Finite element method based design approach for low volume roads using dynamic cone penetrometer results

Abstract

Road networks are fundamental to national development, but their provision should prioritise structural efficiency and long-term sustainability rather than accessibility alone. Despite significant global advances in road construction, a large proportion of roads, particularly in developing and emerging economies, remain unsealed and prone to rapid deterioration. South Africa exemplifies this challenge: although it has the continent’s longest road network (764,978 km), almost three-quarters of its proclaimed roads are unpaved. Sustainable and cost-effective upgrading of such networks to sealed low-volume roads is therefore a pressing need, particularly under financial constraints. The aim of this study was to develop a Finite Element Method (FEM) model that utilises existing Dynamic Cone Penetrometer (DCP) correlations to improve the efficiency and cost-effectiveness of low-volume road (LVR) design, benchmarked against conventional empirical methods. Trial sections were established in two climatically distinct provinces—Northern Cape (dry) and KwaZulu-Natal (wet)—to enable material collection and in-situ testing representative of different geotechnical environments. The methodology integrated in-situ testing, laboratory characterisation, and computational modelling. DCP testing was undertaken across the trial sections to establish penetration resistance profiles, which were correlated with laboratory-derived parameters obtained from grain size distribution, Atterberg limits, California Bearing Ratio (CBR), and repeated load triaxial tests (RLTT). AfCP-LVR software was used to establish empirical DCP–CBR–modulus relationships, while comparative pavement designs were produced using CBR charts, AASHTO 1993, TRH 20, Odemark’s method, mePADS, and FEM simulations. FEM models (2D and 3D) were developed in Abaqus®/CAE to simulate pavement responses under traffic loading, incorporating both unsealed and sealed surface conditions. The findings indicate that while existing design guides such as TRH 20:2009 remain valuable references for unsealed road design, their limitations in accounting for surfacing seal effects underscore the need for integrated analytical approaches. In this study, the FEM model was developed to incorporate material parameters derived from DCP correlations, enabling a mechanistic evaluation of pavement performance under various loading and environmental conditions. This integration provided more consistent and realistic predictions of structural behaviour, particularly with respect to pavement deflections, stresses, and service life, than conventional empirical approaches. Model validation demonstrated strong agreement between mePADS, 2D FEM and 3D FEM Abaqus® simulations, confirming the robustness of the developed modelling framework. Furthermore, the inclusion of surface seals, both single and double treatments, significantly reduced critical tensile strains and extended pavement service life, emphasising the influence of binder stiffness and temperature on overall performance. This study concludes that the integration of DCP testing with FEM modelling offers a robust, field-applicable, and cost-effective approach for the design and upgrading of low-volume roads in South Africa. The research further delivers a simplified design model that incorporates new construction and rehabilitation options, supporting the use of surface seals as alternative wearing courses to achieve durable and economical LVR solutions.