1. CHALLENGES IN DESIGN & MAINTENANCE FOR MIXED TRAFFIC REGIME ON IR
OF TRACK STRUCTURE
FOR MIXED TRAFFIC REGIME ON IR
- Vipul Kumar, ED/Track-I
- Ajay Kumar, Director/Track-II
RDSO

2. INTRODUCTION
Operation upto 25 t axle load at 100 kmph in mixed traffic regime is being envisaged by IR.
These operations shall be on the same track having/planned for semi high speed passenger operation.
Further, some of the routes are being planned for upgradation to 200 kmph passenger operations

3. SEMI HIGH SPEED OPERATIONS
Basic Requisites from Track
Much more accurate track geometry in comparison to that for kmph to provide at least same degree of ride comfort and stability to stocks
Considerable reduction in rail-weld failures ( should preferably be zero) as these may lead to devastating consequences at higher speeds
Basic requirements of rolling stock
Small track - vehicle interaction force/accelerations
responsible for distortion of the track geometry and effecting fatigue failures of rails and welds
i.e. Track friendly design in line with international standards

4. UIC Leaflet 724-R (track equipment for 25t axle load on ballasted track)
International study and literature indicate that
- Best way to decrease the deteriorating effects on track when operating with high axle load is through reduction in dynamic wheel loads
Pre-conditions for reducing dynamic wheel loads include:
Good track geometry quality
Adapted speed
Good wheel quality
Track friendly vehicle design
However, there are limitations as regards to maintenance of good track geometry and good wheel quality.
So, the track friendly vehicle design becomes most important factor

5. REQUIREMENTS FOR HEAVY AXLE LOAD WAGON
So the primary requirement for high axle load stocks to operate in mixed traffic regime is a Track friendly design
imparting low forces & accelerations on track
(otherwise required level of geometry and continuity of track for semi-high speed passenger operation shall not be sustained)
Accordingly, the wagon clearance criteria needs to be based on following parameters as done internationally
Track loading limit (track fatigue criteria), limiting dynamic wheel load as specified by UIC
Acceleration limits
Lateral force limits

6. Comparison Of Acceptance Criteria (Freight Stocks)SN
Parameters
IR Limits
UIC-518/EN Limits
British Standards 1
Vertical acceleration
Not specified
0.5g
0.25g (mean)
0.44g (max.) 2
Lateral acceleration
0.3g
0.2g (mean)
0.33g (max.) 3
Vertical Ride Index
4.5 NA
4.25 (mean)
5.0 (max ) 4
Lateral Ride Index 5
Track loading Limit
(Q lim) – track fatigue criteria
Not Specified
( 90 + Q0 )
Max 210 KN
Not Available 6
Lateral Force (Hy2m)
0.85(1+P/3) t
P=axle load
0.85(10+Po/3) kN Po=axle load
0.85(1+2Q/3) t 2Q= nominal wheel load

7. Problems With Existing Heavy Axle Load Designs
Track loading (dynamic forces on rail ) are not known
High acceleration values much beyond the international norms
High vibrations imparted to track in the high stress state due to high axle load causes increased incidences of fatigue as well as sudden failures
Smaller wheel dia :
higher contact stress, increased rate of surface crack propagation
increased risk of fatigue failure
Increased cycles of impact on track in case of wheel flat/deformed wheel, increasing chances of failure when coupled with track & other vehicle defects of higher degree

8. Acceleration values of existing stocks
25 T AXLE LOAD WAGONS
LOADED CONDITION
WAGON
SPEED
MAX LAT.ACC (g)
MAX.VER. ACC.(g)
C&M-I VOL-I Or OTHER
REPORT NO.
REMARKS
Detailed run
Long run
BOBSNM1
60/80
0.48
0.65
0.45
0.49
Other
726/2006
BOXN 25M
125
0.23
0.25
0.69
0.81
C&M-I
1217/2012
(i) UN-A0 (ii) 2 degree curve at 80kmph
BLC 25M
0.21
0.47
0.51
1288/2013
UN-A0, TW-A0, AL-A0
BOXNHL 25T 85
0.38
0.36
0.41
1427/2015
0.4
0.42
0.37
BOXNEL 90
0.66
0.31
0.72
1437/2016
BOYEL
0.74
0.57
0.73
0.76
1439/2016
BOXNS
100
0.19
0.87
1463/2016

9. Acceleration values of existing stocks
22.9 T AXLE LOAD WAGONS
LOADED CONDITION
WAGON
SPEED
MAX LAT.ACC (g)
MAX.VER. ACC.(g)
C&M-I VOL-I Or OTHER
REPORT NO.
REMARKS
Detailed run
Long run
BOXNHL
110
0.64
0.66
0.78
0.73
C&M-I
929/2009
BOXNHL (PU TYPE CCSB PAD)
0.53
0.47
0.45
0.41
936/2009
BCNHL
0.48
0.57
0.61
1007/2009
BOXNHL (Series 1) 85
0.23
0.31
0.56
Other
1341/2014
BOXNHL (Series II)
0.25
0.33
0.5
1342/2014

10. Effect Of Increased Axle Load
Studies reported in ORE, D/141/RP 1:
For increase in axle load from 20t to 22t, the fatigue failure in rails will increase based on the relative increase in mean axle load raised to a power of 3 to 4
for increase from CC to CC+ 8+2 loading - It culminates into 40-60% increase in fatigue failure of rails
Further increase from 22.9 t to 25 t - the expected further increase in fatigue failure of rails may be 30-40%
Studies reported in ORE, D/141/RP 5:
10% increase in axle load – increase in maintenance cycle by 33 %
Study by ZETATECH Ass
10% increase in axle load may cause damage to track higher by 20%

11. Experience Of Heavy Axle Load Operation On IR
Operation of 22.9t at 75 kmph & limited operation of 25t at 50 kmph
Based on limited data captured and provided by ECOR, SCR & SECR , the track related issues may be summarized as under:
Excessive wear in switches and crossings
Crossing zone requires frequent packing
CMS crossings required frequent replacement/repair
Excessive wear of outer rails of curve and flattening of inner rails
Increased cases of glued joint failure and fish plate fracture
Stretches on weak formation/black cotton soil causing frequent ballast puncture resulting into abrupt cross level variation
Fish plate of stock rail joints getting battered, leading to failure of fish plates

12. Experience Of Heavy Axle Load Operation On IR
K – K Line
9944 no. of 25t axle load trains in 9 years- approx 1100 trains/year
GMT of the section is 25
substantial increase in rail /weld failure under heavy axle load
Year
No of 25 t axle load trains
Total
RF + WF
829 3
1843 8
832 7
1997 18
796 11
1398 57
1134 12

13. Experience Of Heavy Axle Load Operation On IR
South East Central Railway
Total 222 IMR detected in Bilaspur division in the year
100 IMR were detected in the 1st round i.e. without being classified as OBS in previous round
112 IMR upgraded from OBS
In spite of above detection, 138 rail fractures
The trend is almost same in
The rate of detection of IMR and rail fracture in the route under operation of CC+8+2 loads is too high

14. Issues In Heavy Axle Load Operation On IR
(A) Issues in design of track structure
Most critical parameters for track design i.e. Track loading is not known
Design with old data of obsolete wagons measured at lower speed and on different track structure
Even with these old values
rail stress in 60 kg/90UTS rails are exceeding the limits at 100 kmph for 25t axle load
close to limit at 75 kmph
The wagon having reduced wheel diameter (780mm condemning)
Higher contact stress on rail – increased rate of surface crack propagation

15. Issues In Heavy Axle Load Operation On IR
(A) Issues in design of track structure
High DA permitted during operation - Critical WILD alarm at 35t ( 280% DA for 25t axle load)
rail stress of Kg/mm2 against the permissible limit of Kg/mm2 in 60 kg/90 UTS rail
No track structure can be designed for such high dynamic load
High values of accelerations of present heavy axle load wagons;
high vibrations imparted to rail under high stress condition, reduced fatigue life, increased chances of fatigue and sudden failures

16. Issues In Heavy Axle Load Operation On IR
(B) Major issues in operation
Indiscipline in zonal railways in monitoring and remedial action on impact loading on track
Meagre availability of WILDs – no monitoring of 90% of loads
Poor response of zonal railways on WILD alarms – hardly 7 to 8% detachment
Alarms up to 50 t are generally ignored and allowed to run
Instantaneous wheel load upto 59t (DA – 400%) are recorded – indicating poor maintenance
Limitations: 60 kg rail has safety limit of approx. 21t, AT welds are having even less

17. Issues In Heavy Axle Load Operation On IR
(B) Major issues in operation
Poor monitoring of overloading and corrective action by zonal railways
Inadequate powering – stalling, damage to rail
Impact: Unusually high number of rail fractures and IMRs as reported in BSP division, KK line - enormous cost of replacement and track down time, safety hazard

18. Issues In Heavy Axle Load Operation On IR
(B) Major issues in operation
Required enhanced maintenance blocks and resource
But the situation is grim – corridor blocks have vanished, severe resources constraints putting lot of pressure on infrastructure
maintenance arrears, in-service failures, passengers safety at risks, downtime
Problem of corrosion of rails and fastenings due to human excreta from coaches
reduced sectional area at critical locations as foot, sudden breakage of rail

19. CONCLUSION & WAY FORWARD
Increase in through-put with increased axle loads and introducing semi-high speed on the same track can be justified to cater to the needs of ever burgeoning population, assuming certain risks.
Mostly, these risks are associated with the high rail-wheel forces.
Keeping the rail-wheel forces low is the only way for economically sustainable heavy axle load operations along with safer semi-high speed passenger operations.

20. CONCLUSION & WAY FORWARD
For reducing these risks, various elements and regime of heavier axle loads and semi-high speed operations needs to be conceived and implemented meticulously. Main elements are
Proper design of track structure
- needing real time measurement of dynamic forces on track
world class freight suspension system with limited dynamic loading
Regime of clearing rolling stocks in line with international std
- in order to ensure that rolling stock passes through the track with worn out limits having low dynamic forces

21. CONCLUSION & WAY FORWARD
Enhanced monitoring and maintenance of rolling stocks:
way side monitoring equipment, Installation of WILD at all important/specified locations required
Enhanced monitoring and maintenance of track:
- high speed TRC, Vehicular USFD, Broken rail detection system, completely mechanized maintenance
Timely maintenance and replacement of both aged rolling stock and fixed infrastructure
Well laid maintenance regime: 4 hrs corridor block, enhanced funds and material arrangement, better mobility (MMU, RCRV etc)

22. THANKS