坑道直流电阻率测深异常研究

A study on anomalous bodies of DC resistivity sounding in tunnel

电阻率测深数据可利用坑道的四个面和四个角得到 .但由于受到坑道本身和体积效应影响 ,坑道内电阻率测深资料解释的困难很大 .本文用有限单元法对坑道内的直流电阻率测深进行数值模拟计算 .首先给出坑道中正常电位的取值 ,并利用有限单元异常电位计算法对坑道内电阻率测深进行正演计算 .结果表明 ,在异常体断面尺寸、埋深及所用电极距与坑道截面尺寸相差不大时 ,坑道面上的测深断面反映的基本是本坑道面外侧地质体的信息 ,对其他位置的地质体没有明显反映 ,坑道角断面则反映的是相邻两个坑道面外侧地质体的综合信息 .

The resistivity sounding data can be obtained on four corners and four surfaces in tunnel. It is difficult to interpret the sounding data in tunnel because of the influence of tunnel and volume effect. In this paper, we perform modeling of DC resistivity sounding in tunnel using the finite element method (FEM). First, the value of normal potential in tunnel is presented. Then, modeling of resistivity sounding in tunnel using anomalous potential method of FEM is performed. The result shows that, when the size, the depth of bodies and spacing of electrodes are little different from the size of the cross section of tunnel, the section maps of sounding on surface of tunnel mainly reflect the geologic bodies outside the surface and weakly the bodies on other positions. The section maps of sounding on corners of tunnel show the bodies outside the two adjacent surfaces synthetically.