GEOTECHNICAL SITE INVESTIGATION USING SEISMIC REFRACTIVE METHOD AT COLLEGE OF EDUCATION, WARRI

The seismic refraction method is a key geophysical technique in geotechnical site investigations.Seismic refractive method is employed for shallow depth investigation.it uses seismic wave propagation and refraction to map subsurface geological structures, providing essential data for engineering and environmental applications. The seismic waves used in the study area are generated using sledgehammer that has impact on a coupled plate placed on the ground .These waves travel through the subsurface and are detected by geophones placed along a seismic line. The travel times of the waves are recorded and processed to create travel time curves and these curves are analyzed to determine wave velocities in different subsurface layers. The theoretical background of this research work is based on Snell’s Law and is applied to estimate the depths and characteristics of these layers. A practical application of the seismic refraction method was conducted at the College of Education, Warri in order to delineate subsurface lithology. The survey aimed to determine the depth to bedrock and identify various soil layers to support the design and construction of any new buildings that will be erected on campus .During the survey, the data acquired provided detailed information about the depth and characteristics of the subsurface materials. Six shots were generated from the study area,and these shots revealed three geological layers of different velocities. The travel time generated from the first transverse has the velocities of 267.1m/s for the first layer, 505.9m/s for the second layer and 998.0m/s for the third layer. For the second transverse the velocities of 164.5m/s for the first layer , 255.6m/s for the second layer and 689.6m/s for the third layer. The other geotechnical parameters generated from the study area are poisson’s ratio, density, bulk modulus , shear modulus and young modulus. The values generated for all these parameters revealed the morphorlogy of the subsurface layers in which the first layer is the top soil that is not consolidated , the second layer is the mixture of clay and sand while the third layer is more consolidated and compacted to withstand any structure. However, these results of the survey revealed the depth to bedrock and identified several distinct soil layers, which were crucial for the geotechnical assessment of the site and this geophysical information has helped engineers to design stable and safe foundations for the new structures, ensuring the long-term integrity of the buildings. Finally, the seismic refraction method is an efficient and accurate tool for geotechnical site investigations, offering detailed subsurface information that supports a wide range of engineering and environmental applications.