Experiment in metal disturbance during advanced detection using a transient electromagnetic method i

MINING. Science DirectSCIENCE ANDTECHNOLOGYELSEVIERMining Science and Technology 20(2010)0861-0863www.elsevier.com/locate/jcumtExperiment in metal disturbance during advanced detectionusing a transient electromagnetic method in coal minesJIANG Zhihai12,YUE Jianhua. Yu JirngcunSchool of Resources and Geoscience, China University of Mining Technology, Xuzhou 221008, china'State Key Laboratory of Geomechanics and Deep Underground engineerinChina University of Mining Technology, Xuzhou 221008, ChinaAbstract: Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods In our experiment, we used a coincident-loop and centralloop type of configuration, where the coil plane 1)vertical to and 2) parallel to the working face. A SIROTEM instrument at different locations was used to observe the transient electromagnetic responses of the excavator and to analyze the response amplitudesThe result shows that the tunneling machine affects the advanced detection data and is related to the way the coil is coupled, Whenthe excavator is 6 m from the observatory, the interference of tunneling machine can be ignoredKeywords: transient electromagnetic method; advanced detection; metal disturbance; driving face1 IntroductionThey proposed a corresponding processing tech-nique-I5. However, research into the effect of drivWater inrush accidents commonly occur in the face ing machinery on excavation faces is rareof tunnel excavations. Therefore, in order to stay It is not easy to move the large excavators used forclear of buried water bodies, such as water transmis- tunnel excavation in a space-limited heading face. Insion lines or other water-bearing structures, geo- actual coal mining situations, when performing tran-physical techniques should be used before excavation sient electromagnetic advanced detection in the formand safety measures taken in advance are the key for of continuous-wave tracking, the longest distance thethe prevention of water related incidents in coal excavator can be moved backward is 10 m, but itmines. Since 1998, the China University of Mining cannot move forward. Because a transient electro-Technology, the Chinese Academy of Geological magnetic field occupies the whole space, the excava-Sciences and the Xi'an Branch of the Coal Research tor behind the heading face acts as a large-scale,Institute have carried out experiments on a transient low-resistance metal body, which directly affects theelectromagnetic method. This method is used to de- data acquisition of advanced detection and then alsotect the presence of water in both roofs and floors, affects the accuracy of detecting geologic anomaliesconcealed water conduits and water-bearing struc- in front of the heading face. In order to avoid or totures in front of the direction of the working face, as eliminate the interference from excavators and to im-well as water accumulation in boreholes and goaf prove reliability to interpret transient electromagneticareas.Chang an University uses this technology advanced detection data, we need to investigate theresponse characteristics of a transient electromagneticbodies in tunnels o. Facilities such as metal racks, field from excavation machines given circumstanceswire mesh, rails and heavy machinery in tunnels se- of different couplings. For this reason, we performedriously interfere with transient electromagnetic data some physical experiments in an underground tunnelin mines. Yu et al. have carried out some preliminaryinvestigations into transient electromagnetic response 2 Experimentalcharacteristic of metal racks, wire mesh and rails.2.11中国煤化工Received 12 March 2010; accepted 21 June 2010Corresponding author. Tel: 86 13645203339CN MHGspecialized TEME-mailaddress:jiangzhihai@cumt.edu.cninstrument,developed by CISCO, which is highldoi:10.1016S1674526409)×02969automated for sampling, has a good ability to sup-Mining Science and TechnologyVol20 No 6press noise interference and monitors real- time well. 2.2 ConditionsData acquisition is controlled by a microcomputerwhich can automatically record and store data ande arranged four measuring points between theperforms data dumps if the acquisition equipment isheading face and the excavator as shown in Fig. laconnected to the microcomputerSpace between adjacent points is 3 m, point 1 is lo.Two types of loop configuration, coincident and cated at the heading face, point 4, I m from the exca-or andcentral, were tested. For the coincident-loop configu- are set at the center of the tunnel. Given that of theration, the transmission coil was 2 mx2 mx32 circlestwo coils, one coil plane is parallel to the headingand the receiving coil 2 mx2 mx50 circles, while for face(Fig. Ib)and the other vertical(Fig. Ic), we col-the central loop configuration, the transmission coilwas 2 mx2 mx32 circles and the receiving coil I mxl lected data at the four points in the correct order.Duemx 50 circles. A valid sampling window sequence is: to the excavating machine vary, the coupling differs1.325,1.625,2.025,2425,2.825,3.425,4.225,5.025,5.825,7.025,8625,10.225,11.825,14.25,17425for the primary field and the excavation machine,which has a different interference on normal data.20.625, 23.825, 28.625, 35.025, 41.425, 47.825, Thus, we can determine the effect of the level of in-57. 425 and 70.225 ms, i.e, the sequence contains 23terference from the excavator from that of advancedtime windows. For the purpose of suppressing noise detection data, by comparing the amplitude of theinterference, we used 64 stacking techniques and anemission current of 3-4 A. The tunnel is 3.5 m wideduced electromotive force response from the fourand 2.5 m high and the excavator was a distance of 10 ponm removed from the heading face.Driving:3machineryFloorRight side(a) Location(b)Positionc) Horizontal viewFig 1 Location, position and horizontal view of observation stations3 Results and discussionTheoretically, when the distance between the coil andthe excavation machine is reduced, the response am-When the coil plane was parallel to the heading plitude of the signal should improve gradually, i.eface, as shown in Fig. 2, we obtained the attenuation the induced electromotive force received will be pointcurves of the induced electromotive force at each 4>point 3>point 2>point Ipoint. Fig. 2a shows the results for the coinddent-loop configuration and Fig. 2b the result for thecentral loop configuration, where the abscissa indi-103ates the sampling time (in ms) and the ordinate the主腿normalized value of the electric current of the in-210duced electromotive force in the receiving(V/(Am)). Fig 3 shows the results when theThe excavator is only 10 m from the heading face. 310/plane is vertical to the heading face.Therefore, both the roof and the floor within this dis-tance can be considered as a horizontal continuumi.e, our experimental results show that the transientelectromagnetic field response from both the roof andthe floor contribute equally to the measurements at100010.111010each point. Therefore, the amplitudes of the inducedTime(ms)electromotive force response at each point are deter-mined by the comprehensive response of the excavator and rock mass in front of the heading face. The中国煤化工 oil plane wasexcavator is a large metal unit with very small resis-CNMHGtance and under the same coupling, its response am- Figs. 2 and 3 show, respectively, that for the coin-plitude is much greater than that of the rock mass. cident-loop configuration and the central loop con-JIANG Zhihai et alExperiment in metal disturbance during advanced detectionfiguration, the order of the induced electromotiveReferencesforce received actually was as follows: point 4>pointI=point 2>point 3. Accordingly, we may infer that[1] Jiang Z H. Study on the Mechanism anpoint 3 is only slightly affected by the excavationAdvanced Detection with Transientmachine. Because points 2 and 1 are far removeMethod for Roadway Drivage Face [Phfrom the excavation machine, neither are very muchXuzhou: China University of Mining Technology008. (In Chineseaffected by the excavator, and their signals mainly [2] Jiang Z H, Yue JH, Liu S C. Prediction technologyreflect geological information from the heading faceburied water-bearing structures in coal mines using tranThis result shows that when the coil plane is parallelsient electromagnetic method. Joumal of China Univeto the heading face and when the excavator drawssiry of Mining Technology, 2007, 17(2): 164-167.back 6 m or more from the heading face, interference [3] Jiang Z H, Yue JH, Liu z x Application of mine tran.from the excavator can be avoidedsient electromagnetic method in forecasting goaf water.Chinese Journal of Engineering Geophysics, 2007, 4(4):291-294.(In Chinese)[4] Yu J C, Liu Z X, Tang JY, Wang Y Z. Tranmagnetic detecting technique for water hazardof fully mechanized sub-level caving faceChina University of Mining Technology, 20542-546.(In Chinese)≤[5] Yu J C, Liu ZX, Liu S C. Tang J Y. Theoretical analysisof mine transient electromagnetic method and its appliation in detecting water burst structures in deep coalstope.Journal of the China Coal Sociery, 2007(8): 818-821. (In Chinese)[6] Yu J C, Liu Z X, Tang J Y. Research on full space tran-sient electromagnetism technique for detecting aqueousstructures in coal mines. Journal of China University offining Technology, 2007, 17(1): 58-62[7] Yu J C, Wang Y Z, Liu J, Zeng X B. Time-desion of transient electromagnetic method used0010.I0100mines. Jourmal of China University of miningtechsology,2008,18(4):546-550(a) Coincident(b)In-loop[8] Liu Z X, Yu J C, Guo D. The application of the minirFig 3 Decay curves when the coil plane is verticaltransient electromagnetic method to the exploration ofto the heading facehydrological borehole. Geophysical and Geochemicalloration, 2006, 30(1): 59-61. (In Chinese)[9 Guo C, Liu B Z, Bai D H. Prediction of water disasters4 Conclusionsahead of tunneling in coal mine using continuous detection by uwtem. Seismology and Geology, 2006, 28(3)The quality of the results of our small loop456-462 (In Chinesdetermined by the coupling between the small loop [10) Li x. wu JJ, Cao d m Advanced geologic forecastingems and the rock mass. For a large excavationdevice in thesimilar to a large low-resistanceGeotechnical Investigation and Surveying, 2006(3): 70-76. (In Chinese)body, it willaffect the reliability of the re- [11] Yu J C, Liu S C, Wang Y Z. Response characteristic ofsults of advanced detection. when the excavatortransient electromagnetic to metallic facilities in coalwhich has no medium for spreading a vortex current,mines and the disposal technology. Journal of chinamaintains a specific distance from the coil, the reCoal Society, 2008, 33(2): 1403-1408 (In Chinese)sponse received by the coil is very poor and its inter[12] Tang J Y, Yu J C, Wang Y Z, Liu J Human noise influ-ence on transient electromagnetic surveying and procference can be avoided. In practice, the distance bessing technology. Coal Mining Technology, 2008, 13(2)tween the excavator and the coil must be more than 632-34. (In Chinese)[13] Jia H L, Wang E Y, Song X Y, Zhang H J, LiZ H Cor-relation of electromagnetic radiation emitted from coalAcknowledgementsor rock to supporting resistance. Mining Science andTechnology,2009,193):317-320.The authors gratefully acknowledge the financial [14] Jing H W Zhang Z Y,XuG A Study of electromagneticsupport received from the National Basic Researchand acoustic emission in creep experiments of wa-ter-containing rock samples. Joumal of China UniversityProgram of China(No. 2007CB209400), the NationalMining Technology, 2008, 18(1): 42-45Natural Science Foundation of China(No. 50774085) [15]w, Wang P. Chaoticand the Young Scientists Fund of the School Science中国煤化工IsSIon sigFoundation of CUMT (No. 2008A046). Specialthanks to Editor Li and Dr. Liu for their valuable ad-CNMHGMining Science andvice and support.