任意形状水平电性源瞬变电磁全区视电阻率计算  

Calculation of All-time Apparent Resistivity for Arbitrary Horizontal Electrical Source Transient Electromagnetic Method

作　　者：商天新 张继锋[1] 冯兵[1] 刘长生 SHANG Tian-xin;ZHANG Ji-feng;FENG Bing;LIU Chang-sheng(School of Geological Engineering and Geomatics,Chang an University,Xi an 710054,Shaanxi,China;Hunan Provincial Engineering Research Center for Aircraft Maintenance,Changsha 410124,Hunan,China)

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054 [2]湖南省飞机维修工程技术研究中心,湖南长沙410124

出　　处：《地球科学与环境学报》2020年第6期749-758,共10页Journal of Earth Sciences and Environment

基　　金：国家重点研发计划项目(2017YFC0602202);四川省峨眉至汉源高速公路工程科研项目(LH-HT-45);湖南省自然科学基金科教联合项目(2019JJ70025)。

摘　　要：传统电性源瞬变电磁法的资料解释多采用反函数迭代法计算长直导线源的全区视电阻率,该方法计算效率低,适用性有限。考虑到野外实际工作中水平接地导线源形状可能发生变化,给出了一种适应于复杂电性源发射的全区视电阻率定义方法。首先,利用电偶极子叠加原理得到了任意形状水平电性源瞬变电磁场的表达式;接着,研究了均匀半空间下磁场强度及其时间导数的平移特性,通过理论公式推导给出了基于两种方式定义的全区视电阻率计算方法,该方法无需迭代,计算精度高、速度快;最后,通过设计几种不同的地电模型,验证了用该方法求取全区视电阻率的可行性及有效性。结果表明:全区视电阻率能够很好地反映目标体的地电断面信息,对于低阻异常体的分辨能力要明显优于高阻异常体;相比于磁场强度,用磁场强度时间导数定义的全区视电阻率有更大的异常幅值,且更接近地层的真实电阻率;另外,全区视电阻率只与地层的电性结构特征有关,与装置的收发距无关。在对陕西省渭南市华州区华阳乡的实测数据处理中,将观测的二次感应电压转换成磁场强度时间导数,再运用平移算法求取全区视电阻率,取得了较好的应用效果。In traditional data interpretation of electrical source transient electromagnetic method,the inverse function iteration method is used to obtain all-time apparent resistivity for long straight wire source,which is low efficiency and poor compatibility.Considering the shape of horizontal grounded-wire source may change in field survey,a definition method of all-time apparent resistivity was presented,which can adapt to complex electrical source emission.Firstly,the expression of arbitrary horizontal electrical source transient electromagnetic field was obtained by using the principle of electric dipole superposition.Then,the translation features of magnetic field intensity and its time derivative in uniform half space were revealed,and a calculative method of all-time apparent resistivity based on the above two ways was given by theoretical formula derivation.The method does not require iteration with quicker speed and higher precision.Finally,several different geoelectric models were designed to verify the feasible and effective of the method for calculating all-time apparent resistivity.The results show that all-time apparent resistivity can reflect geoelectric section well and distinguish conductive target better,and the resolution of low resistivity abnormal body is obviously better than that of high resistivity abnormal body.Compared with magnetic field intensity,all-time apparent resistivity defined by its time derivative has a larger anomalous amplitude,which is closer to true resistivity of layers.In addition,all-time apparent resistivity is only related to geoelectrical structure and has nothing to do with the offset.In processing field data for a place in Huayang town,Huazhou district,Weinan city,Shaanxi province,the induced voltage is transformed to the time derivative of magnetic field intensity,then the translation algorithm is used to calculate all-time apparent resistivity with a good complication result.

关 键 词：电性源瞬变电磁法 全区视电阻率 叠加原理 平移特性 磁场强度 时间导数 电性结构 陕西 

分 类 号：P631.3[天文地球—地质矿产勘探]