Lateral Resistance Characteristics of Ballasted Tracks with Countermeasures against Rail Buckling

Transcription

1 Lateral Resistance Characteristics of Ballasted Tracks with Countermeasures against Rail Buckling Yokohama National University (YNU) Kimitoshi Hayano Railway Technical Research Institute (RTRI) Takahisa Nakamura Railway Technical Research Institute (RTRI) Yoshitsugu Momoya

2 Background Increase of axial force with the increase of rail temperature Lateral resistance of ballasts Damage observed after an earthquake (Momoya et al. 2013) Earthquake affects.

3 Nakamura et al. (2014) conducted a series of shaking table tests on full-scale ballasted tracks. They found that lateral resistance of ballasts was reduced during and after seismic motions. Shaking table tests on a full-scale ballasted track (Nakamura et al. 2014)

4 Koike et al. (2014) performed single-sleeper pull-out tests and track panel pull-out tests in the laboratory on 1/5-scale models to evaluate the lateral resistance of ballasts with various shapes of concrete sleepers. Sleepers prepared for model tests (Koike et al. 2014) Track panel pull-out test on1/5-scale models (Koike et al. 2014)

5 Horizontal Load, R (kn) mm-winged (trapezoid) 20-mm-winged (rectangle) 3H Rectangular parallelepiped They found the effects of winged sleepers on the lateral resistance of ballasts under various conditions Horizontal displacement, d h (mm) Horizontal loads and horizontal displacements relationships from track panel pull-out tests (Koike et al. 2014) Winged sleepers are introduced in one of high-speed railways to increase the lateral resistance of ballasts. Winged sleepers implemented in a line

6 However, the ballasts at transition zones or structure boundaries are affected not only by seismic motions but also local settlements. Rail Hanging sleepers Hanging sleepers Ballasts Sleeper Abutment Ballast settlement Embankment Foundation ground Angular folding

7 Yamamoto et al. (2016) performed model tests to evaluate the lateral resistance of ballasts subjected to angular folding. Hanging sleepers due to local settlements Angular folding (folding angle: 19/1000) Lateral resistance About 60% Boundary Sleeper s location with respect to the boundary Lateral resistance under the track panel condition 100% Schematic image of the effect of angular folding on the lateral resistance of railway ballasted track (modified after Yamamoto et al. 2016)

8 Rail Hanging sleepers Hanging sleepers Ballasts Sleeper Abutment Ballast settlement Embankment Foundation ground Lateral resistance of ballasts subjected to local settlements at transition zones or structure boundaries should be increased by appropriate countermeasures. Installation of buckling prevention plates to sleepers are expected instead of winged sleepers, though more time and efforts may be necessary to install them at sites. Buckling prevention plate

9 The increase of the lateral resistance of ballasts can be expected by the installation of buckling prevention plates to sleepers. However the lateral resistance can be affected by several factors such as the size and shape of plates, as well as the sleepers hanging situation. They have not been well investigated so far. Objectives From scaled model tests, lateral resistance characteristics of ballasts in which sleepers are equipped with bucking prevention plates are investigated. The followings are investigated in detail. 1) Effects of sleepers hanging situation on the lateral resistance. 2) Effects of size and shape of plates on the lateral resistance.

10 Effects of sleepers hanging situation on the lateral resistance Rail Hanging sleepers Ballasts Sleeper Abutment Ballast settlement Embankment Foundation ground

11 Dry density of 1.60 g/cm 3 Sleepers 1/5th scale model for track panel pull-out test Loading direction Load cell Percentage passing, P (%) B allast /5 S tan d ard R an ge S tan d ard R an ge P article d iam eter, D (m m ) Parallel gradation of PSD Rigid frame LVDTs Ballasts Track panel pull-out test with five sleepers

12 Wire is used to hang the rigid frame and the sleepers. Pull-out direction for evaluating lateral resistance

13 3H sleeper (in 1/5th scale) Ballast settlement S =0, 10, 20, 30mm 3H sleeper with buckling prevention plates (in 1/5th scale) Ballast settlement S =0, 10, 20, 30, 40mm Test cases for pull-out tests

14 Pull-out direction for evaluating lateral resistance

15 Track panel pull-out test 3H Track panel pull-out test 3H with buckling prevention plates Pull-out force, R (kn) S=10mm S=20mm Ballast settlement S=0mm S=30mm Sleepers' horizontal displacement, d h (mm) Pull-out force, R (kn) S=10mm Ballast settlement S=0mm S=20mm S=40mm S=30mm Sleepers' horizontal displacement, d h (mm) Horizontal loads and horizontal displacements relationships from single sleeper pull-out tests With increase of ballast settlement the lateral resistance of sleepers reduces irrespective of installation of buckling prevention plates. Sleepers with buckling prevention plates show lateral resistance higher than that of sleepers without buckling prevention plates.

16 Ratio of lateral resistance of hanging sleepers to that of non-hanging sleepers, LR hang /LR (%) Track panel pull-out test Bottom resistance may be lost at the start of settlement. Amount of track settlement was not well controlled? LR hang /LR=66.7*(1-S/h) Ballast settlement, S (mm) 3H h: Sleeper height(51mm) Ratio of lateral resistance of hanging sleepers to that of non-hanging sleepers, LR hang /LR (%) Track panel pull-out test 3H with buckling prevention plates LR hang /LR=66.7*(1-S/h) 2 h: Height of buckling prevention plate(81mm) Bottom resistance may be lost at the start of settlement Ballast displacement, S (mm) Ratio of lateral resistance of hanging sleepers to that of non-hanging ones plotted against ballast settlements Bottom resistance disappear at the start of settlement. The ratio of lateral resistance of hanging sleepers to that of nonhanging sleepers is reduced with increase of ballast settlement. The ratio can be estimated by the proposed equation.

17 Effects of size and shape of plates on the lateral resistance

18 Height increases. 3H sleeper without plates (a) ss (b) sl Width increases. (c) lz (d) ls (e) ll (f) lz(rec) (g) ll(rec)

19 Single-sleeper pullout tests Track panel pullout tests

20 Horizontal load, R (kn) S-sl S-3H S-ss Single sleeper pull-out test Narrow width Horizontal displacement, d h (mm) Horizontal loads and horizontal displacements relationships from single sleeper pull-out tests Horizontal load per one sleeper, R (kn) T-3H Track panel pull-out test Plate: Narrow width T-sl T-ss Horizontal displacement, d h (mm) Horizontal loads and horizontal displacements relationships from track panel pull-out tests Lateral resistance of ballasts increase with increase of plate height. However the degree of depends on the pull-out test type.

21 Lateral resistance per one sleeper, LR f (kn) LR f : Lateral resistance from single sleeper pull-out tests LR f : Lateral resistance from track panel pull-out tests A : Area of 3H sleeper's end or area of buckling prevention plates 3H ss lz sl ls lz(rec) ll ll(rec) without plates Type of buckling prevention plate 20,000 16,000 12,000 8,000 4,000 0 Area of 3H sleeper's end or area of buckling prevention plates, A(mm 2 ) Lateral resistance obtained from different type of buckling prevention plates and the respective plate s area Lateral resistance of ballasts do not always increase with increase of plate area. This tendency is remarkable in the single sleeper pullout test compared to the track panel pullout test.

22 Lateral resistance per one sleeper, LR f (kn) Experiment results Approximation curve using plate area as a variable LR 3H + LR(kN)= *10-6 * A(mm 2 ) Approximation curve using plate width and height as variables LR 3H + LR(kN)= *10-5 * W(mm)+1.25*10-3 * D(mm) Single sleeper pull-out test 3H ss lz sl ls lz(rec) ll ll(rec) without plates Type of buckling prevention plate Lateral resistance per one sleeper, LR f (kn) Approximation curve using plate width and height as variables LR 3H + LR(kN)= *10-4 * W(mm)+8.81*10-4 * D(mm) Experiment results Approximation curve using plate area as a variable LR 3H + LR(kN)= *10-6 * A(mm 2 ) Track panel pull-out test 3H ss lz sl ls lz(rec) ll ll(rec) without plates Type of buckling prevention plate Lateral resistance obtained from different type of buckling prevention plates together with approximation curves Approximation curve using plate width and height as variables gives better agreement with experimental results rather than that using plate area. The effect of plate height is more significant than that of the plate width.

23 Conclusions 1. A scaled model test method for evaluating lateral resistances of ballasted tracks where hanging sleepers are appeared due to ballast settlement is developed. 2. The test results showed that with increase of ballast settlement the lateral resistance is reduced. Sleepers with buckling prevention plates show lateral resistance higher than that of sleepers without buckling prevention plates. 3. The ratio of lateral resistance of hanging sleepers to that of non-hanging sleepers is estimated by the simple equation which considers the sleeper height or the buckling prevention plate height.

24 4. Lateral resistance of ballasts increase with increase of plate height. However the degree depends on the pull-out test type. 5. Lateral resistance of ballasts do not always increase with increase of plate area. This tendency is remarkable in the single sleeper pull-out test compared to the track panel pull-out test. 6. Approximation curve using plate width and height as variables gives better agreement with lateral resistance obtained from experiments rather than that using plate area. The effect of plate height is more significant than that of the plate width. Acknowledgements: We highly acknowledge Mr. Koike, Ms. Yamamoto and Mr. Ichikawa (formerly YNU students) for conducting a series of experiments.

25 Thank you very much for your kind attention.