On-line version ISSN 2309-8775
J. S. Afr. Inst. Civ. Eng. vol.50 n.2 Midrand Jun. 2008
The falling weight deflectometer (FWD) is used worldwide as an established, valuable, nondestructive road testing device for pavement structural analyses. The FWD is used mostly for rehabilitation project level design investigations and for pavement management system (PMS) monitoring on a network basis. In project level investigations, design charts based on both empirical relations and mechanistic or theoretically based approaches are often used to provide structural evaluations and rehabilitation options. The full mechanistic approach normally uses multi-layer linear elastic theory and back-calculation procedures that have come under scrutiny owing to the inaccuracy of results. A semi-mechanistic, semi-empirical analysis technique has been developed in South Africa in terms of which deflection bowl parameters, measured with the FWD, are used in a relative benchmarking methodology in conjunction with standardised visual survey methodology to give guidance on individual layer strengths and pinpoint rehabilitation needs. This benchmark methodology enables the determination of the relative structural condition of the pavement over length and in depth without the requirement for detailed as-built data. A further correlation study with calculated surface moduli and deflection bowl parameters is presented here for granular base pavements, which can enhance benchmarking methodology.
Keywords: falling weight deflectometer, bowl parameters, benchmarking, surface modul
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Jaco de Clerq, whose final-year research project contributed to a portion of the correlation studies, as well as the contribution of Nelson Gale and Martin van Veelen, of Jeffares and Green Consultants, to the back-analysis with ELMOD software are acknowledged.
Coetzee, N F, Van Wijk, A J and Maree, J H 1989. Impact deflection measurements. Proceedings of the Fifth Conference on Asphalt Pavements in Southern Africa, Swaziland. [ Links ]
Committee of State Road Authorities (CSRA) 1997. Flexible pavements rehabilitation investigation and design. Draft Technical Recommendations for Highways 12 (TRH 12). Department of Transport, Pretoria. [ Links ]
CSRA 1992. TMH9: Pavement management systems: standard visual assessment manual for flexible pavements. Pretoria: CSRA. [ Links ]
Dehlen, G L 1961. The use of the Benkelman beam for the measurement of deflections and curvatures of a road surface between dual wheels. CSIR, Special report R2 NITRR, RS/11/61. Pretoria: CSIR. [ Links ]
Freeme, C R 1983 Evaluation of pavement behaviour for major rehabilitation of roads. NITRR Technical Report RP/19/83. Pretoria: CSIR. [ Links ]
Horak, E 1987. The use of surface deflection basin measurements in the mechanistic analysis of flexible pavements. Proceedings of the Fifth International Conference on the Structural design of Asphalt Pavements, Ann Arbor, Michigan. [ Links ]
Horak, E 1988. Aspects of deflection basin parameters used in a mechanistic rehabilitation design procedure for flexible pavements in South Africa. PhD thesis, Department of Civil Engineering, University of Pretoria, Pretoria. [ Links ]
Horak, E, MareeJ H and Van Wijk, A J 1989. Procedures for using impulse deflectometer (IDM) measurements in the structural evaluation of pavements. Proceedings of the Annual Transportation Convention, Volume 5A, Pretoria. [ Links ]
Horak, E and Emery, S 2006. Falling weight deflectometer bowl parameters as analysis tool for pavement structural evaluations. Proceedings, 22nd Australian Road Research Board (ARRB) International Conference, Brisbane, Australia, October. [ Links ]
Horak, E 2007. Surface moduli determined with the falling weight deflectometer used as benchmarking tool. Proceedings of Southern African Transportation Conference, Pretoria, June. [ Links ]
Jordaan, G J 1988. Analysis and development of some pavement rehabilitation design methods. PhD (Civil Engineering) thesis, Department of Civil Engineering, University of Pretoria, Pretoria. [ Links ]
Jordaan, G J 1990. An assessment of the South African (SA) mechanistic pavement mechanistic pavement rehabilitation method based on the linear elasticity theory. DRTT Research Report DPVT 69. Pretoria: CSIR. [ Links ]
Lacante, S C 1992. Comparative study of deflection basins measured on road structures with various non-destructive measuring devices. MTech thesis, Technikon Pretoria, Pretoria. [ Links ]
Maree, J H and Bellekens, R J L 1991. The effect of asphalt overlays on the resilient deflection bowl response of typical pavement structures. Research report RP 90/102 for the Department of Transport. Chief Directorate National Roads, Pretoria. [ Links ]
Maree, J H and Jooste, F 1999. Structural classification of pavements through the use of IDM deflection basin parameters. RDAC Report PR 91/325. Department of Transport, Pretoria. [ Links ]
Rohde, G T and Van Wijk, A J 1996. A mechanistic procedure to determine basin parameter criteria. Southern African Transportation Conference, Pretoria. [ Links ]
Ullidtz, P 1987. Pavement analysis. New York: Elsevier. [ Links ]
Ullidtz, P 2005. Modelling flexible pavement response and performance. New York: Elsevier. [ Links ]
Department of Civil and Biosystems Engineering
University of Pretoria
EMILE HORAK completed his undergraduate studies at the University of Pretoria and his postgraduate studies at the University of Stellenbosch, the School for Business Leadership (University of South Africa, Unisa) and the University of California, Berkeley. He was head of the Department of Civil and Biosystems Engineering at the University of Pretoria from 1998 to 2007. Before that he was a senior executive at Murray & Roberts Contractors, Roads and Earthworks and Tollcon, executive director of the Roads and Works Division of the Johannesburg City Council, head of service delivery at the Greater Johannesburg Transitional Metropolitan Council, and with Transportek, CSIR where he was actively involved in research and technology transfer. He has published more than 70 papers in international conference proceedings and refereed journals and does specialist consultancy work. Emile is currently a visiting professor at the Council for Scientific and Industrial Research (CSIR) Built Environment during his sabbatical leave.