scholarly journals The use of Geoeletric Methods for Post-foundation Assessments of Distressed Buildings in Ebute-meta, Mainland Local Government Area of Lagos State

2021 ◽  
pp. 104-119
Author(s):  
O. J. Airen
Keyword(s):  
Soft Clay ◽  
Maximum Depth ◽  
Silty Sand ◽  
Silty Clay ◽  
Clayey Sand ◽  
Near Surface ◽  
Cone Resistance ◽  
Sandy Clay ◽  
Geotechnical Investigations ◽  
Support Engineering

Geophysical and geotechnical investigations were combined to investigate the immediate causes of the distresses and foundation failures of buildings in Ebute-Meta area of Lagos, south-west Nigeria. Six (6) traverses were mapped in the study area across which six (6) 2D Wenner ERI, and fourteen (14) VES geophysical data were acquired. One (1) boring and five (5) CPT geotechnical data were also acquired. 2D ERI results reveal that resistivity values vary from 4.62 – 293 Ωm across the study area. Three resistivity structures were identified which denoted peat/clay, sandy clay, clayey sand and sand. The resistivity of the peat/clay varies from 4.62 – 27.9 Ωm with thickness varying from 12 - 25 m. The sandy clay varies in resistivity and thickness values from 26 – 86 Ωm and 8 – 29 m respectively. The clayey sand from 84.4 – 182 Ωm and 10 -15 m, and sand, having resistivity and thickness values of 293 Ωm and 3 – 5 m. The VES reveals similar results to the 2D ERI, delineating six geoelectric layers which are the topsoil, peat, clay, sandy clay, clayey sand and sand at maximum depth of 35.8 m. The borehole (BH) reveals a maximum boring depth of 45 m with eight zones comprising dark grey sandy clay, firm to stiff silty clay, soft, dark organic silty peaty clay, grey silty sand, dark grey silty sandy clay, dark grey organic peaty clay, grey silty sandy clay and medium dense to dense grey sand with occasional gravels. The CPT, which penetrated a maximum depth 15.8 m reveal that the cone resistance values vary progressively from 0 – 162 kg/cm2indicating very soft clay to soft clay near-surface and medium dense to dense geologic material at deeper depth. The peat/clay delineated by the 2D ERI and VES at 5 – 25 m depth with resistivity value varying from 4.62 -17 Ωm in the study area, and also revealed in the BH at 5.75 – 27.75 m depth as soft, dark organic silty peaty clay, having cone resistance values varying from 0 – 20 kg/cm2 is laterally extensive and incompetent to support engineering foundation.

scholarly journals Distribution and diversity of cumacean assemblages in Admiralty Bay, King George Island

2011 ◽  
Vol 32 (4) ◽  
pp. 341-354 ◽  
Author(s):  
Krzysztof Pabis ◽  
Magdalena Błażewicz-paszkowycz
Keyword(s):  
Abundant Species ◽  
Silty Sand ◽  
Silty Clay ◽  
Central Basin ◽  
Depth Range ◽  
King George Island ◽  
Admiralty Bay ◽  
Core Species ◽  
Sandy Clay ◽  
Key Species

Distribution and diversity of cumacean assemblages in Admiralty Bay, King George IslandEleven species of cumaceans were found in 105 samples collected in Admiralty Bay (King George Island) in the summers of 1984/85 and 1985/86, from 20 to 500 m depth range. Four cumacean assemblages were distinguished using the multivariate analysis. They were characterized by the dominance of one or two species often with low density values. Two assemblages were found in open waters of Admiralty Bay. The first inhabited on sandy-clay-silt and silty-clay-sand bottom deposits in the depth range from 140 to 330 m, withCampylaspis maculata(1.6 ± 2.1 ind./0.1m2; F = 72.4%) andLeuconsp. (1.4 ± 1.6 ind./0.1m2; F = 68.9%) as key species. The second assemblage was found in the depth range from 50 to 120 m with silty-sand sediments, and it was characterized by the presence of Vauthompsonia inermis (6.5 ± 6.6 ind./0.1m2; F = 92.0%). A third assemblage was found in shallow waters influenced by glaciers in the bottom area of Ezcurra Inlet. It was characterized by sandy-clay-silt sediments and the presence ofEudorella splendida(14.6 ± 9.4 ind./0.1m2; F = 100.0%) as a core species. The last assemblage was found in the shallow sublittoral (50-100 m) of Ezcurra Inlet and the central basin, withDiastylis anderssoni armata(1.5 ± 1.1 ind./0.1m2; F = 85.7%) andDiastylopsis goekei(1.1 ± 1.0 ind./0.1m2; F = 71.4%) as the most frequent and abundant species.V. inermisis considered a eurytopic species with high frequency in the whole material, and was present in all four distinguished assemblages.E. splendidaandD. goekeiwere also recorded in each of the assemblages, but their total frequency was lower.

scholarly journals Investigating Road Pavement Failure in Oworonshoki, Kosofe Area of Lagos, Using Geophysical and Geotechnical Methods

2021 ◽  
pp. 56-67
Author(s):  
O. J. Airen ◽  
K. K. Oboshenure
Keyword(s):  
Cone Penetration ◽  
Clayey Sand ◽  
Near Surface ◽  
The Road ◽  
Cone Penetration Tests ◽  
Cone Penetration Testing ◽  
Road Pavement ◽  
Sandy Clay ◽  
Electrical Sounding ◽  
Lateral Extent

An assessment of the immediate causes of persistent road pavement failure in Oworonshoki, Koshofe area of Lagos, Nigeria using geophysical and geotechnical methods was carried out. Six traverses were occupied in the study area along the alignment of the road. Electrical Resistivity Imaging (ERI) data using the Wenner array were acquired along the six traverses. These were followed by six (6) Vertical Electrical Sounding (VES) data along the traverses. On traverse 1 are VES 1 and 2, on traverse 2 are VES 3 and 4, on traverse 3 are VES 5 and 6. One boring and three Cone Penetration Testing (CPT) were conducted along traverse 6 while the three CPTs were carried out on traverse 3, 4 and 5 respectively. The inverted 2D results reveal that resistivity values vary from 6.74 – 1333 Ωm in the study area. Four resistivity structures are delineated which are peat, clay/sandy clay, clayey sand and sand. The peat has resistivity values ranging from 6.74 – 17.7 Ωm, clay/sandy clay (20.9 – 86.9 Ωm), clayey sand (96.3 – 194 Ωm) and sand (245 – 1333 Ωm). The peat is laterally extensive and occurs from the surface to a depth of 25 m. The peat is underlain by the clay which is fairly extensive across the area of study with a thickness of 2.5 – 20 m in most location. The Cone Penetration Tests (CPT) reveal cone resistance values that progressively varies from 0 – 101 kg/m2 from the surface to a depth of 17 m, indicating dense earth materials at deeper depth while at near surface, they are incompetent soft clayey earth materials. The laterally extensive peat and clay units underlying the road pavement, extending up 30 m depth as revealed from the 2D ERI, the geoelectric investigation and the borehole are suspected to be responsible for the persistent settlement, rutting and pitting of the road pavement. The thickness of the peat/clay and the lateral extent may not be economically admissible for excavation during construction. Pile foundations to the dense gravely sand at 40 m depth along the stretch of the road is therefore recommended for stable road pavement.

scholarly journals A Case Study on Stratified Settlement and Rebound Characteristics due to Dewatering in Shanghai Subway Station

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Jianxiu Wang ◽  
Tianrong Huang ◽  
Dongchang Sui
Keyword(s):  
Soft Clay ◽  
Subway Station ◽  
Silty Clay ◽  
Metro Station ◽  
Absolute Value ◽  
Sandy Clay ◽  
Centrifugal Model ◽  
Shanghai Metro ◽  
Different Soils

Based on the Yishan Metro Station Project of Shanghai Metro Line number 9, a centrifugal model test was conducted to investigate the behavior of stratified settlement and rebound (SSR) of Shanghai soft clay caused by dewatering in deep subway station pit. The soil model was composed of three layers, and the dewatering process was simulated by self-invention of decompressing devise. The results indicate that SSR occurs when the decompression was carried out, and only negative rebound was found in sandy clay, but both positive and negative rebound occurred in the silty clay, and the absolute value of rebound in sandy clay was larger than in silty clay, and the mechanism of SSR was discussed with mechanical sandwich model, and it was found that the load and cohesive force of different soils was the main source of different responses when decompressed.

scholarly journals Application of 2-dimensional tomography to investigate subsurface lithology in Auchi polytechnic, auchi, Edo state, nigeria

2020 ◽  
Vol 39 (3) ◽  
pp. 905-910
Author(s):  
C.O. Aigbogun ◽  
D.A. Babaiwa ◽  
B.J.O. Mujakperuo
Keyword(s):  
Maximum Depth ◽  
Electrode Spacing ◽  
Clayey Sand ◽  
Sandy Clay ◽  
Edo State ◽  
Subsurface Resistivity ◽  
Schlumberger Array

The Wenner – Schlumberger array was used for Constant Separation Traversing (CST) to investigate subsurface lithology in Auchi Polytechnic, Auchi. All the traverses were carried out with electrode spacing of 5 m with a spread of 200 m. The data was obtained using Pasi terrameter (16-GL) and processed with the Dipro software. The subsurface resistivity values ranged from 207 Ωm – 8357 Ωm. The results obtained from this survey classified the subsurface lithology into topsoil, clayey sand, sandy clay and sand. The maximum depth penetrated was 50 m. Keywords: Lithology, resistivity, subsurface, Wenner-Schlumberger, 2-Dimensional.

scholarly journals Faecal Pellets in Deep Marine Soft Clay Crusts: Implications for Hot-Oil Pipeline Design

2011 ◽  
Author(s):  
Matthew Y-H. Kuo ◽  
Malcolm D. Bolton
Keyword(s):  
Soft Clay ◽  
Faecal Pellet ◽  
Major Constituent ◽  
Biological Origin ◽  
Near Surface ◽  
Faecal Pellets ◽  
Oil Pipeline ◽  
Average Grain Size ◽  
Time Required ◽  
Pipeline Design

In recent years, the presence of crusts within near surface sediments found in deep water locations off the west coast of Angola has been of interest to hot-oil pipeline designers. The origin for these crusts is considered to be of biological origin, based on the observation of thousands of faecal pellets in natural crust core samples. This paper presents the results of laboratory tests undertaken on natural and faecal pellet-only samples. These tests investigate the role faecal pellets play in modifying the gemechanical behaviour of clayey sediments. It is found that faecal pellets are able to significantly alter both the strength and the average grain-size of natural sediments, and therefore, influence the permeability and stiffness. Hot-oil pipelines self-embed into and subsequent shear on crusts containing faecal pellets. Being able to predict the time required for installed pipelines to consolidate the underlying sediment and thus, how soon after pipe-laying, the interface strength will develop is of great interest to pipeline designers. It is concluded from wet-sieving samples before and after oedometer tests, that the process of pipe laying is unlikely to destroy pellets. They will therefore, be a major constituent of the sediment subject to soil-pipeline shearing behaviour during axial pipe-walking and lateral buckling. Based on the presented results, a discussion highlighting the key implications for pipeline design is therefore provided.

scholarly journals Subsurface characterization of a quick-clay vulnerable area using near-surface geophysics and hydrological modelling

Solid Earth ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 1685-1705
Author(s):  
Silvia Salas-Romero ◽  
Alireza Malehmir ◽  
Ian Snowball ◽  
Benoît Dessirier
Keyword(s):  
Large Scale ◽  
Geophysical Methods ◽  
Hydrological Modelling ◽  
P Wave ◽  
Coarse Grained ◽  
Near Surface ◽  
Reflection Seismic ◽  
Geotechnical Investigations ◽  
Quick Clay ◽  
Near Surface Geophysics

Abstract. Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identify coarse-grained materials associated with the development of quick clays. We present the results of reflection seismic investigations on land and in part of the Göta River in Sweden, along which many quick-clay landslide scars exist. This is the first time that such a large-scale reflection seismic investigation has been carried out to study the subsurface structures associated with quick-clay landslides. The results also show a reasonable correlation with radio magnetotelluric and travel-time tomography models of the subsurface. Other ground geophysical data, such as high magnetic values, suggest a positive correlation with an increased thickness of the coarse-grained layer and shallower depths to the top of the bedrock and the top of the coarse-grained layer. The morphology of the river bottom and riverbanks, e.g. subaquatic landslide deposits, is shown by side-scan sonar and bathymetric data. Undulating bedrock, covered by subhorizontal sedimentary glacial and postglacial deposits, is clearly revealed. An extensive coarse-grained layer (P-wave velocity mostly between 1500 and 2500 m s−1 and resistivity from approximately 80 to 100 Ωm) exists within the sediments and is interpreted and modelled in a regional context. Several fracture zones are identified within the bedrock. Hydrological modelling of the coarse-grained layer confirms its potential for transporting fresh water infiltrated in fractures and nearby outcrops located in the central part of the study area. The modelled groundwater flow in this layer promotes the leaching of marine salts from the overlying clays by seasonal inflow–outflow cycles and/or diffusion, which contributes to the formation of potential quick clays.

scholarly journals Evaluation of Salt-water Intrusion in the Coastal Area of Igbokoda, Southwestern Nigeria

2018 ◽  
Vol 6 (01) ◽  
Author(s):  
Talabi A. O ◽  
Ajayi C. A ◽  
Afolagboye L. O ◽  
Oyedele A. A ◽  
Ojo O. F ◽  
...  
Keyword(s):  
Coastal Area ◽  
Salt Water ◽  
Silty Sand ◽  
High Resistivity ◽  
Salt Water Intrusion ◽  
Southwestern Nigeria ◽  
Major Threat ◽  
Sandy Clay ◽  
The World ◽  
Electrical Sounding

Saltwater intrusion into the coastal aquifer has long been recognized as a major threat to groundwater quality around the world. Groundwater evaluation of salt water intrusions in Igbokoda coastal area, southwestern Nigeria was carried out employing combined Horizontal Profiling and Vertical electrical sounding. Two traverses each with two sounding points were occupied. The result from the survey revealed 4 to 5 major layers comprising the unconsolidated silty sand and sandy clay (overburden), clayey zone, consolidated sand zone, partly intruded salt water intruded sandy clay zone and salt water intruded clay zone. The curves were the complex types KQH, KHA, QH and HKH curves. The overburden has resistivity that ranged from 253 to 1316.7Ω-m, thickness that ranged from 0.2 m to 7m. The clayey zone had resistivity of 846.0 Ω-m and thickness of 4m. The consolidated sand zone had resistivity that ranged from 2848.7 to 2865.7Ω-m and thickness that ranged between 4 and 21m. The partly intruded salt water zone is characterized by resistivity that varies between 18.4Ω-m and 93.0Ω-m and thickness of about 7-25m. The salt water intruded zone is characterized by resistivity that ranges between 4.1Ω-m and 9.7Ω-m and thickness of 4-48m. The partly-salt water intruded zones and salt water intruded zone were characterized with low resistivity while the high resistivity zones of consolidated sand layer constitute fresh water bearing zone that could serve as boreholes in the study area.

scholarly journals Suitability Assessment of Selected Lateritic Soils For Highway Construction In Anambra State, Nigeria

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Charles M.O. Nwaiwu ◽  
Ibeawuchi S Chidera ◽  
Franklin C Uzodinma
Keyword(s):  
Highway Construction ◽  
Soil Samples ◽  
Silty Sand ◽  
Coarse Grained ◽  
Unit Weight ◽  
Index Properties ◽  
Clayey Sand ◽  
British Standard ◽  
Lateritic Soils ◽  
Anambra State

Fifteen samples of coarse-grained lateritic soils obtained from different parts of Anambra State were assessed for their suitability as materials for highway construction. The soil samples were subjected to laboratory tests to obtain their index properties, compaction and California bearing ratio (CBR) characteristics. Three compactive efforts namely, British Standard Light (BSL) compaction, West African Standard (WAS) and British Standard Heavy (BSH) compaction were employed in the compaction tests. Samples were soaked for 48hrs prior to CBR testing. The index properties of the soils were used to classify the soils as   silty sand (SM) or silty sand/clayey sand (SM-SC) based on the Unified Soil Classification System (USCS) classification as well as silty soils (A – 4) or silty/clayey gravel and Sand (A – 2 -4) based on American Association of State Highway and Transportation Officials (AASHTO) classification. All the fifteen soils fell under “grading F” based on AASHTO standard specification designations for particle size distribution. The maximum dry unit weight (MDUW) of the soil samples ranged from 16.203 kN/m3 to 19.424 kN/m3,17.385 kN/m3 to 19.996 kN/m3 and from 18.126 kN/m3 to 21.473 kN/m3 with  corresponding optimum moisture content of 11.4% to 21.4%, 12.45% to 12.5%  and 8.5% to 11.75% for BSL, WAS and BSH respectively. The CBR values ranged between 7.92% and 18.87%. Most of the soil (more than 50%) did not meet the lower values of MDUW while only 20% of the soils had CBR values above 10% which is specified for subgrade soils by the AASHTO standard and the Nigerian Highway Design Manual, Federal Ministry of works and Housing.Keywords: coarse-grained, lateritic soils, highway pavement materials, USCS, AASHTO

A coring device suitable for paleomagnetic sampling of unconsolidated subsurface deposits

1983 ◽  
Vol 20 (4) ◽  
pp. 845-848 ◽  
Author(s):  
René W. Barendregt ◽  
W. J. Vreeken
Keyword(s):  
Hydraulic Properties ◽  
Maximum Depth ◽  
Fine Grained ◽  
Hydraulic Machine ◽  
Geotechnical Investigations

Research in paleomagnetism requires the collection of continuous, undisturbed, and oriented cores from fine-grained sub-surface deposits. The authors have found the Giddings coring machine to be a suitable device which offers a rapid and accurate alternative to hand-cut sampling from natural outcrops. This hydraulic machine collects undisturbed and oriented cores to a maximum depth of 16 m. It has been widely used in the study of soil engineering and hydraulic properties as well as in other geotechnical investigations of fine-grained materials. Keywords: paleomagnetism, coring, oriented sampling.

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