PROJECT OVERVIEW N3/3 ATHLONE TO HILTON Dennis Rossmann

1. PROJECT OVERVIEW N3/3 ATHLONE TO HILTON Dennis Rossmann

2. N3/3 ATHLONE TO HILTON

3. CONTRACT No NRA N0303012/6: REHABILITATION OF ROUTE 3, SECTIONS 3& 4 ATHLONE TO HILTON km 19,130 (N3/3) TO km 1,160 (N3/4) CONTRACT DETAILS Employer: SANRAL Contractor: Basil Read / Milling Techniks : Consortium Consulting Engineers: BLN Consortium (Ingérop Africa, Letsunyane Associates (Pty) Ltd and Preben Naidoo & Associates) Tender Sum: R65 535 800-64

4. CONSTRUCTION HISTORY Construction by Provincial Roads Department NBC commenced – 1957 completed – 1962 SBC completed – 1971 Subsequent reseal and overlay

6. TRAFFIC ADT – 22 560 ADTT – 3058

10. TOPOGRAPHY Grades – 7% max Up to 6% over 40% of length Superelevation – Up to 12%

13. TRAFFIC ACCOMMODATION Closures to one lane limited to outside peak periods Two lanes open in each direction outside working hours Facility for removal of broken down vehicles

16. GEOTECHNICAL INSTABILITY Infilled gullies Talis creep Requires continuous management

18. PAVEMENT DESIGN Rigid pavement overlay Block paving Flexible pavement (Asphalt overlay) Composite pavement (Concrete / asphalt)

21. COMPOSITE PAVEMENT • Appropriate pavement • Cost benefit • Labour enhancement

24. CRCP INLAY EXPERIENCE • Riding quality / smoothness • Longitudinal joint ( rigid / flexible) • Pop-outs • Subsurface drainage

29. QUALITY CONTROL

33. GEOMETRIC DESIGN Peter Unstead

34. GEOMETRIC DESIGN PHILOSOPHY • PARTIAL CONCRETE INLAYS TO PRESCRIBED LEVELS • FINISHED ROAD LEVEL TO BE RAISED ENABLING: • SMOOTHING OF VERTICAL ALIGNMENT • ELIMINATION OF UNDULATIONS CAUSED BY FILL SUBSIDENCES • REGULARISATION OF THE SUPERELEVATION TO A LIMITED EXTENT • CARRIAGEWAYS TO BE WIDENED WITHIN GEOTECHNICAL AND BUDGET CONTSTRAINTS

35. HORIZONTAL AND VERTICAL ALIGNMENT • CARRIAGEWAYS HAD BEEN CONSTRUCTED IN SEPARATE SECTIONS UNDER VARIOUS CONTRACTS AND OVER AN EXTENDED PERIOD OF TIME • A TRULY GEOMETRICAL MODEL OF THE VERTICAL ALIGNMENT COULD NOT BE ESTABLISHED WITHOUT RESULTING IN EXCESSIVELY THICK OVERLAYS • EXISTING ROAD LEVELS "SMOOTHED" BY GRAPHICAL METHODS • SUPERELEVATION CORRECTIONS APPLIED • VARIOUS THICKNESSES OF OVERLAY LESS THE 80mm MILLING DEPTH ADDED TO PRODUCE THE FINISHED ROAD LEVELS.

36. DESIGN METHODOLOGY • DETAILED TOPOGRAPHICAL SURVEY USING GPS METHODS TO CREATE A DIGITAL TERRAIN MODEL OF THE EXISTING ROAD AND WIDENING AREAS. • POINTS SURVEYED: • AT EACH EDGE OF ROAD • ON THE LANE MARKINGS • IN THE INVERT AND ON THE OUTER EDGES OF THE EXISTING SIDE DRAINS. • A “BEST-FIT” GEOMETRIC HORIZONTAL ALIGNMENT DERIVED FOR EACH CARRIAGEWAY • THE CENTRE-LINE CHOSEN BETWEEN THE SLOW LANE AND THE CENTRE LANE • THE NBC REALIGNED BETWEEN km 23,2 AND km 23,7 TO CONTINUE THE THREE LANE SECTION PAST THE HILTON INTERCHANGE BY WIDENING THE CARRIAGEWAY IN THE MEDIAN.

37. DESIGN METHODOLOGY • USING ROAD DESIGN SOFTWARE EXISTING ROAD LEVELS DETERMINED ON CENTRE-LINE, FUTURE LANE MARKING POSITIONS AND EDGES OF THE CARRIAGEWAY • LEVELS TRANSFERRED TO A SPREADSHEET • COLUMN PROVIDED TO ADJUST THE DESIGN CENTRE LINE LEVEL RELATIVE TO EXISTING LEVEL TO PRODUCE A SMOOTH LONGITUDINAL PROFILE • EXISTING CROSSFALLS ASSESSED FOR UNIFORMITY WITH RESPECT TO LHS AND RHS OF CENTRE LINE AND COMPLIANCE WITH STANDARDS. • DESIGN CROSSFALLS CHOSEN • DESIGN LEVELS DERIVED AT VARIOUS OFFSETS LEFT AND RIGHT OF CENTRE-LINE • EDGE LEVELS DETERMINED BY THE CROSSFALLS CHOSEN.

38. DERIVATION OF DESIGN LEVELS • DIFFERENCES BETWEEN EXISTING ROAD LEVELS AND THE PROPOSED DESIGN LEVELS CALCULATED AND INFLUENCE ON PAVEMENT DESIGN ASSESSED • THE SMOOTHNESS OF THE LONGITUDINAL PROFILES ON CENTRE-LINE AND AT THE EDGES ASSESSED GRAPHICALLY BY APPLYING A SLOPING DATUM LINE. ADJUSTMENTS APPLIED AND CHECKED UNTIL A SATISFACTORY PROFILE WAS OBTAINED.

39. SMOOTHING OF LEVELS N3/3 SOUTHBOUND CARRIAGEWAY

45. WIDENING OF THE CARRIAGEWAYS • EXTENT SUBJECT TO GEOTECHNICAL AND BUDGET CONSTRAINTS • NORTHBOUND CARRIAGEWAY • BETWEEN RICKIVY VIADUCT AND km 21,2 WIDENING WOULD ENTAIL EXTENSIVE EARTHWORKS AND RETAINING WALLS • NORTH OF km 21,2 TO HILTON INTERCHANGE: • TO EASE TRAFFIC CONGESTION, A 3m WIDE SLOW SHOULDER WAS MORE ESSENTIAL ON THE LONG SUSTAINED 6% GRADE WHERE HEAVY VEHICLES TEND TO TRAVEL TWO ABREAST UP TO HILTON • HEAVY VEHICLES BREAK DOWN MORE OFTEN IN THIS AREA THAN FURTHER SOUTH • THICK MIST MORE PREVALENT

46. WIDENING OF THE CARRIAGEWAYS • EXISTING 15,1m WIDTH AVAILABLE FROM km 21,7 TO km 23,4 • A RELATIVELY FLAT AREA AVAILABLE ON THE RIGHT HAND SIDE OF THE NBC TO ALLOW WIDENING IN THE MEDIAN AVOIDING WIDENING OF CUTTINGS AND CONSTRUCTION OF RETAINING WALLS ON THE LEFT HAND SIDE • EXTENSION OF THE EXISTING 15,1m WIDE SECTION BACK TO km 21,2 AND FROM km 23,2 OVER THE RIDGE TO THE DOWNGRADE APPROACHING CEDARA COST EFFECTIVE DUE TO RELATIVELY MINOR EARTHWORKS INVOLVED

47. WIDENING OF THE CARRIAGEWAYS • SOUTHBOUND CARRIAGEWAY • LIMITED TO EXTENDING EXISTING 15,1m WIDTH FROM km 24,7 TO km 25,5 AT HILTON • HEAVY VEHICLES GENERALLY CONFINED TO CRAWLER LANE BETWEEN RICKIVY VIADUCT AND HILTON • HEAVY VEHICLES SELDOM BREAK DOWN • WIDENING THE 12,0m WIDE CARRIAGEWAY BETWEEN km 21,2 AND km 22,9 CONSTRAINED BY VERY HIGH FILLS ON RHS AND THE NEED TO AVOID CUTTING INTO THE HILLSIDE ON LHS • WIDENING OF THE 11,0m WIDE CARRIAGEWAY BETWEEN THE ARRESTOR BED AND km 21,2 CONSTRAINED BY DEEP SEATED FILL INSTABILITY

50. Pavement Design and Details Herman Wolff