GEOMECHANICALCHARACTERISTICS OF THE CONGLOMERATIC LAYER IN AKURE, SOUTHWESTERN NIGERIA.

Abstract

The project work investigated the Geomechanical Characteristic of the Conglomeratic layer in Akure, southwestern Nigeria. This is with a view to determining the spread as well as the physical and mechanical properties of the layer for possible engineering uses. The samples were physically and texturally examined on the field and described accordingly. Two methods were employed in determining the Uniaxial Compressive Strength (UCS). These included indirect determination using Schmidt rebound hammer to determine the rebound number as described by ISRM and ASTM.The values obtained were used to estimate the Uniaxial Compressive Strength of the rock with the aid of Deere and Miller chart. The direct method involved laboratory testing using MTSServo Hydraulic Compressive Testing machine in accordance with ISRM guidelines. ISRM (1989) procedures in determining the bulk density, dry density and water absorption. The immersion method was employed to determine the porosity and moisture content. The physicomechanical tests results were used to develop mathematical models. The results from the natural moisture content range from 1.32% to 3.88%, the dry density varies from20.5 to 29.0KN/M3, bulk density ranges from 25.38KN/M3to 30.38KN/M3, water absorption 4.36% to 6.58%, porosity values ranges from 11.08% to 18.80%. The Uniaxial Compressive Strength (UCS) values range from 32MPa to 69MPa. The UCS shows a very high degree of correlation 0.8 and 0.77 with the moisture content and water absorption capacity respectively. Comparing the UCS with those obtained for associated soils by previous researchers showed a wide difference. The layer therefore serves as semi-impervious layer with high strength protecting the lower layers of soil and aquifer from pollution and erosion. The knowledge of the strength and physical parameters of the conglomeratic layer are of paramount importance in civil engineering design for road construction.