Geophysical investigation of road pavement instability along part of Akure-Owo express way, Southwestern Nigeria

Abstract

ABSTRACT:Integrated surface geophysical methods were used in investigating causes of pavement instability along a portion of Akure-Owo expressway, southwestern, Nigeria. The methods comprise of ground magnetic profiling, Very Low Frequency Electromagnetic (VLF-EM) profiling and geoelectric sounding. The magnetic profile shows a drop below 31500nT at distance 100m and above 32500nT at distances 140 and 310m, these drops in value could correspond to lithological contacts or bedrock depressions. The combined plots of raw real and filtered real VLF-EM data show conductive zones at distances 70m, 230-240m and 350-360m, which could be indicative of fractured zones or conductive clay materials. The 2-D geoelectric section shows bedrock depressions at distance 80-160m (stable segment) and 240-360m (unstable segment), while bedrock fractures was delineated beneath VES points 1, 3, 5 and 10, corresponding to distances 0, 80m, 160m and 400m respectively. The topsoil resistivity varies from 83 to 865 ohm-m, while resistivity in the weathered layer materials ranges from 182-1139ohm-m along the stable segment and 27-262ohm-m along the unstable segment. The low resistivity values observed beneath the unstable segment are typical of expansive clay. Thus the instability of the road pavement along the studied portion of the road is probably precipitated by the presence of near surface bedrock depressions, occupied by low resistivity weathered materials, typical of expansive clay and sandy clay, adjudged unsuitable construction materials.

Geotechnical and Mineralogical Evaluation of Soils Underlying a Failed Highway Section in South Eastern Nigeria

“…This is similar to the swelling behaviour of expansive shales from the middle region of Saudi Arabia which causes severe and widespread damage in residential buildings, sidewalks and pavements due to the development of heave and swelling pressure in the expansive shales [19]. Also in south-western Nigeria underlain by basement rocks, pavement distress due to poor subgrade performance in addition to poor engineering construction has been reported [20][21][22][23]. This work is an attempt to determine critical factors in the pavement performance by correlating the mineralogical and the geotechnical index properties of soils developed over the underlying Imo Shale between Umuahia and Okigwe to the pervasive road failure in the section.…”

An Investigation Into the Cause of Road Failure Along Sagamu-papalanto Highway Southwestern Nigeria

“…It was revealed from the study that geotechnical and geophysical investigation provide a very practical way for delineating near surface earth which can be productive in site preparation preceding to completion (Osinowo et al;. Adeyemo and Omosuyi (2012) investigated by using geo-electric sounding , Very low Frequency Electromagnetic (VLF-EM), and ground magnetic profiling top unravel the cause of instability of road pavement along Akure-Owo expressway; it was concluded from the study that low resistivity values acquired underneath the failed section which denotes clay and the vulnerability of the road pavement is likely precipitated by the appearance of near surface bedrock depressions filled by low resistivity eroded weathered materials, representative of problematic expansive clay and sandy clay that is classified unfit as construction materials (Adeyemo and Omosuyi ,2012). Jatto et al 2014investigated the cause of road failure along Sarkin Pawa-Mangoro Highway Niger north central Nigeria using Magnetic method and Schlumberger Vertical Electrical Sounding (VES); the research employed 28 VES stations at a partition of 50mwhich was set up side by side to the road pavement on individual side of the road; it was concluded from the study that the geo-electric section along the stable section showed mainly resistive subsurface whereas the magnetic profile revealed a uniformed subsurface void of near surface water table, geological substratum and a substantial low magnetic linear attributes that is considered to be fault within the basement or an ancient stream channel which has been engulfed with sand.…”

Geoelectric investigation of the suitability of a proposed foldot ventures potable water factory site, Ipinsa, near Akure, southwestern Nigeria

“…al., 2014). Geotechnical and geophysical methods have been used successfully for foundation beds competence investigations (Mesida, 1986(Mesida, , 1987Adeyemo and Omosuyi, 2012).…”