A Study On The Acoustic Landmine Detection Model Based On Acousto-seismic Coupling

In recent years, the proliferation of landmines in many regions of the globe leads to thousands of civilian casualties every year and has focused worldwide attention on humanitarian landmine detection. Plastic and other nonmetallic mines have been developed, and used on a global scale. Because of the small contrasts in electrical properties between soil and nonmetallic mines, the most widely used handheld metal detectors and ground-penetrating radars are not always effective. In contrast, the mechanical properties of plastic and metal mines vary significantly from those of the soil, which may make acoustic excitation a more reliable mechanism to detect mines.Acoustic-to-seismic (A/S) coupling techniques are currently being studied and have shown promise as a method of detecting mines made of different materials buried in a variety of soils. However, some of these approaches are still being investigated under laboratory conditions, due to the complexity of mine field terrain, the diversity of mine style, big bulkiness and high cost of the system. As far as we know, there are few reports published about landmine detection by means of acoustic methods in China. The aim of this thesis is to study acoustic mine detection technologies and develop their fundamental theory on the basis of relevant publications and our own creative achievements. Besides, a lab-scale experimental system has been designed. The main work done and the innovation points of this thesis are as follows.(1) The acoustic theory and the basic mechanism of A/S coupling are reviewed and analyzed.Acoustic mine detection method belongs to acoustic applications. It relies on many acoustic concepts, terms and principles. It is the porous nature of the ground that plays an important role for A/S coupling to be used successfully in the detection of buried land mines. The penetrating sound waves generate a series of seismic waves within the soil, which may mechanically interact with buried mines.(2) The resonance mechanism of soil-mine system is studied.Frequency response transfer function is used to solve the soil-mine resonance system model. Furthermore, modal analysis theory is adopted to study the function in depth. It is shown that the soil-mine vibration system may display resonance and anti-resonance mechanisms.(3) A lab-scale experimental system for acoustic landmine detection has been built.A loudspeaker and geophone based lab-scale experimental system is presented. The software development platform of Labview is used to realize data acquisition, analysis and processing. The experimental data show that the mines can result in distinct changes to the acoustically coupled ground motion, which is consistent with the theory analysis.(4) The numerical simulation technology for investigating acoustic mine detection is presented.The acoustic landmine detection method relates to a few subjects such as acoustics, geology, electromagnetism and many others. The surroundings around the hardware detection system are very complex. The latest multi-physics modeling technology is brought forward to deal with those complex parameters.(5) Average algorithm curve-fitting method is studied to process acoustic mine detection signals. The thesis ends with suggestions for some further work.