Chair and Institute of Road, Railway and Airfield ConstructionMunich, Germany

Professor Dr.-Ing. Stephan Freudenstein

Fon: 089/289-22431

Fax: 089/289-25384

E-Mail: verkehrswegebau-lst@vwb.bv.tum.de

Internet: www.vwb.bv.tum.de

Lateral Stability of Ballasted Track with Conventional Ties

and with Under Tie Pads

Agenda

• Study of elastic under tie pads

• Measuring of lateral resistance of conventional ties and with under tie pads in both laboratory as well as in real operational tracks

• Application of the recorded parameters to FEM

Determination of bedding modulus of elastic tie pads

Geometric Ballast Plate (GBP)

Standard Ballast Plate (SBP) Even Plate

TUM-Plate with gluedreal ballast stones

Determination of bedding modulus of elastic tie pads

on bottom side of tie

on smaller specimen (300x300 mm)

on ties in ballast bed

SBP

20 cm Concrete

SBP

Determination of bedding modulus of elastic tie pads

bedding modulusdecreases

Static bedding modulus of tie pad [N/mm3]

Analysis area: σ = 0.01 – 0.10 [N/mm2]

method of testing300 x 300 mm tie pad with concrete block

PM G04 with fleece G04 with LVD

Even Plate 0.96 0.34 0.21

SBP 0.25 0.09 0.08

GBP 0.34 0.07 0.07

TUM-Plate 0.12 0.05 0.05

SBP

bottom side of tie

PM G04 with fleece G04 with LVD

0.25 0.08 0.08

on ballast bed

tie B 70 with under tie pad

PM G04 with fleece G04 with LVD

0.09 0.06 0.05

Minimal bedding modulus of underground and ballast

min Ctotal = 0.05 N/mm3

best load-distribution effect of rail 60 E2 could be activated allowable tensile stress on rail foot will not be exceeded

1/Ctotal = 1/Ctie pad + 1/Cunderground+ballast + (1/Crail pad ~ 0)

minimal total bedding modulus

Ctotal

[N/mm3]

tie pad type

bedding modulusCtie pad

[N/mm3]

(B70 consolidated ballast)

minimal bedding modulus underground and ballast

Cunderground+ballast

[N/mm3]

0.05

PM 0.14 ≥ 0.08

G04 with fleece 0.07 ≥ 0.20

G04 with LVD 0.06 ≥ 0.36

Simulating the service loading

- Measurement of lateral resistance in consolidated condition

- Contact stress between ballast and bottom side of tie

Contact stress between ballast and bottom side of tie

0 1,000,000 2,000,000 3,000,0000.1

1

10

Contact stress between ballast and bottom side of tie

load cycles

co

nta

ct

str

es

s [

N/m

m2

]

B 70 with soft tie pad (G04 with fleece)

B 70 with stiff tie pad (PM)

conventional B 70

mm²

N

areacontact

loadseat rail stresscontact

conventional tie with tie under tie pad

Lateral resistance of conventional ties and with under tie pads

The lateral resistance of ties with UTP depends firstly on:

- Elastic material properties of UTP- Tie geometry- Properties of the ballast

Required laboratory tests:

- Determination of elastic properties of the UTP- Determination of ballast properties- Determination of lateral resistance of ties with and without UTP

Investigations on ballast type A (quarry A) und type B (quarry B), both class “S”

Lateral resistance is positively influenced by:

Lateral resistance of conventional ties and with under tie pads

(EN 933-1)

Far tiered grading curve

High mass percentage ofgravel stones > 40 mm

Less fine grain < 0.5 mmLess fines < 0.063 mm

(EN 933-4)

Compact grain shape

length : width < 3:1

(EN 1097-2)

Los Angeles-Test:

high impact strength

(EN 1097-1)

Micro-Deval-Test:

high abrasion resistance

- ballast type B shows better properties regarding lateral resistance as type A

lateral resistance with ballast type B is about 20 % higher as with type A

Determination of lateral resistance of ties B 70 in laboratory

Lateral resistance of conventional ties and with under tie pads

Measurements in both unconsolidated and consolidated conditions

Determination of static and dynamic lateral resistance

Determination of lateral resistance under wet ballast conditions (rain fall)

Determination of individual parts of lateral resistance

tie

ballast rig tie pad

neutral axis

ballast

- bi-linear load-displacement curve, continuously slope change point due to under tie pads

- ties with under tie pads show a higher lateral resistance than conventional ties

- lateral resistance is increasing with decreasing of the tie pad stiffness

Lateral resistance of conventional ties and with under tie pads Load-displacement curve of single ties B 70

horizontal force FH (at 2 mm displacement)

B 70 with G04, LVD(very soft)

8.5 kN

B 70 with G04, fleece(soft)

8.1 kN

B 70 with PM(stiff)

7.4 kN

B 70 without tie pad 6.7 kN

B 70 with pad G04, LVD (very soft)

B70 with pad G04, fleece (soft)

B 70 with pad PM (stiff)

B 70 without tie pad

ho

rizo

nta

l fo

rce

[kN

]

lateral displacement of the tie [mm]

consolidated ballast type B

Determination of lateral resistance in laboratory

Lateral resistance of conventional ties and with under tie pads

ballast type/ underground

B 70 with or without under

tie pad

unconsoli-dated track

consoli-dated track

increasing of lateral resist.

due to consolidation

consolidated track

wet ballast bed(rain fall)

dynamic loadingF = 2 kN, 50Hz

lateral resist. [N/mm] [%] lateral resist. [N/mm]

type A, concrete ground

without tie pad 6.4

G04 with fleece 8.3

type B,

concrete ground

without tie pad 8.3

Paul Müller 9.6

G04 with fleece 9.2

G04 with LVD 9.5

ballast type/ underground

B 70 with or without under

tie pad

unconsoli-dated track

consoli-dated track

increasing of lateral resist.

due to consolidation

consolidated track

wet ballast bed(rain fall)

dynamic loadingF = 2 kN, 50Hz

lateral resist. [N/mm] [%] lateral resist. [N/mm]

9.3 45 %

11.2 35 %

11.3 36 %

12.4  29 % 

13.4 46 %

14.2 49 %

ballast type/ underground

B 70 with or without under

tie pad

unconsoli-dated track

consoli-dated track

increasing of lateral resist.

due to consolidation

consolidated track

wet ballast bed(rain fall)

dynamic loadingF = 2 kN, 50Hz

lateral resist. [N/mm] [%] lateral resist. [N/mm]

type A, concrete ground

without tie pad 6.4 9.3 45 % 7.8

G04 with fleece 8.3 11.2 35 % 9.1

type B,

concrete ground

without tie pad 8.3 11.3 36 % 8.4

Paul Müller 9.6 12.4  29 %  -

G04 with fleece 9.2 13.4 46 % 10.9

G04 with LVD 9.5 14.2 49 % 12.1

ballast type/ underground

B 70 with or without under

tie pad

unconsoli-dated track

consoli-dated track

increasing of lateral resist.

due to consolidation

consolidated track

wet ballast bed(rain fall)

dynamic loadingF = 2 kN, 50Hz

lateral resist. [N/mm] [%] lateral resist. [N/mm]

type A, concrete ground

without tie pad 6.4 9.3 45 % 7.8 4.7

G04 with fleece 8.3 11.2 35 % 9.1 6.3

type B,

concrete ground

without tie pad 8.3 11.3 36 % 8.4 5.0

9.6 12.4  29 %  - -

G04 with fleece 9.2 13.4 46 % 10.9 6.4

G04 with LVD 9.5 14.2 49 % 12.1 6.4

PM

Determination of lateral resistance in service track

Lateral resistance of conventional ties and with under tie pads

location

tie B 70 with or without under tie pad

consolidated track

lateral resist. [N/mm]

service trackwithout tie pad 12.7

G04, fleece 14.4

laboratoryballast type B

without tie pad 11.3

G04, fleece 13.4

• Difference of absolute values of lateral resistance due to:

- ballast properties and underground performance - width of front ballast- initiated tamping work

• Qualitative agreement of results in laboratory and service track

Application of recorded parameters to FEM

rail tie

structure points of tie structure points of rail

Verifying FE-Model for straight track from full-scale test section in Rohrbach

Application of recorded parameters to method of Meier and to FEM

failure of track irregularity = 23 mmlength of track irregularity = 16,2 mlateral resistance = 9,2 N/mm

Verschiebeweg des Gleisrostes [mm]

Verifying FE-Model for curved track with R = 360m from full-scale test section in Daglfing

Application of recorded parameters to FEM

failure of track irregularity = 13 mmlength of track irregularity = 16,8 mlateral resistance = 4,4 N/mm

Results of FEM: Influence of service load on lateral track stability

Application of recorded parameters to method of Meier and to FEM

- increasing of lateral resistance- under wheel loads

- application of dynamic lateral - resistance

- considering the uplift wave (reduction of bottom resistance)

- simulation of track conditions: perfect conditions, rain falls, vertical track irregularity, insufficient ballasting of ties

lateral resis-tance

Ties B 70 with tie pad G04 and fleece, straight track

rail

de

fle

cti

on

[m

m]

Results of FEM regarding lateral track stability

Application of recorded parameters to FEM

Lateral resistance and imperfections have significant influence

Lateral resistance- ties with under tie pads are better than conventional ties

Critical imperfections - bigger track failures- length of track irregularity appr. 10 m - 12,5 m (straight track)

- length of track irregularity appr. 5 m (curved track with R = 360 m)

Rail profile - smaller Cross sections are saifer against track buckling

Q

- increasing of track elasticity reduction of rail seat load protecting the other track components - increasing of contact area between ballast and bottom side of tie reduction of contact stress extension of maintenance interval

- allowable tensile stress on rail foot should not be exceeded - ballast deterioration on the tie sides

• The application of elastic under tie pads has many advantages

• Elastic under tie pads should not be too soft

Conclusion

Chair and Institute of Road, Railway and Airfield ConstructionTechnical University Munich, Germany

Univ. Prof. Dr.-Ing. Stephan Freudensteinstephan.freudenstein@vwb.bv.tum.dewww.vwb.bv.tum.de