Research on Geological Structure Mark of Coal and Gas Outbursts in Pingdingshan Mining Area

Jun 2ournal of China University of Mining & TechnologyVol 12 No. 1Research on Geological structureMark of Coal and Gas outbursts inPingdingshan mining areaGUO De-yong(郭德勇), HAN De-xin(韩德馨),丿 ANG Guang-jie(姜光杰)2(1. Department of Resource Exploitation Engineering, CUMT, Beijing 100083, P. R. China:2. Pingdingshan Coal (Group Co. Ltd, Pingdingshan, Henan 467000, P.R. ChinaAbstract: Based on the study of regional displaying rules ofd gas outburst controlled by geological struc-ture in Pingdingshan mining area, the geological structure features in outburst sites were investigated emphatically. The combination type, orientation and least seam thickness in out burst sites were put forward. This re-search provides a geological mark for forecasting gas outbursts in deep miningKey words: coal and gas outbursts geological structure; structure coal forecasting indexCLC number: TD713Document code: AArticle ID:1006-1266(2002)01-0072-05The researches of relationship between geo- entation of geological structures in this mininglogical structures and coal and gas outbursts 1-5 area parallels nearly with the axis of Likou synshow that a geological structure is the main geo- cline. The combination feature of its geologicallogical index for forecasting coal and gas out- structures can be divided into three structure arbursts. And the study of gas geology made in eas, i. e. eastern, central and western areas. Irmany coal mining areas shows that there are small the eastern area, the transition area of Likou synstructures in many outburst sites (over 80%),so cline, the condition of geological structures isit is widely used as the forecasting index of coal most complicated, and No 8, No. 10 and No. 12and gas outbursts. A farther study on the dis- Collieries are in this area. The central area, in-playing rules of coal and gas outbursts and the ge- cluding No. 1, No. 4 Collieries and the easternological structure features of outburst sites is the part of No 6 Colliery, has a simpler condition oftechnical basis to improve the forecasting accura- geological structures. The main geological struc-ures in the western area, including No 5, No. 71 The Distribution of Coal and Gas Outand No. 11 Collieries, are Guodishan fault, Jiulishan fault and synclines in the middle area, and itsburst Sites Controlled by the structuresgeological structure condition is relatively compliin the Mining Areacated( Fig. 1). The showing of coal and gas ouPingdingshan coal mining area is an one with bursts is different in the three areas Three col-serious coal and gas outbursts, above 80 times lieries in the eastern area have outburst threatencoal and gas outbursts have occurred. Its coal ing, and more than 50 outbursts have occurred;mines are mainly on the southwest of Likou synH中国煤化工 place in No.5 Collierycline, a regional structure, and the displaying ori-CNMH Gome areas in No. 7 andReceived date: 2002-03-21Foundation item: National Natural Science Foundation of China (40002010 and Research Fund for Doctoral Program of Higher Education(9229008)BiographDe-yong(1966-), male, from Henan Province, associate professor. Ph. D., engaged in the research of safety technol右教据GUO De-yong et alesearch on Geological Structure Mark of Coal and73No. 11 Collieries are highgas area; Gas contententry 22200 in coal seam F1s 17 in No. 5 Collierythe central area is relatively low, so the dynami- and three outbursts in the axis and hinge zone ofcal phenomenon of gas is not serious. This shows Niuzhuang syncline in tailentry 16081 and headen-that the displaying rules of coal and gas outbursts try 16101 in coal seam Fs-17 in No. 12 Colliery.s controlled by the regional geological struc- 2.2 Fault-controlled belta fault structure causes certain disturbedcoal in a coal seam, and because of the difference3 kmof the scale and feature of faults, the damage de-gree and influential scope are different. A beddingfault affects the thickness of coal seams ess, buits influential scope is great, coal seams are broken in a great scope, and coal and gas outburstsNo 9No,12No5easily occur in the place where the thick ness ofNo. 7Niuzhuangdisturbed coal increases. The data of gas geologyJulishandaotangin Pingdingshan coalfield shows that the possibility of coal and gas outbursts is great in the upperpart of faults because of the serious extrusion ofsyni图Anticline| -a fault2. 3 Combination type of faultsFig. 1 Geological structures and distribution of2. 3. 1 Horst typeoutburst mines in Pingdingshan mining areaThe characteristics of this type of combina1. Niuzhuang reversed fault: 2. Xindian normal faulttion are that two parallel faults occur in a close2 Feature of Structure Combination in distance, and the damage of coal seams is seriousCoal and Gas Outburst sitesin their common part due to fault extrusion andkneading. Furthermore, the fault surfaceStructure combination, which reflects the re-compressive structure plane, the structure of coallationship between structures and their geometrseams in the middle part is damaged, and gasforms, is the direct mark of a structure areapressure is high, which provides the condition ofThrough the study of structure combination feaoutbursts There aretures in an outburst site, coal and gas outbursts faults in headentry 14131 in coal seam Eg lo in Nocan be forecasted with the analogy method. Based 8 Colliery. Ihey have the same orientation andn the structure combination features of moreopposite inclines, and their throws are respectivethan 80 outburst sites in the coalfield, 4 types of ly 1.5 and 1.8 m, forming a horst structure. Onethe geological structure of outburst sites can be i- coal and gas outburst occurred during the excavation, the amount of coal and gas outbursts being2. 1 Axis and hinge zone of folds20 t and 390 m respectively. There are two re-Because of intensive extrusion and internal versed faults, respectively with a throw ofcutting and sliding in the axis of a fold structure, and 0. 4 m, in headentry 21150 in coal seam F,the structure of coal seams is destroyed fracH中国煤化工 ctrusion and torsion oftures in surrounding rock develop well, and tec-CNMHGommon parttonic stresses concentrate, resulting in the in-develops well in the entire cecrease of gas content and pressure. So the axis of Coal and gas outburst occurred during the excavaa fold structure is a dangerous place to coal and tion, the amount of coal and gas outbursts beinggas outby为数据 o outbursts have takenrespecthe sub-anticline axis of Guodishan fault in head- 2Journal of China University of Mining & TechnologyVol. 12 No. 1The characteristic of this type of combination seam on the lower wall of the fault is pressed intois that they are a group of parallel normal faults a fold, and its thickness ranges from 6.0 to 1.2with the same incline, forming the structure comm, only 0.8 m in some place. And entire seam isbination of a ladder shape. The extrusion of coal highly damaged to become disturbed coal. Antheir common part, the fault outburst occurred during the excavation, with therface is a compressive structure plane, and the outburst amount of coal and gas being 91t andclosed system formed in their common part is easy 4284 m respectivelyto cause coal and gas outbursts. There is a ladder 2. 4.2 The intersection of fault and foldstructure in a headentry in coal seam FIsi in NoCoal seams are acted by the multi-periodic5 Colliery, and the throws of two faults are re- tectonic activities, and the crossing of fault andspectively 1.3 and 3. 0 m. And the coal seam be- fold in some area increases the damage degree oftween them is at a creep status due to compresoal and surrounding rock Coal seams are damsion, and the thickness of the coal seam changes aged, fractures in surrounding rock develop wellgreatly, from 2.0 to 6 m. One outburst occurred and tectonic stresses concentrate. As a resultin the excavation process, the amount of coal and the dangerous area of coal and gas outbursts isgas outbursts being respectively 20t and 1286 m. formed. District 160 in No. 12 Colliery is in the2. 3. 3 Intersection typecommon influential range of Niuzhuang synclineThe characteristic of this type of combination axis and Niuzhuang reversed fault, and severalis that several faults with different features cross outbursts have occurred ithere littlein the same place, which leads to not only the faults develop well, with the total amount of coalfurther damage of coal seams, but also the damandut bursts bg 900 t and 5age of roof and floor strata and well developed spthe combinatiefractures, providing the condition for gas congre- structure action, forming the geological conditiongating in a limited place. Because tectonic stress- of coal and gas outburstes are relatively concentrated, coal and gas out3 Fault Orientation in Coal and Gas Outbursts are easy to occur. There are 4 faults cross-burst sitesing in the same placheadentry 20080 in coalseam Fg-10 in No 10 Colliery, and one outburst ocThe main orientation of structures is nw incurred during its excavation, the amount of coal this coalfield. There are mainly two groups of litand gas outbursts being 15 t and 600 m respec- tle faults developed, and their orientations aretivelynw and Ne. The statistics result of outburst2. 4 Combination of fault and foldsites in No 12 Colliery shows that Nw and ne2. 4. 1 The parallel of fault and foldfaults have different effects on coal and gas outThe parallel of fault and fold shows thbursts. Faults in outburst sites have three feaconcomitant relation, i.e. the fault is formedtures: 1) The strike of faults is mainly NW;2)the two wings of the fold or the fold is one part of The faults are mainly normal ones, only one rethe fault. Fractured zones are formed in coal versed fault in the statistics: 3) The smallestseams and the disturbed coal develops well. At throw of faults is 2. 0 m and the throw of reversedthe same time, the creep of coal is caused by fold中国煤化工action. The change of coal seam thickness isCNMHG and NE faults in thegreat, and the disturbed coal develops well in thedifferent. and nw faults are moreentire seam in some place. This is the dangerous developed than NE ones. When the throw is thearea of coal and gas outbursts. There is a re- same, an Nw fault can form a greater damageversed far)方数据ange than an ne fault. Besides the scope of dis6041 in coal seam F1s-17 in No 12 Colliery. Coal trued coal is wider, its damage degree is higherGUO De-yong et alesearch on Geological Structure Mark of Coal andStatistic results show that Nw faults with a 4 The End of Structures, Main Sites ofthrow of more than1.4m, can formⅢandⅣCoal and Gas Outburst Occurringclasses of disturbedand the width of dishe data of the distribution of coal andturbed zone in coal seams can get 15 m if theout burst sites in Pingdingshan coalfield show thatthrow is greater than 2.0 m. There are usuallythere are two main areas of coal and gas outburstsstrong disturbance phenomena in coal seams, andF.8 outbursts occurred in workinghe entire intensity of coal is decreased, so out- face 13170 in No 8 Colliery, which takes 62% ofbursts easily occur in a high gas area. But the total outbursts in the colliery, and 10 outburstsdamage degree and developing thickness of disoccurred in working face 16101 in No. 12 Colturbed coal for NE faults are obviously loliery, which takes 63% of total outbursts in theTable 1 Fault feature statistics for coal andgas outburst sites in No 12 Collierycolliery. It is obvious that there are the workingThrowfaces with more serious outburst danger in theseOutburst time Fault typeOrientation Inclinecollieries with coal and gas outbursts. The reasonFeb, 13. 1989 Normal fault2N35°WNEMar 18, 1989 Normal fault 2.2N35°WNEof concentrated distribution of coal and gas outMar 22, 1989 Normal faulN45°WNEbursts is analyzed as followsApr. 2, 1989 Normal fault 3.5 N45 W NEIn No. 8 Colliery, the outer section ofMay 15. 1989 Normal fault 2.0N5°WNEMay 22. 1989 Normal fault 2.0N15°WNEhaulage roadway of working face 13170 in coalMay 24, 1989 Normal fault 2.0115W NEseam f is situated at the end of xindian normalFeb 21. 1993 Reversed fault 6.0 N20 WNEfault (Fig. 2 a)with tharly ew, thThe analysis of fault formation shows that incline of N, and the largest throw of 20 m.AtnW faults are vertical to ne. the main stress di the eastern pinching-out end of the fault is workrection of the regional stress field, and parallel ing face 13170, the 8 outbursts occurring duringith the strike of strata. The upper and lowerwalls of faults are easy to slide under the action of tributed in the areas near the pinching-out endNE stress, resulting in the increase of the width and the second-order normal faults, The actualand range of NW faults. In the process of gas measurement values ofgas pressure are 1movement, Nw faults provide the passage for gas1. 99 MPa. The observation shows that the twistto move from lower to upper places, and when ing of coal seam in the haulage roadway is serithe scale of a fault is little, a close system is easi- ous, the structures of coal are mainly classes lly formed, causing the concentration of gas. So and N, and the thickness is great. And fissuresthe reason of the relation between the outburstsdevelop well in surrounding rock, and the contentand the orientation of faults is the formation and of gas in coal gets to 12.8 m/t, so that the geofeature of faultslogical conditions of the outbursts are formedsynclineXindian中国煤化工CNMHGKNormal faultDI Reversed fault区The outburst distribution at the pinching-out end of faults in Pingdingshan mining area The distribution in the pinching-out end of xindian fault in no.8 Collier(b)The distribution in the pinching-out end of Niuzhuang fault in No 12 CollieryJournal of China University of Mining & TechnologyVol. 12 No. 1Niuzhuang reversed fault is developed in the geological structure indexes to outburst forecastof Niuzhuang syncline, and working face For No 8 Colliery, it should be made to strength16101 in coal seam F in No. 12 Colliery is at the en the forecast of nw normal faults and the faultspinching-out end of the fault (Fig. 2 b). The syn- with developed disturbed coal, and the forecastcline axis passes through the middle of the work- and prevention of coal and gas outbursts in theing face and inclines to N60W, with an inclined working faces at structure ends. The factorsangle of 3 to 6. The inclined angle of its nw wing which affect the danger of coal and gas outburstsis 5 to 8, and that of its nE wing changes from 7 are structure scale, structure pty, structure10 to 25. There are several normal faults, de- stress, disturbed coal and gas in a structure areaveloped at the pinching-out end of Niuzhuang re- and the forecast and adjustment of outburst danversed fault, with different throws H (H=2.4 ger should be made on the basis of these factorsH2=2.0m,H3=3.5 m). Ten out bursts oc-5 Conclusionscurring during the excavation of coal roadways aredistributed collectively on the upper walls of threeCoal and gas outbursts are controlled bynormal faults. In coal road ways in the axis of syn- structures in Pingdingshan coalfield, and the zonclines and the influential area of the pinching-out ing of geological structures results in their regionend of faults, the sliding between coal seam layers al displaying. There are 4 types of structure com-develops well, and the damage degree of coal binations of outburst sites, which form a closemainly classes l and N. The actual system liable to cause outbursts. The faults Inmeasurement values of gas pressure in coal are outburst sites have obvious orientation, and there45 and 2. 06 MPa, and the rate of gas emission is a relatively high outburst danger to NE faults inis abnormally high, all these provide potential the coalfield. The action essences of these struc-conditions for coal and gas outbursts.tures can result in the concentration of gas andThe research result of change in the stress tectonic stresses, and disturbed coal, etc. whichfield near faults shows that after faults move, the are the necessary conditions for coal and gas out-stress field is disturbed, and stresses at their bursts, and all these can be used in the forecastingpinching-out ends concentrate. It is obvious that of coal and gas outbursts in the adjacent district.the tectonic stress field plays an important part in Acknowledgementscoal and gas outbursts occurring collectively at therted by thchpinching-out end of faultsFund for the Doctoral Program of Higher Educass researchesgeological tion and the National Natural Science Foundationstructures controlling coal and gas outbursts, it is of China and helped by Gas Research Institute andsuggested that before the research of geological Geology Division, Pingdingshan Coal Groupstructures, the research of the features of geological structures be made firstly in the application ofReferences[1 Shepherd J. Outbursts and geological structure in coal mines: A review [J. 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