GPR investigation of the cause of persistent failure of a university road
Vietnam Journal of Science, Technology and Engineering (Ministry of Science and Technology)/Vietnam Journal of Science, Technology and Engineering, Jun 15, 2024
Dutse Journal of Pure and Applied Sciences, Apr 24, 2024
In this study, we present the results of a ground-penetrating radar (GPR) survey aimed at imaging... more In this study, we present the results of a ground-penetrating radar (GPR) survey aimed at imaging the lateral root systems of a section of a tree groove lined by the Tectona Grandis (Teak) species. This was to set the basis for deploying a multi-frequency GPR system for the non-invasive monitoring of rootmass development and evaluation of plant development and health. The survey involved a single GPR Transect with a total length of 60.1 m established along the middle of a line of matured Teak trees. Data was collected at 250 MHz, 500 MHz and 1000 MHz, simultaneously using a wheel-triggered Utsi Trivue system. Data processing involved a dewow, static corrections, gain application and background removal. A root zone consisting of two layers was delineated and a total of 159 hyperbolae were interpreted as roots. The roots were limited to the shallow subsurface, the upper 1.1 m of a potential root zone 1.6 m deep. Imaged roots generally occur in clusters that create much disturbance of the otherwise continuous reflections in the root zone. Often, roots may be laterally offset from the location of tree bases on the Transect. We further identified a potential set of laterally migrating roots in a zone of undisturbed ground outside the main groove indicating the lateral reach of the usually shallow roots of the Teak tree. The results set the basis for further work in root-mass estimation and monitoring tree health within our team.
Double-BSRs are enigmatic seismic data reflections with implications on subsurface fluid migratio... more Double-BSRs are enigmatic seismic data reflections with implications on subsurface fluid migration and phase, and hydrate stability in shallow subsea sediments. From 3D exploration seismic data, we detail the occurrence of a double BSR from the Offshore Niger Delta. Identified in an earlier study, we delineate the areal extent of the double-BSR and model expected temperatures at the deeper BSR to provide constraints on its origin. The deeper BSR occurs at a minimum estimated depth of 114 m below the upper BSR. Temperature modeling results indicate Structure I hydrates are unstable at the current depth of the deeper BSR. The lower seismic amplitudes and discontinuous nature of the deeper BSR and its apparent hinterland tilt relative to the upper BSR suggest it marked the base of the gas hydrate stability zone in the climatic (GHSZ) and tectonic past when the pressure-temperature (P-T) conditions were significantly different. We propose that recent tectonic uplift on the thrust-cored ridge system considerably altered local P-T conditions which led to the dissociation of gas hydrates and consequent upward migration of the base of the GHSZ to shallower levels until it reached its present state, leaving behind a tilted relic of its former position. The relic likely benefited from low advective rates which encouraged its preservation through time. We further reckon that the tilt of the Relict BSR relates to the rotation of the fold limb during recent thrust activity and as a result we aver that Relict BSRs may record limb rotation on fault-bend folds.
Surface–subsurface characterization via interfaced geophysical–geotechnical and optimized regression modeling
Modeling earth systems and environment, Jun 13, 2024
Surface-subsurface soil-rock modeling is crucial for infrastructure design and borehole groundwat... more Surface-subsurface soil-rock modeling is crucial for infrastructure design and borehole groundwater yield optimization, especially in terrains like Penang Island, Malaysia, prone to soil and slope instabilities exacerbated by heavy rainfall. With the increasing demand for potable water due to population growth and tourism, this study provides vital insights into sustainable groundwater management and infrastructure development. Optimized geophysical-geotechnical methods, including regression modeling, were employed to integrate seismic P-wave velocity (Vp) and resistivity models with borehole lithologic logs, revealing distinct soil-rock characteristics and deep-weathered/fractured zones. The study area's eastern to northern sections exhibit thick, saturated, and loose silty to sandy bodies, contrasting with sandy compositions and penetrative fractures in the southern part. Good correlations between rock quality designation (RQD) and standard penetration tests (SPT N-values) were observed, with intra-bedrock weathered/fractured unit depths varying between 12 and > 35 m. Suitable foundation sites were identified at sections with high RQD values (> 90% at Site 1) and N-values (> 50 at Sites 1 and 3). However, pile foundations were recommended due to varied weak and water-filled zones. It is important to investigate deep sections and the site-specific nature of the uncovered areas, necessitating validation in terrains with comparable geology. Nevertheless, the established lithology-based empirical relationships offer significant benefits for geophysical-geotechnical studies, reducing associated costs across large areas.
International journal of advanced geosciences, Feb 12, 2024
Bottom simulating reflectors (BSRs) and seismic pipe features have been used as proxies for defin... more Bottom simulating reflectors (BSRs) and seismic pipe features have been used as proxies for defining the distribution of gas hydrate sediments in the offshore Niger Delta. This is the most extensive mapping of gas hydrate sediments in the Delta as of today. The seismic data merge comes from multiple surveys acquired with different parameters and seismic resolutions over the course of decades of oil and gas exploration in the region. Indicated gas hydrate distribution generally follows the structural fabric of the Niger Delta with BSRs occurring along the apexes of the thrust-related ridges that have bathymetric relief on the seafloor. The presence of swarms of seismic pipe features landwards of BSR locations suggests hydrates occur beyond BSR locations. The potential gas hydrates sediment acreage in offshore Niger Delta is 17600 sq-km, representing 20% of the area with a thickness of the gas hydrate stability zone reaching 440 m in the more outboard regions of the Delta. Total gas hydrates sediment coverage likely exceeds this value as BSRs become indistinguishable from sediment strata in regions of flat dips. The presence of double BSRs further suggests the presence of thermogenic gas hydrates in the region and allows to extend the thickness of the potential hydrate zone to 550 m in the outboard regions of the Delta.
Electrical resistivity imaging has been employed to investigate the causes of structural failure ... more Electrical resistivity imaging has been employed to investigate the causes of structural failure related cracks on a set of administrative buildings in southwestern Nigeria. The goals were to determine the distribution of subsurface geologic lithologies beneath the set of buildings and therefrom infer the relative strengths of such lithologies. Data were collected along four geo-electric traverses using the ABEM1000 Terrameter unit. The dipole-dipole array was utilized with an electrode separation of 5 m. Observed field data were processed and inverted using a 2.5D finite-element modeling inversion algorithm. Results indicate that the northeastern half of the site is underlain by unweathered basement rocks overlain by thin (generally < 4 m) soil cover, while the southwestern region is dominated at depths beyond 4 m by low-resistivity water-saturated clays and some weathering tills. The clays apparently receive abundant supply of water from a seasonal stream channel adjacent to the westerly administrative blocks. The block presenting with the most damage has been built out over the edge of the shallow basement rocks onto these less competent water-saturated clays in the southeastern region resulting in cantilever-style differential settling. A second damaged block is situated entirely on low resistivity water-saturated clays. Differential settling on this block is likely related to the difference in thicknesses of the clays between sites of the north and south facing walls of the structure. Beneath the northern wall, the clays are thinner and could be expected to compress less than at the southern wall. Though uncalibrated to core or log data, the results allowed a first insight into possible causes of structural failure on the buildings and it is hoped that palliative measures will benefit from these results.
In this study, we implement a series of conventional interpretation procedures and advanced imagi... more In this study, we implement a series of conventional interpretation procedures and advanced imaging techniques to unravel the paleo-geomorphology, tectonic history and fill architecture of a hydrocarbon target within the Okari Oil Field.
IOSR Journal of Applied Geology and Geophysics, 2014
Geochemical analyses of domestic groundwater sources within Okeagbe-Akoko, Southwestern Nigeria h... more Geochemical analyses of domestic groundwater sources within Okeagbe-Akoko, Southwestern Nigeria have been conducted. A total of twenty (20) water samples, sourced from hand-dug wells, deep wells and streams, were analyzed for their physico-chemical characteristics, with the aim of determining their suitability for local domestic consumption. The physico-chemical analyses involved the determination of Electrical Conductivity (EC), Acidity (pH), Total Dissolved Solids (TDS) and the determination of the concentration of a heavy metals suite consisting of Zinc (Zn), Nickel (Ni), Cadmium (Cd), Copper (Cu), Lead (Pb), and Chromium (Cr), using the Atomic Absorption Spectrometry (AAS). Result ranges obtained for the physical parameters were pH: 5.82 to 7.08, total dissolved solids: 43 to 492 mg/l, and electrical conductivity: 71.681 to 820.164 µs/cm. The heavy metal concentrations for Cu and Zn ranged from 0.001 to 0.014 mg/l and 0.001 to 0.030 mg/l respectively. Ni, Cd, Pb and Cr were not detected in any of the water samples. All determined physico-chemical parameters were well below the current World Health Organization (WHO) acceptable limits for safe water sources. This indicates that the domestic water sources in the area are relatively contaminant free and safe for domestic use. The Cu 2+ concentration distribution pattern however, provides insight into the likely nature of heavy metal contaminant migration path in the event of an impact.
We have employed 2D geoelectric imaging to reveal the geometry and nature of a fracture zone in U... more We have employed 2D geoelectric imaging to reveal the geometry and nature of a fracture zone in Uneme-Nekhua, southwestern Nigeria. The fracture zone is discernable from an outcropping rock scarp and appears to define the course of a seasonal stream. Data were acquired using the dipole-dipole survey array configuration with electrode separation of 6 m and a maximum dipole length of 60 m. Three traverses with lengths varying between 72 m and 120 m were laid orthogonal to the course of the seasonal stream. 2D geoelectric images of the subsurface along the profiles imaged a north-south trending fracture zone. This fracture zone appears to consist of two vertical fractures with more intense definition downstream. The eastern fracture is buried by recent sediment, while the western fracture appears to have experienced more recent tectonic activity as it appears to penetrate through the near surface. Perhaps at some point, deformation ceased on the eastern fracture and further strain was ...
Environmental Research, Engineering and Management, 2015
In this study, 2-dimensional electrical resistivity surveying has been used to reveal the nature ... more In this study, 2-dimensional electrical resistivity surveying has been used to reveal the nature and development of a thin clayey aquitard on basement complex rocks of the Adekunle Ajasin University campus, Akungba-Akoko southwestern Nigeria. The aim was to evaluate the occurrence, geometry and groundwater viability of this clayey aquitard as an alternative source of water supply on the Campus. Prior, a hand-dug well, which supplied moderate volumes of water all year round, had been abstracting water from this aquitard. Three east-west geo-electric traverses were surveyed using the dipole-dipole array configuration with an electrode separation of 5 m and a maximum dipole length of 45 m. Each of the three traverses was 60 m long. The observed field data were inverted for subsurface 2D resistivity structure using a commercially available 2.5D finite element modelling inversion software. The clayey aquitard is imaged to exist as low resistivity response patterns which have developed in elongated trough-like depressions created as a result of deep weathering of the feldspar and amphibolite-rich sections of the basement rocks of the area. This clayey layer reaches a thickness of 10 m at the southern end of the survey and in some sections is compartmentalised into segments by basement rocks which have better resisted weathering. Where the topographic slope of the ground surface is low enough as to allow the accumulation of runoff , the clayey aquitard develops into visible marshy swamps. Although, clayey aquitards of this nature supply water at low rates, their capacity to store high volumes and to be available all-year-round could prove essential to ameliorating acute water shortages experienced in the area during the dry season.
We have employed 2D geoelectric imaging to reveal the geometry and nature of a fracture zone in U... more We have employed 2D geoelectric imaging to reveal the geometry and nature of a fracture zone in Uneme-Nekhua, southwestern Nigeria. The fracture zone is discernable from an outcropping rock scarp and appears to define the course of a seasonal stream. Data were acquired using the dipole-dipole survey array configuration with electrode separation of 6 m and a maximum dipole length of 60 m. Three traverses with lengths varying between 72 m and 120 m were laid orthogonal to the course of the seasonal stream. 2D geoelectric images of the subsurface along the profiles imaged a north-south trending fracture zone. This fracture zone appears to consist of two vertical fractures with more intense definition downstream. The eastern fracture is buried by recent sediment, while the western fracture appears to have experienced more recent tectonic activity as it appears to penetrate through the near surface. Perhaps at some point, deformation ceased on the eastern fracture and further strain was ...
The subsurface structure and propagation geometry of the fracture system controlling the Orle Riv... more The subsurface structure and propagation geometry of the fracture system controlling the Orle River Channel in the Igarra Township, Southwestern Nigeria, have been investigated via a multi-method geophysical survey. The goal was to delineate the nature, distribution, and spatial propagation geometry of the fracture system and evaluate its potential to serve as storage and distribution features for groundwater within adjoining areas. 2D electrical resistivity, total field magnetic, and co-planar loop conductivity measurements were collected along four traverses using an ABEM1000 Terrameter unit, a GEMS Magnetometer, and an EM34 Co-planar loop electromagnetic system. Traverses were established to run across and parallel to the river channel. The observed electrical resistivity field data were inverted for subsurface 2D resistivity structure using a commercially available 2.5D finite element modelling inversion software. Magnetic field intensity data and ground conductivity data were p...
Electrical resistivity imaging and co-planar loop electromagnetic conductivity measurements have ... more Electrical resistivity imaging and co-planar loop electromagnetic conductivity measurements have been employed to delineate the bedrock topography and subsurface distribution of structural features at a construction site on the campus of Adekunle Ajasin University. The goal was to map the subsurface geological disposition and to identify features which could adversely impact on the ongoing construction works. Data were collected along three geophysical traverses using the ABEM1000 Terrameter unit and the EM34 Co-planar loop electromagnetic system. Traverse 1 trend roughly east-west for a total length of 155m while traverses 2 and 3 are trend north-south for 80m each. The collection of electrical resistivity data utilized the dipole-dipole array with an electrode separation of 5 m and maximum dipole spread of 35m. Observed field data were processed and inverted using a finite-element modelling inversion algorithm. Conductivity were collected at 10m coil separation and plotted against station positions. A station separation of 5m was maintained on all traverses for both data sets. Three geo-electric layers were delineated; a thin highly discontinuous low resistivity layer representing the humus-rich top soil, a continuous consistently high resistivity layer with a highly rugose upper layer and several near vertical scarps representing the fresh bedrock and intermediate resistivity layer representing the weathered bedrock separating the upper low resistivity and basal high resistivity signatures. Overburden thickness rarely exceeds 4 m with the exception of the deep weathering section in the southwest and at fracture points with the bedrock. Perennial groundwater flow at the site is restricted to the southeastern sections of the site.
We have applied a wavelet-based spectral decomposition scheme and a multi-layered feed-forward ne... more We have applied a wavelet-based spectral decomposition scheme and a multi-layered feed-forward neural network to interpret turbidite depositional systems from threedimensional reflection seismic data and well logs for a prospective hydrocarbon zone in the outer fold and thrust belt of the Niger Delta. The goal was to overcome difficulties in interpreting depositional systems from deep sections of the Field, occasioned by loss of seismic resolution with depth and the sparse distribution of wells. The decomposition scheme allowed us to delineate multiple depositional systems not apparent on the conventional seismic amplitude display. These systems include linear channel systems with terminal splay lobes, a sinuous channel system and its abandoned meander loops, and sediment wave features in overbank areas. Delineated channel morphologies and transport directions varied both laterally and vertically and were possibly dependent upon the disposition of the pre-thrusting paleo-seafloor. Terminal splay lobes are fragmented and coincident with the locations of topographic lows, which are possibly related to the initial configurations of the oceanic basement below. Predicted porosity and resistivity distributions have morphologies that correlate well with the mapping provided by the spectral decomposition scheme. The property distributions indicate that reservoir prone systems in the Field and possibly within the outer fold and thrust belt are composed primarily of channel systems, both linear and sinuous, and their associated splay lobes. The channel systems appear vertically stacked, and this situation possibly increases the potential success rate for exploration wells in the region. Beyond channel limits, redistributive bottom currents varying rapidly in speed and direction apparently encouraged the dispersal of sand-rich sediments to form sediment waves. Despite the limited well control, the methodology significantly aided our interpretation. It proved effective at revealing the distribution of reservoir prone facies within the Field and provided insight into the dominant factors that controlled deposition within the Field.
Reservoir characterization using 3D seismic data has advanced from conventional mapping of reserv... more Reservoir characterization using 3D seismic data has advanced from conventional mapping of reservoir horizons to attempts at predicting subsurface reservoir properties away from well control using seismic data volumes. The need to process and screen large volumes of data, optimize field-development, reduce exploration risks and ensure economic success of exploration objectives has driven the development and application of a host of methodologies. These usually exploit the possibility of extracting new dimensionality of data (attributes), and processing same multi-variate framework. Each technique, attempts to take advantage of new and viable discriminant information provided by additional data components.
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