Assessment of Road Pavement Failure Along Amuro-Okigwe Trunk Road, Imo State Nigeria

Authors: Obianyo JI

DOI Info: N/A

ABSTRACT

This paper studied the geotechnical properties of soils along Amuro to Okigwe trunk road, Imo State Nigeria to assess the causes of incessant road pavement failure. Samples were collected from five boreholes and sub-grade soil 0.16 to 0.40 m depth range and subjected to soil tests using standard methods. Initial moisture content was 75.25%, plasticity index was 16.63% and colour indicated weak red which showed slight presence of organic matter and iron (III) oxide Fe₂O₃. In sieve analysis, uniformity coefficient (C_U=5.14) was less than 6 and while the coefficient of curvature (C_U=0.40) was below the specified range of 1 to 3. In consolidation test, coefficient of volume compressibility (M_v) was 4.4445×10-4 m²/MN which is evidence of soil of very high compressibility. The coefficient of permeability (k) was 10.333×1010 m/s which indicates high soil permeability. The soil experienced compression of 1.546 mm at maximum load of 40 kg during loading process and swell of 0.456 mm after unloading process, which is typical of clay minerals. Shear strength of soil at 60 kg load was 163.5 kN/m² showing evidence of firm soil. In the compaction test, optimum moisture content was 19.22% corresponding to maximum dry density of 18.58 kg/m³. California bearing ratio (CBR) was 28.8% against high quality sub-base value that range between 80% to 100%. It was concluded that pavement failure was due to poor geotechnical properties of soil since results from Atterberg limits, sieve analysis, consolidation and CBR tests results were below standard values for interfacing of engineering structures with soil.

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