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Soilconditioning.
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ShieldTail sealing system.
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Annulargap Grouting system.
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MachineTechnology and Equipment.
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TunnelSealing.
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Shotcrete.
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Subsoil Injection and Sealing.
Now, on the basis ofconstruction method, Tunnelling technology can be categorised as being:
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MechanicalTunnel Construction, or
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Conventionaltunnel construction.
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MECHANICAL TUNNEL CONSTRUCTION
The inherent safetyand efficiency of mechanised tunnelling makes it particularly suitable indifficult geological formations and in inner-city projects. Aside from thegripper and slurry methods, EPB technology (earth pressure balance) isespecially important as it offers certain economic advantages in tunnel boring.Its success depends not only on careful planning and execution but also – andcritically – on ensuring optimum interaction between the machine technologyemployed and the speciality chemistry of the systems supporting it.
With their expertisein all areas of soil conditioning, shield skin lubrication, shield tailsealing, backfill grout mortars, and tunnel segment construction andwaterproofing, MC is able to assist the project managers in finding the ideallymatched system solutions for any tunnel boring operation.
Soil Conditioning System for MechanicalTunnelling
EPB (Earth PressureBalance) Shields are being increasingly used, even in geological formations thatare difficult to penetrate. Soil conditioning and attendant measures are, therefore,also becoming ever more important. Modern conditioning agents and technologies arekey to successful EPB tunnelling.
MC Montan Driverange of Soil Conditioning system provides following benefits in soilconditioning system in Mechanical Tunnelling construction system:
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Optimisedconditioning of soils with high water content.
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Protectionagainst water ingress from highly permeable soil.
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Exceptionalwater binding properties.
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Improvedsoil removal from the excavation chamber and screw conveyor.
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Fastreduction of foam formation in the event of over-dosing of foaming agent.
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Cleaningof foam-forming surfaces.
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Highlevel of sustainability/environmental compatibility.
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SoilConditioning for EPB Shield TBMS
The efficient use ofearth pressure balance shields requires an even-pressure support of the work face.Soil conditioning has to be carried out in order to meet the requirementsplaced on the excavated soils serving as the support medium. The aim is toensure their appropriate flow behaviour, their ability to transmit the supportpressure, reduce water permeability, increase drainage resistance, and reducethe internal angle of friction.
Aside from enhancingsafety and increasing tunnel driving progress, suitability for landfill and reusabilityof the conditioned soil are becoming ever more important factors. Hence, conditionedsoil also has to meet certain geotechnical and environmental requirements aswell.
MC offersconditioning agents specifically adapted to geological conditions, enabling youto achieve high tunnelling advance rates with a good degree of reliability. And,in terms of ecological and environmental compatibility too, you will always beon the safe side with MC systems along with the following benefits:
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Reducedenergy consumption, thanks to minimised cutting head torque.
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Minimisationof adhesion and agglomeration in the excavation chamber and screw conveyor.
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Conditionedsoil offering optimised flow and conveyance.
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Reducedwear of the cutting tools.
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Environmentallyfriendly and readily biodegradable.
Shield Tail and Annular Gap Sealing
A major component ofthe sealing concept of a tunnel boring machine is the shield tail which,equipped with pilaster strips, serves to inject backfill grout mortar into theannular gap. Backflow of the backfill grout mortar and penetration ofpressurised water are prevented by brush seal elements in combination withshield tail sealing compounds.
Particularly undervery high water pressure, leaks in this system can jeopardise the safety of theentire project. Additional protection against the penetration of water isprovided by a travelling annular gap and soil injection system using soft elasticsealant materials.
MC Montan RangeShield Tail Material provides following benefits:
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Shieldtail sealing and lubrication for safe and reliable driving operations.
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Protectionagainst water and mortar ingress even at very high pressures.
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Soft-elastic,swelling injectable shield tail sealant for temporary protection.
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Readilyusable in conjunction with annular gap grouting mortars thanks to exceptionalalkali resistance.
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Highexpanding dry for effectively sealing and stabilising of soil and rock.
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Promotesoptimum excavation and conveying properties of the injected soil.
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Groundwater-neutralinjection substance for use in dry, damp and water-filled cavities.
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Optimumsolution for additional shield tail sealing precautions.
Individuallyformulated grouting mortar systems for reliably stabilised tunnel profiles
The annular gap thatresults during tunnel driving between the tunnel lining and the soil is filledwith grouting mortar to minimise surface settlement and stabilise loose soil. Injectedinto the annular gap over the full area, the mortar is formulated for stiffnessand strength values aligned to those of the surrounding soil.
MC has a range ofone-component and two-component backfill grout mortars formulations that can bespecifically aligned to the in-situ soil conditions specific to your tunnelconstruction project. This means that every tunnel profile is provided with theoptimum bedding solution for minimum settlements and high heading rates.
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TunnelSegment Technology
In mechanisedtunnelling, tubbings of segment construction serve to both stiffening andsealing. Consequently, these precast concrete elements have to meet the veryhighest of quality demands.
MaximumConcrete Quality and Durability
Tunnel segments aresubjected to the highest demands on quality and durability. They have to beable to withstand not only the forces imposed upon them by the surrounding soilbut also the pressures generated during the tunnel driving operation. Properlyreinforced designs based on high-performance concrete are, therefore,essential.
MC is able to offeryou an integrated solution individually aligned to your project. Working inclose collaboration with their customers, their concrete technologists andallied experts put together a tailored system solution from their comprehensiveproduct portfolio, thereby helping their customers to meet even the highestdemands on quality and durability. MC Powerflow range Super plasticiser formaximum quality demands on the concrete and the final finish.
Centrament RangeAccelerator provides very high early strength combined with minimal decrease infinal strength values. Centrament range retarders provide long-lasting, goodflow-ability for high concrete quality. Centrament Range stabilizers optimisedprotection against sedimentation and blooming.
Centrilit range Admixturesare very much suitable for HPC and SCC type concretes. Centrilit rangeadmixtures reduce chloride migration and improve abrasion resistance byincreasing concrete density.
Concreterepairs for a perfect finish
Once installed,tunnel segments are exposed to huge loads. Any incorrect placement of thesegment in the annular assembly or its displacement due to external forces canresult in the concrete spalling. The comprehensive range of reprofiling solutionsavailable from MC means you have at your disposal all the high-performance productsneeded, including for concrete cosmetics.
Integratedsystems from a single source
MC offers acomplete, integrated system comprising both the requisite machine technologyand the speciality additives you need to achieve the highest performance interms of soil conditioning. Through the use of the HDT Montan Device FG TBM, youwill be able to create mono-cellular foam of optimum quality for outstandingconditioning results, even under difficult geological conditions.
Each integratedsystem is specifically adapted to the geology of the project. For shield tailsealing, too, it is essential not only to have high-performance sealing compoundsbut also optimised pump and conveying technology.
MC’s speciality pumpand sealants ideally matched to it ensure the shield tail remains impermeable.
CONVENTIONAL TUNNEL CONSTRUCTION
Conventionaltunnelling using mining techniques is still encountered in infrastructureprojects around the world. Conventional tunnel construction has alwaysrepresented a significant engineering challenge, demanding from allparticipants a high degree of technical expertise, care and attention. Themethods that fall under this heading range from soft ground to drill-and-blast tunnelingin hard rock.
Conventional tunnelconstruction imposes the most exacting of standards on the temporary andpermanent consolidation and shoring, the lining work, and the waterproofingsolution selected. Hence, MC offers a portfolio with in-built adaptability, allowingtheir product systems to be effectively aligned to a particular tunnel project.Thus, even before the tunnelling work begins, you can be sure that the qualityand reliability you require are readily to hand.
Maximumquality for the highest shortcreting standards
Inherently flexible,shotcrete accommodates conditions as they change. Shotcrete is used primarilyas a temporary means of consolidating and sealing the in-situ material and forsmoothing the excavated sections. As a means of rock edge reinforcement, italso serves to close gaps and prevent small cavities from forming as a resultof the arching effect in the profile.
Shotcrete can bemanufactured in a variety of ways. The processes differ in terms of theadmixtures used, the initial materials, and the way the shotcrete is delivered.
In the dry sprayprocess, a dry mixture is pumped using the thin-stream technique to the nozzlewhere it is then wetted with water. In the wet spray process, a supply mixture isgenerally delivered using the thick-stream technique to the nozzle where it ismixed with a hardening accelerator and air.
Tunnelsealing systems – permanently watertight, and highly resistant
Whether forcross-cuts, galleries, access points, adits, or entire tunnel sections, MC isable to provide with exactly the right waterproofing solution for the tunnelconstruction project. Sealing in conventional tunnelling is provided by plasticswaterproofing sheet or sprayable waterproofing membranes. Both systems have acommon objective – to ensure that the tunnel remains dry over its plannedservice lifetime exceeding 100 years.
This objectiveplaces particularly high requirements on the sealing systems. They are expectedto protect the support structure and technical installations while, at the sametime, ensuring disruption-free operation. Hence, they need to be able to bothwithstand chemical attacks and resist mechanical stress phenomena.
Particularly, in thearea of station structures, galleries or access tunnels, that is to say wheregeometries become difficult, high-performance and flexible sealing systems areessential.
Durableconcrete quality with optimised application properties
The final supportmeasure in conventional tunnel construction frequently takes the form of aninner shell – or lining – created using in-situ concrete. However, the project-specificrequirements may vary considerably.
MC, therefore,offers individualised concrete formulations specifically adapted to the requirements.The concrete for this lining has to meet both specific application requirementsto ensure ease of placement, and exacting durability demands.
The prevailingexposure classes and conditions under which construction takes place willaffect the concrete formulation, the quality of which is critical to thesuccess of the project.
ATTENDANT MEASURES AND REPAIRS
Tunnelling projectsrequire a very high level of technical expertise, care and attention on thepart of all those involved in the construction process. This applies right fromthe planning phase, and even more so during execution of the work.
Each tunnelconstruction project, whether carried out in conventional method or usingmechanised tunnel boring equipment, represents a unique set of engineeringchallenges, with success dependent on a large number of different factors. Despitethe best possible planning, high-performance technologies and optimumconstruction execution, problems can still arise at the driving stage, dependingon the rock and soil encountered.
In such cases, attendantmeasures, such as soil stabilisation and soil sealing and temporary shield tailsealing, need to be implemented. Such activities can help sustain the requiredrate of advance. Damage and leakage in the tunnel lining or shell can berepaired immediately by attendant systems following the excavation.
Promptlyimplemented, attendant measures, such as injection, concrete repair, andsurface protection following the excavation, minimise the risk of structuresfailing or degrading. This not only reduces repair and maintenance costs in thefuture but also has a positive effect on the durability of the entire tunnelsystem.
AttendantMeasures
Depending on thein-situ geology and the tunnel cross-section having to be cut, additional attendantactivities may accompany the excavation in order to ensure achievement of therequired advance rates. Such activities may take the form of soil stabilisation,or sealing.
Fillingof cavities and soil consolidation
Knowledge of thegeology along the tunnel axis is essential for the planning and execution oftunnel construction projects. Ensuring progress will involve both, planned andad-hoc activities aligned to soil stabilisation, with the focus on filling cavitiesand consolidating the soil so as to achieve the required advance rate.
The objective is tostabilise the soil in critical areas. The properties of the thus consolidatedstrata have to ensure that, here too, high rates of advance can be achieved. Inaddition, any materials introduced into the in-situ soil will also need tooffer full groundwater neutrality and environmental compatibility.
Consolidation Grouting procedure
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Consolidationgrouting requires Self-Driven Anchors having 38mm dia to inject grout to sealfissures and channels within a rock mass to consolidate the soil around theweak zones. To accomplish this, the hole shall be drilled to a defined depth asper the requirement of the site. Then, the grout is delivered through the tubewith the control of a single packer – or double packer – under limitingpressure. This method is commonly used to reduce hydraulic conductivity acrossa soil/rock mass by injection of resin grout into the soil.
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Consolidationgrouting shall be carried out specified in this proposal or as directed by the engineer-in-chargefrom the face of the tunnel.
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Consolidationgrouting at the crown and two side walls of the tunnel shall be completed intwo stages of holes, i.e., Stage 1 and Stage 2. The requirement of Stage 2holes and grouting would depend upon the efficacy and results subsequent to Stage1–hole grouting. The pattern and depth of holes shall be as specified in theproposal, or as modified based on the site conditions.
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Insertionof the self-driven pipes or grouting stud with perforations, placing inflatableor direct connection to the pipes.
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Itis advisable to begin with a low initial pressure of 20Bar/Kg of overburden andbuild pressure up gradually. The pressure shall be raised only when the intakerate falls or as specified otherwise. Unlessspecifically directed by the engineer-in-charge, the grouting pressure shall be20-40Bar, but this pressure may be increased up to 80Bar/kg or more in specialcases provided that there is adequate cover and the cavities inside the soilare not likely to open up by this pressure.
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Startinjection of material. First, it will take a while to fill the pipes. And, oncethe pipes are filled, the injection process starts.
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Injectionprocess has to be done in steps. Insert the self-driven packer or connect it tothe pipe placed in drilled hole and inject Resin (additives can be used toaccelerate setting time and making it non-foaming). When the pressure raises,this is a sign that the area is filled and you are pushing the material deeperinto the soil. Stop injection when the pressure reaches a (defined) limit orwhen you reach the defined stop criterion. Wait a short time (depending onreaction time of material). Do the next step of injection.
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Inthe end, the area should be injected, sealed and strengthened, depending on thenumber of holes.
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TheMC Injekt 2700L Polyurethane-based Duromer resin Component A, which is mainly aresin mixed with equal quantities of hardener MC Injekt Component B – bothmaterials mixed thoroughly for three minutes. However, in the field conditions,both the materials get mixed through special 2 component Injection Pump MC I700/maximator, which will mix the material at Injection Gun and inject in tothe weak rock/soil/fracture/concrete structure, pressure range can be adjustedfrom 4-200 bars.
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TheMC Injection product fulfils the requirement for consolidation of soil andstabilization in fractured areas where loose soil can be consolidated withstrength and sealing leakages. This also influence factor of safety that can beincreased. MC Injection resins also provide high durability and excellentbuilding capacity of materials.
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Sincethe material will have a (variable) flowing time, it is possible to reach awide spread of material in order to seal, consolidate and stabilize the loosemasses. If necessary, MC-Additives can be used to accelerate the reaction timeof material, as required.
Rapidand reliable prevention of water ingress
Water is anever-present constituent of the soil and is an important design and planning considerationfor both conventional and mechanised tunnelling. Flowing and pressurisedgroundwater can hinder driving operations and endanger safety.
Erosion of thebackfill grout mortar, and water-filled gaps and cavities are among thephenomena encountered in the presence of pressurised water flows. The solutionto quickly and effectively stem water ingress in such cases is the injectiontechnology.
For this, MC canoffer a range of speciality injection resins, designed to meet the specificrequirements of the project. The product systems applied have to be not onlyfast and reliable in their sealing capability but also groundwater-neutral andenvironmentally compatible.
Rehabilitation
As a major factorgoverning asset value and durability, the damage undergone by tunnels as theyare used needs to be rectified quickly and effectively. Such problems can occurthroughout the tunnel’s life and right from its initial construction.
What all cases ofdamage have in common is that they require rapid response based on technicallyproven and utterly reliable measures, whether in the form of injection, concreterepair and reprofiling, or the application of a surface protection system.
Effectivesealing with swell-able injection resins
Injection systemsare widely used for component sealing, whether the leaks occur over a widearea, in joints, or as a result of cracking. The application may involve thesubsequent provision of an external waterproofing membrane, rehabilitation ofleaky joints, the sealing of water-bearing cracks, or provision of a rigid sealto close off cracks and cavities in the concrete.
Where wide-area damppenetration or leaky joints are the problem, soft elastic product systems withadditional security of swelling ratio serve the optimum solution. With theiroutstanding penetration capability in combination with exceptional bondingproperties, MC’s systems quickly result in successful rehabilitation, leaving thecomponents dry, joints sealed, and even waterproofing membranes effectively repaired.
Sealingof cracks and cavities
Cracks are a normaloccurrence in concrete, which means that their presence cannot be excludedeither in the course of the tunnelling operation or during the service lifetimeof the finished construction.
Cracks becomeproblematic where they give rise to rebar corrosion due to the ingress of waterand chlorides. Such phenomena jeopardise the durability of the structure andmay also reduce service lifetime.
Crack injectionsserve to seal, strengthen and rehabilitate damaged components. There are alsoproduct systems designed to fill and seal voids and cavities in concrete, thusreturning the associated structures to full serviceability.
Highly fire-resistant concrete replacementsystem
Spalling and otherconcrete defects that occur in tunnel sections during excavation need to bequickly repaired in order to protect the rebar from corrosion. However, wherecorrosion has taken place in existing tunnels, the areas affected can also be permanentlyrehabilitated and protected.
In railway and roadtunnels in particular, the systems employed have to offer high fire ratings. Giventhis imperative, particularly high-performance products – capable of keepingwhat they promise in an emergency – are essential for such repair work.
Comprehensiveconcrete protection with long-lasting dirt-repellent effect
Surface protectionsystems in tunnel constructions are required not only to perform standardfunctions in protecting the concrete but they also have to meet certain safetycriteria, e.g., that of exhibiting a non-reflective yet bright surface so as tocontribute to traffic and transit visibility. Further requirements also includea minimal tendency towards soiling, high abrasion resistance, good clean-abilityand low scratch-ability. Appropriately high-performance products used in suchapplications can greatly reduce the maintenance costs of a tunnel.
Technicalsite support and expert advice
Every tunnel is anindividual construction with its own special challenges. So, it goes withoutsaying for MC that we need to work together with our customers in order to developindividual system solutions tailored to the specific requirements of the job inhand – and, thereafter, to support the product application phase.
The company’s expertsalso travel to the site in order to provide any individual advice, support andspecialist knowledge that one may need.