Physical and Mechanical Characteristics of the Conglomeratic Layer in Akure, Southwestern Nigeria.

• O.A. ADEMESO

  Federal University of Technology, Akure, Nigeria

• B.I. ADEYEMO

The highly indurated sedimentary layer in Akure, southwestern Nigeria was investigated for the physical and mechanical properties for the purposes of defining the spread, identify and classify it as well as determine the engineering value. The samples were physically and texturally examined on the field and described accordingly. The Uniaxial Compressive Strength (UCS) was determined with the indirect and direct methods using the Schmidt rebound hammer and the MTS Servo Compressive Tester respectively. ISRM procedures for determining the bulk density, dry density and water absorption were adopted. The immersion method was employed to determining the porosity and moisture content. The physico-mechanical tests results were then used to develop mathematical models. The layer was found to contain clasts embedded in reddish brown matrix. The clasts which are angular to sub-angular are mainly quartzites. Subordinate dark brown ferruginous clasts were found in parts of the study area. The results from the natural moisture content range from 1.32% to 3.88%, the dry density varies from 20.5 to 29.0KN/m³, bulk density ranges from 25.38KN/m³ to 30.38KN/m³, water absorption from 4.36% to 6.58%, porosity values from 11.08% to 18.80%. The Uniaxial Compressive Strength (UCS) value ranges from 32MPa to 69MPa. Correlation between UCS and rebound values gave a coefficient of 0.92. Comparing the UCS with those obtained for associated soils by previous researchers showed the layer having higher values. The layer is therefore classified as clast supported conglomerate and is believed to serve as semi-impervious layer protecting the lower layers of soil and aquifer from erosion and pollution respectively. The preservation of the layer should therefore be of paramount importance to the managers of land and underground resources.

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