Design and supervision of 2km low cost seal of low volume road within Omoro Town Council (Opit - Awoo road), Omoro District.

Abstract

Based on general field investigations, the targeted project road typically carries less than 300 vehicles per day with MESA falling below 1 million cumulative equivalent standard axles (<1.0 MESA) for which appropriate sealing technology for the low-volume traffic roads applies. The expected performance and cost effectiveness of sealing a low volume District road network with appropriate seals adopted for the project are un-comparable with conventional highly capital intensive approaches that are not affordable by most District Local Governments and Urban Councils in Uganda. The adopted design approach in this case involves; carrying out road condition surveys, taking levels (cross sectional and longitudinal), traffic estimation, determination of in-situ sub-grade strength, environmental factors (Weinert number, N) and laboratory investigation of material properties for road layers. The materials studied are sub-grade soils whose results were processed using the UK 3.1 DCP software and laboratory tests, and gravel whose engineering properties were determined in the laboratory such as gradation, California Bearing Ratio, and Atterberg Limit tests. The aggregates were analyzed using standard procedures for Gradation (BS 1377: Part 2:1990), ACV (BS 812: Part 110:1990), FI (BS 812: Section 105.1:1989) and AIV test on aggregates (BS 812: Part 112:1990). The LAA (ASTM C-131-89) was not conducted. The road layers were designed based on sub-grade strength with a 10 %tile CBR of 11% for Opit-Awoo Road-(Ch.0+000-2+000) equivalent to in-situ sub-grade class-S4, Weinert N =1.75 (N<4), traffic level LV4. The aggregates registered; ACV= 20%, AIV=22.5%, 10% Fine Value =185 and FI = 21%. The aggregates were found to be suitable for surfacing and hence no need for alternative source. Borrow Pit 1 (BP 1) Gravel 3 point 95% soaked CBR= 25% (Max), PI=16%, MDD=1.93kg/m3 and OMC=11.8% was registered. Hence the need for stabilization to achieve 65% base CBR. 120mm sub-base thickness with 30% CBR and 175mm base thickness with 65% CBR are the final specified pavement designs and low cost wearing course for surface dressing was designed using the surfacing parameters outlined above. Finally, this design recommends that Low Cost Design approach (innovation to design for fitness) be adopted as an alternative to re–graveling and traditional bituminous surfacing with Premix surfacing Option adopted for the road. These reduce on maintenance backlogs and can stimulate social and economic growth of the Country.