International Journal of Research and Innovation in Applied Science (IJRIAS) |Volume VII, Issue IX, September 2022|ISSN 2454-6194
Emeka Nwadisia1, Leonard I. Nwosu2 and Bright O. Nwosu3
1,2Department of Physics University of Port Harcourt, Nigeria,
3Department of Geology University of Port Harcourt, Nigeria.
Abstract: Excavation of sand and gravel occurs along Njaba River bank for Civil engineering purposes which occasionally results to landslides that lead to casualties. Hence, Geoelectrical and Geotechnical techniques were adopted for mapping and characterizing the sand and gravel deposits and at the same time assess the slopes stability. Ten vertical electrical soundings (VES) were carried out at different locations, using OHMEGA-500 resistivity meter. The field data were interpreted using Advanced Geosciences Incorporation (AGI) ID resistivity inversion software and Schlumberger Automatic analysis version. The model results revealed that the sand and gravel layers have high resistivity values ranging from 1359Ωm to 7353Ωm. The geologic information, the borehole data and VES model were integrated to map the sand and gravel bed. The thickness of the beds ranges from 15.70m to 67.60m. Four samples collected at different locations were tested and analyzed in laboratory to determine basic geotechnical parameters. Average values obtained were: moisture content (10.7%), bulk density (2.10g/cm3) maximum Dry density (1.73g/cm2), California Bearing Ratio (24%). The particle size distribution obtained revealed that the coarse sand, medium sand, fine sand are 3.7%, 34.52%, 61.26% respectively, implying that they are of good grade and in conformity with civil engineering requirements. The slopes instability in the study area is as a result of the low shear strength.
Key words: Sand, Gravel, Geoelectrical, Geotechnical, Civil engineering
I. INTRODUCTION
The knowledge of the rock deposits in an area is not adequate if the deposits are not properly characterized. Also the location and quantity of the deposit are important in other to harness their potentials. The rock deposits form the basis for civil engineering projects ranging from conceptualization to commissioning. The rock material have played significant role in foundation design, material selections and cost control. In design, consideration is made of the stability of earth surfaces, in terms of their compressibility and load bearing capacity. The nature of the soil determines it’s suitability for use in construction work. Slopes and erosion sites sometimes have caused great disasters, constituting menace to the environment. Apart from soil or rock application in civil engineering construction such as roads, bridges, buildings and structural works in general, they