Comparative experimental investigation of chemical grouting into a fracture with flowing and static

Mining Science and Technology (China) 21 (011)201 -205Contents lists available at ScienceDirectMining Science and Technology (China)ELSEVIERjournal homepage: www. elsevier. com/locate/mstcComparative.experimental investigation of chemical grouting intoa fracture with flowing and static waterZhang Gailinga*, Zhan Kaiyuab, Gao Yue a, Wang Wenxuea"State Key Laberatory of Geomechanics and Deep Underground Eng ineering School of Resources and Ceosciences, China University of Mining 6 Technology. Xuzhou 221008. China"Choneqing Design 5 Research Institute. Sino Coal hermarional Engineering Croup. Chongqing 400016. ChinaARTICLE 1 NFOABSTRACTArticle history:We present a series of experimental tests on chemical grouting into a fracture with flowing and starticReceived 2 August 2010water, using a transparent fracture grouting experimental device. Variations of seepage pressure andReceived in revised formgrout propagation were compared in our investigation. The results show that flowing water results inAcceRealiorober 2010drops of seepage pressure, development of penetration radi in the upstream side and drops of propa-gation area during the same period, compared with grouting in static water. The propagation area instatic water is always round before grouts reach the joint boundaries. However, the propagation shapeKeywords:changes from round to an lliptic shape for grouting into a fracture with flowing water. A theoreticalRock fracturemodel for the grout penetration radius in a fracture considering flowing velocity was developed andChemical groutingvalidated by our experimental results. These results are helpful in improving understanding of fractureFlowing water groutinggrouting mechanism and in guiding engineering practices.Static water groutingCopyright。2011, China University of Mining & Technology. All rights reserved.Scale model test1. Introductionexplosion efect of cement and chemically grouted material of thesurrounding rocks in a tunnel [16],Groundwater hazards in underground coalmines in China haveGrouting in flowing water is a common problem encountered inresulted in thousands of fatalities and threatened mining safety,practice, especially in the treatment of groundwater, sudden inrushsocial stability and sustainable development. Grouting for sealingand seepage control [2.4,17- -21]. However, the effect of flowoff groundwater pathways can mitigate environmental effects andvelocity on grout propagation has not been thoroughly consideredgroundwater resource loss due to long term drainage. Therefore, itin grouting design and implementation. Ren derived a propagationis one of the most widely used groundwater hazard treatmentformula for chemical grout in flowing water [22 His result showsalternatives, including dewatering. constructing bulkheads andthat grout propagation is a series of columns with increasing radigrouting|1-5].and moving the center of the circles downstream. However, thisMany researchers have studied grouting theory for fssured rockmass. For instance, Hao et aL and Yang et al developed a theoreticalorder to identify the mechanism and to establish a grouting modelmodel to simulate grout propagation in fractured networks based onfor fracture grouting with flowing water, it is important to inves-the Monte-Carlo approach[6- -8].Liet al. derived a grout propagationtigate comparatively the propagation and seepage pressure varia-formula for grouting into an lliptic fssure [9]. Yang et al experi-tions during grouting into fractures with flowing and static water.mentally studied the factors affecting cement-based grout propa-We present a comparative study on fracture grouting under thegation both in a single fracture and a fracture network [10] Funehagconditions of both flowing and static water, using scaled modelet al. developed a new method for calculating the penetration lengthtests and theoretical analysis.and radius for fracture grouting with silica sol and validated themethod by experiments and in-situ measurements [11-13]. Gothall2. Experimentalet al. investigated fracture dilation and fracture- fracture interactionduring grouting [14,15]. Zhu et al. experimentally studied the anti-2.1. EquipmentFigs. 1 and 2 show the experimental equipment, which includesE-mail address: gailing-zhang0cumtedu.cn (亿Calilingh(8-11中国煤化工2), a grouting system: data acquisition system1674-52641S - see fron matter Copyright。2011 China Universiy of Mining 8 Technology. ATYHCNMHGdol10.1016/j.mstc.201102 021202z Glling et al/ Mining Scene and Tchnolo (Chino)21 (011)201 -205Dat aquistionSeepage pressure transducerGrouing ystem虽--F83| 887Grout hole一nImagc squisiton;Flow rate'10000Water resoureTransparent fracturem3. Layout of sepage pessre transducers (mm)电1. Test equipmentin a gllig time of 75 s. The total volume of the grout was2L for(12- -15 in Fig. 2). A slot is located in the front of the simulated each test and the pumping rate 14.8 mL/s. The water flow rate wasfracture, which can transfer the conduit flow from the water source2 m/s during grouting. A standing water condition was reachedtank into a plate flow fling the fracture.When the water tank was iowered to the same level of the simu-when the water tank was lowered tothe sametevetorunesmusThe simulated fracture has a length of 1000 mm, a width of lated fracture and the flow stopped. Grout propagation and seepage500 mm and a variable thickness. Four seepage pressure trans- pressure were recorded during grouting into the fracture withducers are located at -15 cm, +15 cm, +30cm and +45 cm fromthe flowing and static water.grout hole, where "+"or"- " indicates the upstream or downstreamside from the center of the grout hole (Fig. 3).3. Results and discussion22. Procedure3.1. Seepage pressureThe experimental parameters are the same for both flowingFig. 4 shows seepage pressure variation during grouting into thewater and static water conditions. The thickness of the fracture in fracture with flowing and static water. The seepage pressure inthis experiment is 1 mm. A urea-formaldehyde (UF) grout wasstatic water grouting is always higher than that in flowing waterselected, composed of liquid A(50% uF with aditives) and B(acidicgrouting at the same point, implying that flowing water results insolidifying agent). The volume ratio of liquid Aand Bis 7:5 resulting a drop in pressure. The transducer located at -15 cm showed theseepage pressure in the standing grouting near zero or evennegative, while in flowing water grouting the drop in pressure wasrelatively small. This demonstrated that grout propagationoccurred mainly along the direction of water flowing near the endof grouting.The seepage pressures for static water groutingat -15 cm and +15 cm incre15 cm increased after a drop before the end ofBeureranutludecreased.even togrouting, while the seepage pressures gradually decreased, even to15the point of a negative value before the end of flowing watergrouting. This may be due a slowly downstream movement of thegrout in flowing grouting at the end of the grouting; however, thegrout propagated relatively uniformly within a range of a certain2radius from the grouting hole in static water grouting3.2. Grout penetrationFig. 5a and b shows grout propagation during grouting into4a fracture with flowing and static water. Fig 6a and b presents the12; 0.i 0.s 0.2040608010Q12040108.8..200220Hg2 Photo of test equipment 1. Frame; 2. Water pipe; 3. Water tank; 4. Water outlt:5. Water overflow pipe; 6. Tank for overlow: 7. Transparent fracture: 8. Grout pump:9. Fig 4 L s:0YHC NM H Gwih Rowim 20d waPressure sabilizer: 10. Oi pump: 11. Piston propeller; 12. Flow rate measurement; 13.Pessure transducer: 14. Pressure acquistion; 15. image acquisition5. -15cm;6. +15 cm;7. +30 cm: 8. +45 cm; 5-8 for static water grouting.2 Cailing e1 ol 1 Mining Science and Tchnologv (Chino)21 (011)201 205035s0I40sSs45s102010s 0一50s10s.0115s55s写10, 2020s60sC10g020s 0S5s20125s65sE060s王30s70s30s 035s75s80s20020406000204060-200204060Propagation lengh (em)Propagation length (cm)a With flowing walerb With statie waterFlg 5. Propation of grouts during grouting into a facur.corresponding penetration boundaries during grouting A compar- water. This indicates that flowing water in a fracture is helpful inative analysis indicates that the propagation for static water downstream grout propagation.grouting was round in shape during the first 20 s, i.e. before thegrout reached the fracture boundaries; however. the propagation 3.3. Propagation areagradually changed from a round shape in the initial stage into anelliptic shape for flowing water grouting during the same time.Fig. 7 shows a comparison between propagation areas forTThe penetration rate for static water grouting and for flowing fnowing water and those for static water. The data were calculatedwater grouting in the upstream side decreased during grouting from propagation images Captured at ifferent times. The figurewhile the penetration rate basically remained constant in the shows that the propagation area is bacally the same at the initialdownstream direction for flowing water grouting.stage (up to 20 s). However, the propagation area for static waterIt took 55 s for the grout to reach the exit of the simulatedgrouting becomes obviously larger than that for flowing waterfracture for flowing water grouting. while it took 70 s for staticgrouting after 20 s. The penetration rate for static water decreasedoips.20f 3545 35-30-20-10 010203040506070中国煤化工。Propagation length (em)YHCNMHGFg 6. Crout propagation during grouting into a fature.204z Cailing et al 1 Mining Science and Tcnology (Chin) 21 (01) 201 -20550004. Conclusions40003000Using a transparent fracture chemical grouting device, seepageg 2000pressure and grout propagation during grouting into a fracture甘With flowing water1000under both flowing and static water conditions were investigated+ With standing waterin our study. The main diferences for these two kinds of grouting20406080100are as fllows:Time (S)，比7. Propagation area for grouing into a fracture with flowing and static water.1) The seepage pressure in static water grouting is always higherthan that in flowing water grouting at the same point, implyingthat flowing water results in drops in seepage pressure.2) The grout propagation shapes are different for flowing andstatic water grouting. The propagation area for static waterlinearly until the fracture was flled. The flowing water restrainedgrouting was round before the grout reached the fracturegrout propagation upstream; therefore, the propagation area forboundaries, while the propagation area gradually changedflowing water grouting was less than that for static water groutingfrom a round shape in the initial stage into an elliptic shape forduring the same period.flowing water grouting.3) The rates of grout penetration and propagation area arempar3.4. A theoretical modeldifferent for flowingvith those in .static water grouting,. The penetration rate for static waterAccording to a theoretical fracture grouting model for flowinggrouting and for flowing water grouting in the upstream sidewater [23], the relationship between penetration radius and time isdecreased during grouting, while the penetration rate basicallyshown in Eq. (1) for downstream and (2) for upstream. Eq. (1) can .remained constant in the downstream side of flowing waterbe used for static water grouting in the case whenv= 0.grouting. The flowing water restrained grout propagationupstream; therefore, the propagation area for flowing watergrouting was less than that for static water grouting during the1)4) The grout penetration radius in a fracture with flowing watersame time.b2(po+50w2)(%气国from a theoretical model considering flow rate was validatedby our experimental results.5n_2)2(Po - 2Pw2 - Pc(哈-5国)AcknowledgementsFinancial support for this work, provided by the Nationalwhere t is grouting time, n viscosity of grout, Po pumping pressure,Natural Science Foundation of China (Nos. 40772192 andPe static water pressure, Pw density of water, V water flow rate,41072237), the State Key Laboratory of Geomechanics and Deepb thickness of fracture, r penetetration radius of grout and ro theUnderground Engineering (No. SKLGDUEK0903). the SpecializedC.ureLt Penetradius of the grouting borehole.Fig. 8 shows the relationship between penetration radii andResearch Fund for the Doctoral Program of Higher Education oftime, calculated from Eqs. (1) and (2) for both flowing water andChina (No.20100095110015) and the editorial help from Dr. Jinyuanstatic water conditions with those from our experiments. TheLiu of Ryerson University, Canada, are gratefully acknowledged.results from our experiments and calculations are basically thesame. However, after 20 s the difference in penetration lengthReferencesdownstream between experiment and calculation increased. This isbecause the flow rate increased near the exit of the fracture, which川Hang Y. Zhang GL. Yang GY. Numerical simulation of dewatering thickalso demonstrated the significance of the boundary effect in a scaleunconsolidated aquifers, for safety of underground coal mining MiningScience and Tconolgoy (China) 209130313-62- silalisisansasasesimulation experiment.Sciences 201 1;62(4):735- 49. dol: 10.1007/s12665 010-0562-y.[3| Wang DL jiang zQ Charateristics of water Tnlow and Chemical grouting70[.treatment of a Liu Yuanzi coal mine shaft in the Ordos Basin. Mining Sciencethrougha fractured shaft wall in an underground coalmine. in: Ceologiallyactive - proceedings of the 11th [AEG Congress. New Zealand: Tailor & Francis三40|+85| Sui WH, u YT, u GT. Wang GQ Seepage prevention grouting in coalmine shaft92200:22):21412 lin Chinesel.[6| Hao z Wang JQ He XR. Computerized simulation of crack grouting in rock21mass. Chinese Journal of Geotechnical Engineering 199.21()2727-30 lin20107] Yang Mj He YN, Chen MX. Law of grouting penetrating through fractureTime (8)8|Y中国煤化工iction o grout penetration innadian Geotechnical JourmalFg &. Comparison of penetration radi from theoretical model and experimentalresults. 1.Calculated, downstream: 2. Experiment. downstream: 3. Calculated,91fHC N M H Gstudy on the dfusion lawoftream; 4. Experiment, upstream; 5. Calculated, static water; 6. Experiment, staticwater.(Natural Scence 200(5)57-36 tm CheieesrorehenewereurZ Gailing et al / Mining Science and Technology (China) 21 (2011)201-20520101 Yang M. 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