Study on Filling Cross-Roadway in Fully-Mechanized Coal Faces with High Water-Content Material

Dec.2001Journal of China University of Mining & TechnologVol 11 No. 2Study on Filling Cross-Roadway inFully-Mechanized Coal Faces withHigh Water-Content MaterialZHOU Hua- qiang(周华强), WANG Guang-eei(王光伟)LEI Wen-cheng(雷文成)2, Ll Feng(李峰)2, Q0 Qing-he(曲庆贺)21. College of Mineral and Energy Resources, CUMT, Xuzhou, Jiangsu 221008, P R China2. Baodian Colliery, Yanzhou Mining Group Co. Ltd, Zoucheng, Shandong 273513, P R ChinaAbstract: A new method using high water-content material to mechanically fill cross-roadways to formartificial bottom for coal faces was introduced. The reasonable determination of filling range, the opti-mization of the compounding ratio of high water-content material, and the filling technique were dicussed in detail. This new method has been spread after industrial testing in Baodian Collierwith the traditional method, the manual wooden chock method, the new one decreases about 40% ofthe filling range and cost in dealing every one set of cross-roadway in the testing conditionKey words: fully-mechanized coal face; cross-roadway high water-content material; filling; artificialCLC numnrt: TD 327 Document code:a Article ID: 1006-1266(2001)02-0113-05In Chinese coal mines, sublevel main entries theoretical study. The method has the followingare often used where thick coal seams or/and multi- backwardness such as high wood consume, highple coal seams are mined in strips. It is very conve- cost, slow construction speed, great air leakagenient for auxiliary haulage, but requires driving an easy spontaneous combustion and so on. Thereforeinclined cross-roadway at a interval of several hun- it is very useful and necessary to explore an economdred meters to connect the production heading and ic and convenient way of forming artificial bottomthe sublevel main entry. The cross-roadways that and roof. UShigh water-content materiallocate inside a coalface must be filled in advance to (HwCM) to mechanically fill a cross-roadway toform artificial bottom or/and roof for the supports form artificial bottom for mechanized coal faces,aand conveyer of the coalface to pass across. The new test is discussed in detail as follows. It has beenamount of work to fill a cross-roadway inside a coal successively used in Baodian Colliery.face is not big, but very important. If the filling 1 Optimization of Filling Parametersfails to lead to production stop of a high-output and1.1 Conditions of the test fieldhigh-efficiency coalface for one day, the economicThe in-situ test of filling HWCm was arraloss will be up to several million RMBIt the first cross-roadway of the center extractiime. the manual wooden chockgallery of fully-mechanized coal face 23.05 in Baomethod has been used to fill this kind of cross-roadH出中国煤化工1. the testing roadN MH G ofand parameters has been mainly dependent on engiand the drainage roadway of the wining districtneer's experience because of lack of systematicallyBicgrapdlda a ua qian 963-), male, from Chonging. Ph. D. asociate profesor, engaged in the th on strata control and fill-114Journal of china University of mining & TechnologVol, 11 No. 2downward. The distance between the open-off cut 400 mm in thickness. The bolt spacing is 700 mmand the roadway is 165 mX 800 mm. The thickness of shotcrete layer isTrack way100 mm. Before filling test, the road way has everundergone the influence of mining overlaying coalface 2306. The surrounding rock of the testingroadway is still in good condition. The deformationsbetween bottom and floor and bet ween two sides areabout 100 mm. Only has the minority of shotcretelayer taken place smallLocation of coal face 172125Observation date(Nov, 1999The average thickness of the coalseam In coface 23 05 is 3. 4 m, and the depth of excavationnear the testing spot 430 m, the dip angle 3. The(I-I section)bottom and roof conditions of the coal seam areshown in Fig. 2. The phenomenon regulations ofFig 1 Location of the test roadwayunderground pressure of coalfaces in 3d coal seamadjacent to the test spot are shown in Table 1This cross-roadway consists of two parts. Oneis the horizontal portion whose bottom is 0. 6m low-Rock Column/Thickness[ Lithologic characterer than the floor of the coal seam. and the other isShallow grey, small slicesthe inclined portion. The heFinesandell jointed, hard and 5-6trapezoid cross section, whose width is 3. 2 m at topand 4. 3 m at bottom and height 3 m. The slopeof the inclined roadway is 20, and the cross0.5 Grey and black coloon is a semi-circular arch with a height of 3 mFinesandWell beddirsiltstone slicesa width of 3.2 m, and a net section area of 8.6 m2The two portions are supported with bolt-shotcretDunesand13.0bedding hard and denseing. All the bolts are 16X 1 600 mm in specifica-tions, which are anchored with concrete ofFig 2 Columnar section of rocks around the test roadwayTable 1 Phenomenon of underground pressure of coalfaces in 3a coal seamCoalface First caving Periodical caving Front pressure influence Load on support/kNDynamic pressuredistance/mdistance/mdistance/m31274340331351.17FDT4X554K chock-shield power supports are way lower than the floor of the coal seam must beused in coal face 23.05. From the data in Table 1filled, and the allowable specific pressure of fillithe theoretical value of the specific pressure on sup- materials is required properly higher than the pres-port floor-bar is 1.8 MPa under the condition of av- sure on the floor-bares of power supports.erage support working resistance and 2. 1 MPa unThe interaction between an inclined roadwayder the maximum support working resistanceand a coal face should be concerned in order to deal2 Selection of filling range中国煤化工This interaction dependso fill a cross-roadway as artificial bottom of aHCNMHGdway to the coal seatcoal face must assure that supports in the coal face The farther the inclined roadway is from the seamcan stride across the roadway safely, and the floor, the smaller the influence of mining will beamount and the cost of filling are as low as possibleThus, the roadway can keep stable more easily.It is c554 eal with the horizontal portion of And the stabilization of roadway has less effect ona cross-roadway. The part of the horizontal roadthe coal face. When the distance from the roadwayZHOU Hua-qian et alStudy on Filling Cross-Roadway in Fully-Mechanizedto the seam floor is far enough, it will not affect the of the supports will not make the maintain conditioncoal face even though the roadway falls apart during of the roadway worse. Therefore, the preliminarymining. On the contrary, if the roadway is too close choice of filling range, which is 3 m downward toto the coal seam and its support is not strong e- seam floor, or 8. 5m in length, is confirmed. Thenough, it will collapse under the action of abutment filling range is 43% less than the filling range deterpressure, and the partial related seam floor will sink mined by the traditional method in Baodian Colbviously. The supports of the coalface will be diffiult to move ahead and the production of coal will be 1.3 Selection of water-cement ratio of HWCMconstrained to stop until proper measures are adoptUsing hwCm to form the artificial bottom ofed. Therefore, in order to make a coal face keep coal face, there are two points to need to take intoormal production and stride across the cross-road- account. One is that the allowable specificway safely, the suitable strength of filling material of artificial bottom directly exposed to floor-bars ofand the filling scope must be considered properlycoal face supports should be higher than the normalFLAC3. 3. a two-dimensional explicit finite specific pressure of floor-bars, and the other is thatdifference program, is used for the selection of the the part of artificial bottom indirectly exposed tofilling range. The procedure of determining the fill- floor-bar should pledge to the stabilization of roading range is divided into three stages. In the first way under the condition of excavating the overlyingthe mechanical properties of surrounding coal seamrock are defined with a symmetrical 80 m X80mWhen the water-cement ratio of the hwcm ismodel, through modeling the process of mining the 2.75compression strength3d coal seam and its ground behaviors under differ- 3. 0 MPa, and the allowable specific pressure isent values of the mechanical parameters of sur- 2.5 MPa, which is higher than the average pres-rounding rock. Under the condition of finally de-sure acting on floor by the floor-bars of supportsfined mechanical properties of rock, the position of (1.8 MPa)and very close the maximum pressurepeak abutment pressure is at 5 10 m inside the (2. 1 MPa)u, Obviously, it can satisfy the requirecoal face, the concentration factor of abutment pres-mentthe water-cement ratio for thesure 1.7-2.4, and the deformation of roadway in first part is determined to be 2.75: 1 in test. Fill3, coal seam 80 mm after the coal seam is mineding body per cubic meter is made up from 325 kgThe modeling results are very close to the case ob- HWCM and 895 kg water under the above water-served in situ. In the second stage, the mechanical cement ratioparameters of rock are the same as the ones in theIn order to determine the required strength offirst stage and the behaviors of rocks around a road- the second part, the filling cases using the manualway are compared with a 60 mX 26 m model under wooden chock method were investigated. In Basthe condition of different distances downward from an Colliery, the traditional filling method can alsothe roadway to the coal seam. When the distance satisfies the requirement of safety, and the deformaeaches 3 m and the roadway is just supported by tions of the filled road way are less than 10%.Genbolt-shotcreting, it keeps moderate stable under the erally, the supporting strength of manual woodenimpact of mining the 3d coal seam. The deforma- chock is about 0. 8tions between two sides of the roadway and betweenits bottom and roof are 250 mm and 440 mm re-spectively. The distance is preliminarily taken as theTHE中国煤化工 equired strength of theCNMHGI I MPa. It must bet in the testing site the water-cementnecessary filling range. At the last stage, the influ- ratio of the HWCM is still 2.75: 1 for the secondence of supports in the coal face, which act on the part due to the first test. But the investigation isloor of co5 553%ith the maximum working resis- still full of meaning and shows the potential furthertance, is assessed. The result shows that the action to reduce fil116Journal of China University of mining & TechnologyVol, 11 No. 22 Filling Method and Test Effectthe No. 76 and No 81 supports passed across2. 1 Filling methodthe filled zone, and the No. 71 and No. 123 supportsa double-liquid filling system was used in thewere out of the filled zone and always passed acrossfilling test. The system is composed of two TBWnormal rock bottom50/15 mud ram pumps and four JBJ-300 agitatorsFig 3 and 4 respectively show the variation inIts theoretical filling ability is 6 m/h, and the max- pressure on the front props and the rear props ofimum pressure 1.5 MPa. The two components of power supports during the coal face passing throughthe HWCm were mixed with water and pumpedthe filledcanigh two high-pressure hoses to the filling site Fig 4b that the peak pressure on the front and rearrespectively. The two slurries were mixed with aof the No. 7mixer before pumped out20 MPa, respectively. At the same time, the peakIn order to form a proper filling space as de- pressure on the front and rear legs of the No 76 andsigned in an inclined roadway, a separating wall was No 81 supports is respectively 1530 and 10built up at first in the roadway at the low end of the 15 MPa. So the peak support resistance is not deThe wall is 0.7 m in width. It was creased obviously due to filling workonstructed with two bags filled the HWCM iplace. Several wooden props and thin wooden plateswere used as the formwork of the wall1M6业0002. 2 Test effect and analysis920212223242526272829The coal face smoothly passed across the zone(a)No7I supportfilled with the hwcm from 26 to 29 November1999. In the procedure, the advance speed of thecoal face was 9.8m/d, obviously higher than theaverage advance speed of 6. 9 m/d in that monthThis shows that the artificial bottom filled with tI1718192021222324252627282930HWCM completely satisfies the requirement of production of the coal face. In that month. the totaladvance distance of the coal face was 214 m and theoutput of coal 6 262 t/d20According to in-situ observations, the influence1617181920212223242526272829range of the front abutment pressure in coal face23405 is within 50-60 m. During the impact of th(c) No 8I supportfront abutment pressure, the deformations betweenbottom and roof of the horizontal connecting road- Fig 3 Variation in pressure on the fore props of supportsway and between its two sides increased 150 andduring coal face passing through filled area220 mm respectively. And new cracks occurred inBut there is difference between the averagesome parts of the shotcrete layer in the roadway, support resistance of supports on rock or on the artieven part of shotcrete fell in. The deformation of ficial bottom. from the 26th to 28th daye averthe downward-unfilled inclined roadway was littleYH中国煤化工 ont legs was13andless than that of the horizontal connecting roadwayCNMHGthe No 71 and No 81in the same period. Generally, the roadways were supports, while it was only 8.8 MPa for the No. 76still at a medium stable state, which is approximate- support. The average resistance on rear legs of thely consistent with the above analysisNo. 71 support was 8. 1 MPa, while it was onlyTherertexetr supports monitored with auto- 3. 2 MPa for the No 81 support. Why is the sup-matic circle diagram logs, shown in FigZHOU Hua-gian et alStudy on Filling Cross-Roadway in Fully-Mechanizedroadway so small? There are three reasons. First, 3.2 Filling with H WCMthe strength and the stiffness of the HWCM areIn the test, the material consumption to fill thelower than those of surrounding rock. Second, the crossing road way with the hWCM is as follows 88strength of some part of the filled area is less than t HWCM, 2 filling bags, 3. 1 m square timberdesigned value because the two slurries of the and 10. 5 kg nail. The price of the HWCM isHWCM cannot completely mix together due to an 550 RMB/t. One filling bag costs 2 820 RBMimproper operation. Finally, the stiffness of wooden And the depreciation charges are considered aschock in the roof of the inclined roadway above the 5 000 RMB in addition The total material cost forcoal seam is lothe hwcm to fill one cross-road61 256 RMB. Compared with the traditional woodchock filling method, the new one can save 41.6%MiNdyof material cost. It should be pointed out that during171819202122242526the test the hWCm agglomerated quite badly, andlead to block up pipes very often and wasted materi-(a]No 76 supportals because of transporting the hwCm to the un-derground spot too early (10 days before used ). All41H~A人these problems could be resolved after normaliza1617181920212324252627282930tion. In a normal condition, the wastage of materials could be reduced to further extent and a better e-(b) No 123 supportconomic effect could be achievedFig 4 Variation in pressure on rear props of support4 Conclusionsduring coal face passing across filled area3 Economic Analysis of Filling with1) To mechanically fill the HWCM is an eco-HWCMnomic and efficacious method to build up artificial3. 1 Traditional wooden chock fillingbottom of a mechanized coal face wherFilling wooden chock to form artificial bottom Toad way. Compared with the traditional woodasng time to deal with crchock method, it has such advantages as low materoadways in Baodian Colliery. Usually, its fillingrial cost, quick construction speed and good sealinglength is 15 m downward from the bottom of coal abilityseam. The lumps of wood are set skin-to-skin for2)The method of calculating the filling rangethe top two layers, and less than 500 mm Xfor an inclined roadway as artificial bottom is correctand the result is reliable. In the condition of 3, coal500 mm in spacing for the other low layers. To filthe inclined and horizontal portions of one crossseam of Baodian Colliery, the theoretical filliroadway needs square timber of 72 and 76mrange is 8. 5 m in length, being 43 less than thespectively. The total consumption of square timbertraditional fillin3) To fill the hwcm as artificial bottom of ais 148 m for one cross-roadddition420 kg nail will be used to connect the lumps of mechanized coal face, the water-cement ratio for thewood. On the basis of current prices, the prices ofzone directly contacting with power supports shouldimber and nail中国煤化工 pressure larger than the680 RBM/m and 10.28 RBM/kg. So the total PCNMHG by floor-bars of powermaterial cost to fill one cross-roadway with wooden Supports. I he strength of the HwCM in the otherchock is 104 949 RBMzones can be about I MPReference1]周华强,王光伟,曲庆贺,等.高水速凝材料容许比压的实验研究[J].中国矿业大学学报,2001,30(4):337-340.