Peat stratigraphy mapping using ground penetration radar and geotechnical engineering implications

Abstract

A Combined Land and Marine Ground Penetrating Radar (GPR) surveys was carried out in Southwestern part of Lagos, Badia, Nigeria with a view of delineating the subsurface peat stratigraphy that would aid geotechnical engineering design of the appropriate soil stability processes. The GPR study was conducted along eight parallel traverses trending East-West, using the Geophysical survey system incorporated (GSSI) SIR-3000 200MHZ Monostatic shielded antenna. Geographically, the study area is approximately between latitude 715000N and 716000N and longitude 538600E and 540300E of the universal traverse Mercator. The antenna was present with three gain points in order to improve the scans during data acquisition while 33 scans per meter were taken (representing 3cm station spacing) with a sampling window of 400ns with offset of +25ns.The topography is generally flat with localized undulations due to sand heaps from canals dredging and sand filling activities in the area. The peat depth was found to vary from 1.5m to 6m and the thicknesses from traverse one (1) to eight (8) on chainage 625m to 1100m. The area belongs to Dahomey Basin which is also known as Dahomey Embayment or Benin Benin or as West Nigeria Basin. The mineralogy, micro-fabrics and Morphology of the delineated stratigraphy was determined using the Scanning Electron Microscope (SEM) and X-Ray diffraction (XRD) methods. The results obtained revealed the presence of five subsurface (Topsoil/ sand filled Layer, Silty Clay, Peat, sandy Clay and Silty Sand) geological Layers, distinct geomorphological features, and high, moderate and low amplitudes, to continuous and discontinuous planer relax Facies structures. SEM and XRD analyses of the field samples obtained showed the dominance of Kaolinite, illite and quarts minerals in the clay/peat mapped. The derived engineering parameters suggest that the peat found in the study area are “fibrous peat” with low strength and medium to low bedding stress. It is observed that the peat generally depict high compressibility value, low internal frictional angle, they exhibit low elastic properties such as low shear modulus, low bulk modulus and young modulus values. The findings confirm the efficacy and relevance of GPR technique for pre-construction engineering investigation.

Geophysical Subsurface Mapping Using the Electrical Resistivity Technique: A Comprehensive Study of the Petroleum Training Institute Main Campus in Effurun

“…This methodological choice underscores our commitment to providing a comprehensive and deep understanding of the subsurface, along with a nuanced grasp of the spatial arrangement of resistivity and geophysical properties across the studied region. Such insights hold immense value for advancing geological and environmental research, contributing significantly to the development of a more accurate and detailed depiction of the subsurface (Akpabio et al, 2017).…”

Archaeological Prospection in Wetlands—Experiences and Observations from Ground-Penetrating Radar Surveys in Norwegian Bogs

“…In general, the potential of the GPR method for geoarchaeological investigations of wetlands is considerable [10]. GPR surveys have been tested and used for quite some time already for the study of bogs and ponds [11,12], mapping peat depth [13,14], and studying peat stratigraphy [15]. Regarding archaeological prospection in wetlands and bogs [16], the use of GPR has been reported by several authors over the past two decades [17][18][19][20], even for the detection of organic material in waterlogged sediments [21].…”