斜阶跃场源关断时间对测量结果的影响及校正研究  

Correction of Ramp Function Turn-Off Effect on the Transient Electromagnetic Response

作　　者：孙天财[1] 付志红[1] 谢品芳[1] 

机构地区：[1]重庆大学电气工程学院高电压与电工新技术教育部重点实验室,重庆400044

出　　处：《工程地球物理学报》2008年第3期287-293,共7页Chinese Journal of Engineering Geophysics

基　　金：国家自然科学基金(编号:50577071);重庆市自然科学基金(编号:2006BB2211)

摘　　要：论文推导了斜阶跃场源激励下,采样延时零时刻在发射电流关断起始点的高阻围岩中导电球体、不导电基底上水平薄板和均匀导电半空间的瞬变响应解析式,分析了发射电流关断时间对三种模型全程瞬变响应的影响。根据均匀半空间瞬变响应解析式,讨论了斜阶跃场源激励下的磁场、感应电压与全程视电阻率的对应关系,提出了一种全程视电阻率直接计算方法。此方法将发射电流关断时间作为系统参数参与视电阻率的计算,无需关断效应校正,可以方便地直接计算出中心回线装置下测量目标的全程视电阻率。理论模型及实例计算数据都证明了这种数值算法的可行性。由于斜阶跃场源技术的成熟,该算法具有一定的实用价值。The transient responses of a sphere in high resistive rock, a thin plate above resistive basement and a homogeneous half--space excited by a linear ramp turn-off transmit ter current are proposed in this paper. For time zero selected as the start of the turn--off ramp, the transient electromagnetic response analytic expression is presented, and the effect of ramp function turn--off on the TEM response of these models is analyzed. Since the voltage may lead to multiple or no apparent resistivity, the relationship between apparent resistivity, voltage, and magnetic field is discussed. For a central loop array, a numerical method calculating the all--time apparent resistivity is proposed. This method can be applied to calculate apparent resistivity regarding turn--off time as one of the system parameters. Model calculation and field data experiments show the practicability of this method. Therefore, with the development of linear ramp turn--off source, this method is of some important practical value.

关 键 词：瞬变电磁法 中心回线 关断效应 全程视电阻率 

分 类 号：P631.3[天文地球—地质矿产勘探]