from the micro as well as themacro perspective. The study results show that rock fracture can generate infrasoundsignal which possess particular features. This study has laid a theoretical foundation for the development of the techniques applied to the monitoring and warning ofevolutional trend of rocky geo-disasters.