Cooperative Research Centre (CRC) for Rail Innovation
                       Showcase Event
                    Thursday 3...
Problems in Rail Track Substructure
       Clay Pumping    Differential Settlement




Void Clogging            Degradatio...
Ballast Fouling
            Void Contaminant Index (VCI)
                  (1+ef)       Gs.b        Mf
         VCI =     ...
Permeability Test Measurements and Predictions
                                1.E+00                   kb  k f
         ...
Seepage model with SEEP-W
                                                   4m                        Total Head =0.5m


...
Track Drainage Assessment
                                                                      Shoulder ballast maintenan...
Performance of ballast upon impact – use of shock mats
Drop Hammer - Impact Testing equipment   Weight of drop hammer = 5....
Impact Response

                          Impact force excitation during 1st Blow                                        ...
Assessment of ballast breakage during impact

  1                                                                         ...
Use of Geosynthetics – Process Simulation Testing
                                                                        ...
From Theory to Practice: Use of Geosynthetics in Bulli Track




                 Details of instrumented track




      ...
Preparation of Fully Instrumented Trial Track in Bulli




                          Geocomposite layer
                  ...
Field Instrumentation in Bulli




      Settlement pegs            Displacement
      installed at ballast-      transduc...
Deformation of Ballast
(Indraratna et al, ASCE, JGGE, 2010)
                                                              ...
Use of Shock Mats & Geogrids in Practice: Singleton (NSW) – R3.117




      Soft Subgrade: Embankment fill      Stiff Sub...
Instrumented Track for Performance Monitoring - Singleton




                                              Settlement peg...
PLAXIS - Finite Element Analysis
                                                                                         ...
New Design Procedures – UoW method
        (Systematic Method of Analysis of Rail Track – SMART)
    Criterion 1: Critical...
Criterion 2: Critical track deformation
  (Plastic vertical strains for (a) ballast = 8%; (b) subgrade = 2%)




         ...
Single Subgrade Layer    Formulation of            Multiple Subgrade Layers


                        SMART Approach
     ...
Conclusions

•   The track drainage is assessed using a new parameter, ‘Void
    Contaminant Index’ - VCI that takes into ...
Acknowledgement
 Australian Research Council (2 Discovery Projects and 3 Linkage
  Projects since 1993).
 Cooperative Re...
Test materials – Specifications
Material   Particle   dmax   dmin    d50    Cu                100
           Shape      (m...
Multiple Impact Loading with Shock Mats
                                                                     Number of blo...
2010 CRC Showcase - Performance - Ballast Design R3.106
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2010 CRC Showcase - Performance - Ballast Design R3.106

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2010 CRC Showcase - Performance - Ballast Design R3.106

  1. 1. Cooperative Research Centre (CRC) for Rail Innovation Showcase Event Thursday 30 September 2010 Integrated Ballast–Formation-Track Design and Analysis including the Implications of Ballast Fouling and High Impact Loads CRC Projects R3.106 - Ballast Design Buddhima Indraratna Professor of Civil Engineering Director, Centre for Geomechanics & Railway Engineering Faculty of Engineering, University of Wollongong Other Researchers: Dr Sanjay Nimbalkar; Dr Cholachat Rujikiatkamjorn, Nayoma Tennakoon (PhD student) Industry Partners: David Christie and Sandy Pfeiffer (RailCorp); Mike Martin and Damien Foun (QR), Tim Neville (ARTC)
  2. 2. Problems in Rail Track Substructure Clay Pumping Differential Settlement Void Clogging Degradation Coal Fouling Poor Drainage
  3. 3. Ballast Fouling Void Contaminant Index (VCI) (1+ef) Gs.b Mf VCI = x x x 100 eb Gs.f Mb eb = Void ratio of clean ballast ef = Void ratio of fouling material Gs-b = Specific gravity of ballast material Gs-f = Specific gravity of fouling material Mb = Dry mass of clean ballast Mf = Dry mass of fouling material kb  k f k k f  VCI  (kb  k f ) 100
  4. 4. Permeability Test Measurements and Predictions 1.E+00 kb  k f k k f  VCI  (kb  k f ) Clay fouled ballast-Theoretical Hydraulic Conductivity /(m/s) 100 1.E-01 Coal fouled ballast-Theoretical 1.E-02 Clay fouled ballast-Experimental Coal fouled ballast-Experimental 1.E-03 1.E-04 Hydrulic conductivity of coal fines 1.E-05 Hydraulic conductivity of clayey fine sand 1.E-06 0 20 40 60 80 100 Void Contaminant Index,VCI /(%)
  5. 5. Seepage model with SEEP-W 4m Total Head =0.5m Zero pore water pressure 0.3m 45 o Clay fouled ballast Degree of Fouling Hydraulic conductivity VCI (%) k (m/s) – Lab data Drainage Criteria – PhD work of Ms. Nayoma Tennakoon 0% 0.3 25% 0.02 50% 0.00012 Free Drainage Q/Qc>50 100% 2.3 x 10-8 Good drainage 5<Q/Qc<50 Acceptable drainage 1<Q/Qc<5 Equivalent Maximum Flow rate ,Qc = 0.4 litres/sec. Poor Drainage 0.25<Q/Qc<1 (based on an extreme precipitation event of 300mm/hour) Very Poor 0.0005<Q/Qc<0.25 Drainage capacity of the track, Q Impervious Q/Qc<0.0005
  6. 6. Track Drainage Assessment Shoulder ballast maintenance requirement Shoulder ballast with 0% VCI Shoulder Shoulder ballast with ballast with Shoulder ballast 100% VCI 25% VCI with 50% VCI Poor Drainage Poor (k2,k3,k4) Drainage (k2,k3,k4) L=0.2m L=0.1m Min. VCI = (50,50,50) Min. VCI = (50,50,50) Poor Drainage in all cases Poor Drainage (k2,k3,k4) Min. VCI = Top ballast layer k4 (25,25,25) Middle ballast layer k3 Impervious in all cases Bottom Ballast layer k2 L L
  7. 7. Performance of ballast upon impact – use of shock mats Drop Hammer - Impact Testing equipment Weight of drop hammer = 5.81 kN (0.6 t) Maximum Height = 6 m Maximum drop velocity = 10 m/s Dynamic load cell capacity = 1200 kN Height of the ballast sample = 300 mm Diameter of the ballast sample= 300 mm Low confining pressures in track are similar to rubber membrane encasement
  8. 8. Impact Response Impact force excitation during 1st Blow Impact force excitation during 9th Blow 360 360 Fast Fourier Transform: Fast Fourier Transform: Low Pass Filter (cut-off frequency 50000 Hz) 320 Low Pass Filter (cut-off frequency 50000 Hz) 320 280 280 Multiple P1 type peaks 240 240 Impact force (kN) Impact force (kN) 200 Separation between the impactor and sample 200 160 160 120 120 P2 type peak 80 80 40 40 0 0 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 time (sec) time (sec) 1st Blow 9th Blow In the application of continuous blows on the same specimen, multiple instantaneous P1 peaks are followed by a longer duration P2 peak. It is force P2 that causes predominate ballast damage. With greater breakage and subsequent compression, P2 peak becomes more distinct with increasing number of blows.
  9. 9. Assessment of ballast breakage during impact 1 Subgrade Position of shock Ballast Breakage d95i A type mat Index (BBI) BBI  A dmax B A B Without shock mat ge ka PSD = particle size distribution ea br Stiff - 0.170 Fraction Passing 2.36 = smallest sieve size um d95i = d95 of largest im ax sieve size Soft - 0.080 m of ry With Shock mat da Shift in PSD un caused by bo degradation Stiff Above ballast 0.145 ry tra bi Ar Stiff Below ballast 0.129 Initial PSD 0 Final PSD Stiff Above & below 0.091 2.36 0 Sieve Size (mm) 63 ballast Indraratna et al., 2005 Soft Above ballast 0.045 Soft Below ballast 0.056 Soft Above & below 0.028 ballast
  10. 10. Use of Geosynthetics – Process Simulation Testing Number of load cycles, N 0 100000 200000 300000 400000 500000 600000 0 Fresh ballast (wet) Recycled ballast (wet) 5 Rapid increase Recycled ballast with geotextile (wet) Settlement, S (mm) in settlement Recycled ballast with geogrid (wet) 10 Recycled ballast with geocomposite (wet) 15 20 Stabilisation 25 Settlement of ballast with and without geosynthetics Grain size (mm) 0 10 20 30 40 50 60 70 4 Highest breakage Effect of geosynthetics Prismoidal Triaxial Rig to 2 Simulate a Track Section D Wk (%) 0 (Specimen: 800600600 mm) -2 Fresh ballast (wet) Recycled ballast (wet) Recycled ballast with geotextile (wet) -4 Recycled ballast with geogrid (wet) Recycled ballast with geocomposite (wet) -6 Effect of Geosynthetics on Ballast Degradation
  11. 11. From Theory to Practice: Use of Geosynthetics in Bulli Track Details of instrumented track Section of ballasted track bed with geocomposite layer
  12. 12. Preparation of Fully Instrumented Trial Track in Bulli Geocomposite layer (geogrid+geotextile) before ballast Ballast placement placement over the geocomposite 8 October 2006 Geotextile Recycled Ballast Fresh Ballast Bonded Geogrid from Chullora Quarry, Sydney Bombo Quarry, Wollongong
  13. 13. Field Instrumentation in Bulli Settlement pegs Displacement installed at ballast- transducers installed at capping interface sleeper-ballast interface
  14. 14. Deformation of Ballast (Indraratna et al, ASCE, JGGE, 2010) Number of load cycles, N Number of load cycles, N 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 0 1x10 2x10 3x10 4x10 5x10 6x10 7x10 8x10 9x10 0 1x10 2x10 3x10 4x10 5x10 6x10 7x10 0 0.00 -0 -0.00 Average lateral displacement of ballast, (S h)avg (mm) Fresh Ballast (uniform graded) Fresh Ballast (uniform graded) Average vertical strain of ballast, ( 1)avg (%) Mean settlement of ballast, (S v)avg (mm) Average lateral strain of ballast, 3)avg (%) 3 Recycled Ballast (well graded) 1.00 -2 Recycled Ballast (well graded) -0.08 Fresh Ballast with Geocomposite Fresh Ballast with Geocomposite Recycled Ballast with Geocomposite -4 Recycled Ballast with Geocomposite -0.16 6 2.00 -6 -0.24 9 3.00 -8 -0.32 12 4.00 -10 -0.40 15 5.00 -12 -0.48 18 6.00 -14 -0.56 0 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 12 14 time, t (months) time, t (months) Mean settlement (Sv)avg and Average lateral displacement (Sh)avg average vertical strain (1)avg and average lateral strain (3)avg The recycled ballast performs well, if a well-graded PSD is adopted (Cu = 1.8) and stabilised with geogrids. A well-graded recycled ballast (Cu>2) can provide a higher placement density, hence a reduced settlement compared to a Uniform ballast (Cu<1.5) .
  15. 15. Use of Shock Mats & Geogrids in Practice: Singleton (NSW) – R3.117 Soft Subgrade: Embankment fill Stiff Subgrade: Hard rock cutting Types of Geosynthetic Biaxial Geogrid - TerraGrid TG3030 (Polyfabrics) Biaxial Geogrid - Tensar Geogrid SSLA30 (Geofabrics Australasia) Biaxial Geogrid - EnkaGrid MAX 30 (Maccaferri) Geocomposite - Combigrid 40/40 Geogrid + Geotextile (Global Synthetics) Shock mat (10 mm thick)
  16. 16. Instrumented Track for Performance Monitoring - Singleton Settlement pegs Geogrid layer placed placement in the track above the capping Pressure cells below the sleeper Mudies Creek Bridge pressure cells installation
  17. 17. PLAXIS - Finite Element Analysis Vertical stress under rail, v (kPa) 0 50 100 150 200 250 300 0 Depth below base of sleeper, z (mm) 150 Ballast layer 300 Sub-ballast layer Elasto-plastic Model Field Data 450 Ultimate redistribution of vertical stress Settlement under rail, Sv (mm) 0 5 10 15 20 25 30 35 0 Depth below base of sleeper, z (mm) Because of symmetry, adequate to consider half of the 150 track Ballast layer Axle load of 25 tonnes and dynamic impact factor of 300 1.43 (@ speed of 80 km/h on standard gauge) Sub-ballast layer Elasto-plastic Model FEM predictions are underestimated because 450 Field Data breakage is not captured well Ultimate settlement with depth If breakage is captured with associated plastic flow, then the settlement prediction will be more accurate.
  18. 18. New Design Procedures – UoW method (Systematic Method of Analysis of Rail Track – SMART) Criterion 1: Critical Shear Strength (ballast or subgrade) UOW Conventional Li and Selig approach UoW Ballast Parameters
  19. 19. Criterion 2: Critical track deformation (Plastic vertical strains for (a) ballast = 8%; (b) subgrade = 2%) UOW Conventional Li and Selig approach UoW ballast parameters
  20. 20. Single Subgrade Layer Formulation of Multiple Subgrade Layers SMART Approach (to be completed in 2012 under R3.117 project)
  21. 21. Conclusions • The track drainage is assessed using a new parameter, ‘Void Contaminant Index’ - VCI that takes into account the specific gravity of different fouling materials. • Recycled ballast stabilised with Geosynthetics can perform as well as fresh ballast • Shock mats improve the performance of ballast by reducing the breakage caused by impact loads. Effectiveness depends on the subgrade stiffness. • Field trials conducted in Bulli and Singleton (NSW) demonstrate the advantages of Field Performance Monitoring, apart from calibrating FEM-based design technique. • UOW research outcomes are continually captured in a MATLAB based design approach: SMART (Systematic Method of Analysis of Rail Tracks).
  22. 22. Acknowledgement  Australian Research Council (2 Discovery Projects and 3 Linkage Projects since 1993).  Cooperative Research Centre for Railway Engineering and Technologies (Rail CRC) (Project 6/139) from 2000-2007  Cooperative Research Centre (CRC for Rail Innovation)  ARC Centre of Excellence for Geotechnics (funded in 2010).  Industry Partners: RailCorp, QR, and ARTC.  David Christie (RaiCorp, Sydney)  Tim Neville (ARTC, Newcastle)  Michael Martin, Damien Foun (QR, Brisbane)  Sandy Pfeiffer (RaiCorp, Sydney)  UOW Researchers: Dr Joanne Lackenby, Dr Wadud Salim, Dr. Sanjay Nimbalkar, Ms. Nayoma Tennakoon, Dr Cholachat Rujikiatkamjorn  UOW Technical Staff: Alan Grant, Cameron Neilson, Ian Bridge
  23. 23. Test materials – Specifications Material Particle dmax dmin d50 Cu 100 Shape (mm) (mm) (mm) 90 Fresh Highly 63.0 19.0 35.0 1.6 Ballast angular 80 Sand Subgrade - 4.75 0.075 0.48 2.3 70 (sand) Fresh Ballast 60 % passing 50 40 Australian Standard 30 AS 2758.7 (1996) 20 UoW new gradation Indraratna and Salim (2005) 10 0 0.010 0.100 1.000 10.000 100.000 Particle Size (mm) Fine sand as subgrade Shock mat (10 mm thick) made of recycled rubber (polyurethane) Damping Ratio = 0.08
  24. 24. Multiple Impact Loading with Shock Mats Number of blows, N Number of blows, N 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 52 52 No Shock mat 48 48 Shock mat at top Maximum Impact Force, P 2 (kN) Shock mat at bottom Maximum Impact Force, P2 (kN) 44 44 Shock mat at top and bottom 40 40 36 36 32 32 28 28 No Shock mat 24 Shock mat at top 24 Shock mat at bottom 20 Shock mat at top and bottom 20 0.0 0.6 1.2 1.7 2.3 2.9 3.5 4.1 4.6 5.2 5.8 0.0 0.6 1.2 1.7 2.3 2.9 3.5 4.1 4.6 5.2 5.8 Cumulative Impact Energy, E (kNm) Cumulative Impact Energy, E (kNm) Very Stiff Subgrade – steel plate Natural Softer Subgrade - sand The P2 force shows a significant increase with the extent of cumulative impact energy. For stiff subgrade, shock mat is more effective in reducing P2 when located at the bottom of ballast than at the top. A soft subgrade itself serves as an energy absorber, hence the benefits of the shock mat are generally marginal. However, if the shock mat is placed at the top of ballast to attenuate the impulse waves, then P2 is reduced (less breakage).
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