1、 第116页翻译部分英文原文Detecting Abandoned Coal Mine Entries by High Resolution Earth Resistivity MethodXianxin Shi, ProfessorShu Yan, ProfessorMingsheng Shen, ProfessorXian Branch, CCRI (China Coal Research Institute) Xian, Shaanxi, ChinaABSTRACTIn surface electrical exploration the high resolution earth re
2、sistivity method (HRRM) is a very effective method for detecting abandoned drift mines workings. When the abandoned mines are more than 500 ft (150 m) deep, its detection capability reduces greatly and requires more effort to implement. In Yan Quan coal mine, Shanxi province, we tried to adapt this
3、method for underground application. Two survey lines were designed with the spacing of current and potential poles 20 m and 10 m, respectively and measuring points at 2m. The measurement radius of I line and II line were 140 m and 60 m, respectively, and the infinitely far pole was 12002000 m from t
4、he survey line. (Note the I and II lines are located on the north and south ribs of main tunnel, respectively). The survey results showed that abandoned workings were located at 25-70m, Survey Line I and at 80-110m, Survey line II. Based on this finding, the longwall panel gateroads and set up entry
5、 were properly located thereby providing safe mining of the No. 15 Coal seam.Key Words: Abandoned coal mine, High resolution earth resistivity, Underground electrical explorationINTRODUCTIONThe development of roadways for the 9th mining district for the #15 coal seam, Nanzhuang Coal Group Co Ltd, Ya
6、ngquan, Shanxi Province are approaching the Hougou abandoned gobs. Since the data regarding the extent and condition of Hougou gobs were not reliable, it is difficult to finalize the panel layout for the #15 coal seam. In order to provide sufficient geological data for rational layout and safe devel
7、opment of mains and setup entry, the Hougou gob conditions (i.e. area and location) must be known clearly first.Based on our experience gained in the past 10 years, when coal seam is less than 150 m deep, the high resolution surface resistivity method can produce better results. But the Hougou aband
8、oned mine gobs were 350 m deep. For this reason, we tried to use the high resolution resistivity method underground to detect the gobs from entry ribs to facilitate the development of #15 coal seam.CHARACTERISTICS OF EARTH RESISTIVITYThe #15 coal is the major coal seam in the reserve. Seam thickness
9、 is 5.25-6.63 m averaging 5.89 m and consistent throughout the whole reserve. It is anthracite with low-medium ash, very low-low sulphur and high heating value. Its electric resistivity is relatively low. After mining, if the gob is not flooded with water, its apparent resistivity will increase sign
10、ificantly and behave as a high-resistivity material regardless whether the gob is caved or not. This is the prerequisite of physical property for the application of high resolution resistivity method.UNDERGROUND HIGH-RESOLUTION RESISTIVITY METHODAs mentioned above, good seam quality is the prerequis
11、ite for high resolution resistivity method. But what devices are needed to perform the resistivity exploration deserves further study. Due to the fact that a gob is a man-made isolated geological body and its not uniform as a bedded deposit, special devices that can superimpose its electric informat
12、ion and focus on its location such that it can distinguish it from the surrounding rocks, must be used to detect this type of geological body.The underground high resolution resistivity method employs special three-pole devices, i.e. monopole-dipole device densely dispatched that can increase the le
13、vel of observation and control, add the number of superposition, enlarge the amount of information, and improve the resolution of gob detection so that the gobs can be identified from the surrounding rocks. Figure 1 shows the array of survey stations.The parameters adopted for the underground earth
14、resistivity method are:1.Distance between power supply stations, A and A: 20 m2.Distance between survey stations, C and C: 2 m3.Distance between poles, MN: 10 m4.Radius of survey lines: Line I 140 m, Line II 60 m5.Location of infinite distance pole: 1,200 2,000 m from the lines.Figure 1 Survey array
15、 for underground earth resistivity methodUnderground survey data were collected by flameproof microvolt digital direct current resistivity meter. In underground survey, the power supply station was located at 20 m interval. For every power supply station, the voltage difference between both directio
16、ns of measurements must be recorded. The maximum distance of MN on both sides of each power supply was 140 m, i.e. the maximum offset distance was 140 m. This way double coverage observation can be realized and the exploration area can cover up to 140 m.In order to insure the accuracy of the data obtained underground, the following measures were adopted:1.In order to insure the power supply w
