TECHNICAL PAPER

 

Benchmarking the structural condition of flexible pavements with deflection bowl parameters

 

 

E Horak

 

Correspondence

 

 

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ABSTRACT

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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ACKNOWLEDGEMENTS

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.

 

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Correspondence:
Emile Horak
Department of Civil and Biosystems Engineering
University of Pretoria
T 012-420-274'
emile.horak@up.ac.za

 

 

 

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.