地电阻率交流观测系统关键技术研究

发布时间：2018-06-27 02:40

本文选题：地电阻率 + 交流观测方法　；参考：《中国地震局地壳应力研究所》2015年硕士论文

【摘要】：针对目前地震地电阻率直流观测中面临的地铁、轻轨等电磁干扰问题,开展地电阻率交流观测方法的研究。重点对地电阻率交流观测中涉及到的关键技术问题进行了研究,总结了地电阻率交流观测方法中的信号检测方法和地电阻率交流观测系统的关键技术指标要求。地电阻率交流观测方法基于电法勘探和地电阻率直流观测的理论基础,由于交流信号频率在10-3Hz-103Hz时,可以近似认为其仍然遵循欧姆定律,这时的低频交流电场为似稳电场。因此地电阻率交流观测方法在此频段范围内可以采用与直流观测相同的理论基础。首先,对地电阻率交流观测的实际工作过程进行了数值模拟,用单一频率的正弦信号作为供电信号,高斯信号作为噪声信号,接收装置在测量极得到的输入信号为二者的叠加信号。常用的信号检测方法有带通滤波器法、相关检测法和频谱分析法,利用数值方法模拟三种方法在不同信噪比、采样率和采样时间条件下三种信号检测方法对输入信号的检测精度。通过对比分析检测结果,并结合三种方法在实际系统中实现的难易程度,给出了对叠加高斯白噪声的己知频率正弦信号进行信号检测的最适宜的方法——频谱分析法。其次,使用多通道数据采集器对北京西集台、天津青光台、辽宁新城子台和江苏江宁台四个受地铁干扰严重的台站的场地环境进行24小时左右的测试,通过对测试数据的时、频域特征分析,总结了地铁干扰信号的特征：地铁干扰信号的周期主要在120s-180s范围内；干扰信号幅度在10mV～30mV左右,特别严重的可以达到90mV左右；由于地铁干扰引起的地电阻率测量时的信噪比下降约20-30dB。第三,根据地铁干扰的特征分析,使用频谱分析法作为信号检测方法以地铁干扰信号作为噪声信号,仿真地电阻率交流观测方法的信号检测结果。结果显示,供电信号频率在0.5Hz以上,当信噪比为0dB,采样时间满足400s时,或信噪比为10dB,采样时间满足200s时,得到的相对误差能够满足地电阻率观测规范的要求。由此,验证了地电阻率交流观测方法的可行性。最后,在上述研究的基础上,给出了地电阻率交流观测系统的主要技术指标要求。以期能够为地电阻率交流观测系统的研制提供理论参考和技术依据。
[Abstract]:In view of the problems of subway, light rail and other electromagnetic interference in the current observation of seismic ground resistivity, the study of the method of earth resistivity AC observation is carried out. The key technical problems involved in the earth resistivity exchange observation are studied, and the signal detection method and the ground resistivity intersection method are summarized. The key technical index of the flow observation system requires that the ground resistivity exchange observation method is based on the theoretical basis of the electric exploration and the direct current observation of the earth resistivity. Because the frequency of the AC signal is at 10-3Hz-103Hz, it can be considered that it still follows the Ohm law, and the low frequency alternating current field is a quasi stable electric field. In the range of this frequency band, we can use the same theoretical basis as the direct current observation. First, the actual working process of the earth resistivity AC observation is numerically simulated. The sinusoidal signal of a single frequency is used as the power supply signal, the Gauss signal is used as the noise signal and the receiving device has the superimposed signal of the input signal of two. The common signal detection methods include bandpass filter, correlation detection and spectrum analysis, and use numerical methods to simulate the detection accuracy of the three methods on the input signals of three signal detection methods under different signal to noise ratio, sampling rate and sampling time. By comparing and analyzing the test results, and combining the three methods in the actual system, the results are compared and analyzed. The most suitable method for signal detection of the known frequency sinusoidal signal superimposed on Gauss white noise is given. Secondly, four stations of Beijing West set platform, Tianjin green platform, Liaoning Xincheng sub platform and Jiangsu Jiangning platform are used to use multi channel data collector. After 24 hours of testing, the characteristics of the subway interference signal are summarized through the analysis of the test data and frequency domain characteristics: the cycle of the subway interference signal is mainly in the range of 120s-180s; the amplitude of the interference signal is about 10mV to 30mV, and it can reach about 90mV. The signal to noise ratio of the quantity is reduced by about 20-30dB. third. According to the analysis of the characteristics of the subway interference, the frequency spectrum analysis is used as the signal detection method, and the subway interference signal is used as the noise signal to simulate the signal detection results of the ground resistivity AC observation method. The result shows that the frequency of the power supply signal is above 0.5Hz, when the signal to noise ratio is 0dB, the sampling time is full. At the time of 400s, or when the signal to noise ratio is 10dB and the sampling time satisfies 200s, the relative error can meet the requirements of the earth resistivity observation specification. Thus, the feasibility of the earth resistivity AC observation method is verified. Finally, the main technical requirements of the earth resistivity observation system are given on the basis of the above research. It provides theoretical reference and technical basis for the development of ground resistivity observation system.
【学位授予单位】：中国地震局地壳应力研究所
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.722

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