Webinar, TRB, June 2008Sponsored by AFS40

Lining procedures and limit states for structural design

Ian D. Moore, PhD, PEng

GeoEngineering Centre at Queen’s-RMCQueen’s University, Canada

Summary

1. Stability of existing culverts2. Lining procedures3. Liner strength limits

– External fluid pressure– External earth pressure and vehicle

live loads4. References

Stability of existing culverts : structure

Deterioration characteristics are different for rigid & flexible culverts and so are the effects of the damage

Metal Culvert: Invert Rigid pipe: Longitudinal and waterline corrosion fractures: excess moment

Stability of existing culverts : erosion

Perforations or fractures allow water ingress and this can lead to soil erosion.Voids generally occur at the springline and they jeopardize both rigid and flexible culverts.

0

0.2

0.4

0.6

0.8

1

0255075100

% t left

FOS Y

Cor

rode

d /

FOS Y

Inta

ct90o Invert Corrosion H=3.0m D=2m135o Invert Corrosion H=3.0m D=2m180o Invert Corrosion H=3.0m D=2m90o Invert Corrosion H=3.0m D=4m135o Invert Corrosion H=3.0m D=4m180o Invert Corrosion H=3.0m D=4m90o Invert Corrosion H=3.0m D=6m135o Invert Corrosion H=3.0m D=6m180o Invert Corrosion H=3.0m D=6m90o Invert Corrosion H=1.5m D=4m135o Invert Corrosion H=1.5m D=4m180o Invert Corrosion H=1.5m D=4m90o Invert Corrosion H=10m D=4m135o Invert Corrosion H=10m D=4m180o Invert Corrosion H=10m D=4m

Metal culvert deterioration

El Taher and Moore (2008) : stability againstyield (wall crushing) - decreases in proportion toloss of wall thickness (if zero soil erosion)

Rigid culvert deterioration

e.g. Concrete Pipe Culverti Joint leakage – ingress of

groundwaterii Erosion of backfilliii Less uniform soil supportiv Increased moments :

fracture accelerates erosion

Tan and Moore (2007) and Moore (2008) indicate thatdeformations infer the level of soil erosion

2. Lining procedures

• Slip-lining (insert preformed pipe & grout)• Cast in place pipe liner (resin-impregnated

tube pulled into place, inflated and cured)• Strip-winding (form tube in-place by

helically winding a strip, & grout)• Tunnel lining (assemble from plates etc)• Sprayed linings (concrete or polymers)

and others (sewer processes) : fold and form (a.k.a. deform-reform), swage-lining etc.

Lining procedures : Slip lining

Use any preformed pipe (metal, polymer, …)

Lining procedures : Cast-in-place lining

Felt impregnated with epoxy or other resinHot water, steam, or UV light curedCircular prismatic shapes easy; new techniquespermit non-circular and variable diameter liners

120” CMP CulvertPanel Lok IIIE

Lining procedures : Strip-wound lining

Polymer stripswelded, glued orlocked togetherGrout or reversewind to treat gap

Two dominant loads (“demands”)

1. External fluid loads• water in embankment

after high-water event• grout during

construction

3. Liner strength limits

ExternalPressure

FracturedHost Pipe

FlexibleLiner

Two dominant loads (“demands”)

2. External earth loads• overburden pressure

changes after lining• vehicle loads

DamagedCulvert

FlexibleLiner

Earth Load

3. Liner strength limits

ExternalPressure

FracturedHost Pipe

FlexibleLiner

Resistance

1. External fluid loads(water or grout)

> Controlled bybuckling strength

3. Liner strength limits

Buckling of cylinder under external pressure

0.01

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1.00

10 100DR (D/t)

Levy (1884)Pcr=3EI/R3

P cr/E

x10

3

0.01

0.10

1.00

10 100DR (D/t)

Aggarwal and Cooper (1984)

Levy (1884)Pcr=3EI/R3

7 x Levy(1884)

P cr/E

x10

3

Nonlinear: scatter due toimperfections

Old pipe increases stability – CIPP: ASTM F1216

Comparison with experiments

Effect of fractured pipe imperfections

OVALITY Rq : noncircular shape of fractured pipe

Δ

WAVINESS RΔ : liner waviness over invert

ASTM F1216 proposalMoore (2005,2008)Pcr = E (t/D)2.2 Rq RΔ

Effect of rigid pipe deformation on liner buckling strength

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10 30 50 70 90DRliner

RqR

Δ

ΔDH/D=20%

15%

12.5%

10%

7.5%

5%

2%

1%0.5

Moore (2008)

Resistance

2. External earth loads> Controlled by local effects(e.g. Law and Moore, 2003,7: bending in liner deforming within rigid pipe:vertical diameter decrease after repair) – notconservative designing liner as ‘new pipe’

3. Liner strength limits

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40%

0% 2% 4% 6% 8% 10%

allowable strain

max

imum

thic

knes

s t/D

liner%

ΔDV/Dliner=20%

10%

7.5%

5%

3.5%

2%0.5% 1%

Moore (2008)

Effect of rigid pipe deformation: liner bending strength

Resistance – rigid pipe culvertsChoice of liner thickness

tmin to resist buckling <t selected <tmax to resist bending after installation

3. Liner strength limits

Relevant tasks• Verify strength of deteriorated

culverts• Develop culvert assessment guide• Establish earth load effects on liners

in metal culverts and concrete boxes• Develop culvert repair guide

NCHRP 14-19“Culvert Rehabilitation to Maximize Service Life

While Minimizing Direct Costs and Traffic Disruption”

ReferencesEl-Sawy, K. and Moore, I.D., 1997. Parametric study for buckling of liners:

effect of liner geometry and imperfections. Proc. Int. Con., Pipeline Division, ASCE, pp. 416-423.

El-Sawy, K. and Moore, I.D., 1998. Stability of loosely fitted liners used to rehabilitate rigid pipes. Journal of Structural Engineering, ASCE, Vol. 124, No. 11, November, pp. 1350-1357.

El Taher, M. and Moore, I.D. 2008. Finite element study of corroded metal culvert stability, Transp. Res. Board Annual Conf. (accepted TRR).

Law, T.C.M., and Moore, I.D., 2007. Numerical Modelling of tight fitting flexible liner in damaged sewer under earth loads, Tunneling and Underground Space Technology, Vol. 22, (2007), p. 655-665.

Law, T.C.M and Moore, I.D. 2003. Response of repaired sewers under earth loads, Transp. Res. Record, No. 1845, pp. 173-181.

Moore, I.D., 2005. "Buried Infrastructure Repair Using Liners : Construction Techniques, Structural, And Geotechnical Issues”, 11th Int. Symp. on Structural and Geotech. Eng., Cairo, Egypt.

Moore, I.D. 2008. Keynote. Pipe rehabilitation: effect of damage to existing pipes and design of pipe repairs, Trenchless Australia 2008, 7th National ASTT Conf. and Exhibition, 2-5 March, 12pp.

Tan, Z. and Moore, I.D. 2007. Effect of backfill erosion on moments in buried rigid pipes, Transp. Res. Board Annual Conf. Washington 29pp.