ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Development of a Long-term Accelerated Pavement Testing Programme and Structural Design Models Paper I-1 S V Kekwick, H L Theyse and E G Kleyn (presented by Dr M de Beer)
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Introduction • HVS development since late 1960s; • Three production machines operational from late 1970s to 1990s, plus prototype; • Latest SA HVS commissioned 1999, with dynamic load simulation capability; • Underpins SA pavement engineering efforts and developments - a significant track record;
MACRO-CLIMATE: SOUTH AFRICA North & MAJOR ROAD SYSTEM DRY DRY N1 # Botswana N1 # N4 # # N17 Namibië N14 MODERATE MODERATE # N11 DRY DRY # N3 DRY # N1 DRY N14 # # # N12 N10 N5 # WET # WET N14 # DRY DRY # N14 N12 # DRY N10 DRY # # N1 # N6 Durban # N2 West N7 N12 WET # # WET N10 # # N10 Coast East MODERATE MODERATE R12 # N1 N9 # # Coast # WET N2 WET # Capetown N2
Surfacing Types of National Roads in South Africa (1997/8) CRCP (0,5%) PCC (7,5%) Chip & Spray HMA Seals (46,3%) (45,6%)
Base and Subbase Types G1/G2 Base on Stab Subbase (29%) of National Roads in G1/G2 Base on Nat gravel South Africa (1997/8) Subbase (27 %) HMA (13 %) 3% 6% 6% 29% PCC (9 %) 7% C3/C4 Base on Nat gravel HMA Subbase (7 %) 9% C3/C4 Base on Stab gravel Subbase (6%) G3/G4/G5 Base on Nat 13% Gravel Subbase (6%) 27% G3/ G4/ G5 o n Stab Subbase (3%)
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE This paper..... • reviews factors that contributed to long- term success of SA HVS programme • describes strategic and operational components of the programme • discusses some specific examples of development of design transfer functions
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Objectives of the SA HVS programme • Long-term: development of structural design models and transfer functions appropriate for local applications; • Short-term: address specific pavement needs and problems as identified; • Ultimate goal - to achieve optimal pavement design and most cost-effective structures
Before...... ......after Before...... ......after HVS 1979 HVS 1979 1994 1994
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Components of the SA HVS programme • Steering Committee/Project Champions will define: – Goals – Specific tasks/purposes – Policies – Strategic plans – Work programme/activities – Operational statistics – Deliverables/end products
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Components of the SA HVS programme • Technology Transfer/Implementation – Test level: interaction of champions and Steering Committee – Test level: broader dissemination through presentations, workshops, site demonstrations – Longer-term: development of generic design parameters, higher degree work – Longer-term: inclusion in National guidelines
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Some significant SA APT- related developments • Mechanistic - Empirical analysis • Damaging effect exponent quantification • Dynamic Cone Penetrometer (DCP) design and analysis • National guidelines/specifications • Stress-In-Motion (SIM) technology • Technology management • Design transfer functions
315/80 R22.5 HVS TIRE ON VRSPTA
Vertical Contact Stress: Variable loads: 315/80 R22.5 Tire
Lateral Contact Stress: Variable loads: 315/80 R22.5 Tire
Longitudinal Contact Stress: Variable Loads: 315/80 R22.5 Tire
Basic organizational process of converting needs to a products UNDERSTANDING PLANNING Managerial QUALITY guidelines, statistics, CONTROL goals, purposes, policies, plans, programmes, PRODUCING deliverables FINANCING DESIGN THE SOLUTION
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Process for partnered research and practice NEED NEED UNDER- RESEARCH PRACTICE STANDING PROCESSES DEFINED ENHANCED ENHANCED PRODUCTS UNDERSTANDING & UNDERSTANDING CAPABILITY & CAPABILITY
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Examples of structural pavement design models • Transfer functions for: – effective fatigue and crushing of lightly cemented layers – permanent deformation of natural gravel base and subbase layers – permanent deformation of imported (selected) and in situ subgrade layers
Fatigue Cracking and aging
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Fatigue Number of load applications 1.00E+08 1.00E+07 1.00E+06 1.00E+05 1.00E+04 1.00E+03 1.00E+02 1.00E+01 0 1 2 3 4 5 6 Strain Ratio / b A (95%) B (90%) C (80%) D (50%) Road Category (Expected Performance Reliability)
SURFACE DISINTEGRATION
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Crushing Number of load applications 1.00E+09 1.00E+08 1.00E+07 1.00E+06 1.00E+05 1.00E+04 1.00E+03 1.00E+02 1.00E+01 1.00E+00 0 0.2 0.4 0.6 0.8 1 Stress Ratio v /UCS A (95%) B (90%) C (80%) D (50%) Road Category (Expected Performance Reliability)
RU RUTT TTING NG
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Permanent deformation VERTICAL STRESS (kPa) 300 250 200 150 100 50 0 1E+03 1E+04 1E+05 1E+06 1E+07 1E+08 NUMBER OF LOAD REPETITIONS Permanent Deformation 1 mm 2 mm 3 mm 5 mm 10 mm 20 mm G89TF50
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Conclusions • SA HVS programme has been the dominant force in SA pavement engineering development for more than 20 years • significant advances in SA pavement engineering have arisen directly from the programme
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Conclusions • Factors influencing the success of the SA HVS programme include: – identification of longer-term goals from the outset – interactive relationship between funders and research team – mechanisms for technology transfer and information dissemination
ACCELERATED PAVEMENT TESTING – 1999 INTERNATIONAL CONFERENCE Conclusions (continued) • Factors (continued): – developed understanding of the role of APT in pavement engineering – formalisation of processes such as strategy development, progress monitoring, definition of deliverables – appreciation of the need for higher-level analysis to attain long-term benefits • up to four HVSs operating at the same time gave added impetus...
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