Design of Picton Railway Overbridge for Mine Subsidence

Transcription

1 Design of Picton Railway Overbridge for Mine Subsidence Geraint Jones Long Bai Small Bridges Conference 24 November 2015

2 Introduction - Presentation Structure >Project Background >Longwall Mining >Location & Setting >Proposed Works >Stakeholders >Program Milestones >Detailed Design > Mine Subsidence > Articulation > Spherical Bearings > Modular Joint > Maintenance Manual >Conclusions

3 Longwall Mining

4 Location & Setting

5

6 Proposed Works

7 Stakeholders

8 Program Milestones >Oct 2014 >Jan 2015: >Mar 2015: >May 2015: >June 2015 >Nov 2015: >Dec 2015: >Jan 2016: >Mar 2016: Commence Detailed Design Detailed Design Complete Tender Period Award Contract Commence Construction Demolish Existing & Open New Bridge to Traffic Anticipated first impact of Longwall Longwall expected to be directly under the Bridge Longwall expected to be complete

9 Erection of Bridge Girders

10 Demolition of Existing Bridge

11 Bridge Design 1. Design Strategy 2. Bridge Articulation 3. Mining Subsidence Movements 4. Maintenance 5. Conclusion

12 Bridge Geometry

13 Design Strategy >Design Guidance: BD10/97 >Special consideration is required if the displacement between two points exceeds 1/1000 times the distance >Mine subsidence prediction was carried out by Mine Subsidence Engineering Consultants (MSEC) >Not economical to design all the elements and connections to accommodate the worst predicted movement >Key challenge: A economical articulation system that requires minimum intervention and adjustment during or after the mining activities.

14 Mine Subsidence Movement Register >Subsidence Movement Scenario >Potential Response of Overbridge >Potential Impact on Overbridge >Predicted Movement >Design Strategy >Proposed Design Capacity >Subsidence Management Strategy >Trigger Level

15 Mine Subsidence Movement Subsidence movement scenario Closure between abutments Opening between abutments Lateral differential movement between abutments Vertical differential movement between abutments Predicted Movements 1% Probability 0.05% Probability Worst Observed Maximum 80 mm 230 mm 330 mm 500 mm 35 mm 70 mm 80 mm 150 mm 40 mm 80 mm 84 mm 150 mm 50 mm 100 mm 330 mm 400 mm or 10mm/m whichever is greater Uniform lateral tilt Transverse differential tilt (twist) between abutments N/A N/A - 10mm/m mm/m Curvature of ground at abutment transverse to bridge Hogging or sagging curvature of 0.10km -1 Tension strain of ground at abutment transverse to bridge 1.5mm/m 2.9mm/m - - Compression strain of ground at abutment transverse to bridge -3.5mm/m -9.7mm/m - -

16 Articulation Abutment A > Modular Expansion Joint Abutment B > Strip Seal Expansion Joint Girders > Spherical Bearings Traffic Barrier Connector Cover Plate Safety Screen

17 Bearings & Lateral Restraints Abutment A > Free floating bearings under all girders > Later restraint block between two middle girders Abutment B > Free floating bearings under two outer girders > Fixed bearing under middle bearing

18 Articulation Movement Capacity Element Opening Closing Vertical Rotation Modular Expansion Joint (Abutment A) Horizontal Rotation 185 mm 535 mm +/ rad +/ rad Strip Seal Joint (Abutment B) Free Floating Bearing (Abutment A) Free Floating Bearing (Abutment B) 82 mm 43 mm mm 535 mm +/ rad - 28 mm 28 mm +/ rad - Traffic Barrier 120 mm 100 mm - - Connector Cover Plates 100 mm 230 mm - - Safety Screen 55 mm 20 mm - -

19 Closure Between Abutments Predicted conventional closure: 20 mm. 1 in 100: 80 mm 1 in 2000: 230 mm Worst observed: 330 mm Maximum Predicted: 500 mm

20 Opening Between Abutments Predicted conventional opening: 25 mm. 1 in 100: 35 mm 1 in 2000: 70 mm Worst observed: 80 mm Maximum Predicted: 150 mm

21 Lateral Movement Between Abutments 1 in 100: 40 mm 1 in 2000: 80 mm Worst observed: 84 mm Maximum Predicted: 150 mm

22 Vertical Movement Between Abutments Predicted conventional tilt: 2 mm/m. 1 in 100: 50 mm 1 in 2000: 100 mm Worst observed: 330 mm Maximum Predicted: 10 mm/m or 400 mm (whichever is greater)

23 Modular Expansion Joint Picture Courtesy to Mageba

24 Modular Expansion Joint Picture Courtesy to Mageba

25 Modular Expansion Joint Picture Courtesy to Mageba

26 Spherical Bearings 1. Concave lower part 2. Sliding sheet (UHMWPE - ultra-high molecular weight polyethylene) 3. Convex polished chrome surface 4. Sliding sheet (UHMWPE) 5. Sliding plate 6. Guide bars 7. Anchor dowels Picture Courtesy to Mageba

27 Maintenance >Design Life of Bridge Elements >Maintenance Diary of Bridge Elements >Inspection and Maintenance Instructions >Work-As-Executed Drawings Asset element/sub-element Minimum Design life (years) Permanent Structural Elements 100 Spherical Bearings 40 Bridge Joints Joint sealant 15 Bridge Joints Expansion joint rubbers 35 Safety Screens Protective Coating 15 Asphalt Wearing course 40 Traffic Barrier Railings Protective coating 20

28 Conclusion The design for this single span bridge of modest dimensions was relatively complex due to the requirement that the bridge should accommodate potential significant mining induced ground movements without intervention or adjustment. Through consultation with a wide range of parties an efficient and robust design solution was achieved. The existing bridge was demolished and the new bridge constructed with minimum disruption to road and rail users and with no delay to the longwall mining operations. Acknowledgements Kevin Golledge Tahmoor Coal David Talbert Tahmoor Coal Ian Sheppard Tahmoor Coal Daryl Kay MSEC Mark Dolan Robson Civil Virendra Ghodke Mageba