PROJECT OVERVIEW N3/3 ATHLONE TO HILTON Dennis Rossmann
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N3/3 ATHLONE TO HILTON
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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 (Ingrop
Africa, Letsunyane Associates (Pty) Ltd and Preben Naidoo &
Associates) Tender Sum: R65 535 800-64
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CONSTRUCTION HISTORY Construction by Provincial Roads
Department NBC commenced 1957 completed 1962 SBCcompleted 1971
Subsequent reseal and overlay
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TRAFFIC ADT 22 560 ADTT 3058
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TOPOGRAPHY Grades 7% max Up to 6% over 40% of length
Superelevation Up to 12%
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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
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
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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.
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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.
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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.
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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.
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SMOOTHING OF LEVELS N3/3 SOUTHBOUND CARRIAGEWAY
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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
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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
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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
PAVEMENT DESIGN PRINCIPLES CRC partial inlays used in slow
lanes Slow moving heavy traffic on steep incline High ambient
temperatures CRC to allow for future overlays CRC partial inlay in
NBC centre lane Heavies overtaking on uphill sections Joint between
slow and centre lanes concrete to concrete Asphalt base and
surfacing used in SBC centre lane Lower traffic because of
dedicated crawler lane Easier traffic accommodation. Asphalt
surfacing used in fast lanes Low traffic loading
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DESIGN TRAFFIC Cumulative E80s over 15 years Slow lanes:40
million NBC centre lane:20 million SBC centre lane:10 million Fast
lanes:1 million
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PAVEMENT MODELS Derivation of pavement models for mechanistic
analysis As-built information Backcalculated elastic layer moduli
from FWD testing Asphalt cores
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FLEXIBLE PAVEMENT DESIGN Asphalt and cemented layers SAMDM
stochastic transfer functions based on linear elastic material
behaviour and failure in fatigue Granular layers Stochastic
transfer functions based on non- linear elasto-plastic material
behaviour and failure in permanent deformation Subgrade layers
Transfer function based on linear elastic material behaviour and
failure in permanent deformation
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ASPHALT TRH4 Revision (1995): Phase 1: Updating Transfer
Functions for SAMDM.
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RIGID PAVEMENT DESIGN Manual M10 Deterministic Nomograms
Underlying pavement modelled by a single semi-infinite layer with
an equivalent support stiffness CNCRISK computer program Developed
by C and CI Stochastic (Monte Carlo Simulation) Computerised
Underlying pavement modelled by multiple layers characterised by
thickness and stiffness (MPa)
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PAVEMENT STRUCTURES - FLEXIBLE Fast lanes 30 SMA, 20 40 asphalt
levelling layer 30 SMA, 60 asphalt base, asphalt levelling layer
Fast lane widenings 30 SMA, 60 asphalt base, 150 C3 subbase, 300 G7
and G9 selected layers, subgrade (improved) SBC middle lane 30 SMA,
150 asphalt base 30 SMA, 100 asphalt base, 250 C3 subbase
(reworked)
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PAVEMENT STRUCTURES - RIGID Thickness varies between 180 and
220 mm depending on loading and support 30 mm asphalt bedding layer
where no existing asphalt Existing structure
ROAD WIDENING:NBC Fast lane and shoulder - 4,0km NBC Slow
shoulder - 0,5km SBC Fast shoulder - 0,8km CONCRETE PAVEMENT: NBC
Slow shoulder, slow lane and middle lane 4,5km SBC Slow shoulder
and slow lane - 4,6km Thickness 190 to 220mm Area 75 000m Volume 16
000m Reinforcement 720tonnes
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MILLING:12 000m ASPHALT:NBC Fast lane and fast shoulder - 7,0km
SBC Middle lane, fast lane and fast shoulder - 6,3km Bedding (below
concrete) 6 200tonnes Base and Levelling 17 500tonnes SMA Surfacing
108 000m DRAINS:Concrete for Side Drains 3 560m Mass concrete (Make
up) 600m CONCRETE BARRIERS: 6,8km