The Research Of Tunnel Engineering Geological Exploration Imaging Method Based On Induced Polarization Method

Electrical exploration is a geophysical prospecting method to find different types of useful deposits, check the geological structure and solve the geological problem. The method is mainly based on the difference between the electromagnetic and electrochemical properties of all kinds of rocks or ore bodies. It can be obtained through observing and researching the space distribution and time characteristics of the artificial or natural electric field, electromagnetic field and electrochemical field. This topic researches the tunnel engineering geological exploration inversion imaging methods of genetic algorithm and conjugate gradient method in different devices. It's based on induced polarization method. In this paper the central gradient device, double-pole device and fixed point source device of electrical exploration are adopted to be the test devices. In the paper, genetic algorithm and conjugate gradient method are adopted. The exploration abnormal results of apparent resistivity are inversely analyzed under the anomaly condition of the central gradient device, double-pole device and fixed point source device of electrical exploration. The inverse results of the model and theoretical analysis are compared.Through the theoretical study, inverse and calculate the measured data which is collected from the test platform, and get the apparent resistivity curve. The experiment test platform of data acquisition system is designed on LabVIEW platform. It is made up of the electrodes, the data acquisition card PMD-1608 and computer. Electrodes are made into and incentive electrode. The real-time data which is from measurement electrode is put into the computer directly through the USB. The data is processed, displayed and kept in the computer. Use the genetic algorithm and conjugate gradient method in the three different devices for inversion analysis. Use the MATLAB software program to show the inversion results visualization.Comparing the inversion results of genetic algorithm and the conjugate gradient method in the three different devices, the conclusion can be drawn. When the middle gradient device is adopted, the inversion result is the most ideal by using the genetic algorithm, and practical difference the minimum. When the double-pole device is adopted, the inversion result is the most ideal through using conjugate gradient method. When the fixed point source device is adopted, the two algorithms are fitted. The difference is that the inversion results of the conjugate gradient method overall are larger than the actual results, but the curve trend is as the same as the one of the actual curve. The whole inverse curve shifts to the right when the genetic algorithm is used. But the error is smaller when it is far away from the central position of the polarization sphere.