Numerical Simulation Of Borehole Radar For Metal Mine Detection

Mineral resources are very important to the economy and development. At present in our country about 80 present of raw and processed materials and 96 present of energy sources are come from mineral resources. Most part of mineral resources used as raw and processed materials are mining. So the exploration of mining is very important to the economy.Borehole radar detects the high ground medium basing on high frequency electromagnetic. In China at present, there are not very much applications of using borehole radar to detect mining. The bore-radar can detect in the borehole, and it has higher resolution. The borehole radar can detect larger horizontal range, and it also can receive more strata information. These excellences make borehole radar playing a important part in mining exploration, especially in detailed investigation and exploration of blind ore body.Bore–hole radar has three survey methods. They are single-hole reflection, cross-hole survey and surface-borehole survey. In this paper we use FDTD to simulate the borehole radar detection. We simulate the single-hole reflection and cross-hole survey. Taking into account the output of three-dimensional body can be Orebody (refers to solid mineral) is divided into three categories, namely, equiaxed-like, tabular and columnar. Axis of the body such as fingers roughly balanced three-dimensional extension of the ore body; tabular ore body refers to the direction of the two (length, width) and the other an extension of a larger direction (thickness) on the extension of a smaller body ; pole in one direction means an extension of a very long (up to 100m vertical depth and above) the direction of extension of two other very short (often round or oval) of the ore body. In order to output a variety of different simulated ore body, and from time to time in order to simplify the general model, this article were spherical body, instead of thin rectangular and cylindrical bodies of the three forms of output. Ore bodies have different outputs in addition to its occurrence and drilling the relative spatial location different from the probe will have different results.The target used in this paper has low resistance and high dielectric constant. This is similar with mining. First we simulate the single-hole reflection. When the target is spherical bodies, in the profile the direct wave and reflect wave are in focus. The direct wave is linear. The reflect wave is hyperbolic. Using migration, we get the figure and the position of the target. When the target is plate body, we chose two representational models, one is the borehole cross the target, the other is the borehole perpendicular the target strike. When the borehole cross the target, the direct wave is cut, and blind spot appeared in the rear we can determine the drilling through the high dielectric constant and low resistance target, which is the main features of ore. When borehole does not pass through target but vertical the strike, the reflection wave is clear into hyperbolic curve shape. When the target is cylindrical body, we also chose two representational models, one is the borehole cross the target, the other is the borehole perpendicular the target strike. When the borehole cross the target, the direct wave is cut, and blind spot appeared in the rear we can determine the drilling through the high dielectric constant and low resistance target, which is the main features of ore. When borehole does not pass through target but vertical the strike, the reflection wave is clear into hyperbolic curve shape. Finally, a simulation of the actual deposits, see the single-hole survey has good detect result to detect the complex geological conditions, the adoption of a comprehensive explanation of a number of bored, we can accurately determine the location and form of the deposits. Yet it must be noted is that the low resistance of the electromagnetic waves experience strong absorption, so the follow-up media can not be detected. By simulate he single-hole reflection surveys, it shows that the single-hole reflection surveys has very good results detecting deep underground target, when drilling through the target can also determine ore body of low resistance and high dielectric constant.After simulating the single-hole survey, we simulate the cross-hole survey. The goal of a simple form, such as spherical bodies, plate body, and the cylindrical body, in the detection of cross-hole reflection mode, as a result of the different detection methods, analysis becomes very complicated, but still be able to roughly determine the depth of target location, and determine along the direction of the drilling target is a point or a certain extension. In order to accurately determine the target location and form, this article uses the intersection method. The shape and specific location of the target can gained, but the intersection method only have good identification where the target is planes in the plane of the two drilling, for example, spherical body.The simulation results for the above can be seen: single-hole reflection surveys on the ground floor has a very good target identification, and through the drill hole through the target can be of high dielectric constant of the low resistance metal body for confirmation; cross-hole detection although the analysis is complex but has a very good effect on the simple target detection. So borehole radar is a very effective geophysical method, a necessary complement to electromagnetic methods and Logging. In the future borehole radar will play a important role.