Geotechnical Evaluation of Road Failure along 20th Street BDPA, Benin City, Nigeria

Abstract

This work investigated the cause of road failure using geotechnical analysis along the 20^th Street, BDPA, Benin-city, Nigeria. Soil samples from the failed section of the road were analyzed to ascertain their particle size distribution, limit liquid, plastic limit, maximum dry density, optimum moisture content and California bearing ratio using the British Standard Institution (BS 1377 1990). The result from the particle size distribution analysis showed that soils were well graded (GW) with percentage fines ranging from 26 to 49.7%, specific gravity from 2.4 to 2.6, liquid limit from 21.52-29.79%, plastic limit ranged from 11.73-18.80%, plasticity index 8.29-12.49% and California bearing ratio(unsoaked) from 9-29%. The compaction test results showed that the Maximum Dry Density (MDD) ranged from 1.7mg/m³-1.8mg/m³ and Optimum Maximum Content from 11-14%. It was found that there is a significant difference between the geotechnical characteristics of the soil and the standard for geotechnical characteristics set by the Federal Ministry of Works. This led to the conclusion that the soil geotechnical characteristics is a causative factor of road failure as well as the geology. Hence, it was recommended that the geotechnical and geological characteristics of sub-grades and fill materials be taken into consideration during road construction.