瞬变电磁隧道超前预报成像技术

为解决隧道掌子面前含水带病害快速有效探测问题，尝试把对含水带结构反映敏感的瞬变电磁法引入到隧道掌子面前进行工作.文中介绍了瞬变电磁超前预报的工作装置形式;通过对掌子面特定环境的分析，提出引用“浮动薄板”理论，以二次电导微分参数为特征量建立隧道超前预报成像系统.推导出以等效导电薄板为虚拟像源的磁场响应与电导之间的非线性关系式. 通过引入辅助函数，采用遗传算法求得电导参数.最终以二次电导微分参数绘制成像剖面.对地电模型进行数值模拟和对应用实例进行了成像,结果表明成像方法对隧道掌子面前方水体病害预报效果明显.

The technology of TEM tunnel prediction imaging

In order to solve the problem of fast and effective detection of the water-bearing structure ahead of tunnel wall,we try to introduce the transient electromagnetic method(TEM),which is sensitive to water-bearing structures,into tunnel condition working.In this paper,we give the TEM tunnel prediction configuration.After analyzing the special condition of tunnel location,we introduce "moving plate" theory and create the imaging system of TEM prediction based on the parameter of secondary differential conductivity.We deduce the non-linear function of conductivity and magnetic response excited by imaginary equivalent plate source.By introducing an auxiliary parameter,we obtain the parameter of conductivity by using Genetic algorithm.We at last draw the imaging section with the parameter of secondary differential conductivity.Numerical simulation of thin layer model and the survey of a tunnel has been carried out.Both results of modeling and survey show that it is effective and successful to use TEM imaging method to explore the unfavorable geology body in tunnel.