Research On Array Source Transient Electromagnetic Detection Dam

In recent decades,in order to meet the needs of the peoples lives and social development for water resources,China has built a number of embankment dams,and the total number of embankment dams ranks among the top in the world.However,there are a large number of high-risk dams in China.These dams have been overloaded for many years due to their long history of disrepair and neglect of management.Leakage,piping,and ants' hidden dangers may occur at any time and threaten people at all times for the people's property and personal safety.With the development of science and technology,many scholars have studied the hidden dangers of dams and applied their methods to the detection of hidden dangers,such as high-density electrical methods,nuclear magnetic resonance methods,etc.At present,it is necessary to find a non-destructive,fast,efficient and accurate detection method to detect hidden dangers within the dam,and conduct thorough hidden investigations and engineering repairs on a large number of dams in China.Transient electromagnetic method is a fast and non-destructive detection method.It uses excitation source to excite the primary field and instantaneously shuts off to receive the secondary field.It has been widely used in mineral exploration,tunnel water inrush and mud outbreak prediction detection,goaf area.Investigation,mine water inflow,site selection for engineering survey,etc.Based on the previous researches,this paper introduces the transient electromagnetic array source into the hidden danger detection of the dam,analyzes the radiation characteristics of the array source,and simulates the hidden dangers of the array source transient electromagnetic detection dam.Production and on-site construction provide theoretical support.Array source transient electromagnetic is a "complex emission,complex reception'" exploration method."Complex emission" refers to obtaining the best secondary field response of the detected target by changing the transmission waveform loaded on the transmission source.Since the transmit waveform determines the spectral characteristics of the field,the best response of the detected target body can be obtained by shortening,lengthening the pulse width of the transmit waveform or changing the transmit waveform.Trapezoidal wave is currently the most widely used transmit waveform of transient electromagnetic method.It is known through Fourier transform that shortening the pulse width time can increase the percentage of high-frequency harmonic components in the frequency spectrum of the transmitted waveform,and the main role of low frequency components in the spectral components.It is to increase the penetration depth,and the main function of the high-frequency component is to distinguish the detection target.When the high-frequency harmonic components increase,the resolution of the detection target will be greatly enhanced,But shortening the pulse width of the transmitted waveform will result in a reduction of the emitted energy and also a reduction in the amplitude of the spectrum.By using an array source and increasing the array source size,the energy of the emitting source can be increased without increasing the emission current,and the spectrum amplitude can be increased.In order to ensure that the low-frequency harmonic components do not decrease,the high-frequency harmonic components are increased.Improve the resolution,suppress the noise and improve the signal to noise ratio.In this paper,the three-dimensional time-domain finite difference method is used to simulate the response of levees and dams.Based on previous studies,the loading method of 3D finite-difference time difference at the radiation source is modified,and the 3D finite-difference time domain simulation of the array source is realized.Simulating and comparing the magnitude of the three-field response of secondary field with different scale and current source array,it is confirmed that the array source can increase the response amplitude by enlarging the scale;The characteristics of the electromagnetic transient response of the array source and the distribution of the electromagnetic field under different depths of river water and different water resistivity conditions were simulated and compared.By simulating dam leakage,dam bottom leakage,embankment leakage and piping damage,we analyse the response characteristics and electromagnetic field distribution.Analyzes its response characteristics and electromagnetic field distribution law,It was found that the y-component of the attenuation voltage is more pronounced on the attenuation curve than the x-component of the attenuation voltage.Based on the results of three-dimensional forward modeling,the proposed array source detection of the hazard response characteristics of the dam will provide guidance and assistance for the future production of equipment and on-site construction.Comparing with the loop source,the array source has a better detection effect under the tubular leak hazard.