Experimental study on stability control technology of surrounding rock of deep roadways in coal mine

Experimental study on stability controltechnology of surrounding rock ofdeep roadways in coal mineLuo Yong,.Yuan liang,. Yang Yang(l. National Engineering Research Center for Coal Gas Control, Huainan, Anhui 232001, China2. Huainan Mining( Group)Co Ltd, Huainan, Anhui 232001, China)Abstract: In order to solve effectively the problems of deep mining with safety and high efficiency, the multiple factors influencing the stability of deep rock roadway and technical problems are analyzed in the light of thesevere situation of effective mining for deep coal resource, and the stability control methods for deep rock roadway are provided, which are based on the idea of combined support with separated steps and integral control ofsurrounding rock of deep rock roadway. The suggested methods were applied to a deep rock roadway with-648 mdepth in Gubei coal mine of Huainan area. The field test was carried out and the in-situ monitoring was implemented, and the support scheme was optimized and adjusted to improve the stability of the surrounding rock ofthe roadway based on the feedback analysis. The results showed that the stability can be improved greatly by theprovided control methods for deep roadway. The present methods for stability control of deep rock roadway canbe used to other deep rock roadways with the similar conditionsKey words deep rock roadway; mining with safety and high efficiency: stability; in-situ monitoring; softrock1 Introductioncreep; outstanding phenomena of dilatancy arshown as internal joints, fractures, cracks and theirwith the development of coal mine production, opening under high deviatoric stress; the concussioncoal resources in shallow are gradually exhausted and of coal and rock deformation is displayed as suddenthe inevitable trend of coal extraction is to stretch to and sharp increase in the course of deformation indeep. At present, the major countries of coal produc- stead of continuous and gradual deformation. Accor-tion in the world have successively gone into deep ex- ding to the actual mining practices at home andtraction, such as England, Japan and poland, etc.abroad, once the mining depth reaches 700 m toThe mining depths of these countries reach 1 1001 000 m, obvious characteristics of deep mining willto 1 400 m In Germany, the mining depth is general- be presentedly between 700 m and 1 500 m, and the averageDeep mining environment and the deformationdepth is close to 930 m. The mining depth of many behavior of coal and rock bring a series of severe chalmining areas in our country had already exceeded lenges to surrounding rock control and mining safety800 m, even some were over 1 000 m. Compared to Theoretical researches and practices indicate that thethose in shallow, the deformation characteristics of load of support in deep roadway is related to self-loadcoal and rock in deep change radically as followcapacity and released expansion energy of surrounBrittleness in shallow is transformed into plasticity in ding rock. The stronger the latter two influence facdeep; strong time effect of coal and rock under tors are, the smaller support load and the easier road-highstrata stress is presented as obvious rheology or way support are. But the contradiction between sur-Received 11 January 2013中国煤化工CNMHG12 ENGINEERING SCIENCErounding rock self-load capacity and released expan- size and the direction of ground stress have a directsion energy is that they cannot reach their maximum impact on roadway section optimization, roadway po-ly. In deep roadway, a large sition selection, support scheme, supporting parameamount of expansion energy at the beginning of road- ter design, etc. In particular, horizontal stress has anway excavation must be released in some ways. It cer- important impact on the stability of roadway surtainly will cause the strength of surrounding rock to rounding rock Because underground rock is not ondecrease rapidly if it is uncontrolled, which goes ly influenced by gravity but also affected by geologiagainst roadway maintenancecal structure movement the direction of maximumHuainan mining area, in which geological corstress is consistent with the stress direction in generalditions are very complicated, is characterized by frac- which is revealed by geological structure movementtrajectod stressconcentration stress caused by mining can reach 2- field of the coal and rock must be grasped by field5 times of original rock stress. The scope of fracture tests and other research means before the design ofzone and plastic zone of roadway surrounding rock roadway direction, shape and supporting parametersusually reaches 3-5 m, and roadway will be serious- With the development of mining depth, geological enly damaged by high stress and roadway maintenance vironment deteriorates, cracked rock increasesvery difficult. So it is the typical represd stress upind inflsoft strata mining area in our country. In Huwater increase, and ground temperature also rises. Soarea, based on introducing and employing ad- a series of severe challenges will be encountered fored foreign technologies, technical route for sudeep coal mining 2.3)rounding rock overall control by rock self-strengthFirst of all, because of ground stress increaand pre-stress truss support in"wedge-shaped rein- strength and deformation characteristics of surroun-proposed, and a series of support ding rocks in deep are vastly different fromtechnical systems with independent intellectual prop- shallow, and most surrounding rocks in shallow areerty right, which can be applied to different types of in elastic state. After mining in deep due to the seriroadways, are successfully developed, such as high ous contradiction between high ground stress and lowpretension steel strand truss support technology, small self-strength of surrounding rocks, high stress con-aperture steel strand pretension cable beam technolo- centration, which is caused by secondary stress fieldleads to the result that thehigh stress and extreme soft rock bolt-grouting sup- focus stress exerted on superficial surrounding rockport technology. Effective technical measures for soft exceeds the rock strength, and surrounding rocks enrock roadway and coal roadway and their repair in ter into the condition of fracture and plastic dilationdeep mines are provided, and support and repair tech- from exterior to interior accordingly, and then intenologies of rock roadway and gas extraction roadway gral instability is easily caused by large deformationare basically resolved within -700 m level 1, 2)Secondly, with increase in mining depth, see-However, due to dynamic variation rule of sur- page pressure of groundwater increases accordinglyrounding rock movement, stress field and crack and pore-water pressure of superficial surroundingfield, and the multi-field coupling rules are not com- rock considerably decreases after roadway excavapletely mastered; support technology system and ef- ting. As a result, near-field surrounding rocks effec-fective support design parameters of high pre-stress tive stress of roadway increases and surrounding rockanchoring support or bolt-grouting support cannot be stress exceeds its strength further. Hence, destructionprovided for different kinds of surrounding rocks. and instability of superficial surrounding rock areExisting research results cannot meet the needs of surexacerbatedounding rock stability control in deep roadwayThirdly, with increase in development depthwhich is urgent for further researchground temperature increases. After roadway excava-2 Difficulties of roadway surroundingting, higher temperature gradient and additionalstress, which are produced in certain depth of surrock controlrounding rock because of roadway ventilation, causeAs far as mining engineering is concernedlayer separation of surrounding rock and have asiderable influence of中国煤化工 pact ofCNMHGNo.2,Apr.201413cumulative damage caused by seasonal temperature dingshan and Xinji 3.31variation on layer separation is consideredthe extent 4 Surrounding rock control of deep rockof surrounding rock rupture propagation will becomemore serIousroadwaydeep roadway is influenced by comprehensive effectAs a matter of fact, stability of surrounding rocknot only depends on its strength and defcof high ground stress, high osmotic pressure and higltemperature gradient. Although extent and scope of property(they are collectively called mechanical prop), but also its stress state. Stability control ofthe impact on surrounding rock stability are differentit can increase contradictions between stress androunding rock should be started with improvement ofstrength of surrounding rocks The difficulties ofits mechanical property and stress state s.5.surrounding rock control and roadway support under 4.1 Restoration and improvement of surroundingrock stress stateBar. plex conditions with high stress in deep mineBefore roadway excavation, although surroun-have become a major technical problem which affects ding rock bears high ground stress, it is in a state ofmine safety production and economic benefits now high confining pressure, thereby it has very high com-and in future. What's more, the problem becomespressive strength which is much larger than its maximore and more seriousith the increase of miningmum deviatoric stress, and it is still in elastic stateExcavation leads to lateral pressure decrease in cer3 Classification system of roadwaytain range of surrounding rock, and lateral pressuresurrounding rockof superficial surrounding rock is decreased to zeroMeanwhile, the stress moves to circumferential direcor theoretical research on control of deep road- tion of roadway section, then stress concentration issurrounding rock stability, the first research caused by the change, and circumferential strneeded is surrounding rock classification method and creased by 2-3 times. For roadway with buriedcriterion so as to reasonably select design theory, cal- depth about 800 m, if unloading amplitude of conficulation parameter, construction method and processPerficial surrounding rock reachesIn recent years, through geological investigation of above 20 MPa, circumferential stress will increase bydeep rock roadway, ultrasonic testing of surrounding 40-60 MPa and the maximum shear stress will inrock, testing of in-site ground stress and analysis of crease to 60-80 MPa. However, comprehensivesurrounding rock stability under various conditions in comparative analyses according to three researchtypical mining area, and referring to relevant national methods(calculation based on results of rock mechanand industry standards of classification method of sur- ics experiment and modified H-B criterion, back anal-gysis calculation of surrounding rock parameters basedting in tunnels, classification system of deep roadway on results of field deformation observation and methis proposed under comprehensive consideration of sur- od of engineering analogy) show that maximum ofrounding rocks integrity, character of structure plane uniaxial compressive strength is only 15 MPa. Se-and its filler, in-site stress distribution and self-stabili- rious contradictions between high ground stress ofzation time of surrounding rocks without support. surrounding rock and its low self-strength lead to rapDeep roadway surrounding rocks are classified into id deterioration in surrounding rock afteI,Ⅱ,Ⅲ,ⅣandⅤ in the system, and deformation The cracks quickly emerge and propagate from extestrength parameters of all kinds of surrounding rocks rior to interior, and certain range of surroundingare obtained by comprehensive analysis 24. The clrocks are disrupted and enter into a stage of post-peakfication system is only a classification method of or residual strength. The stress in excess of surroundsurrounding rock specializing in deep roadway of ing rock strength transfers to deeper rock, as showncoal mine at home and abroad. It has availability and in Fig. 1, in which X-coordinate denotes the distanceoperability to the judgment of deep rocks roadway sta- between the given point in surrounding rock and roadbility and direction of support design and construc- way surface, and y-coordinate shows the rock stresstion. The system has been widely verified in deep of the same point, and t is the corresponding time af-rock roadway in mining areas such as Huainan, Ping- ter roadway excavatiHi中国煤化工eCNMHG14 ENGINEERING SCIENCEment shows that the scope of fractured zone in deep in order to make stress disperse effectively, guniterock roadway and stress disturbed zone can reach 5- concrete layer should have sufficient bending7 times of roadway width, or even more B 6. There- strength 51fore, in order to keep stability of roadway surroun- 4.2 Surrounding rock reinforcement andding rock, it has to be supported immediately afterconsolidation measuresexcavation and the stress state has to be restored andAfter roadway excavation, high stresses accumuimproved as soon as possible by reasonable meansated in surrounding rock are released into roadway diand then make the stress peak be transferred to deep rection. Then stresses in a certain range of roadwayfar as possiblesurrounding rock decrease drastically, and with thepassage of time, degree and extent of the decreaswill be further raised, which means that self-bearingcapacity of surrounding rock is reduced graduallysurrounding rock looseness range will be widened af-ter the influence of excavation, and stability of suOriginal rock stress oorounding rock is decreased. Coal and surroundingrock will be broken under pressure. Especially in thebottom of roadway, rocks will fracture and lose itsFig 1 Process of stress peak of surrounding rockstability easily, and present drastic floor heave. Its de-transferring to the deep rock after excavationformation and destruction are present not only as distorted destruction of rock material, but also mainly asintegral structure deformation and instability 2-8.Sorock stress after extraction, traditional passive sup- stability control of deep roadway must concentrate onport method (U-shaped steel support)and bolt support the control of surrounding rock integral structurenod (ow pre-stress) cannot provide sufficient and effective support measures should be taken onholding power in time, so they cannot promote inhe- roadway roof, sides and especially on floorrent strength of surrounding rock. The restorationAs a matter of fact, in soft rock roadway withquantity is far below the need of surrounding rock sta- high stress, disadvantages of U-shaped steel supportbility maintenance 2)lie in that it cannot actively provide sufficient holdingSurrounding rock control demands that support power foobject itself has sufficient shear strength. Because of uneven and the cost is high, which means it cannotthe brittleness of surrounding rock, very small shear be used as a main support form. However, combiningdeformation can cause failure of adhesion. Therefore, with back filling and other support measures suchthe support structure must have sufficient shearcables and grouting, U-shaped steel sup-strength and sufficient toughness which is called de- ports are used as the supplement support of deep roadformability, and the intrinsic strength of surrounding way surrounding rock, the effect will be satisfactorock can be increased. High and super-strength boltrysupport taking resin roll as anchor agent, which is theIn order to control deep surrounding rock effec-notion of active support such as high pre-stress bolt tively besides improving the stress state of surrounsupport, can meet well the requirements mentioned ding rock, Its intrinsic strength(cohesion and internalbove 2. Considering the present technical levfriction angle)needs to be increased by reinforcementeconomic factors, what we can do now is to exert suf- measures, so self-bearing capacity of it can be im-ficient high-tightening forces on anchor, and exert apreate that cracks ofcertain surface stress actively on roadway free- ding rock can be sealed effectively by grouting reinsurface by stress dispersion of gunite concrete layerforcement, and its integrality and adaptability to miTherefore, exerting a reasonable pre-stress is the key ning pressure are improved, so long-term stability ofof technical measure availability, which contains two surrounding rock structure is further improved. Ataspects: on one hand, special outfitting tools for high present, the main economically viable measures ofpre-stress anchors need to be researched and devel- surrounding rock reinforcement which can be technioped, with which the reasonable quantity of precally achieved are stronchored supports. inclu-stress can be exerted on anchors; on the other hand, ding super-strong and中国煤化工e,andCNMHGNo.2,Apr.20141high-Strength and high-toughness grouting reinforce- faster measures of stress state improvement and resto-mentration are used, the larger the stress peak transferredThe technology mentioned above includes two to the distance from roadway surface is, and the biges:aback filling grouting, whose main purpose ger the load-bearing ring is, the lower the level of suris to improve stress property and bearing property of rounding rock breach propagation and the more stableU-shaped steel, and in which shallow hole cement the surrounding rock is>grouting predominates; b. surrounding rock crackMechanical characteristics of deep roadway sur-grouting, of which the main purpose is to improve rounding rock are intensively studied in Ref [8]rock mechanical property and bearing property of an- which points out that support measures must be coor-chorage zone, and in which deep hole chemical grou- dinated with mechanical property of surrounding rockting predominates. Stability of surrounding rock struc- in deep roadway. It cannot be finished at one time biture can be greatly increased and deformation can be needs coupling supports for two or more times, socontrolled by flexible application of these two grou- that the surrounding rock can be collectively con-ting measurestrolledWhen obvious water penetration is found in roadTherefore, the stepped combined support sys-way tunneling and excavating, the common measures tem, which is made up of following several kinds ofat present are immediate cessation of tunneling, and technical methods, can be used in the control of surusing good permeability, rapid cure and grouting ma- rounding rock stability in deep roadway b5.erial with high consolidation strength to implementThe first is to make normalpre-grouting in working face and consolidating within roadway free surface be restored maximally in thecertain depth of surrounding rock, so water channels shortest time after excavation and improve the stresscan be sealed, pore pressure decreases and effective state of superficial surrounding rock broken by roadstress increases, and integrality and integral strength way excavation, so that the extrinsic strength and theof surrounding rock can be increased simultaneouslydeformation modulus of surrounding rock can be in-4. 3 Control measures of stress transfer andcreased, and the opening deformation in the normalload-bearing ring extendingdirection of roadway free surface and structural surIn order to prevent roadway surrounding rock face can be limitedfrom quick deteriorating after excavation, appropriateThe second is to use high-strength support to reures must be taken as soon as possible to transfer inforce surrounding rockthe stress peak controlled to the deeper surrounding strength and strictly limit its shear deformation alongrock which has stronger load capacity. At present, the gliding plane of initial fissure and secondary crackcommon measures are controlling expanding of fracThe third is to consolidate surrounding rocktured area by orderly arrangement in space-time with fractured zone and restore it in damaged zone, so thateveral supports such as high pre-stressed super- integrality and integral strength can be restored andstrong anchor, high- strength and high- toughness improvedgrouting, pre-stressed cable, etc. The stressThe fourth is to transfer high stress peak withinpeak controlled can be transferred to the deeper sur- certain range nearby roadway surface into deeperounding rock. Finally, anchoring reinforcement rock, and integrate bolt-grouting reinforced area withone, grouting consolidation zone and deep stabi- deep stable rock, so that the load-bearing ring of sur-lized zone can be connected into a joint bearing like rounding rock can be extendedsandwich structure. Load-bearing ring of surroundingThe techniques described above should be joint-rock can be enlarged to expected thickness, and road- ly used and implemented step by step For complicaway deformation can be controlled within allowable ted surrounding rock(such as grade l and grade Vextent, so that long- term stability of roadway sur- surrounding rock), on the basis orounding rock can be realized. The methods men- measures of low-grade surrounding rock, temporarytioned above are control measures of stress transfer support measures can be used, which use advancedand load-bearing ring extending 2.3grouting bolts to make broken surrounding rock pre-4.4 Technology system of roadway surroundingconsolidate and pre-strengthen in working face, androck controlsupports with sheds are necessarv. Tempo-Both the theory and the practice indicate that the rary support has two中国煤化工 preventCNMHG16 ENGINEERING SCIENCEadway roof and sides from caving, and control con- mesh in working face support super-high strengthstruction safety: the second is to exert passive stress bolt with high pre-stress, the second support which ison the surface of surrounding rock because of its de- carried out by cables and in 80-100 m behind worformation, and form a combined support system in king face, and grouting reinforcement which is carsurrounding rock together with bolts and anchors, so ried out in 200 m behind working face. Based onthat confining stress can reach a higher levelthese, and according to actual situation of the mine5 Engineering casenumerical simulations of multiple plans are used tooptimize support projec5.1 General situation of the caseway support areThe southern main return airway, at -648 m leyFirstly, horseshoe section was selected after optiel of Gubei coal mine in Huainan, is 12-15 m away mization of roadway shape; secondly, grouting boltfrom the floor of 11-2 coal seam in vertical direction. was used; thirdly, steel mesh U-shaped steel supIts total length is 2 000 m. Its surrounding rock is port grouting in whole section are used to realizemainly composed of carbon mudstone, sandy mud- first support; finally, super-high strength bolt withstone and weak cemented siltstone, etc, and is char- high pre-stress high strength pre-stressed cable areacterized by low strength, rich fissure and bedding used for second support. Thereinto, the reasonableand poor integrity. Some parts of the airway pass time of carrying out second support is determined bythrough the F9.2 fault, nearby which there are four field monitoring after first support, and the periodsecondary small faults. Within the fault zone, rocks that rock deformation trends to slow or stress trendsare fractured, lithologies are very bad and self-stabili- to stabilize can be considered as the reasonable timeties of the rocks are extremely bad, too. So, it is very and roadway roof is supported by bolt support. Specif-difficult to supportic supporting parameters are as follows5.2 Roadway support design5.2.1 Roadway sectionpression strength of siltstone specimen is o0, 3Results of laboratory experimentsRoadway section is designed as horseshoe shapeRadius and angle of circle on top of section are 2.7 m86.7 MPa, elastic modulus is 33. 4 46 GPa, Pois- and 140, respectively. The radius of circle on roadsons ratio is 0. 13 -0.28; uniaxial compression way side is 4.0 m and the angle is 63. Roadway secstrength of carbon mudstone is 3 1.24 MPa, Poissons tion designed and supporting parameters are shown inratio is 0.23Fig 2mudstone is 3 1.24 MPa. Poissons ratio is 0.24. Acording to the modified H-B criterion and consideU-steel support2L28007000 Concrete spray layer150msurrounding rock obtained is about 3. 23 8.31 MPa17 boltsIn addition, tests show that longitudinal wave veloci-ty of its surrounding rock is about 1 800 m/s, and its418.24Lstrength-stress ratio is.54. field tests show that the00R2700maximum horizontal stress is 19. 1 x 20.2 MPahich is at a high stress level obviously. Azimuth ofR4000the maximum horizontal stress is 329 N 341. Coef-Side and bottom boltsficient of lateral pressure is 1.10 on average, whichBase angel boltsmeans horizontal stress is close to vertical stress inthe test area. According way surrounding rock oftion system 2, the roaFig 2 Cross section and supporting parameters ofsouthern main return airway, at-648 m level of Gu-5.2.2 Laying of steel meshbei coal mine, which is in a typical high stress fieldbelongs to grade Iv. This type of roadway usuallySteel mesh is laid in arched top and two sides ofroadway, which is 6 mm in diameter and made fromneeds to be supported by combined support methodssteel, The size of mesh is 100 mmx 100 mmIngvanced grouting bolt in front of working face, the firstAfter shed suppsupport which is carried out by guniting with bolt中国煤化 I WhoseCNMHGNo.2,Apr.201417thickness is more than 50 mm should be sprayed to next step is grouting in deep borehole, and groutingseal surrounding rock and to prevent roadway sur- palarameters are altingrounding rock from weathering and roadway surface hole is 2 000 mm and length of pipe is 1 800 mm;arcaving. Strength grade of concrete is C20. Ratio of ray spacing is 2 000 mm; length of sealed borchole iswater to cement is 0.4-0.6, weight ratio of cement, 400-500 mm; grouting pressure is 3.5 MPa; eachsand and gravel is 1: 2: 2, and the amount of accele- section has 13 grouting bolts. Two bolts at the bottomrating agent is 3 of that of cementare made from seamless steel pipe which is 48 mm in5.2.4 Steel supportdiameter and 3.5 mm in thickness. the other bolts areThe roadway roof is supported by 36 U-shaped made from 6 inches(I inch=2. 54 cm)seamless steelsteel supports and the spacing is 500 mm. U-shaped pipe. In order to prevent leaking from roadway floorsteels are joined by traditional clips, prefabricated on a preventing- grout layer with 100 mm in thicknessthe ground and assembled underground. The back of and strength grade of Mu10 is constructedsupport is filled with gravels to let supports work actively as soon as possible and to prevent large moveGrouting holeL=2000ment of surrounding rock5.2.5 Advanced groutingIn order to prevent roof from caving, arched topof roadway is grouted by advanced grouting boltswhich is 4 500 mm in length and is installed with a20 angel to the direction of roadway. Distance of twobolts is 500 mm and array spacing is 2 000 mm. Eachsection has 13 grouting boreholes. Grouting bolt ismade from 6 inches seamless steel pipe. Sealed borehole length is 400- 500 mm. Before grouting, working face should be constructed by guniting to preng during the process of groutingmaterial is p52.5 sulphoaluminate high strength andFig 4 Cross section of grouting andsupporting parameters(unit: mm)quick-setting cement. The amount of grouting is50 kg/m. Layout of grouting bolt is shown in Fig 35.2.7 BoltThlongitudinal bar lefthanded high-Strength and pre-stressed bolt. Bolt mateSpacing 500rial is screw-thread steel with architectural grade ofI. Bolts diameter is 22 mm and length is 2 800 mmThe arrangement of bolts are quincunx with the spacing of 700 mm between two adjacent bolts, and anchoring length of bolt is more than 1 800 mm. Pre-stress is no less than 50 kN. layout and technical requirement of bolt are shown detailedly in Fig. 25.2.8 CableCable material is low -looseness steel strand withFig3 Distribution of grouting bolts and supporting18.24 mm in diameter and 8 000 mm in length. cablelayout is perpendicular to roadway outline; each sec-5.2.6 Grouting on the whole sectiontion has 9 cables. The spacing between two adjacentThe first step is grouting in shallow borehole, cables is 1 400 mm. Each cable pre-stress is no lessand grouting parameters are as follows: length of than 120 kN and is anchored by resin anchoringgrouting pipe is 500 mm and length of grouting bore- agent. The whole borehole should be grouted excepthole is 1 000 mm; array spacing is 5000 mm; each for anchored parts Layout and technical requirementsection has 5 pipes; grouting pressure 1s 2.5 MPa. of cable are shown detailedly in Fig. 2Layout of grouting borehole is shown in Fig 4. TheIn order to ens中国煤化工e andCNMHG18 ENGINEERING SCIENCEsafety of construction, the ring-cutting method is shown in Fig. 6- Fig 9adopted, which is a technology that constructs largesection roadway in fractured and weak rock mass. Itsmiddle of working face to ensure stability of working45三40face. Particular construction process is shown in Fig. 520406080100120140160180(a) Deformation curve of roadway sides092040608010012014016013Fig 5 Construction drawing of ring-cutting5.3 Analysis of ground pressure monitorin(b) Dcformation curve of roadway roofAfter the first support, ground pressure of road-way was monitored as soon as possible. Field measure-ment results show that in the period of 30- 35 d afterfirst support, deformation of roadway surroundingrock becomes slow, so reasonable time of the second58osupport is 30- 35 d after the first support. After completion of the second support, support effect wasmonitored in the field. monitoring contents includeobservation of roadway section convergence, obser-Time(c) Deformation curve of roadway floorservation of the force acting on bolts, cables and steelig. 6 Deformation curves of deep surrounding rocksupports, and observation of floor heave. Results are120001180◆ Left shouldeFig 7 Monitored curves of stress on anchor force vs time中国煤化工CNMHGNo.2,Apr.201419800Time/d-e-6m3m→ Borehole entrancentrance(a) Left side of roadway(b) Right side of roadwayFig 8 Monitored deformation curves of deep surrounding rock of roadway一米- Roof -Left side· Right sideand on left shoulder is 75 kn. The results show that-Left shoulder-+Right shouldersurrounding rock stress on right shoulder is slightly0.5bigger than the others, so the roadway is a bias-stressoneDisplacement of roadway left side in deep in-Timedcreases fast within the first 15 d. then becomes slowFig 9 Monitored curves of support forceafter about 90 d trends to stabilize and the maximumis about 80 mm. In contrast, displacement of rightMonitoring results show that roadway surrounside increases fast within the first 10 d. then becomesding rock becomes stable after the second support.slow after about 85 d trends to stabilize, and its maxHorizontal displacement variations of surroundingimum is about 60 mm. The results show that the dis-rock show that deformation at initial stage is large. placement of left side is larger than that of right sideWith increase of distance from working face to monwhich is consistent with the result of stress on cablestoring section, deformation becomes fast within the Displacements of roadway sides trend to stabilize fi-first 60 d, then becomes slow, and after about 140 d nally, which shows roadway deformation trends totrends to stabilize. Deformation of arched roof is fast stabilize, and it shows that support has good effectswithin the first 90 d of its falling, then slow and af- accordinglyter about 150 d trends to stabilize. a similar linear inBecause guniting was not carried out in timecrease of floor heave is fast within the first 50 d, and pressure cells didn t completely contact with road-early floor heave deformation is much larger than that way surface after being installed. So pressure moniof arched roof falling. Obviously, support of road- tored by pressure cells is very small at early stage(theway floor should not be neglected. Therefore, road- first 10 d)and even approaches zero. Then pressureway floor must be supported in time. After 50 d, due gradually increases, after about 40 d the speed of in-to construction of support measures against floor crease becomes slow, and after about 55 d trends toheave, deformation speed decreases obviously, and stabilize. Pressure on arched top is the largest and thatafter about 150 d trends to stabilize. Results illustrate on shoulder is the smallest, however, the overallthat the measures against floor heave are effective andpressure of support is not large. Obviously the resultood effects are obtainedis related to guniting which is not carried out in timeAfter about 15 d. stress on bolts trends to stabi- after installing pressure cellslize. The maximum stress, about 1 kN, appears ofIn conclusion, the overall support effect is satisroadway shoulder, and maximum stresses of bolts on factorytwo shoulders are both 115 kN. Maximum stresses of 6 Conclusionsleft side bolt and right side bolt are 100 kn and 75 kNwhich are slightly smallerBy research on stability control methods oftwo shoulders from the overall trend of curve stressrock roadway and its case, good support effecton cables raises gradually, which increases fast in the tained, and conclusions are as followsfirst 5 d. then becomes slow, and after about 20 d1) Theories on stabilization and support of sur-trends to stabilize. The maximum stress of cable on rounding rock in deep rock roadway are quite differight shoulder is 182 kN, and that on top is 120 kNrent from that in colH中国煤化工AfterCNMHG20 ENGINEERING SCIENCEmining in deep, deterioration of geological condi- supplied accordingly to keep anchoring force alwaystions and obvious increase of strata stress, water pres- in a higher force state, so that surrounding rock stabchallenges ity can be effectively improvedto surrounding rock stability and safety constructionof roadway. So, specific support methods should be Referencesapplied according to different types of surrounding [] Yuan Liang. Theoory and Technology of Gas Drainage and Capturerock and different influencing factorsSoft Multiple Goal Seams of Low Permeability [M]. Beijing2)Stability of surrounding rock not only deChina Coal Industry Publishing House, 2004. (in Chinese)[2] Yuan Liang. Control of Surrounding Strata in Deep Mine roadpends on its strength and deformation property, butay and Practice in Huainan Area [M]. Beijing: China Coal In-also its stress state. Stability control of surroundingdustry Publishing House, 2006.(in Chinese)rock should start with improvement of its mechanical B3] Yuan Liang, Liu Quansheng, Xue Junhua Stability control theo-property and stress statery and technology of surrounding strata in deep mine roadway[R]. Huainan: National Engineering Research Center for Coal3)Support and maintenance of coal and rockGas Control, 2009. (in Chinese)roadway in deep should be started with deep strata [4] Yuan Liang Stability classification of coal roads in Huainan mi-stress field and existing conditions of surroundingning area and engineering countermeasures [J]. Chinese Journalrock. Roadway support should be coordinated withof Rock Mechanics and Engineering, 2004, 23(S2): 4790-4794(in Chinese)mechanical property of its surrounding rock. It cannot (5) Liu Quansheng, Zhang Hua, Lin Tao. Study on stability of deepbe finished at one time but needs to be carried out tworock roadways in coal mines and their support measures [] Chi-times or more, so that the surrounding rock can benese Journal of Rock Mechanics and Engineering, 2004, 23(21)collectively controlled. Technical route using self-3732-3737.(in Chinese)strength and integral control of surrounding rock must[6] He Yongnian, Han Lijun, Shao Peng, et al. Some problems ofrock mechanics for roadways stability in depth [J] Journal of Chi-e emonana University of Mining and Technology, 2006, 35(3): 288-295.4)Roadway surrounding rock control is a dy-(in Chinese)namic process. With the improvement of stress rela[7] Kang Hongpu, Wang Jinhua, Lin Jian. High pretensioned stressxation characteristic and integral displacement of surand intensive bolting system and its application in deep roadwaysrounding rock, in order to ensure effective support[J. Journal of China Coal Society, 2007, 23(12): 1233-1238(inanchoring force and surrounding rock displacement [8]Chang Jucai, Xie Guangxiang Mechanical characteristics and sta-must be monitored for a long time. and according tobility control of rock roadway surrounding rock in deep mine [j]monitoring results, supporting parameterournal of China Coal Society, 2009, 34(7):881-886(in ChAuthorLuo Yong, male, born in 1977, PhD. Now, he is a senior engineer. He has published over 40 papers. Hiscurrent research is coal mining and safety engineering. He can be reached by E-mail: yongluo(@ustc. edu中国煤化工CNMHGNo.2,Apr.2014