Herman Mostert, Element Consulting, Namibia
SPEAKER PRESENTATION
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With ever-increasing transport needs, accessibility requirements and construction costs, the implementation of Low Volume Sealed Roads (LVSR) has increased in Namibia. Namibia’s Road Authority has launched a 5-year LVSR strategy for 2021 – 2025 to construct about 1 600 km of LVSR.
According to the Road Authority's Integrated Road Asset Management System (IRAMS), 82.9% of the road network is unsurfaced, with more than 90% carrying between 100 and 300 vehicles per day. The upgrading to LVSR reduces routine maintenance actions required on the unsurfaced roads, which in turn preserves increasingly scarce road building materials.
Several guidelines and manuals exist within southern Africa, but no formal document for the design and construction of LVSR has been adopted by Namibia’s Road Authority. The current practice in the design of LVSR uses these reference guidelines. Still, it leaves room for variability in designs between practitioners, leading to mixed performance and success in the field.
The general pavement design approach conducts DCP testing of the in-situ materials to determine the implicit strength expressed as a DN/penetration value (mm/blow) rather than a converted CBR (%) value. The typical outcome in Namibia is to rework the existing wearing course as a subbase layer and add a new gravel base layer before surfacing. Many LVSRs are surfaced with 14mm Cape seals, while 20mm Cape seals have also been widely adopted in Namibia to consider traffic volumes and the associated embedment. Geometric adjustment and drainage improvement are considered as needed to adhere to safety requirements.
About the author
Herman Mostert is a Transportation Engineer with Element Consulting Engineers Namibia. He has a N.Dip Civil (CUT), BTech Civil (UNISA), BSc (Hons) Applied Science: Transportation Planning (University of Pretoria), and an M.Eng Civil (University of Stellenbosch).
