61 research outputs found
Radionuclides proportion and radiological risk assessment of soil samples collected in Covenant University, Ota, Ogun State Nigeria
The activity levels of 238U, 232Th and 40K in soil surrounding major office complexes in Covenant University were analyzed for radiological hazards to determine the safety of the residents in such environment. Sixteen (16) soil samples were collected, prepared and sent to Acme laboratory in Canada for analysis with the use of high purity germanium detector. The mean activity concentrations of 238U, 232Th and 40K were found to be 45?±?10, 135?±?8 and 195?±?20 respectively. The concentrations of 238U and 232Th were found to be higher than the world recommended standard of 35 and 30, while the result for 40K was noted to be lower than the world safe limit. The average values of Raeq, D, AED, Iyr, Hex and ELCR in this study were estimated to be 252.33?Bq/kg, 110.15 nGy/h, 0.13 mSv/y, 1.78, 0.68 and 0.47?×?10-3 respectively. It was noticed that none of the measured parameters was higher than the internationally recommended safe limits. 232Th was found to be the major contributor to the environmental radionuclides in the area of study. Therefore, the inhabitants of the office complexes whose environment was assessed are considered not be exposed to any radiological hazards
Application of Shallow Seismic Refraction Method and Geotechnical Parameters in Site Characterization of a Reclaimed Land
The recent incessant cases of building collapse have made it necessary for building site to be characterized before they are developed especially when the land is reclaimed from water bodies. On the basis of the above, both geophysical and geotechnical methods are engaged to determine the subsurface structure of a land for construction purposes. In this research effort, near surface seismic refraction method together with relevant geotechnical methods were used to characterize the subsurface condition of the study site. Nine seismic refraction profiles were surveyed with some of the profiles laid parallel and some others overlain one another. The result of this study revealed three geologic layers in the site with varying geotechnical parameters. The Young’s modulus, bulk modulus and shear modulus all have values that ranges from 0.071-25.685, 0.083-30.042 and 0.0286-10.395 GPa respectively in the site. From these results, it can be concluded the third layer having the highest value of geotechnical parameters is the most competent and this layer is between 7.5 m and 18 m into the subsurface. The information obtained from other geotechnical methods in the site confirmed the results of this study. Thus, near surface seismic refraction method is recommended for a non-invasive, non-cumbersome and reliable site characterizatio
Application of Geophysical and Geotechnical Methods to Determine the Geotechnical Characteristics of a Reclaimed Land
Near-surface seismic refraction method and electrical resistivity methods were used to characterise the subsurface of a site reclaimed from
water bodies, in order to determine the depth to the most competent layer for construction purposes. Nine seismic refraction profiles were
surveyed and the data was interpreted using SeisImager software package. Also, twelve vertical electrical soundings were carried out and the
acquired data was interpreted using WinResist computer package. The seismic refraction method delineated three layers while the electrical
resistivity method revealed between four and five geoelectric layers. The result of the seismic refraction method showed that the third layer is
the most competent layer having the highest elastic moduli. Furthermore, the resistivity method revealed that the third geoelectric layer is the
most competent having resistivity ranging between 23.3 and 1107.2m . It was also discovered that the depth to the most competent layer is
between 7 m and 18 m in the subsurface. It was concluded that piling will be the most appropriate foundation for any building in the study area
Foundation Settlement Determination: A Simplified Approach
The heterogeneous nature of the subsurface requires the use of factual information to deal with rather than assumptions or generalized equations. Therefore, there is need to determine the actual rate of settlement possible in the soil before structures are built on it. This information will help in determining the type of foundation design and the kind of reinforcement that will be necessary in constructions. This paper presents a simplified and a faster approach for determining foundation settlement in any type of soil using real field data acquired from seismic refraction techniques and cone penetration tests. This approach was also able to determine the depth of settlement of each strata of soil. The results obtained revealed the different settlement time and depth of settlement possible
Assessment of geogenic natural radionuclide contents of soil samples collected from Ogun State, South western, Nigeria
Background: Natural radionuclides are always present in the environment.
Human exposure to the background radia�on is inevitable. It is therefore
important to assess health risk associated with these radionuclides. Materials
and Methods: The distribu�on of natural radionuclides 238U, 232Th and 40K in
soil samples collected from all the twenty (20) local Governments
headquarter areas in Ogun state, Nigeria were determined by gamma
spectroscopy using a high-purity germanium detector. The measured
concentra�ons were used in es�ma�ng the radiological risk pose to people
living in these communi�es. Results: The ac�vity concentra�ons measured
ranged between 3 ± 1 Bqkg-1(O0a) to 27 ± 6 Bqkg-1(odeda) for 238U, 10 ± 1
Bqkg-1(O0a) to 126 ± 6 Bqkg-1(Ijebu Igbo) for 232Th and 7 ± 6 Bqkg-1(Aiyetoro)
to 497 ± 1 Bqkg-1(Odeda) for 40K. The mean radium equivalent calculated was
77.6 Bqkg-1 which is lower than 370 Bqkg-1 of the world average and the
hazard indices calculated were lower than unity. Conclusion: The absorbed
rate and annual effec�ve dose es�mated for most of the loca�ons are in good
agreement with world average values except for Akomoje, Ake-Abeokuta,
Ogere, Ijebu-Igbo and Odeda
Investigation to determine the vulnerability of reclaimed land to building collapse using near surface geophysical method
Adequate knowledge of the geology and the structures of the subsurface would
assist engineers in the best way to carry out constructions to avoid building collapse. In this
study, near surface seismic refraction method was used to determine the geotechnical
parameters of the subsurface, the results obtained were correlated with the result of borehole
data drilled in the study area. The results of seismic refraction method delineated mostly two
distinct layers with the first layer having the lower geotechnical parameters. It was observed
that in the first layer, the Young’s modulus ranged from 0.168 to 0.458 GPa , shear modulus
ranged between 0.068 and 0.185 GPa, the bulk modulus ranged between 0.106 and 0.287 GPa
while the bearing capacity ranged from 0.083 to 0.139 MPa. On the other hand, in the second
layer, the Young’s modulus ranged between 3.717 and 7.018 GPa, shear modulus ranged from
1.500 to 2.830 GPa while the bulk modulus ranged from 2.383 to 4.449 GPa. Significantly, the
formation of the second layer appeared to be more competent than the first layer, therefore
engineering construction in this geological setting is recommended to be founded on the second
layer at depth ranging between 7 and 16 m
Application of 2D electrical resistivity imaging and cone penetration test (CPT) to assess the harzadous effect of near surface water on foundations in Lagos Nigeria
Adequate information on the condition of the subsurface is very important for site
evaluation for engineering purposes. In this study two dimensional (2D) geoelectrical
resistivity survey and cone penetration tests were conducted to study the hazardous effect of
excess near surface water on the foundation of building in a reclaimed land located at Victoria
Island area of Lagos State. The results of the inverted 2D geoelectrical resistivity data revealed
three distinct geoelectrical layers characterized by low to moderate electrical resistivity of 2.23
and 129 Ωm and 9.46 to 636 Ωm respectively. The topsoil is characterized by wet sandy soil,
which is underlain by sandy clay and banded at the below by a geologic formation of low
resistivity which is suspected to be clay. The clay material may be responsible for the excess
water retention observed in the area. The CPT method on the other hand revealed a geological
formation of low resistance to penetration between 2-3 kg/cm2 from the topsoil to a depth of 7
m, which may be the effect of excess water in the near surface. This study revealed that the
foundation of building may not be founded directly on the soil in any reclaimed land as this
may result in collapse as a result of upward migration of water to the near surfac
Comparative Analysis of Natural Radioactivity Content in Tiles made in Nigeria and Imported Tiles from China
In this investigation, natural radioactive contents in tiles manufactured in Nigeria and tiles imported
from China were measured using gamma ray spectroscopy. High Purity Germanium detector was
used to estimate the concentrations of some radioisotopes present in 17 samples of various tiles from
Nigeria and China. The average activity concentrations of 226Ra, 232Th, and 40K for the tiles were found
to be 68.2 ± 0.5; 173.9 ± 9.2 and 490 ± 15 Bq/kg and 58.2 ± 0.5, 161.5 ± 9.4 and 455.7 ± 15.1 Bq/kg for
the tiles from Nigeria and China respectively. Radiological hazard indices such as absorbed dose rate,
radium equivalent activity, external Hazard Index (Hex), internal Hazard Index (Hin), Annual Effective
Dose (mSv/y), Gamma activity Index (Iγ) and Alpha Index (Iα) were determined for both kind of tiles
from Nigeria and China. The mean values obtained were: 354.56 and 317.16 Bq/kg; 169.22 nGyh−1 and
153.92 nGyh−1; 0.95 and 0.87; 1.14 and 1.08; 1.59 mSv/y and 1.52 mSv/y; 1 and 1.15 and; 0.34 and
0.29 respectively. The mean value of radium equivalent obtained in this study is less than that of the
international reference value of 370 Bq/kg for the both kind of tiles
Comparative Analysis of Natural Radioactivity Content in Tiles made in Nigeria and Imported Tiles from China
In this investigation, natural radioactive contents in tiles manufactured in Nigeria and tiles imported
from China were measured using gamma ray spectroscopy. High Purity Germanium detector was
used to estimate the concentrations of some radioisotopes present in 17 samples of various tiles from
Nigeria and China. The average activity concentrations of 226Ra, 232Th, and 40K for the tiles were found
to be 68.2 ± 0.5; 173.9 ± 9.2 and 490 ± 15 Bq/kg and 58.2 ± 0.5, 161.5 ± 9.4 and 455.7 ± 15.1 Bq/kg for
the tiles from Nigeria and China respectively. Radiological hazard indices such as absorbed dose rate,
radium equivalent activity, external Hazard Index (Hex), internal Hazard Index (Hin), Annual Effective
Dose (mSv/y), Gamma activity Index (Iγ) and Alpha Index (Iα) were determined for both kind of tiles
from Nigeria and China. The mean values obtained were: 354.56 and 317.16 Bq/kg; 169.22 nGyh−1 and
153.92 nGyh−1; 0.95 and 0.87; 1.14 and 1.08; 1.59 mSv/y and 1.52 mSv/y; 1 and 1.15 and; 0.34 and
0.29 respectively. The mean value of radium equivalent obtained in this study is less than that of the
international reference value of 370 Bq/kg for the both kind of tiles
Assessment of natural radionuclides and its radiological hazards from tiles made in Nigeria
Activity concentration of 10 different brands of tiles made in Nigeria were analyzed using High purity
Germanium gamma detector and its hazard indices such as absorbed dose rate, radium equivalent activity,
external Hazard Index (Hex), internal Hazard Index (Hin), Annual Effective Dose (mSv/y), Gamma activity Index
(Iγ) and Alpha Index (Iα) were determined. The result showed that the average activity concentrations of
radionuclides (226Ra, 232Th and 40K) content are within the recommended limit. The average radium equivalent
is within the recommended limit of 370 Bq/kg. The result obtained further showed that the mean values for the
absorbed dose rate (D), external and internal hazard index, the annual effective dose (AEDR) equivalent, gamma
activity index and Alpha Index were: 169.22 nGyh−1, 0.95 and 1.14, 1.59 mSv/y, 1.00 Sv yr−1 and 0.34 respectively.
The result established that radiological hazards such as absorbed dose rate, internal hazard, annual
effective dose rate, gamma activity index and Alpha Index for some samples are found to be slightly close or
above international recommended values. The result for the present study was compared with tiles sample from
others countries, it was observed that the concentration of tiles made in Nigeria and other countries are closer,
however recommends proper radiation monitoring for some tiles made in Nigeria before usage due to the long
term health effec
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