Lateral Stability of Ballasted Track with Conventional Ties

Report
Chair and Institute of Road, Railway and Airfield Construction
Munich, Germany
Professor Dr.-Ing. Stephan Freudenstein
Fon: 089/289-22431
Fax: 089/289-25384
E-Mail: [email protected]
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
Standard Ballast Plate (SBP)
Geometric Ballast
Plate (GBP)
Even Plate
TUM-Plate with glued
real ballast stones
Determination of bedding modulus of elastic tie pads
20 cm Concrete
SBP
on smaller specimen (300x300 mm)
on bottom side of tie
on ties in ballast bed
Determination of bedding modulus of elastic tie pads
Static bedding modulus of tie pad [N/mm3]
Analysis area: σ = 0.01 – 0.10 [N/mm2]
method of testing
300 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
bottom side of tie
SBP
PM
G04 with fleece G04 with LVD
0.25
0.08
0.08
tie B 70 with under tie pad
on ballast bed
PM
0.09
G04 with fleece G04 with LVD
0.06
0.05
bedding modulus
decreases
Minimal bedding modulus of underground and ballast
1/Ctotal = 1/Ctie pad + 1/Cunderground+ballast + (1/Crail pad ~ 0)
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
bedding modulus
minimal total
bedding modulus
Ctotal
Ctie pad
tie pad type
minimal bedding modulus
underground and ballast
Cunderground+ballast
[N/mm3]
[N/mm3]
[N/mm3]
(B70 consolidated ballast)
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
contact stress 
rail seat load
contact area
N
mm²
Contact stress between ballast and
bottom side of tie
contact stress [N/mm2]
100
conventional B 70
10
B 70 with stiff tie pad (PM)
B 70 with soft tie pad (G04 with fleece)
1
0
1,000,000
2,000,000
load cycles
3,000,000
conventional
tie
tie with
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
Lateral resistance of conventional ties and with under tie pads
Investigations on ballast type A (quarry A) und type B (quarry B), both class “S”
Lateral resistance is positively influenced by:
(EN 933-1)
(EN 933-4)
Far tiered grading curve
High mass percentage of
gravel stones > 40 mm
Compact grain shape
length : width < 3:1
Less fine grain < 0.5 mm
Less fines < 0.063 mm
(EN 1097-1)
(EN 1097-2)
Micro-Deval-Test:
high abrasion
resistance
Los Angeles-Test:
high impact strength
- 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
Lateral resistance of conventional ties and with under tie pads
Determination of lateral resistance of ties B 70 in laboratory
tie
ballast
ballast rig
tie pad
neutral axis
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
Lateral resistance of conventional ties and with under tie pads
Load-displacement curve of single ties B 70
horizontal force [kN]
consolidated ballast type B
horizontal force FH
(at 2 mm displacement)
B 70 with G04, LVD
(very soft)
8.5 kN
B 70 with pad G04, LVD (very soft)
B 70 with G04, fleece
(soft)
8.1 kN
B70 with pad G04, fleece (soft)
B 70 with PM
(stiff)
B 70 with pad PM (stiff)
B 70 without tie pad
7.4 kN
B 70 without tie pad
6.7 kN
lateral displacement of the tie [mm]
- 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
Determination of lateral resistance in laboratory
B 70 with or
without under
underground
tie pad
ballast type/
unconsolidated
track
consolidated
track
lateral resist. [N/mm]
type A,
concrete
ground
type B,
concrete
ground
increasing of
lateral resist.
due to
consolidation
wet ballast bed dynamic loading
F = 2 kN, 50Hz
(rain fall)
[%]
lateral resist. [N/mm]
consolidated track
without tie
pad
6.4
9.3
45 %
7.8
4.7
G04 with
fleece
8.3
11.2
35 %
9.1
6.3
without tie
pad
8.3
11.3
36 %
8.4
5.0
PaulPM
Müller
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
Lateral resistance of conventional ties and with under tie pads
Determination of lateral resistance in service track
location
tie B 70
with or without
under tie pad
consolidated
track
lateral resist.
[N/mm]
without tie pad
12.7
G04, fleece
14.4
without tie pad
11.3
G04, fleece
13.4
service track
laboratory
ballast type B
•
Qualitative agreement of results in laboratory and service track
•
Difference of absolute values of lateral resistance due to:
- ballast properties and underground performance
- width of front ballast
- initiated tamping work
Application of recorded parameters to FEM
rail
structure points of tie
tie
structure points of rail
Application of recorded parameters to method of Meier and to FEM
Verifying FE-Model for straight track from full-scale test section in Rohrbach
failure of track irregularity = 23 mm
length of track irregularity = 16,2 m
lateral resistance = 9,2 N/mm
Verschiebeweg des Gleisrostes [mm]
Application of recorded parameters to FEM
Verifying FE-Model for curved track with R = 360m from full-scale test section in Daglfing
failure of track irregularity = 13 mm
length of track irregularity = 16,8 m
lateral resistance = 4,4 N/mm
Application of recorded parameters to method of Meier and to FEM
Results of FEM: Influence of service load on lateral track stability
rail deflection [mm]
Ties B 70 with tie pad G04 and fleece, straight track
lateral
resistance
- 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
Application of recorded parameters to FEM
Results of FEM regarding lateral track stability

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
Conclusion
•
•
The application of elastic under tie pads has many advantages
- 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
Elastic under tie pads should not be too soft
- allowable tensile stress on rail foot should not be exceeded
- ballast deterioration on the tie sides
Chair and Institute of Road, Railway and Airfield Construction
Technical University Munich, Germany
Univ. Prof. Dr.-Ing. Stephan Freudenstein
[email protected]
www.vwb.bv.tum.de

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