• Adedokun I. O
• Abong
• A. A
• Egor
• A. O.,Osang, Jonathan E

Road failures have become a persistent issue in many parts of Nigeria, particularly in Odukpani, Cross River State, where frequent pavement collapse and structural degradation hinder transportation and economic activities. This study presents a geophysical investigation using the seismic refraction method to determine the subsurface conditions responsible for road failure in the area. The primary objective is to assess the geotechnical properties of the subsurface layers, detect weak zones, and identify possible geological factors contributing to road instability. A seismic refraction survey was conducted along failed sections of the road, employing a 24-channel seismograph, geophones, and a controlled energy source. The acquired seismic travel-time data were processed using Tomographic Inversion and Generalized Reciprocal Methods (GRM) to delineate subsurface layers, estimate P-wave velocities, and interpret the geomechanically characteristics of the soil and rock formations beneath the road. The results reveal three major subsurface layers: 1. Topsoil (0–3 m depth) with low seismic velocities (300–800 m/s), indicating weak, unconsolidated materials. 2. Weathered/fractured layer (3–12 m depth) with moderate velocities (800–1800 m/s), suggesting lateritic deposits with varying degrees of compaction. 3. Competent bedrock (>12 m depth) with high velocities (>2000 m/s), signifying stable geologic formations. Interpretation of the seismic profiles indicates that road failure in Odukpani is primarily caused by weak subsurface materials, high moisture content, differential compaction, and possible faulting/fracturing of the underlying strata. Additionally, the presence of clay-rich soil and poor drainage systems exacerbates pavement deterioration through shrink-swell cycles and loss of structural integrity. This study highlights the importance of geophysical surveys in road construction and maintenance, emphasizing the need for proper subgrade stabilization, improved drainage systems, and the use of geotextiles in weak zones to mitigate future failures. The findings provide valuable insights for engineers, urban planners, and policymakers in designing more sustainable road infrastructure in geologically unstable areas.

Seismic refraction, road failure, geophysical investigation, subsurface conditions, Odukpani, P-wave velocity, geotechnical properties.

"REVIEW OF GEOPHYSICAL INVESTIGATION USING SEISMIC REFRACTION METHOD TO DETERMINE THE CAUSES OF ROAD FAILURE AT ODUKPANI, CROSS RIVER STATE IN NIGERIA", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.12, Issue 4, page no.o14-o31, April-2025, Available :http://www.jetir.org/papers/JETIR2504F03.pdf

"REVIEW OF GEOPHYSICAL INVESTIGATION USING SEISMIC REFRACTION METHOD TO DETERMINE THE CAUSES OF ROAD FAILURE AT ODUKPANI, CROSS RIVER STATE IN NIGERIA", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.12, Issue 4, page no. ppo14-o31, April-2025, Available at : http://www.jetir.org/papers/JETIR2504F03.pdf