Detection Of Shallow Buried Objects Research Articles

Математическая модель электродинамического сейсмоприёмника

Electrodynamic geophones are applied in seismic prospecting, seismology and security systems. Devices with a similar design can be used as a generator in devices for energy storage, in active vibration control systems, and for detection of shallow-buried objects, including mines. To control the quality of geophones and verify the constancy of their characteristics during the manufacture, it is necessary to measure their frequency response on a shake table. The mathematical model of the geophone developed by JSC Scientific Research Engineering Institute (Balashikha, Moscow region) installed on a shake table is considered. The geophone schematic design is given, and the sequence of its operation is described. The approach of dividing an electromechanical system into several subsystems with subsequently uniting them into a resulting model is used for developing the geophone overall mathematical model. Detailed descriptions of the electrical, magnetic, and mechanical subsystems are presented. The assumptions used in compiling the overall mathematical model describing the geophone operation on the shake table are listed. A system of equations describing the interaction of the subsystems is compiled. Detailed descriptions of the resulting mathematical model, each of its element, and the interface included in its composition are presented. To estimate the developed mathematical model, the results obtained from the calculations on it are compared with the results from testing two experimental samples in the geophone operating frequency band from 10 to 100 Hz. For better clarity, the obtained results are compared in graphical form. The comparison has shown that the discrepancy between the results does not exceed 5% by the output signal amplitude. From the viewpoint of practical implementation, the developed mathematical model can be used in designing new geophones with other parameters, for example, with another natural frequency, or with a higher value of the output signal. It can also be used to develop more complex mathematical models containing a geophone. The accomplished study became a basis for elaborating a more complex mathematical model of a geophone with two natural frequencies in the operating band.

Acoustoseismic Method for Buried-Object Detection by Means of Surface-Acceleration Measurements and Audio Facilities

An experimental setup for acoustoseismic detection of shallow buried objects is presented. The seismic (Rayleigh) waves were generated by exciting an acoustic airborne source by a series of sine-wave bursts, which were designed to cover a frequency range (100-1000 Hz) large enough to distinguish the vibrational characteristics of buried compliant objects. The signals were recorded by means of contact-acceleration microelectromechanical-system sensors moved above different buried objects (compliant and rigid). Signal acquisitions on only sandy soil revealed the natural variability of the outdoor test bed. This variability of soil parameters pointed out the difficulties of buried-object detection based on the amplitude thresholding of the signal spectrum. For this aim, the signals were processed in both time and frequency domains. An audio-channel output was devised to avail of the human hearing apparatus in distinguishing the buried objects according to spatial variations of the acceleration signals obtained by scanning the soil surface.

A method for the detection of shallow buried objects

Numerous geophysical techniques have successfully contributed to geotechnical engineering and environmental problems of the shallow subsurface. Geophysical surveys are used to: delineate geologic features, measure in-situ engineering properties, and detect hidden cultural features. Most technologies for the detection of shallow buried objects are electromagnetic methods which measure the contrast in ferrous content, electrical conductivity, or dielectric constant between the object and surrounding soil. Seismic technologies measure the contrast in mechanical properties of the subsurface, however, scaled down versions of conventional seismic methods are not suitable for the detection shallow buried objects. In this paper, we discuss the development of a method based on acoustic to seismic coupling for the detection of shallow buried object. Surface vibrations induced by an impinging acoustic wave from a loudspeaker is referred to as acoustic to seismic coupling. These vibrations can be remotely detected using a laser-Doppler vibrometer (LDV). If an object is present below the surface of the insonified patch, the transmitted wave is back scattered by the target towards the surface. For targets very close to the surface, the scattered field produces anomalous ground vibrational velocities that are indicative of the shape and size of the target.

Detection of shallow inclusions in closed-packed granular beds using mechanical impulses

Mechanical energy has been used in the detection of shallow buried objects in granular beds for more than half a century. Here we attempt to answer a fundamental question—at what depths would an object be detectable in an idealized, close-packed, granular bed made of monosized elastic spheres? Systematic particle dynamics based studies reveal the effects of varying the area across which the impulse is generated, object size, and restitution on locating the buried object.