Geotechnical Characterization Of Failed Sections Along Ikole - Oye Ekiti Road, Ekiti State, Nigeria

ABSTRACT

This research project assesses the geotechnical characterization of soils used for the construction

of the failed sections along Ikole- Oye Ekiti Road, Ekiti State, Nigeria. This road spans 23kms.

The study area falls within coordinates 7. 7979306° N (Oye) - 7. 7982660 N (Ikole) and

5.3285505°E (Oye) - 5.5144930°E (Ikole). It is a known fact throughout the world that the

conditions of any road largely depend upon its geotechnical properties such properties includes

soil strength, compaction, particle size classification, etc. Four different locations were

considered in which sampling point method was used in taking disturbed samples from the depth

of 750mm.The coordinates of the locations are sampling point l (7.474693° N, 5.280855° E),

sampling point 2 (7.483325° N, 5.240643° E), sampling point 3 (7.479756° N, 5.220363° E),

sampling point 4 (7.480405° N, 5.189875° E). Laboratory tests was carried on the samples

collected in order to determine soil geotechnical properties of Ikole- Oye road. The tests carried

out are; Compaction test, Sieve analysis , Permeability test, Natural moisture content, Specific

gravity, California bearing ratio test and Consistency limit test.

The results showed that the subgrade soil materials used along the road have high percentages of

clayey and silt/gravel/sand materials respectively (rated as fair to poor materials for road use)

based on AASHTO design standard ( 1986). The Natural and Optimum Moisture Contents are

low for all the Base, Sub-base and Sub-grade courses samples which ranges between 7. 7% and

21.8%. The Maximum Dry Density (MOD) values ranges between I .59-2.0kg/1113 for subgradc,

l.66-2.02kg/m3 for sub-base and I .70-2.02kg/m3 and Optimum Moisture contents values ranges

between 14.5-19 .6% for subgrade, 10-20.20% for sub 7base and 12-15 .5% for base materials.

Sub grade course samples met the specified specification of MOD of not less than l.76kg/m3 but

sub-base and base materials does not meet the specification by AASHTO ( 1986) of MOD not

less than 2.0kg/m3. From the tests result analysis of the Ikole-Oye road stretch within Ikole and

Oye local Government areas, it appears the subgrade materials under the failed sections of the

road is suitable according to AASHTO design standard (1986) while those of sub-base and base

materials are not suitable. Therefore, It is imperative that sustainable solutions addressing the

issue of using sub-standard materials for sub-base and base materials should be focused on, to curtail the incessant occurrence of road failures on the Ikole Oye road stretch.