Electromagnetic Method Detection Of Granite Body Distribution And Internal Structure In Xinchang Area Of Beishan, Gansu

There is a history of over 20 years to carry out the research of high-level radioactive waste disposal in our country. In the geological repository site. People have put Gansu Beishan granite in Xinchang area as a key location to study,and had yielded many important geological research. In order to evaluate the safety and stability of deep rock mass of the structure, to further explore the fine structure and control of rock mass is the main objective in geophysical exploration in the future. In this paper, combining with the research and development project of geological disposal of high level radioactive waste of geological bureau of nuclear industry, and taking Gansu Beishan granite in Xinchang area as the object of study, we carried out the work of magnetotelluric sounding in the geophysical exploration of deep to provide a scientific basis for the evaluation of site characteristics of the preselected area in Beishan.using two kinds of method of Hybrid source electromagnetic and Magnetotelluric for the field data acquisition, and accessed to a large number of magnetotelluric sounding data. On the basis of preprocessing the data, used the one-dimensional OCCAM algorithm to inverse calculation, and obtained the resistivity inversion section of every line. Combined with the drilling data of the section near and the geological conditions to interpret every resistivity profile. Analysis shows that, the resistivity anomalies can reflect the distribution and charactiristics of occurrence for fracture structures well which were developt in the internal or boundary of rock structure, Accordingly determined distribution of the two main goals of rock(the rock and rock mass of jijicao) in Xinchang area, and evaluated the integrity of the rock mass. The results of the study show that,due to most of the tectonic fracture zone which were distribute in the granite of Xinchang area take down cutting depth is less than 300 m,and illustrated that the deep rock mass damage is small and the integrity of rock mass is good.Considering the process of field data acquisition, it was often influenced by various factors, and coupled with time constraints, it will cause data dispersion, jumping or mutation. In order to eliminate the interference In the process of data processing, denoising method and application effect of the filter is studied. Introduced the median filtering denoising method to try to filter and denoise the points measured data which were influenced more serious MT electromagnetic sounding profile. A plurality of filtering window were selected and tested.The results show that 2D window, [4x4] can more effectively prevent the "flying" abnormal, and it can not smooth for the big electrical changes. It can be used as the best window for electromagnetic sounding data denoising, and laid the theoretical foundation for the subsequent data processing.