Combined geophysical and geotechnical investigation of pavement failure for sustainable construction of Owo-Ikare highway, Southwestern Nigeria

Abstract

Very low frequency electromagnetic (VLF-EM) and electrical resistivity methods involving 54 Schlumberger Vertical Electrical Sounding (VES) and 2-D geoelectrical resistivity imaging using dipole-dipole array were utilised along unstable (US) and stable sections (SS) of Owo-Ikare highway to establish causes of its persistent failure. Engineering evaluation of eighteen soil samples from test pits excavated on selected US and SS were investigated. VLF-EM models, geoelectric sections and 2-D resistivity structures revealed existence of conductive subsurface structures, suspected weak zones beneath the US. The road pavement is constructed on poor clayey subgrade with low resistivity values (<100 Ohm-m) which precipitate instability of the highway. Subgrade soils below US have poor geotechnical properties characterized by high moisture content, liquid limit (43.6-63.8% and 20.1-25.2%), plasticity index (13.4-34.4% and 6.5-8.3%), percentage fines (40-67% and 28-30%), A-7-5 to A-7-6 clayey soils, high linear shrinkage (>10%), low compacted density, low CBR, volume changes (Mv) and impervious soils against those of SS. . Thus, deep-weathering, fractured bedrock, uneven bedrock topography with subsurface structures, water-saturated clayey subgrade and unsuitability of the soils for subgrade and subbase road construction are responsible for instability of the road. Replacement of soil beneath the unstable sections and effective drainage enhances its stability.

Geophysical and geostatistical reserve estimates of migmatite-gneiss deposits from parts of southwestern nigeria

“…The electrical resistivity investigation employed Schlumberger vertical electrical sounding (VES) technique with a total of forty-two sounding stations occupied across the entire area of study. The VES data were acquired using ABEM SAS 1000 terrameter with the electrode spread (AB/2) ranging 1 -200 m. This non-invasive technique presents requisite information of subsurface rock properties from varying electrode separation (Ademila, 2021;Ademila, 2022). VES measurements probe the vertical variation in resistivity distribution of geomaterials at each sounding station with depth.…”

“…Electrical resistivity techniques have been gainfully employed in engineering site to investigate and image the subsurface disposition by measuring electrical properties of geomaterials. This in turn has been used in unraveling the stratigraphic sequence of geomaterials, subsoil competence, overburden thickness, nature and distribution of geologic structures and depth to basement (Ademila et al, 2020;Ademila, 2021;Ademila, 2022). These effective noninvasive and non-destructive geophysical tools for subsurface investigation also offer information on quantitative estimates of geologic deposits, geomorphology and tectonic activity of areas (Bufford et al, 2012;Ademila, 2022).…”

Multichannel Analysis of Surface Waves (MASW) to Estimate the Shear Wave Velocity for Engineering Characterization of Soils at Hawassa Town, Southern Ethiopia

“…The predicted Vs were validated using a Cd and comparison of measured Vs in this investigation. Cd is also calculated using equation (6) [67] as the ratio of the difference between the Vspre and Vsmeas divided by SPT-N values where Vsmeas is the measured shear wave velocity, Vspred is the calculated Vs using the newly proposed regression equation for the study area, and SPT-N values are the measured SPT-N values.…”

“…Moreover, the nature/type of soils, geologic sequence, and structures and water bearing units also affect the stability of civil engineering structures. These properties provide reliable information to effectively characterize the heterogeneous subsoil beneath an engineering site so as to construct successful structure [5,6]. Buildings, roads, bridges, and high ways are infrastructures that contribute significantly to the sustainable development of the town.…”

Engineering Geophysical Investigation of Oka-IsuaIbillo Highway Failure; Remedy and Road Sustainability in Nigeria

“…Road failures are related to substandard structural materials and poor plan with no consideration of the subsoil (Ademila, 2018; Integrated geophysical investigations provide the basic information of the subsurface sequence and structural disposition necessary for foundation design. Ademila, 2021 used geophysical approach to establish reasons for construction works failure in Nigeria. They reported that poor subbase materials and poor compaction during construction account for the failure of rigid pavements in Nigeria.…”