Analytical study on rock property of long-deep tunnel with CSAMT method

作者：An Zhiguo^*; Di Qingyun; Wang Guangjie

来源：Chinese Journal of Rock Mechanics and Engineering, 2008, 27(SUPPL.): 3286-3291.

• Analytical study
• Apparent resistivity
• Audio frequencies
• Bearing conditions
• Controlled source audio frequency magnetotelluric (CSAMT) method
• Controlled-source
• Deep tunnels
• Deep-long tunnel
• Electric response
• Geologic information
• Geologic interpretation
• Geophysical explorations
• Inversion results
• Long tunnel
• Magnetotelluric
• Processing flows
• Rock properties
• Rock property analysis
• Smoothing processes
• Tunnel construction
• Tunnel engineering

In geophysical exploration work for deep-long tunnel, the issue is mainly concentrated on bearing conditions of potential unfavourable geologic body near the area of tunnel line. As for deep-long tunnel, the unfavourable geologic bodies mainly include fault and fractures, and because of distinct electric differences between unfavourable geologic body and surrounding medium, the controlled source audio frequency magnetotelluric (CSAMT) method is used to detect such unfavourable geologic bodies. CSAMT method has been adopted for the study on rock property of tunnel line about rebuilt railway in southwestern area. Based on related standard or literatures on CSAMT method, the data are firstly introduced. With the effective data, indoors data processing can be done. The much attention is paid on the analysis of typical apparent resistivity frequency curves, especially on unfavourable geologic body. The electric response of these unfavourable geologic bodies can be known and the differences between normal stratum and those containing unfavourable geologic bodies can be determined. Smoothing process can be done on original data and then processed data can be inverted. With the comparison between inverted data and original data, the fitness curves can be obtained. It is the fitness information that can help us determine the effect of inversion results. If the fitness data are too large to get correct inverted data, processing flow would return to smooth processing and should change parameters to invert again till getting correct result. Combined with geologic information of relative boreholes, the geologic interpretation can be carried out, and inverted results can also be verified. The study results show that CSAMT method is effective in exploring unfavourable geologic bodies and it is applicable for the analysis of rock property of tunnel line. Therefore, CSAMT method is an instructive guide for tunnel construction.

• 出版日期2008