Study on Supporting of Seam Roadways in Deeply Inclined Coal Seams

Vol 4 No. 1 Luo Yong et al: Study on Supporting of Seam Roadways in Deeply Inclined Coal SeamsStudy on Supporting of Seam Roadways in Deeply Inclined Coal SeamsLuo Yong, Shen Zhaowu, Xie Guangxiang, Liu Quanming(1. Department of Modem mechanics, University of Science and Technology of China, Hefei 230026; 2. Department ofResources Exploitation and Management Engineering, Anhui University of Science and Technology, Huainan 232001;3.Beijing Research Institute of Coal Mining, Central Coal Research Institute, Beijing 100013)Received 16 March 2005Abstract: Based on the present problems of the support method of gateways in complex surrounding rock insteeply inclined seams, this paper discusses the support selection of lasting gateways in steeply inclined seamsand evaluates the support effects. It draws the conclusion that the support of bolt-mesh-anchor is theffective support of this sort of gateways by using scale model simulation in lab and practice applicationsupport effects of practice application are satisfactory. It will give a beneficial reference to other analogicalmine and has an extensive application prospectKey words: steeply inclined coal seams; seam roadways; bolt-mesh-anchor; scale model simulation1 Introduction2 General Situations of Tested TunnelThe autostabiligy of roadways which lie inThe tested tunnel is the air-out entry of coaldeeply inclined coal seams degraded becauseseam C at a depth of -220 m in No. 3 mine ofroof had become loose in the course of tunnelinXinji. The thickness of coal seam C, in a staterally, the geological conditions of roof and of stability, is variable and the maximum is notfloor of those coal seams are very complex. more than 3 m, the average dip angle is 80,andAccordingly the supporting conditons will become coal hardness is f=1.5. The immediate roof ofmore deteriorative. At the present time, the coal seam C,, whose average thickness is about 1framed timber support, such as steel I-beam and m, is mudstone partially contains coal seamU-shaped steel support, are widely used in the C); its main roof is sandy mudstone(partiallyroadways in the deeply inclined coal seams. Thecontains the fine grain sandstone), and theuneven stess distribution on the support may makeaverage thickness of main roof is about 20 m. Thethe roadway stability deteriorative. What,'s more, immediate and main floors of coal seam C3 arethe vast cost and the maintenance workload badlyquartz-sandstone and the total thickness is moreaffect the daily routine of coal mines. Therefore, than 20 m['lhow to reasonably solve the bottleneck is theIn view of the conditions at field and thekey point of mining steeply inclined seams safelysupport problem, the cross-section of the roadwayand efficientlywas designed (Luo Y, 2003)to be an irregulBased on the background mentioned above, thetrapezium(shown in Fig. 1). The top of thesupport pattems, support parameters and supporteffects of coal-roadways in steeply inclined coal roadway, i.e. the top of cross-section,islted. Coal seam Ca inverses underground andseams are studied in the paper. The objective ofthe roof and floor of seam Cg is inversive in Figthis research is to effectively support and maintaithis type of roadways, obtain marked economic1. The upper side of roadway(at the floor of coaland social effects and put the technique into seam C) is 2. 1 m and it is parallel to the coalpractice widely中国煤化工ay( at the roof ofCNMHGit is vertical, thebottom of roadway is horizontal. The span lengthesEngineering Sciences Vol 4 No. 1, March 200645Luo yong et al: Study on Supporting of Seam Roadways in Deeply Inclined Coal SeamsVol 4 No. 1nd botte2.5 m and 2respectively. The vertical distance from arch apex9000to roadway bottom is 2.3 m060.81.0I.214I.6I.82.02.22.42.62.8of strain vs. coefficient ofBolt: I-Upper side; 2-Roadway top: 3-Lower sideSib: 4-Upper side: 5-Roadway top: 6-Lower sideBma: 7-Upper side: 8-Roadway top: 9-Lower sideFig 1 Schematic of the cross-section ofthe same: the deformation of the roadway lowerside is greatest, and the correspondingdeformation of upper side is the least. That is to3 Simulation Experiment in Labsay, the deformation laws of roadway surroundingrock cannot change for its support pattern. At theThe experiment was operated in the planar same time, it shows that the lower side of roadwaymodel support(Its length is 3 m)in mining lab of is the major parts of supporting.Hence, whetherAUST. The aims of the simulation experiments the lower side is stably controlled has a crucialare as follows: (1) Simulating and comparing effect on roadway supportingthree frequent support pattems: bolting, bolt-( 2)As illustrated by the modeling resultsmesh-anchor and steel I-beam support. It is a when the stress is little, the displacements ofcontrast experiment, that is to say, in the same roadway lower sides of the three support patternssurrounding and stess conditions, the effects of are as follows: the lower side displacement ofthe three support patterns are compared and the steel I-beam support is the least, thebest one is singled out. For easy of comtrast corresponding displacement of bolt-mesh-anchoranalysis, the simulant loads in experiment are 0.5 support is greater and the corresponding of boltingand 0. 8 times of original rock stess, then increase is the greatest. When the stress becomes greaterto 2.8 times of original rock stess at an increment the adaptabilities of bolting( for short as Bolt inamplitude of 0.2 time. Where, the ratio of the Fig. 2)and steel I-beam supports(for short asstimulant stress to the original rock stess is called Sib) to great load are not as good as thethe coefficient of stimulant load. (2 )Forecasting adaptability of bolt-mesh-anchor for short asthe deformation of the tested roadwayBma)support3.1 Experimental Findings Ananysis(3)Because of the function of the beam andIn order to find the movement laws of the mesh, the supporting force of bolt-mesh-anchorroadway surrounding rock, some strain-gauges support is nearly uniform, which can help exploitwere placed in the top and two sides of the the integral advantages of bolt-mesh-anchorsimulant roadwayThe experiment findings"are support. The plasticity and brittleness of steel 1-plotted in Fig. 2, which shows中国煤化 Applicable to great(1)Under the condition of same load, the loaddeformations laws of the three support patterms areCNMHGities of supportare evidentIEngineering Sciences Vol 4 No. 1, March 2006vol 4 No.1 Luo Yong et al: Study on Supporting of Seam Roadways in Deeply Inclined Coal Seamsdistinguishingthen tend to slack gradually(4)As shown in the experimental resultswhichever support pattem is adopted, horizontal 4 Parameters of Roadway Supportingstress and its controlling have a pivotal effect onthe integral stability of roadway surrounding rockThe supporting parameters were designed by aHence, in order to effectively control horizontal method of synthesis, that is to say, the originalstress,two sides of roadway, that especially they parameters were designed by employing numericallies in coal seams, must be reinforced availably. modeling and engineering experiences according toIn sum, bolt-mesh-anchor supporthe field conditions, and put into practice, thenapplicable to seam roadways in deeply inclined modified according to the supporting effects ofseams than the other two support pattems, i.e. field application and then put into practice againbolting and steel I-beanIn this way, repeating the whole process ofBolt-mesh-anchor support was adopted effects are satisfactov2-61, The original p pporting3.2 Forecast of Deformation of roadwayaccording to the experimental results. In order to designed are as followsforecast the deformation of roadway surface, (1) In the roadway top, the surrounding rockanother modeling simulation was operated in lab is coal. The top bolts equipped with metal meshand deformation of two sides and roadway top were are building thread steel bolts of 18 x 1800 mmexperimenwere three bolts each row, the row and line spacingsconverted into the data shown in Fig 3, which are 700 mm and 800 mm, respectively.Theshowsmiddle bolt is installed vertically and both of theother two bolts are installed at an angle of 300,asshown in Fig 4Quarta-tandateRoof af C3Fig 3 Forecast displacements of theroadway surface1-0ne side(upper of the roadway):2-Roadway top: 3-The other sideFig 4 Schematic of roadway shape andarrangement plan of bolt(1)The deformation of lower side is much1~2: Bolt of中6×1800mm;3~6: Bolt of卓l8x1800mm;7~9: Bolt of中18×200mmm;10: Cable of5000mgreater than that of upper sidemaxiumdeformation of lower side is 69(2)Two sides of roadwaymaximum of upper side is 18 mm; the maximO In the upper sider of roadway, the boltsdisplacement of roadway top is 55 mmequipped with metal mesh, are building thread2)During the digging of roadway, the steel bolts, three boltsdeformation of roadway surface was monitored.Theroadway surrounding rock and supports deformdYH中国煤化工6×180misnost bolt, 18 xdrastically within 3-5 days; after about 5-12CNMHdays, the deformation gradually become little andat an elevation angle of 300; the bottommost boltEngineering Sciences Vol 4 No. 1, March 2006Luo Yong et al: Study on Supporting of Seam Roadways in Deeply Inclined Coal SeamsVol4 No.1φ16×1800mm, installed200 mm from theroadway bottom at a depression angle of 20.Asshown in fig 4(2 The surrounding rock in the lower side ofthe roadway is mainly mudstone, the installationttem is the same of that in the lower side. Allthe bolts are bolts of∮18×2000mm. Each threerows the topmost bolt is replaced by a 5m anchorcable. The anchor cables are reinforced cableswhich used widely in coal mines0369121518212427303336Observation time/dThe designed anchoring load of bolt is ll t andthe initial load is 5 t, all bolts are full-lengthedFig 5 Displacements of the top andanchored. The designed anchoring load of cable isbottom of roadway21 t( the limit is 26 t, its initial load is 10t andI-Total displacement: 2-Roadway top:3-Rowdway bottomits anchored length is 2000 mm. The metal meshare woven by 8# iron wire and the mesh scale50 mm x 50 mm. The fastening, whose resistanceto bending is great, is made of ladder beam welde70by two round steer bar whose diameter is 16mm5 Comprehensive Field ObservationAfter putting the support parameters designedinto practice, and the supporting effects were0369121518212427303336monitored at the same time(1, 2). In order tomonitor the deformation of roadway surface andFig 6 Displacements of two sides of roadwaydeep surrounding rock, five observation stationsI-Total displacement: 2-Upper side of madway3.Lower sidewere placed in tested roadway)5.1 The Deformation of Roadway Surfaceing deformation vaThe observed displacements of roadway surface from the three means are nearly close to eachare shown in Fig. 5 and Fig. 6, which are:other, and all these shows that the design(1)The deformation of lower side is much method is correct and crediblegreater than the corresponding of the other side of 5.2 The Deformation of Deep Surroundingroadway. The maximum deformation of lower side Rock of the Roadwayis 73 mm and the maximum of the other side is 20The observed deformation of deepmm;the maximum displacements of roadway top rock is shown in Fig. 7-Fig.9, which areand bottom are 60mm and 14 mm, respectively(1)In the deep surrounding rock of the lower2)The roadway surrounding rock and supports side( mainly mudstone )of rockway, as shown indeform drastically within immediate 3 -5 days Fig. 7, at the place from the roadway surface isafter it was digged; after about 6-10 days, the 1.0 m -1.5 m, the surrounding rock deformsy becomelittle,and then tend obviouslythe difference between differentto slack gradually after 28-30 daysderat ahnut 20 m 4.0 m. theThe movement laws of roadway surface is the中国煤化工and decreasessame of that monitored by similar materialgracCNMHG discontinuoussimulation and that of forecasted by numerical deformations. At the place from the roadwayEngineering Sciences Vol 4 No. 1, March 2006Vol4 No. 1 Luo Yong et al: Study on Supporting of Seam Roadways in Deeply Inclined Coal Seamsthe place of 1.5 m and 2.0 m from the roadwasurface, there is a much difference ofdeformation. Thus it can be seen that the plasticzone of the lower side of roadway is 1.5 m-2.0000(2)In the other side of rockway (mairandstone), as shown in Fig. 8, at the036912151821242730333639421.5m, the deformation of roadway surroundingtion time/drock is little and it changes uniformly, there areFig7 Displacements of lower side of the roadway no discontinuous deformations, the deformationin deep surrounding rockvelocities of surrounding rock at different depths1-8-The distance from the roadway surface1.0,1.5,2.0,2.5,3.0,4.0,50,7,0msurface is less than 1.510become greater, but between the place ofand the place of 1.5 m from the roadway surfaceeref deformation. Soof this side is lessthan 1. 5 m. In like manner, the plastic zone ofthe top of roadway is less than 1.0 m-1.5 m, asshown in Fig. 9(3)After digging the roadway, thee surrourocks deform drastically, after about 4-5 days3691215182124273033363942the deformations gradually become little and afterObservation time/d28-30 days they tend to slack gradually. TheFig8 Displacements of upper side of the roadway movement law conforms to that law of the roadwayin deep surrounding rocksurface1-5-The distance from the madway surface5.3 The Supporting Effects and Economic0,1.5,2.0,2.5,4.0mEffectFor monitoring the stress of the supports andthe roadway surrounding rock, in several cross5045sections, some anchor stress meters were installedin given anchorage bolts and cable bolts. To bebrief, the supporting effects were satisfactory. Thebolt-mesh-anchor support can effectively controlthe movement of surrrock. Themeseasured average tensile stresses of anchoragebolts and cable are plotted in Fig. 10, which are:3691215182124273033363942Observation time/dAfter the roadway deformations tended to slackgradually, the tensile stresses of the given bolt inFig 9 Displacements of the roadway topthe upper side are 7.8 t-9.2 t, which is lein deep surrounding rockthan thegned anchor1-8-The distance from the madway surface1.0,1.5,2.0,25,3.0,4.0,5.0,7.0mmaximumle stress of the anchorage cable is15.5中国煤化工 an the designedsurface is more than 4.0 m, the roadway loadCNMH Grings shows thesurrounding rock is in a stable state. But betweenssupport patten Is safe, tooEngineering Sciences Vol 4 No. 1, March 2006Luo yong et al: Study on Supporting of Seam Roadways in Deeply Inclined Coal Seams Vol 4 No. 1the lower side of roadway decreased to zero. Thereasons by analysing are as follows: the lower sideof the roadway is unstable mudstone, itsmechanical properties are poor and maybe there2are geological structure zones. What's more,thebolts mentioned above may not anchor the stablesurrounding rock. In view of engineering safetythe initial support parameters were amendedemploying numerical modeling as follows: thbolts in the lower side were lengthened by 0.2 mFig 10 Load of anchor bolts and cablethe initial length is 2.0 m)so that the bolts can1-Stress of anchorage cable;anchor the stable surrounding rock at a deep2-Stress of bolt in the upper side of roadway(mudstone)3-Stress of bolt in the top of roadway;depth. In order to prevent roadway collapse forlocal damages of the lower side, a reinforceanchorage cable was installed each two rows ofDuring the monitoring period, the upper side bolts( three rows in the initial design ). In theand roadway top have been in a state of good end, the roadway was reinforced by gunitingstability, but the tensile stress of several bolts inFig 11 Photos of supporting effect(a)Before guniting:( b)After gunitingAfter amending the initial support parametersand the reinforced pattem, the supporting effects 6 Conclusionsave been very good within the subsequent twyears(shown in Fig. 11). It has bettered the (1) In the seam roadways in deeply inclinedmaintenance of the roadway in deeply inclined seams, bolt-mesh-anchor support is the bestseams. Within the two years, thereno support pattern, compare with bolt-mesh-anchormaintenance workload, obviously the cost of support, bolting and framed timber supports aremaintenance was decreased greatly. If the term of not applicable to the roadways of this typeservice of the roadway is 10 years,comparewith(2)In order to assure the stability of theframed timber support, bolt-mesh-anchor can save road1.35 x 10 RMB according to the analytical data side中国煤化 Tung the unstableof therom the mineCNMHG of successfullsupporting the roadways of this typeEngineering Sciences Vol 4 No. 1, March 2006Vol 4 No. 1Luo yong et al: Study on Supporting of Seam Roadways in Deeply Inclined Coal Seams(3)Basen on the comprehensive studies, the5)Practical application proves that the designstress distrubition and movement laws of roadway is appropriate, the bolt-mesh-anchor support usedsurrounding rock were obtained, and the laws in seam roadway in deeply inclined seams isfrom field observation are similar to that from feasible. The support effects are satisfactory andscale model simulation in lab, the deformations of the economic effects are obviousroadway surrounding rock by the two means arelthough the adopted design method has aclose to each other, which shows that the adoped shortcoming, i.e. the desige cycle is too long, itdesigned method is correct and credible, it wil be perfected by enriching the experimentalsupplies scientific bases to support design and means and improving the accuracy of numerialeffectively controlling the deformation of roadway simulation. At home, the ratio of the deeplyrounding rockinclined seams to the recoverable seams is more(4)The support parameters designed by a than 14%, so the support technique has andynamic method were tested and verified by many extensive application prospect. The researchmeans, the support effects proves that the method findings enriches the support theories angning support pattemparameters is scientific and credible, which fills seams, which will actively speed the developmentthe gaps of designed method of roadway support in of coal industrydeeply inclined seamsReferences[1] Luo Yong. Study on Design of Support ParamenterStructural Stability of Roadway's Surrounding Rocksof Seam roadway in Deeply Inclined Seams[D]and its Controlling Design[ M]. China Coal IndustryHuainan: Aug 2003Publishing House, 1999. (in Chinese)[2]Hou Chaojong, Guo Lisheng, Gou Panfeng Bolting [5] Hou Chaojong, Bai Jianbiao, Zhang Nong.Coalin Coal Roadway [M]. Xuzhou: China Universityroadway bolting under difficult and complexof Mining Technology Press, 1999. (inconditions [J]. Chinese Joumal of GeotechnicalChinese)Engineering, 2001(1):84-88.( in Chinese[3]Ma Nianjie, Hou Chaojiong. Ground Pressure [6] Tan Yunliang, Liu Chuanxiao. Prediction andTheories in Development Entries and ItsControl for Stability of Gate Surrounding Rock MassApplication [M]. Beijing: Coal Industry Pres1995.(in Chinese)Technology Press, 1999.(in Chinese)[4] Jiang Jinquan, Han Jisheng, Shi YongkuiAuthorLuo Yong, male, bom in 1977, received master degree and is a doctor candidate of USTC, specialized in blastingtechnique.HecanbereachedbyE-mail:yongluo@mail.ustc.edu.cn中国煤化工CNMHGEngineering Sciences Vol 4 No. 1, March 2006