Prevention and treatment technologies of railway tunnel water inrush and mud gushing in China

Journal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477Journal of Rock Mechanics and Geotechnical EngineeringRockMechanJournal of Rock Mechanics and Geotechnical。岁然。Engineering20CSRMEjournal homepage: www.rockgeotech.orgPrevention and treatment technologies of railway tunnel water inrush and mudgushing in ChinaYong Zhaoa,*, Pengfei Lib, Siming Tianaa Project Design and Approval Center of Ministry of Railways, Beijing 100844, Chinab College of Architecture and Civil Engineering, Beiing University of Technology, Beijing 100022, ChinaARTICLEINFOABSTRACTArticle history:Water inrush and mud gushing are one of the biggest hazards in tunnel construction. Unfavorable geo-logical sections can be observed in almost all railway tunnels under construction or to be constructed,Recevea n oecemper 0ine 2013and vary in extent. Furthermore, due to the different heights of mountains and the lengths of tunnels, theAccepted 24 July 2013locations of the unfavorable geological sections cannot be fully determined before construction, whichincreases the risk of water inrush and mud gushing. Based on numerous cases of water inrush and mudKeywords:gushing in railway tunnels, the paper tries to classify water inrush and mud gushing in railway tunnelsTunnel engineeringin view of the conditions of the surrounding rocks and meteorological factors associated with tunnelUnfavorable geological regionsWater inrush and mud gushingmechanisms are summarized, and site - specific treatment method is put forward. The treatment methodsPressure relief technologyAdvance grouting technologyinclude choosing a method of advance geological forecast according to risk degrees of different sec-Advance jet groutingtions in the tunnel, determining the items of predictions, and choosing the appropriate methods, i.e.draining-oriented method, blocking oriented method or draining- and-blocking method. The treatmenttechnologies of railway water inrush and mud gushing are also summarized, including energy relief andpressure relief technology. advance grouting technology. and advance jet grouting technology associatedwith their key technical features and applicable conditions. The resuits in terms of treatment methodscan provide reference to the prevention and treatment of tunnel water inrush and mud gushing.⑥2013 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.1. Introductionrium of surrounding rocks undergo drastic changes due to theexcavation of underground projects, which causes instant releaseUp to now, nearly ten thousand kilometers of railway tunnelsof the energy stored in underground water carrying mud and sandhave been built under a variety of complex geological conditions inthat gush to the tunnel face at a high speed (Lin and Song, 2012).China. In tuInnel construction, water inrush and mud gushing aren recentyears, morethan0 casesof watersh andthe challenging isues. They are characterized by the largest geolog-mud gushing have been observed in China, causing serious lossesical hazards and the potential risks (see Fig. 1). In this paper, waterof human life and economics and deterioration of constructioninrush and mud gushing in underground projects basically referto the dynamic destruction of structure in unfavorable geologicalunderground construction are involved. For drainage in large quan-sections. The hydrodynamic system and the dynamic equilib-tity over a long period of time is costly, the ecological environmentscan seriously be undermined, leading to the depletion of waterresources, death of vegetation and destruction of farmlands.Water inrush seriously threatens construction when the tunnel* Corresponding author. Tel: +86 13601 107599.goes through water-rich area, which frequently occurs in unfa-E-mail address: jdzxzhaoyong@sina.com (Y. Zhao).vorable geological sections. For examples, serious water inrushPeer review under responsibility of Instute of Rock and Soil Mechanics, Chineseand mud gushing occurred in the Yuanliang mountain tunnel ofAcademy ofSciences.Chongqing-Huaihua Railway. The peak duration of the water inrushlasted for roughly 051 with watar discharoa nf雷nr 1x 105 m:themud in the tunnel_value of mud wasESEVERI Production and hosting by EIsevierapproximately 1.5MHc N M H Gfwater irush andmud gushing of t1674-7755◎2013 Institute of Rock and Soil Mechanics, Chinese Academy oftain tunnel, accounting for economic losses over RMB 20 million.Sciences. Production and hosting by Elsevier B.V. All rights reserved.http://dx.doi.og/10.1016/jj.imge.2013.07.009In the Malujing tunnel of Yichang-Wanzhou Railway, water inrushY. Zhao et al. /Jourmal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477469Water inush andTable 1Types of water inrush and mud gushing.Landslide or largeClassification criteriaType9%" deformation45(1)Water inrush and mud gushingThe location of water inrush and mud at tunnel facegushing(2)Water inrush and mud gushing■Rockburstat tunnel vault(3) Water inrush and mud gushingat tunnel floor■Others(4)Water inrush and mud gushingat tunnel sidewallsFig. 1. Types of geological disasters in tunnels excavated by dill-and- blast method(1) Sudden burst of water inrushand their percentages.and mud gushing(2) Delayed water inrush and mudand mud gushing occurred in the“DK255 + 978" karst tunnels on(3) Sluggish water inrush and mud21 January 2006, with the value of water inrush of approximately7.2 x 105 m3 and the mud of about 7.0 x 104 m3. The water inrush(1) Super large scale water inrushand mud gushing flooded the 3152 m parallel heading and 2508 mThe quantity of water inrush and mud(2) Large- scale water inrush andmain tunnel in vicinity of exit, and caused the damages of a largenumber of equipment and machinery with economic losses over(3) Medium scale water inrush andRMB 10 million. After that, the treatments of this accident tookmud gushingfor 3 years. In the Yesanguan tunnel of Yichang-Wanzhou Railway,(4) Small-scale water inrush andwater inrus1ud gushing were observed in“DK124 + 602"WateSh andmudgus(5) Mini-scale water inrush andarst tunnels on 5 August 2007, and the peak flow rate reached1.5x 105 m3/h. The volume of mud and broken stones gushing(1)The sudden breaking of karstwas around 5.0 x 104 m3, causing the equipment and machineryThe infuential factors of water inrush cavityin the tunnel to be seriously deformed and/or damaged, flooded(2) The breaking of fault fractureabout 500 m away from their positions. The economic losses werezone of confined waterhuge and subsequent treatments took 2 years. In the Baiyun tunne!(3) Fracture of channel andbedrock in areas of high waterof Nanning-Guangzhou Railway, water inrush and mud gushingoccurred at the stake DK334+ 733 on 16 January 2010, lasting[41Mud Culshingin resionalfor about 30s. The length of mud gushing area is 167 m, and thewater- -rich cystic weatheringvalue of mud and sand gushing is over 2500 m3, also leading tocavitiesserious damages to construction equipment and machinery. TheGuanjiao tunnel of Xining-Lhasa Railway, located at the north-east edge of Qinghai- Tibet Plateau with strong geological activities,2. The mechanisms and infuential factors of water inrushgoes through 19 fault zones with the total length of 2.8 km. Theand mud gushing in tunnelspeak water inrush rate reaches 3.2 x 105 m3/d with water loss of1.5 x 105 m3 /d, inducing the cost of electricity output RMB 5 million2.1. Types of water inrush and mud gushingmonthly.In unfavorable geological sections, it is critically important toWater inrush and mud gushing in tunnels can be classifiedfigure out the mechanism of water inrush for safe tunnel con-nto different types according to various criteria. Based on thestruction, and effective water inrush risk assessment method andresults (Gao et al., 1999; Zhao et al.. 2009; Li, 2010; Guo, 2011), theappropriate measures should be adopted. At present, researcheson the mechanism of water inrush in tunnel construction inmountainous regions, such as the analysis of water inrush mecha-nism in unfavorable geological sections (especially in fault zonesand karst stratum), determination of critical condition of water16%30%■Faulinrush, the quantity calculation of inrush water, are fruitful, pro-■Fractureviding solid supports to tunnel construction (Guan, 2003; Cui,■Karst pipeline2005; Jiang, 2006; Zhang, 2010; Guan and Zhao, 2011). However,1%Cystic weatheringmost researches on water inrush in tunnels are experienced fromcoal mining industry (Gao et al., 1999; Li, 2010; Guo, 2011). Forextra-long tunnels in mountains, the locations of the unfavorable(a) Water inrush.geological sections cannot be fully understood before construction.We still do not have very effective method for advance geologicalFault fracturezoneforecast. We need to have better understanding of the disaster-10%86causing mechanism and dynamic evolution of the disasters, and46%■Karst cavitycorrect theories for the early warning and prevention of water6%inrush and mud gushing.Karst channelBason the characteristics of long tunnels, this paper summa-中国煤化工*ystic weatheringrizes different types of water inrush and mud gushing accidentsHCNMHGlesand tries to understand the influential factors and propose pre-(b) Mud gushingventive measures and treatment technologies which have beensuccessfully applied to many railway tunnels in China.Fig. 2. Types of water inrush and mud gushing in tunnels and their percentages.470Y. Zhao et al. / Journal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477classification of water inrush and mud gushing is shown in Table 1一号and Fig. 2.2.2. Influential factors of water inrush and mud gushingThrough site investigation and available studies of water inrushand mud gushing accidents, it is observed that the tunnels withwater inrush and mud gushing are basically characterized byhigh water pressure, large quantity of water storage, loose fllingmaterials, rich water supply, and known geological conditions.Fig. 3. The erosion- expansion effect of groundwater.The main factors, related to water inrush and mud gushing, are thesources of water supply, water pressure, confining bed, geologicalstructure, tunnel excavation and meteorological impacts. Sourceof water supply is the dominant factor; water pressure is the mainthat of micro-mechanism can provide theoretical basis (Lin andfactor, a driving force determining whether water inrush occursSong, 2012) for an in-depth study on the causes of water inrushand the quantity thereafter; the unbroken rock stratum above theand mud gushing and the mechanism.vault can be regarded as the confining bed to ensure safe tunnelIn karst strata, engineering geology, hydro- geological condi-excavation; geological structure determines the passage of thetions, in situ stress level, and physico- -mechanical characteristicswater inrush in tunnels (most water inrush cases especially that oftunnel locations, lead to differentrentlarge scale are related to geological structure); tunnel excavationmechanisms of tunnel water inrush and mud gushing. Thus, theis the inducing factor of water inrush; temperature, raining andmechanism of emergence of tunnel water inrush and mud gush-other meteorological factors contribute to water inrush and muding is different due to complex geological conditions. In termsgushing. The first four factors are associated with the conditionsof macro-mechanical mechanism, tunnel water inrush and mudof surrounding rocks.gushing can be classified into 4 types according to the stor-age environments of water and mud: karst cave (hole) water2.2.1. Conditions of surrounding rocksinrush, high-pressure geological interface water inrush, and under-The environmental conditions of tunnel excavation, such as theground karst channel (or underground river) water inrush, androck types and lithology, conditions of underground water andfault (fractured) zone water inrush. According to analysis of for-other geological factors, are the basic conditions for water inrushmation of mud passage, the mechanism of tunnel water inrushand mud gushing. Tunnel water inrush and mud gushing usuallycan beclassified irinto 4 types: the fracture of watertightoccur at the structural plane of the rocks, fault zone, intensivelylayer through stretching, the shear-yielding of geological inter-fissured zone, weathered trough, karst cavity and other unfavor-face, the hydraulic impact of discontinuous geological interface andable geological areas. In terms of rock lithology, water inrush andthe instability and slipping of the controlling rocks (Lin and Song,mud gushing are usually observed at dolomite, limestone and otherdissolvable rock strata. The vertical zonation of water and mudThe essence of micro-mechanism of tunnel water inrush is theis closely related to water inrush. The possibility of tunnel watercontinuous physico-chemical impact of water and mud on geolog-inrush emergence from low to upper is karst water aeration zone,ical interface and the impact of the accumulated micro-damages,deep slow flow zone, seasonal change zone, shallow water-richincluding the softening and dissolving effect of water and mud onzone, and water-rich zone with pressure.the strata of the geological interface, the effect on cavity expan-sion, the water wedge effect, and the erosion-expansion effect on2.2.2. Impact of rainingthe water inrush passage. Therefore, tunnel water inrush is a pro-Raining, temperature changes and other meteorologicalcess evolution in which the continuous physico-chemical impactphenomena can also affect water inrush and mud gushing, i.e. mag-of water and mud on geological interface leads to its progressivenitude varying in different seasons. For example, in summer withdamage. The erosion- expansion effect of groundwater is shown instrong rainfall, the construction-induced disturbance in combina-tion of high water pressure and temperature, water scouring efectand other relatively actives (i.e. physico-chemical reactions) caneasily induce large- -scale water inrush and mud gushing.3. Prevention measures and treatment technologies of2.2.3. Construction-induced disturbancetunnel water inrush and mud gushingTunnel excavation can inevitably disturb the original strata.Excavation method and excavation extent are two important fac-.1. Prevention measures .tors. The former is reflected in whether drill-and-blast method orpartial excavation method is adopted and in the design of sup-Comprehensive advance geological forecast is the principalport parameters; the latter is involved in cross-sectional area andmeasure for the prevention of railway tunnel water inrush andexcavation span.mud gushing. Currently, it has been widely used in railway tunnelconstruction in China. The measures include geophysical prospect-2.3. Mechanism of water inrush and mud gushinging and prospecting by drilling. Advance geological forecast shallbe determined according to the risks of different sections in theThe macro-mechanism of tunnel water inrush and mud gushinglepre中国煤化Tis basically concentrated on the analysis of different types of tunnelThe clsiationg. and the items arewater inrush and mud gushing, and the micro-mechanism on theshown in Table2(2CNMHG的the researches ofanalysis of the minor physico-mechanical effect of undergrounddvance geologicalwater exerted on the strata. Thus, analysis of macro-mechanismforecast technology (Li, 2009; Zhang et al., 2010; Li et al, 2011) forcan explain different types of water inrush and mud gushing, andprogressive water-bearing structures is shown in Fig. 4.Y. Zhao et al. /Jourmal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477471Table 2water-rich faults where water pressure is over 0.5 MPa andThe classification of advance geological forecast and items to be forecasted.water leakage from bedrock fissure, or karst deposits afterClassification Geological featuresItems to be predictedenergy relief and pressure reduction.(1) High proneness of(1) Geological sketch.geological disaster are,(2) Long distance forecast:3.2.2. Treatment technologysuch as large underground TSP203 (100 m)(1) Energy relief and pressure rriver system, water-rich(3) Medium distance forecast:Energy relief and pressure reduction method (Zhang, 2010)weak faults with goodadvance level hole drillinghydraulic conductivity.(30-60 m)1-3 holes; ifmeans in karst cavity with high pressure and rich water dur-(2) Existence of majornecessary, HSP or negativeing tunnel construction, accurate blasting or advance drilling isgeophysical anomaly, most apparent velocity method withapplied to drain water, release mud, and reduce water pressureWater inrush and mud .(4) Short distance forecast:in the cavity for the purpose of energy relief. During excavation,gushing at the rate of over geological radar (15- -30 m),structural support and treatment after energy relief and pres-10.000 m3/h, and mostcontinuous infrared watersure reduction can take a certain period of time. Energy relieflikely to induce majorprospecting, advance level holeand pressure reduction method shall be considered in dry sea-environmental anddrilling (30 m) 6 holes; advanceson; ifit is used in rainy season, the constant supply of rainwatergeological disasters.blast hole (5 m) 5 holes, and ifnecessary, use CT or boreholecan pose risk to tunnel construction. The work procedure al. anddetailed items of energy relief and pressure reduction methodA(1) Probable existence of (1) Geological sketch.geologically disastrous(2) Advance grouting technologyareas, such as largeAdvance grouting means flling proper grouting materialsunderground river system, (3) Short distance forecast:into karst cavity, fault (fractured) zone, bedrock fissure andweaktautrocinc water advanceveholerltngother construction bodies through reasonable grouting process. conductity.blast hole (5 m)3- -5 holes:by equipment and machinery, so as to achieve flling, reinforce-geological radar (15-30m), ifment, water-blocking to ensure the safe tunnel excavation andgeophysical anomaly, most necessary, continuous infraredits long-term operation (Mo and Zhou, 2008; Dai, 2009; Zhuangprobable occurrence ofwater prospecting.and Mu, 2009).water inrush and mudCommonly used advance grouting technology includes full-gushing at the rate of over .1000 m3/h, and possibilityce curtain grouting technology and informationized groutingtechnology. Full-face curtain grouting technology is based onthe assumption that the outer strata of the tunnel are uniform,thus the loose area can be reinforced by full-face grouting. InMedium water inrush and (1) Geological sketch.practical engineering, grouting parameters can be determinedmud gushing at the rateof (2) Long distance forecast:according to water pressure as shown in Fig. 6. For informa-of comparatively large (3) Short distance forecast:tionized grouting technology, according to different damagesgeophysical anomaly, fault advance level hole drillingof the strata, sectional division, water blockage from outsidezone, etc.(30m) 1-3 holes; advanceand reinforcement inside, local strengthening is used as shownblast hole (5 m) 3 holes;in Fig.7. Compared with the full-face curtain grouting technol-geological radar (15-30 m) atgeophysical anomaly, infraredogy, informationized grouting technology involves few drillingholes and thus is less time-consuming.water prospecting for 20m.(3) Advance jet grouting technologyCCarbonate and clastic rocks (1) Geological sketch.Advance jet grouting technology (Yang and Zhang, 2008;with relatively good(2) TSP203 (150 m) for majorgeological interface orZhao, 2012) is basically employed for the purpose of deforma-conditions, low probability geophysical anomaly, advancetion control of surrounding rocks. Through measuring core rockof water inrush of mudblast hole (5 m)3 holes..and soil samples, the physico-mechanical properties of sur-than 100 m3/h.Tate essradar(30m)..Scogtcrounding rocks can be determined; accordingly, the states ofthe surrounding rocks, i.e. stable, temporary stable, unstableafter excavation, can be predicted. Then, the informationized3.2. Treatment principle and technologydesign and construction method can be considered to con-trol the geological deformation and to ensure safe passing of3.2.1. Treatment principletunnel's full-section in various strata, in especially complexand unfavorable geological regions. Presently, the technologyAccording to the site- specific groundwater environments, theis introduced to the treatment of railway tunnel water inrushtreatment principles are draining-oriented, blocking-oriented orand mud gushing (see Fig. 8).draining and-blocking.(1) Draining-oriented: such as energy relief and pressure reduc-4. Applications of treatment technologiestion method. It is mainly applied to large- scale high-pressurewater-rich karst, high-pressure and water-rich karst channel,4.1. Application of energy relief and pressure reduction methodand regional water-rich cystic weathering cavities.to Yesanguan tunnel(2) Blocking- oriented: such as advance curtain grouting method.Itis mainly applied to the cases that groundwater environmentAfter the中国煤化工nd mud gushing inrequirement is strict, the faults where water pressure is lessYesanguan tunn. CNMH Gway, it is suggestedthan 0.5 MPa, and the water leakage from bedrock fissure.that the energy|.nethod and grouting(3) Draining-and-blocking: such as pressure relief through watermethod be adopted. A drainage hole of 5250 m long is considereddiversion tunnels, and grouting. It is mainly applied toon the left side of the tunnel, and a branch drainage hole at a472Y. Zhao et al. /Joumal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477Advance comprehensive forecast technology system for water-bearingstructure and other unfavorable geological areasGeological surveyClassification of risk degrees ofStage 1Macro . geologicalgeological hazards, identifyGeology analysishigh risk sectionsSeismic wave methodAccurate identification andStage 2Long . distanceloeation of fault, Karst cavesLand sonar methodand soon within 120mQualitative identification andFull space transientMedium- distancelocation of water-bearingSlage 3lectromagnetic methodstructures wwithin 80 mQuantitative identifieation ofpolarization methodwater-bearing structures andStage 4Short- distanceestimation of water quantityGeological radarwithin 40 mAdvance geological forecast tchnology system forprogressive water - bearing structuresFig. 4. Advance geological forecast technology system for progressive water-bearing structures.high position, 7.5 m above the main tunnel vault, is dug to releasewater-rich regions. In this project, the advance pipe shed and tun-energy and reduce water pressure (see Fig. 9). Accordingly, thenel face fberglass bolt and other advance-supporting measures aremixtmixture of water and mud in the cave was released to mitigatetaken for consideration of safe and quick tunnel excavation. Afterthe construction risks. After that, advance pipe- -shed and other3 years of monitoring, it shows that the tunnel structure remainsmeasures are adopted, andfinally the tunnel construction issafe and reliable.successfully completed. Three years' monitoring results show thatthe tunnel structure is safe and reliable.4.3. Application of informationized grouting method to Guanjiaotunnel4.2. Application of curtain grouting method to Qiyue MountainGuanjiao tunnel in the Qinghai- -Tibet Railway is located betweenTianpeng station (the existing line) and Chahannuo station. ThereQiyue Mountain tunnel is located at the junction of soluble rockare two parallel tracks in the tunnel with length of 32.6 km (cur-and insoluble rock, passing through the fault F11 characterized byrently the longest railway tunnel in Asia). The tunnel passeshigh water pressure. The fault F11 is large-scale stretching aboutthrough many water-rich fault zones and serious water inrush250 m along the tunnel direction, composed of limestone, tectonicdisasters occurred during construction. In order to reduce thebreccia, fault gouges. The rock is broken and poor in agglutination.quantity of water inrush and the costs of water drainage, theWater inrush rate of a single hole disclosed by advance geologi-informationized grouting technology is adopted. The number ofcal drilling reaches 790 m3 /h. The water pressure is observed upnecessary grouting holes is determined considering the results of? tunnel construction, the fault F11 is carefully .advance geological forecast, damage extent of surrounding rocks atinvestigated by comprehensive advance geological forecast meth-the tunnel face, water inrush quantity and forms of water inrush.ods, such as geological sketches, advance geophysical prospecting,The principle of water inrush control is applied from outside to60 m long advance hole drilling, 30 m long advance hole drilling,inside, step by step, through drilling at suitable intervals. Addi-tion of holes andIthening are also considered to achieveand blast hole. As a result, large-scale water inrush and mud gush-the targeted number of grouting holes and the effective grouting.ing are successfully prevented.The principle and method of“pressure relief through drain-The informationized grouting technology adopted in the construc-tion of Guanjiao tunnel is shown in Table 3, and good results areing + reinforcement by grouting" are adopted according to thobtained information by the advance geological forecast methodachieved (see Fig. 12).and field grouting and draining tests. Drainage holes are consideredin the parallel heading and branch drainage areas to relieve water4.4. Application of advance level jet grouting to Liangshan tunnelpressure of the surrounding areas in the tunnel, thus water pressureon the surrounding rocks of the tunnel is reduced, and consequentlyLiangshan中国蝶花fiway isg locatedthe difcultiese in tunnel grouting and excavation are reduced (seebetween Zhangpu "n Fujian Province.Fig.10). With those measures, the scopes of the parallel headingThe tunnel is 98888YHCN M H G! with train speedand the main tunnel by advance grouting are determined at 5 m andof 250 km/h. Durin8 m outside the excavation contour line, respectively (see Fig. 11).frequently occurred, resulting in 230 m of main tunnel filled withAdditional site-specific grouting holes shall also be considered inserious gushed mud. The incident causes a ground subsidence ofY. Zhao et al. /Jourmal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477473Looking for karstUsing advance forecast to findcavitythe karst cavity aheadAnalyzing karst features, hydrologicalAsessing karstdetermining the treatment schemeeavitvisnotargegrouting method willThe scale of karst cavity islarge, there will be high risk ilbe suficicnt .Treatment bygrouinggrouting method and freezingmethod is usedLocking karstSpecialized design for hydrologic monitoringSpcialized design for dainage line inside the unneSpecialized design for the early waming monitoring system inside and outside the tunnelSpecialized safety NSeialized design for the sparation of ajacet cave in the tuneletySpecialzed design for drainage line outside the unneSeinlized design for waring system outside the unnelSpcialized design for safe evacuation route of obervations inside the tnnelOpening karst。 Specialized blasting design on the basis of the tunnel borderingline, making sure that it will be blasted open at one time.Backilling arch protctionReplacement methodConstructiontreatmentGrouting pipe shed methodBench excavation methodTreating karstRe-prospecting and pocessing of tnnel baseDraining through permanent draining holeStructuralStrenghening of anti-hydraulice pressure liningstructureLong-term monitoring of the structureFig. 5. Work procedure and description of energy relief and pressure reduction method.Table 3Types of infrmationized grouting methods employed in Guanjiao tunnel.Types of groutingGrade of surrounding rocksCriteria of initiation groutingCriteria of grouting terminationRadial grouting afterRelatively good surroundingRate of water inrush in a single hole ofThe quantity of water inrush in theexcavationrocks (such as rock casses IIexcavated area is 5-40 m3 /h, existencegrouted sectin does not exceedand II)of many water inrush points10 m3/(md)Local water inrush byLocal water inrush around theRate of water inrush around the tunnelThe rate of water inrush in a singlegroutingtunnel, mainly surroundingin a single hole is over 40m3/hhole in the concentration point ofrocks classes II and IVwater inrush is less than 10m?/hvance groutingLocal water inrush in tunnelThe rate of water inrush in a single holebed, mainly surrounding rocksthe tunnel face is over 40m3/hin the concentration point of waterinrush is less than10 m3/h. and the totalPeriphery curtain groutingWeak and broken surroundingrate of water nrush at the tunnel facerocks classes IV and V中国煤化工”?hFull-face curtain groutingFault, fractured surroundingThe rate of water inrush in;r inrush in a singlerocks classes V and VIhole of the tunnel face is ovMYHC N M H Gentration point ofwater imrusn 15 less than 5m2/h. andthe total rate of water inrush at thetunnel face is less than 100 m/h474Y. Zhao et al. /Jourmal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477上Z乙Water poor areaGrouting area二Water rich area■Water blocking areaRStrengthening area■Reinforcing areaO TunneFig. 7. Schematic diagram of informationized grouting.、 Loose arealong, over 50 cm in diameter, and 35 cm in spacing between pileTTcenters. The interlocking width of grouting piles is 15 cm and cross-distributed. Four rings of level jet grouting piles are set for theFig. 6. Schematic diagram of fll-face curtain grouting.arch wall outside the excavation contour line, and the effectivethickness of grouted body is 1.55 m. Two rings of level jet groutingpile are set for the bottom of the inverted arch, and the effectiveabout 20 m in depth in the area of 1500 m2 (the overburden depththickness of grouted body is 0.85 m. The compressive strength ofof tunnel is 270m). The ground subsidence revealed that the sur-grouted body shall be not less than 3 MPa. Advance support ofrounding rocks are located in intensively fissured zone.φ159 mm large grouting pipe- shed (40 m long) of two layers atAfter the accidents of water inrush and mud gushing, level jetarch wall which is inside the inner ring jet grouting piles shouldgrouting piles were set at the tunnel face in order to (1) ensurebe considered. The pipe shed shall be embedded into the bedrockthe safe construction and long-term operation of the tunnel, (2)with depth not less than 5 m, and circular spacing of 0.3 m. Afterto eliminate mud gushing at weak zone in the main tunnel, andthe jet grouting piles are completed, the effect of reinforcement(3) to enhance the tunnel stability. Jet grouting piles are 40mshall be examined and other related reinforcement works shall beFig. 8. Diagram of advance level jet grouting in tunnels.The boundary of the7∪∪658857karst cavity/6oo70000Branch drainage holeDrainage holeTunnel for track 1; #5.1Yichang#High branch drainage hole about 82 mWanzhou .7.5 m above the tunnel vaultlong中国煤化工Tunnel for traclMYHCNMH GFig. 9. Plane sketch of the treatment of“+602" karst cavity.Y. Zhao et al. / Journal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477475The boundary of the karstcavityBy-pass parallel heading学Parallel率Parallel heading点heading holeYichang菜12#/Wanzhou#11-11 Cross passageMain tunnelLower pressureDrainage and pressure relievinghigh anholeWater blocking zone facing the fault coreHigher pressure and waterrich zoneFig. 10. Plane sketch of the geological features and treatment method of fault F11 in Qiyue Mountain tunnel.carried out before excavation. Thus, the following criteria shouldgushing occurred. As a result, tunnel excavation was stopped asbe met:shown in Fig. 13. After the accident of water inrush and mudgushing, many treatment measures were taken (see Fig. 14),(1) The compressive strength of grouted body should be not lessincluding building retaining dam, stabilizing landslide at thethan 3 MPa.tunnel face, draining inrush water, building by-pass heading, jet(2) Water stream is not allowed at testing hole, tunnel face andgrouting reinforcement at the top of landslide section in the mainside wall after excavation.tunnel. In addition, curtain grouting was used in the main tunnel.) Core sampling rate of jet grouting reinforcement body shouldWith those measures, the water inrush and mud gushing werebe not less than 70%.successfully stopped. .IYIf drilling tests results (image borehole tests, core samplinghole and pipe-shed drilling holes) suggest that the jet groutingdoes not have a targeted effect, additional inspection holes will bedrilled in order to determine the potential weak areas; if necessary,Excavation contour linesupplementary reinforcement measures shall be carried out inthe weak areas through supplement pile jet grouting or grouting,Grout stopping wallor composite grouting to ensure the reinforcement effects of thereinforced rings.Through the observation in each cycle during excavation, itwas observed that the level jet grouting reinforcement ring alwayskeeps its longitudinal continuity in the weak layer. The circularinterlocking is good, and the level jet grouting reinforcement ringsare visible. Point load test results of level jet grouting reinforced250 90090body show that the average strength is 5.7 MPa, with the minimumvalue of 4.8 MPa; the average compressive strength of the standard(a) Profile of advance grouting.grouting samples is 21.7 MPa, with the minimum value of 13 MPa.The values meet the design requirements.4.5. Application of combined method to the Baiyun tunnelThe total length of Baiyun tunnel of Nanning- Guangzhou Rail-way is 2285 m. The tunnel goes through large regional faultsF1, F2.The fault F2 extends more than a dozen of kilometers. The widthof fault F2 is 10-40m, and its deformation influential zone even.reaches 100 m. Fault F2 and its secondary fault F1 form a closely par-alleled combination of reversed fault, thus the stratum is seriouslyfragmented and vertical penetration between faults is induced.Within the faults,there are mixtures of breccia and clay of very .Tunnel cental linelow intensity. So, the mixtures of breccia and clay pose a very highpressure on the stable layer at the top of the tunnel. The inclination中国煤化工angle of the fault is relatively small, only 25°.The tunnel construction started from the lower part of theMHCNMHGdrawing of the opening.reversed fault. The excavation or blasting unexpectedly disturbedthe stratum, and consequently, serious water inrush and mudFig. 11. Design of curtain grouting in Qiyue Mountain tunnel (unit: cm).476Y. Zhao et al. /Joumal of Rock Mechanics and Geotechnical Engineering 5 (2013) 468- 477(a) Before grouting.(b) After grouting.Fig. 12. Comparison of water inrush in the tunnel face before and after cutain grouting in Guanjiao tunnel.Ground collapsingTunnel faceD3K334+800D3K334+733F2 :Fault F2117C25'Fault FI星明0下Fig. 13. Layout of faults in Baiyun tunnel of Nanning Guangzhou Railway and the water inrush and mud gushing disaster.5. Discussionrapid development of railway construction in karst region in WestChina, a series of hot issues concerning safe tunnel construc-Numerous researches on the karst tunnels with engineeringtion or operation should be addressed. These issues are listed asproblems such as water inrush are achieved, however, with thefollows:Grouting to main tunnelbuildinglatenlpine-shedBy-pass headingAdvance grouting in maintunnel and advancelongitudinal pipe-shedCentral line of the tunel中国煤化工出CNMHGFig. 14. Treatment of water inrush and mud gushing section in Baiyun tunnel of Nanning-Guangzhou Railway.