Application Study On Geological Exploration To Deeply-Buried Highway Tunnel With V8 Multifunctional Electrical Workstation In Guangxi Province

Detection to long deeply-buried tunnel is usually lack of effective geophysical methods to identify the deep unfavorable geological body in Guangxi mountainous area due to its dramatic changes in topography and complex geological conditions, especially in the Karst region where unfavorable geological body, such as geological fault and Karst is developed seriously. V8 multifunctional electrical workstation, which has advanced electromagnetic method function module, can make up the deficiency of the shallow geophysical prospecting methods (such as high-density electrical method, shallow seismic method), for example shallow detection depths, large terrain effects, high resistivity etc.In practical application, the key technology of V8 electromagnetic detection (such as the characteristics of electromagnetic sounding curve, static effect, source field effect, electromagnetic interference, the best observation scheme, electromagnetic method inversion etc.) are particularly important. This paper carried out the following specific research:1) based on the research on the characteristics of Cagniard resistivity/impedance phase/Magnetic field intensity-frequency curve, this paper,this paper master variation characteristics of the curves, reflection characteristics of the static effect and the near field effect, associated variation characteristics between Cagniard resistivity-frequency curve and impedance phase-frequency curve, different sensitivity characteristics of Cagniard resistivity and magnetic field strength to geological body, Interference curve distortion characteristics, which is a very useful guidance for us to collecting and Interpreting data; 2) this paper conducted the thorough research to the mechanism caused by the static effect and its correction method, carry out static effect analysis and analyze static effect by using measured data and correct static effect of D (five point filtering method), H (seven point filtering method), Z (median filter), K (longitudinal leveling curve shift method). Through the contrast analysis, the median filtering method of static correction provides the best result;3) this paper conducted the thorough research to Source field effect, and gives a example analysis and correction of near field effect, which achieve the expected effect;4) this paper conducted the thorough research to the electromagnetic interference and its countermeasures and the best observation scheme of CSAMT, including source field design, arrangement, the transmitter receiver distance, measuring electrode distance and the selection of its working frequency. And this paper point out that the importance of selection of the observation scheme, which can not only improve the detection precision but also the working efficiency; 5) this paper conducted research to Electromagnetic method inversion, and focused on the research of the characteristics of inversion methods, such as Bostick inversion, CSAMT model’s quasi two-dimensional inversion and MT model’s two-dimensional topography inversion. This paper point out that CSAMT model’s and MT model’s two-dimensional inversion are better methods to the detection to the tunnel in mountain areas.In this paper, based on detection to several tunnels in Guangxi Province, occurrence and water content of the unfavorable geological body were detected by the use of V8 electromagnetic method. By drilling and excavating verification, the results of V8 detection are in good agreement with the actual geological conditions, and the expected effect is achieved. Research shows that V8 electromagnetic method can make up the deficiency of the shallow geophysical prospecting methods (such as high-density electrical method, shallow seismic method), for example shallow detection depths, weak applicability in mountain area etc; that it can effectively identify the distribution of long deeply-buried tunnel strata, occurrence and water content of the unfavorable geological body, such as fault fracture zone, Karst zone, weak interlayer etc.; that it fill the blank of and highlighting its superiority on geological detection to the long deeply-buried tunnel in Guangxi Province.