浅水域工程地质勘察瞬变电磁法正反演研究与应用

Research and Application of Forward Modeling and Inversion of Transient Electromagnetic Method for Engineering Geological Survey in Shallow Water Area

为解决浅水域综合工程地质勘察过程中勘探精度低、分辨率难以提高等难题,将瞬变电磁法引入到浅水域工程地质勘察中。通过详细分析前人研究瞬变电磁法的成果资料,以麦克斯韦方程组为理论基础,推导基于多匝矩形小框电流源的浅水域高精度瞬变电磁场响应公式,得出感应电压表达式;设计浅水层、水底层半空间仿真模型,正演计算浅水域地层的瞬变电磁响应;研究浅水域高精度瞬变电磁优化反演技术,并利用实际工程项目验证正反演方法的可行性和有效性。通过仿真模型计算结果与实测数据的对比分析,证明该正反演方法计算速度快、精度高,可有效解决工程勘察中水土界线、土石界线、岩溶、断裂等地质难题。

The integrated engineering geological investigation in shallow waters has disadvantages such as low exploration precision and resolution.Therefore,the transient electromagnetic method is introduced into the engineering geological investigation in shallow waters.The research results of existing achievements of the transient electromagnetic method are analyzed.Based on the Maxwell equations,a high-precision transient electromagnetic field response formula based on multi-turn rectangular and small frame current source in shallow water is derived,and the induced voltage expression is obtained.The simulation model of shallow water layer and water bottom half space is designed to calculate the transient electromagnetic response of shallow water layer.The optimal inversion technique of high-precision transient electromagnetic in shallow waters is studied,and the feasibility and effectiveness of the forward inversion method are verified by practical projects.Through the comparison and analysis of simulation model calculation and measured data,it is proved that the forward and inversion method is fast and accurate,which can effectively solve the geological problems such as soil and water boundary,soil and rock boundary,karst and fracture in engineering investigation.