Geotechnical invesigation for towers of electricity transmission line project in Port-Sudan (original) (raw)
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Soil Investigation for Towers of Electricity Transmission Lines Project in Port Sudan
2011
for visual inspection and testing. 3 3. .2 2 S St ta an nd da ar rd d P Pe en ne et tr ra at ti io on n T Te es st t ((S SP PT T)) The Standard Penetration Test (SPT) was performed for each borehole at a depth interval of 1.5 m. and soil samples were taken. A split spoon sampler, 50 mm in diameter was driven by the blows of a standard hammer weighing 64kg and falling freely from a height of 760 mm. The number of blows required to give a tube penetration of 300 mm was taken as SPT-N value of the soil tested at a specified borehole depth. The SPT were done according to International Standards. The results are displayed in the summary tables of Appendix (A). 4 4.. L La ab bo or ra at to or ry y T Te es st ti in ng g The Laboratory program was comprised of performing tests on the disturbed soil samples obtained from the drilling. The testing procedures followed were in general conformance with those recommended in BS 1377 and the soils were classified according to the Unified System for Classifying Soils (USCS). The laboratory tests performed included the following:-Atterberg Limits tests (Liquid Limit & Plastic Limit)-Grain size analysis (Wet sieve analysis) Geotechnical Investigation for Electricity By Dr. Magdi Zumrawi of Transmission Line Towers in Port-Sudan University of Khartoum 6-Shear strength (Direct Shear test)-Chemical tests 4 4. .1 1 A At tt te er rb be er rg g L Li im mi it ts s The tests performed were liquid limit (LL) and plastic limit (PL) tests. These tests were carried out on representative soil samples. Disturbed soil samples were taken at one meter intervals depths of the boreholes. The samples tested were about ninety three samples and the results obtained are listed in the summary tables of Appendix (A). 4 4. .2 2 S Si ie ev ve e A An na al ly ys si is s T Te es st t These tests were carried out on representative soil samples taken at one meter intervals depths of the boreholes. The wet sieve analysis tests were performed on ninety three samples and the results of these tests are shown in Appendices (A) & (B). 4 4. .3 3 S Sh he ea ar r B Bo ox x T Te es st t This test was performed using soil samples taken at certain depths of the boreholes. The test was carried out to determine the soil shear strength parameters (cohesion "C" and angle of internal friction "Ø") of the soil in this locality. The shear box tests were carried out on seventy five soil samples and the results of these tests are given in Appendix (A) & (C).
Geotechnical and Geological Engineering, 2010
A 132 kVA electrical transmission line has been proposed to connect the towns of Eket and Ikot Abasi in the eastern Niger delta in Nigeria. A geotechnical and hydrological study was performed to geotechnically characterize the route alignment and to provide data for design of the foundations for the transmission towers. In this paper, we introduce the study location and its geological, topographical and physiological characteristics, present the hydrological and geotechnical investigations and their results, and make recomendations for the design of the transmission tower foundations. Hydrological inspection of the power line alignment revealed that the route is traversed by numerous tributaries of the Qua-Iboe and Imo Rivers, the two major rivers that control the drainage of the study area. In-situ geotechnical tests consisted of cone penetration tests (CPTs), vane shear tests, test pit sampling (0-2.0 m depth) and lithologic boreholes (20 and 50 m deep). Laboratory tests included grain size analysis, pH determination and Atterberg Limits. Based on the CPT log pattern, no of stratum, and refusal depths, the soils along the transmission alignment were classified into twelve structural domains having common geotechnical properties. Because of the elevated water levels, and the nature of the soils, deep pile foundations were recommended for the towers. Software from the Louisiana Transportation Research Center, was employed to estimate skin friction, end bearing, and ultimate bearing capacities for assumed 225 mm square shaped reinforced concrete pile in each of the different zones of the alignment.
2007
The Building and Road Research Institute (BRRI), Uni v e r si t y o f K h artoum was requested by National Electricity Corporation(Sudan) to undertake a geotechnical investigation program for the angle towers of the Arakiyai-Port Sudan and Port Sudan-Sawakin Transmission lines. The total length of both transmission lines is about 120 km. The investigation included drilling boreholes, excavating test pits, performing in-situ and laboratory tests to reveal sub-soil profiles and reporting on the results with analysis and recommendation for foundation alternatives and treatments for the proposed towers on site
Subsoil evaluation within a proposes site for civil engineering structure by using geoelectrical and geotechnical methods of investigation carry out. The study aims to provide information on the stratigraphy, thickness, nature, and competence of the subsoil. Eighteen (18) Vertical Electrical Sounding (VES) stations using Schlumberger configuration occupy and complement with geotechnical analysis of eighteen (18) soil samples collect at all the VES points at depth not exceeding 1m within the study area. The VES interpretations delineate four main geoelectric sequences which comprise of the top soil, mixture of clay and sand, gravely sand and sandy gravel. The top soils are generally thin (< 2 m) and majorly composes of clayey silt/ silty clay /sandy clay/ clayey sand/ fill materials. The layer resistivity ranges from 0.75-19.6 Ωm for topsoil, 1.71-6.7 Ωm for clay and sand mixture, 0.01 – 2.69 Ωm for saturated gravelly sand layer and 4.23-4.61 Ωm for saturated sandy gravel layer. Low resistivity values at the study area are due to moisture and clay content within deposits at the study area. The geotechnical results show that the soil is relatively high clay content, intermediate to high moisture content and high plasticity. It concludes from the combined results above, that the topsoil is generally geotechnically less competence soil and may not serve as a good foundation material, therefore shallow foundation may not be feasible in studied area and, for engineering structure to be erected on such soil there is need for soil improvement or pilling to the sand layer.
Application of geophysical and geotechnical investigations in engineering site evaluation
Geophysical and geotechnical studies were conducted at a proposed Switch station facility for Telecommunication at a site in the south-eastern part of Nigeria. The aim of the study is to evaluate the sub-soil conditions and electrical properties of the soil which may have effect on the proposed mast and switch facilities system. The geophysical investigation involved the Vertical Electrical Sounding (VES) technique using the Schlumberger configuration and a geotechnical investigation. A total of sixteen (16) VES stations were occupied within the study site. The geotechnical study involved Boreholes drilling as well as Cone Penetration Tests (CPT). A total of six (6) CPTs and three (3) Boreholes drilling were utilised within the study area. This was done to provide controls on the geophysical interpretation. Four subsurface layers were delineated within the study area which include: the topsoil (mixture of sand, silt and clay), coarse sand, clayey sand and sand. This correlated with the sub-soil investigation. The study area is underlain by a stratum of medium stiff to stiff lateritic clayey/silty sand to the depth of about 20 m as explored by the Borehole. The choice of foundation construction for the proposed structure must take care of the settlement characteristics of the clayey material. The subsurface layers up to a depth of 5 m is of moderate to high resistivity values (> 180 ohm-m) and it may not serve as a good electric earthing material, therefore there is a need to improve the subsurface conductivity of this layer most especially within the area where the electrode for the earthling system will be buried.
Electrical resistivity survey was carried out in a site proposed for the construction and installation of a Power sub-station. The project will involve subsurface installation of cables and other objects that easily conduct electricity. Extant laws including EIA also require knowledge of subsurface distribution of resistivity in construction projects that would involve burial of steel pipes and cables. The imperative of this is emphasized by the location of the project in an area of shallow groundwater conditions. Field resistivity measurements were undertaken using ABEM Terrameter SAS 1000, adopting Schlumberger configuration in vertical electric sounding at 12 locations within the study site. The results were used to generate geo-electric log models. Three geo-electric profile models (pseudo- profiles) were also taken NE-SW of the site. Interpretation of the models shows that the area is characterized by two geo-electric layers to the depth of 30m. The upper layer of lower resistivity occurs to a depth of 2-3m. This layer consists of lateritic to silty sands. The lower layer has a resistivity of between 900 - >2000 Ωm and represents fine to coarse sands and gravels. On the Soil Electrical Resistivity Classification (BS 1377), the subsoil falls within non-corrosive class. Objects installed in the soil are not likely to suffer corrosion soon. Similarly, subsurface electrical installations will pose minimal hazards and would require basic precautions to avoid electrical accidents.
Abstract The combination of geophysical and geotechnical methods in foundation investigation has shown to be invaluable in deciphering the depth to bedrock, characterizing the earth materials and extent of variation of allowable bearing pressure of foundation soils. Geophysical and geotechnical methods involving electrical resistivity and cone penetration test have been carried out to investigate the foundation conditions of a bridge site in Ajibode and the newly constructed Abadina-Ajibode Road, located in University of Ibadan, Ibadan, southwestern Nigeria. Eleven vertical electrical sounding (VES) were carried out, seven at the investigated portion of the road and four at the bridge site. While four cone penetration tests were also carried out at the Bridge site. The vertical electrical sounding for investigated portion of the road revealed 2-4 different lithological layers. The first layers is topsoil which has resistivity ranges from 17-321Ωm with a mean of 220Ωm. The wide range in resistivity values of the topsoil can be due to different degree of compaction. The thickness of the topsoil ranges from 0.5-1.7m with a mean of 1.1m. The second layer resistivity from VES 1-VES 6 ranges from 19-46Ωm with a mean of 32Ωm. The resistivity of this layer is less than 100Ωm which is characteristics of clayey formation. The thickness of this layer ranges from 5.9-12.6m with a mean of 8.0m. For VES 7, the second layer is made up of lateritic pan with resistivity of 336Ωm and depth of 6.1m. The fractured/fresh basement layer resistivity ranges from 171-2364Ωm with a mean of 998Ωm and depth value ranges between 7.4-22.3m with mean depth of 10.9m. While for the investigated bridge site, the vertical electrical sounding revealed 2-3 geoelectric layers. The geoelectric layers include: the first layer is topsoil which has resistivity ranges from 31-320Ωm with a mean of 132Ωm. The wide range in resistivity of the topsoil can be due to different degree of compaction. The thickness of this layer ranges from 0.7m-2.5m with a mean of 1.5m. The second layer resistivity for VES 1-VES 2 ranges from 85-138Ωm with a mean of 116Ωm. The thickness of this layer ranges from 1.0-1.1m with a mean of 1.0m: this layer is characterized by weathered basement. The fresh basement layer resistivity ranges from 920-2853Ωm with a mean resistivity of 2067Ωm, is characterize with fresh bedrock. The cone penetrometer tests also revealed that the investigated bridge site has 2-3 different lithologies with cone resistance of 5-40Kg/cm2 with a mean of 18Kg/cm2 at depth range from 0.25-1.0m and at depth range of 1.25-1.7m, the penetrative resistance at CPT 1 and CPT 2 range from 25-250Kg/cm2 with a mean of 148Kg/cm2, this is a characteristics of competent materials which are weathered basement. CPT 3 and CPT 4 penetrative resistance range from 5-10Kg/cm2 with a mean of 9Kg/cm2 at depth range from 1.0-3.75m but from depth range between 4.0m and 5.0m, the penetrative resistance ranges from 200-250Kg/cm2 with a mean of 225Kg/cm2. The results obtained from this study have emphasized the usefulness of geophysical methods in complementing geotechnical studies in variation in lithology accompanied by variation in the allowable bearing pressure of foundation soils. Keywords: Ajibode, VES, Cone penetration test, Schlumberger configuration, Geotechnical survey, cone penetration test, pile foundation
GeoScience Engineering
The subsurface of a proposed site for building development in Mowe, Nigeria, using Standard Penetration Test (SPT), Cone Penetrometer Test (CPT) and Horizontal Electrical Profiling (HEP), was investigated with the aim of evaluating the suitability of the strata for foundation materials. Four SPT and CPT were conducted using 2.5 tonnes hammer. HEP utilizing Wenner array were performed with inter-electrode spacing of 10 – 60 m along four traverses coincident with each of the SPT and CPT. The HEP data were processed using DIPRO software and textural filtering of the resulting resistivity sections was implemented to enable delineation of hidden layers. Sandy lateritic clay, silty lateritic clay, clay, clayey sand and sand horizons were delineated. The SPT “N” value defined very soft to soft sandy lateritic (<4), stiff silty lateritic clay (7 – 12), very stiff silty clay (12 - 15), clayey sand (15-20) and sand (27 – 37). Sandy lateritic clay (5-40 kg/cm2) and silty lateritic clay (25 ...
2019
An Electrical Resistivity survey of a non-functional borehole was carried out at Bondong, Southern part of Kaduna state. Six (6) VES Points were sounded along a profile of 150m which passes through a Borehole with intervals of 30m from each VES Point. The borehole was drilled to a depth of 25m. The profile has four underlying layers: the first layer constitutes of Clay with resistivity range of 10-100Ωm at a depth of 4m. This is taken as the Topsoil layer. The second layer constitutes of sand/laterites with resistivity range of 200-1000Ωm which is taken as the weathered layer which has a depth of 25m and a thickness of 21m. The third layer is the fractured layer which compose of gravels and coarse grain sand with resistivity range of 300-2000Ωm and has a depth of 85m and a thickness of 64m, this layer is suspected to constitute of high water content. The fourth layer is the fresh basement which is taken as the porphyritic granite rock with resistivity value greater than 6000Ωm at a ...
Nigerian Journal of Technology (NIJOTECH), 2020
In this research, an Electromagnetic (E.M) method of groundwater investigations was used as an on-spot assessment tool to test the integrity of the developed borehole in Afe Babalola University, Ado-Ekiti. Some randomly selected functional and abandoned boreholes developed by the Vertical Electrical Sounding (VES) methods were chosen for this study, with the aim to know the potential of the boreholes. Four transverses were established across the institution consisting of two functional and two abandoned boreholes selected from the existing forty boreholes. These were subjected to E.M method of groundwater investigation using a PQWT S500 series machines. The results obtained from this study produced curve graphs and subsurface profile maps of each transverse location. It was observed that boreholes TR 1 and TR 3, were accurately sited on vertical fractures and weathered formations while TR 2 and TR 4 were wrongly sited at the locations of poor groundwater yielding zone.