地電阻影像剖面對非均質地下實體模擬的修正與分析

Analysis of Non-Homogeneous Physical Model Simulated for Resistivity Tomography

地電阻影像剖面法，簡稱RIP（resistivity image profiling, RIP），當施作遇到地形變化劇烈或地下物為非均質狀態，施測電極排列的選用以及施測後，對其視電阻率曲線的初步判讀，將會影響到整體資料判讀上的正確性。由於在傳統軟體正算分析過程中，無法對地表上的地形效應算出視電阻率。本研究提出一室內簡單快速之實體模型配置，利用Wenner電極排列法作電阻量測，將傳統砂箱3-D試驗對於模型材料電阻率及非均質性等問題利用修正幾何因子的轉換，簡化成2-D方式處理。並利用偏差率的觀念，分析視電阻率曲線配合Loke(1999)之正算（RES2DMOD）與反算（RES2DINV）的分析軟體，得出在地形效應下非均質之反算剖面，均獲致不錯的結果。

When plotting the data from a 2-D imaging survey, the pseudo-section contouring method is normally used. However the pseudo-section gives a distorted picture of the subsurface, because the shapes of contours depend on the type of array used as well as the true subsurface resistivity, and there are many kinds of arrays usable in the RIP method. In this paper, we measure apparent resistivity with a 2D plane analogue model to improve the topographic effect, through using cylindrical coordinates with a Laplace equation to solve the potential function, also to correct the geometric factor. On the other hand, we also use the concept of eccentricity and resistivity model software RES2DINV (Loke, 1999) to present the topographic non-homogeneous tomography. By doing this, we can achieve better results.