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    Lec 13 Tunnel Lining II Concrete Lining

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    Mahesh Uniyal
    1) IS 5878-5(1976) and IS 456 govern the concrete lining of tunnels, specifying requirements for aggregates, cement, water, concrete strength and placement. 2) Due to the curved tunnel geometry, concrete must be flowable to fill irregularities and avoid segregation, with a minimum slump of 100mm for direct placement and 50mm where forms are used. 3) There are three primary sequences for concrete lining specified - constructing the kerbs first and proceeding to the walls and arch, constructing the invert first and proceeding to the walls and arch, or constructing the entire section simultaneously using pump concreting.

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    Lec 13 Tunnel Lining II Concrete Lining

    Uploaded by

    Mahesh Uniyal
    43 views13 pages
    1) IS 5878-5(1976) and IS 456 govern the concrete lining of tunnels, specifying requirements for aggregates, cement, water, concrete strength and placement. 2) Due to the curved tunnel geometry, concrete must be flowable to fill irregularities and avoid segregation, with a minimum slump of 100mm for direct placement and 50mm where forms are used. 3) There are three primary sequences for concrete lining specified - constructing the kerbs first and proceeding to the walls and arch, constructing the invert first and proceeding to the walls and arch, or constructing the entire section simultaneously using pump concreting.

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    1) IS 5878-5(1976) and IS 456 govern the concrete lining of tunnels, specifying requirements for aggregates, cement, water, concrete strength and placement. 2) Due to the curved tunnel geometry, concrete must be flowable to fill irregularities and avoid segregation, with a minimum slump of 100mm for direct placement and 50mm where forms are used. 3) There are three primary sequences for concrete lining specified - constructing the kerbs first and proceeding to the walls and arch, constructing the invert first and proceeding to the walls and arch, or constructing the entire section simultaneously using pump concreting.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    43 views13 pages

    Lec 13 Tunnel Lining II Concrete Lining

    Uploaded by

    Mahesh Uniyal
    1) IS 5878-5(1976) and IS 456 govern the concrete lining of tunnels, specifying requirements for aggregates, cement, water, concrete strength and placement. 2) Due to the curved tunnel geometry, concrete must be flowable to fill irregularities and avoid segregation, with a minimum slump of 100mm for direct placement and 50mm where forms are used. 3) There are three primary sequences for concrete lining specified - constructing the kerbs first and proceeding to the walls and arch, constructing the invert first and proceeding to the walls and arch, or constructing the entire section simultaneously using pump concreting.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 13

    TUNNEL LINING II

    CONCRETE LINING
    CONCRETE LINING
    • Governing codes
    • IS 5878-5(1976) : Concrete Lining
    • Gives various requirements of concrete lining construction.
    • IS 456 (2000)
    • For all general rules governing concrete construction.
    SALIENT PROVISIONS OF IS 5878-5(1976)
    • Requirements for aggregates, cement, water and concrete grading with
    corresponding strength as per IS 456.
    • On account of curvature, irregularities in rock profile, thin sections and
    placing of concrete generally requires to be done through concrete pump or
    pneumatic placer.
    • Concrete necessarily should be flowy to avoid segregation and to ensure
    proper filling in.
    • Slump not be less than 100 mm
    • Where concrete placed directly, like in inverts and kerbs, it should be reduced to 50
    mm
    • Max size of aggregate – 40 mm
    • Advisable to use air entraining agent to entrain upto 4% of air for
    improving workability of concrete.
    https://gharpedia.com/blog/air-entraining-admixtures-for-concrete/
    SALIENT PROVISIONS OF IS 5878-5(1976)
    • Seepage to be suitable controlled and prevented from getting mixed
    with green concrete in the lining
    • Appropriate time for placing of concrete (Clause 4)
    • Based on conditions of the rock being tunnelled
    • Where tectonic forces likely to dilate rocks, sufficient time should be allowed for
    such dilations to reduce to reasonable limits.
    • Where required, blocking concrete or shotcreting to be placed with minimum
    possible time lag after excavation.
    Difference between SHOTCRETING VS GUNITING?
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Sequence of Lining(Clause 5)
    • Kerbs first, followed by side walls and arch, finally invert
    • Suitable for horse shoe, D-shaped and other flat bottomed and wide tunnels
    • Kerb built up to a section of sufficient width to serve as base for erection of
    forms for sides
    • Advantages
    • Minimum disturbance to track line on the floor, movement of traffic
    • Bottom concrete surface not damaged
    • Concreting of sides and arch cast simultaneously with excavation after a
    suitable gap.
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Sequence of Lining (Clause 5)


    • Inverts first, followed by sides and arch
    • Suitable when bottom of tunnel narrow or when section circular
    • Also suitable where tunnelling in weak strata and floor tends to wear out fast
    or heave up.
    • Invert concreted first, acts as regular base for erection of formwork for sides
    and arches.
    • Invert concreted first, also acts as a strut to counter large horizontal thrusts
    while placing of concrete in sides.
    • Procedure entails removal of trolley tracks and other service lines and relaying
    over then concreted invert.
    • Also , invert concrete likely to get damaged during operations for laying overt.
    • Above practical difficulties increase if transport is by trucks.
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Sequence of Lining (Clause 5)


    • Inverts , side walls and arch all at the same time
    • Possible only in small and circular tunnels.
    • Difficult to adopt in ordinary course, feasible only where pump concreting
    facilities available and construction programme demands it.
    • It has some advantages in steeply inclined tunnels.
    • In case of soft strata/weak strata where likeliness of collapse of excavated
    surface, it becomes necessary to provide a primary lining over and between
    steel supports(if provided)
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Form Work (Clause 6)


    • Steel form work used in general
    • Speed
    • Economy
    • Multiple use possibility
    • Formwork when placed mechanically in rock tunnels can be removed 16-20
    hrs after placing last batch of concrete
    • Form surface will be well oiled to prevent concrete to stick to the surface
    • Types
    • Rib and Plate or Rib and Lagging
    • Travelling non-telescoping formwork
    • Travelling telescoping formwork
    • Monolithic formwork
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Rib and Plate or Rib and Lagging


    • For tunnels of medium size upto 5 m dia
    • Convenient when concrete is to be hand placed
    • Ribs made of either channels or T Sections
    • Placed at intervals of about 1 m
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Travelling non-telescoping type form work


    • Whole formwork pre-assembled
    • Mounted on a travelling frame fixed on wheels
    • Guided through tracks on invert
    • Screw jacks used for aligning, fixing and collapsing
    the formwork

    • Easy and economical


    • Sides and arches may be concreted in one operation
    • Formwork made in units of 6 to 12 m long and can be
    stuck and reassembled quickly depending on
    requirements of construction traffic and matching
    concreting equipment
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Travelling telescoping type form work


    • Back unit can be collapsed and moved forward
    through front unit without disturbing it.
    • Side plates hinged to arch plate making it possible
    to collapse them
    • This form work is also self supported and equipped
    with jacks and accessories for the above purpose
    SALIENT PROVISIONS OF IS 5878-5(1976)

    • Monolithic formwork
    • Slip formwork for continuous use
    • Suitable for circular or near circular tunnel and
    when lining of full section carried out in one
    operation
    • May be suitable in steeply inclined shafts/tunnels

    https://www.youtube.com/wat`ch?v=8Wc4OsCqv2A
    THANK YOU

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