scholarly journals Aplicações de técnicas geofísicas na parte emersa da Baía de Guanabara: uma revisão bibliográfica

2003 ◽  
Vol 26 ◽  
pp. 117-126
Author(s):  
Paula Lucia Ferrucio da Rocha
Keyword(s):  
Salt Water ◽  
Original Data ◽  
Clay Material ◽  
Signal Attenuation ◽  
Marine Clay ◽  
Stratigraphic Sequence ◽  
Fine Grained ◽  
Deep Layers ◽  
Ground Penetrating ◽  
Fine Grained Sand

This paper presents the application of the geophysical techniques on two investigations around of Baía de Guanabara, Rio de Janeiro. The first one was carried out in the area of the Petroflex, a petrochemical industry, located at Campos Elíseos area in the bank of the bay and the second one at Ilha do Fundão, one of the island slocated in Guanabara bay. According to Anjos et al.. (2001) the research at Petroflex area was part of the company Social Project: "Conheça seu Manguezal" (Knowing your mangrove). For this research the geophysical survey was applied within the industrial park in order to identify solid waste contamination (rubber, plastic and metal barrels). The Ground Penetrating Radar (GPR) technique was used with the RAMAC/MALA equipment. The study area consists of clay and sands deposited in marine conditions, which are frequently contaminated by salt water. In general, the GPR results obtained in both media, clay material and sediments saturated with salt water are not satisfactory. However the results obtained in the Petroflex area were good. The stratigraphic sequence in the area is the following, from top to bottom: The first bed is a clay landfill, the second bed is formed by dark marine clay, and the third bed is composed of fine-grained sand with marine shells. The surveys originated sections with average depths of 14 m and average velocity of 70 m/µs. The results showed two physical discontinuities within the second bed (marine clay), which possibly represent a Pleistocene platform exposition, described in the literature as Guanabariana Regression. It was also possible to identify anomalies within the first bed (clay landfill) represented by signal attenuation, and the others identify waste deposits, where the presence of buried drums was verified. Such work has demonstrated the success of GPR applicability even to clay soil contaminated by salt water. The Ilha do Fundão where the second investigation took place, according to Rocha et al. (1998) is the result of an artificial embankment of a former small archipelago, built in the early 1950's. The aim of this work was to identify, by means of a geoelectric survey, the cores of the original islands. Normally, structures near the seacoast cannot be detected through geoelectric measurements. This is due to the presence of salt water in sediments. However, in the Ilha do Fundão case, the high electric conductivity sediments have a lens shaped with small thickness and correspond to the embankments. This circumstance allows the detection of deep layers and resistive nuclei. Results were obtained from vertical electric soundings using Schlumberger configuration with a maximum aperture (ab/2) of 100 m. The original data was published in Rocha et al. (1998).

Overpressure Identification Using The Eaton Method on The Gumai Formation of Geragai Graben, Jambi Sub Basin

2020 ◽  
Author(s):  
A. O. Marnila
Keyword(s):  
Pressure Data ◽  
Stratigraphic Sequence ◽  
Fine Grained ◽  
Marine Sedimentation ◽  
Plot Analysis ◽  
Significant Reversal ◽  
Porosity And Permeability ◽  
Upper Level ◽  
Type Data ◽  
Fine Grained Sand

Geragai graben is located in the South Sumatera Basin. It was formed by mega sequence tectonic process with various stratigraphic sequence from land and marine sedimentation. One of the overpressure indication zones in the Geragai graben is in the Gumai Formation, where the sedimentation is dominated by fine grained sand and shale with low porosity and permeability. The aim of the study is to localize the overpressure zone and to analyze the overpressure mechanism on the Gumai Formation. The Eaton method was used to determine pore pressure value using wireline log data, pressure data (RFT/FIT), and well report. The significant reversal of sonic and porosity log is indicating an overpressure presence. The cross-plot analysis of velocity vs density and fluid type data from well reports were used to analyze the causes of overpressure in the Gumai Formation. The overpressure in Gumai Formation of Geragai graben is divided into two zones, they are in the upper level and lower level of the Gumai Formation. Low overpressure have occurred in the Upper Gumai Formation and mild overpressure on the Lower Gumai Formation. Based on the analyzed data, it could be predicted, that the overpressure mechanism in the Upper Gumai Formation might have been caused by a hydrocarbon buoyancy, whereas in the Lower Gumai Formation, might have been caused by disequilibrium compaction as a result of massive shale sequence.

Failures of avionic generators and contactors operated under harsh ambient conditions

2012 ◽  
Vol 30 (1) ◽  
pp. 153-176
Author(s):  
Andrzej Gębura ◽  
Tomasz Radoń
Keyword(s):  
Climatic Conditions ◽  
Ambient Conditions ◽  
Power Devices ◽  
Lower Intensity ◽  
Fine Grained ◽  
Rotary Machines ◽  
Paint Coatings ◽  
Corrosion Pits ◽  
Fine Grained Sand ◽  
Final Consequence

The paper outlines failures of selected avionic electric power devices operated onboard of combat helicopters in Iraq and Afghanistan. While the authors were examining the electric power system of aircrafts in order to prolong their operation life they paid attention to numerous symptoms of wear demonstrated by some units of aircrafts. It was peculiar that such symptoms have never appeared during similar examinations of aircrafts operated in our country. By all accounts, the weird wear of components results from high intensity of flights and specific features of operating missions, but harsh climatic conditions seem to be the crucial factor. The authors believe that many of spotted failures experienced by electric power equipment may also happen to aircrafts operated in Poland but obviously, due to much lower intensity of operation and mild impact of environmental factors, such failures shall occur much later. The authors focused their attention on two groups of electric devices and associated destructive factors: 1. Air-cooled electric rotary machines. Fine-grained sand sucked together with air leads to very quick abrasion of protective paint coatings inside the machines. Not frequent but intense rainfalls are the reason for appearance of corrosion pits that lead to such effects as increase of pole shoe volumes. This, in turn, results in shearing of winding insulations with breakdowns (shorts) to ground and, as a final consequence, considerable drop of power demonstrated by an electric machine. 2. Contactors and electromagnets, which are allegedly tight. However, dust penetrates anyway via microfissures and disables operation of moving parts.

Reconstructing the palaeoenvironment at the early Mesolithic site of Lake Duvensee: Ground-penetrating radar and geoarchaeology for 3D facies mapping

The Holocene ◽  
2020 ◽  
Vol 30 (6) ◽  
pp. 820-833 ◽  
Author(s):  
Erica Corradini ◽  
Dennis Wilken ◽  
Marco Zanon ◽  
Daniel Groß ◽  
Harald Lübke ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Three Dimensional ◽  
Sedimentary Facies ◽  
Landscape Development ◽  
Fine Grained ◽  
Stratigraphic Model ◽  
Lake Bottom ◽  
Organic Sediments ◽  
Spatio Temporal ◽  
Ground Penetrating

We investigate the landscape development of the early Mesolithic hunter-gatherer sites of Duvensee (10000–6500 cal. BCE). Based on ground-penetrating radar (GPR) and geoarchaeological drillings, we present for the first time a three-dimensional (3D) reconstruction of the palaeoenvironment of 63 ha covering subarea of the former lake during the Mesolithic. The archaeological aims were (1) to detect the location of former islands possibly hosting hunter-gatherer settlements and (2) to reconstruct the ancient landscape development for understanding prehistoric land use. The research in Duvensee lasts almost 100 years, providing vivid illustrations of early Mesolithic life. Clusters of Mesolithic camps have been found located on small sand hills that formed islands in the prehistoric lake. For this environment, we present depth maps of the three most important sedimentary facies interfaces of the ancient Lake Duvensee. Interface1 represents the transition between coarse organic sediments (peat and coarse detritus gyttja) and fine-grained organic sediments (fine detritus gyttja, calcareous gyttja), Interface2 represents the transition to the underlying clayish-loamy sediments, and Interface3 marks the top of the basal sand deposits at the lake bottom. From Interface3, we identified the location and extent of five former islands with Mesolithic camps. Stratigraphic information from the corings enabled us to create a 3D model of the spatio-temporal development of the Duvensee bog. The locations of the islands and their estimated dive-up times agree with the spatio-temporal pattern of the previous archaeological finds. The model shows where hunter-gatherers could settle and move from one island to another following the shorelines of the overgrowing lake. The 3D stratigraphic model provides growth and shrinking rates of the island and lake areas in the Mesolithic, and volumes of organic and non-organic deposited lake sediments. Besides, it provides a basis for a sustainable groundwater management needed for heritage preservation.

Durable Architectural and Decorative Powder-Activated Concrete Using Waste-Crushing Stone Rocks

2019 ◽  
Vol 802 ◽  
pp. 1-15
Author(s):  
Sergey Victorovich Daletsky ◽  
Yuri Mikhailovich Kolitievsky ◽  
Victor Vasilievich Nikonov ◽  
Nikolay Nikolaevich Sirotin ◽  
Vladimir Vladimirovich Yudaev
Keyword(s):  
High Strength ◽  
High Density ◽  
Term Operation ◽  
Fine Grained ◽  
Concrete Mixtures ◽  
Technical Properties ◽  
Fine Grained Sand

The article consists in the development of compositions of self-compacting powder-activated fine-grained (sand) concrete mixtures, including color ones, for the production of high-density, high-strength and durable architectural and decorative concretes, which do not lose their architectural appeal during long-term operation, on the basis of multi-tonnage waste of stone crushing of various rocks, without the use of expensive mineral reactive components and the study of their physical and technical properties.

Semiautomated suppression of above-surface diffractions in GPR data

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. J43-J50 ◽  
Author(s):  
Stefan F. Carpentier ◽  
Heinrich Horstmeyer ◽  
Alan G. Green ◽  
Joseph Doetsch ◽  
Ilaria Coscia
Keyword(s):  
Ground Penetrating Radar ◽  
Synthetic Data ◽  
Complete Removal ◽  
Original Data ◽  
High Amplitude ◽  
Air Velocity ◽  
Efficient Suppression ◽  
Useful Signal ◽  
Multichannel Filtering ◽  
Ground Penetrating

Diffractions from above-surface objects can be a major problem in the processing and interpretation of ground-penetrating radar (GPR) data. Whereas methods to reduce random and many other types of source-generated noise are available, the efficient suppression of above-surface diffractions (ASDs) continues to be challenging. We have developed a scheme for semiautomatically detecting and suppressing ASDs. Initially, an accurate representation of ASDs is obtained by (1) Stolt [Formula: see text] migrating the GPR data using the air velocity to focus ASDs, (2) multichannel filtering to minimize other signals, (3) setting an amplitude threshold that targets the high-amplitude ASDs and effectively eliminates other signals, and (4) Stolt [Formula: see text] demigrating the ASDs using the air velocity, and remigrating them using the ground velocity. By excluding the obliquity correction in the Stolt algorithms and avoiding intermediate amplitude scaling, we preserve the ASDs’ amplitude and phase information. The final stepinvolves subtracting this image of ASDs from a standard migrated version of the original data. This scheme, which includes some important extensions to a previously proposed method, makes it possible to semiautomatically process large volumes of GPR data characterized by numerous highly clustered and overlapping ASDs. The user has control over the tradeoff between ASD suppression and undesired removal of useful signal. It achieves nearly complete removal of ASDs in synthetic data and significant suppression in field data. Once ASDs have been suppressed, their influence can be reduced further by applying relatively gentle multichannel filters. It is not possible to remove line diffractions that resemble subhorizontal reflections or retrieve subsurface signals from data saturated by ASDs, such that some blank regions may be left after applying the suppression scheme. Nevertheless, subsequent processing and interpretation of the GPR data benefit significantly from the suppression of ASDs, which otherwise would clutter the final images.

Particle size distributions of radioactive pollution soils and its influence on consistence of the shelterbelt forest ranges

2015 ◽  
Vol 5 (2) ◽  
pp. 93-103
Author(s):  
Маркина ◽  
Zoya Markina ◽  
Вечеров ◽  
Vladislav Vecherov
Keyword(s):  
Size Distributions ◽  
Clay Loam ◽  
Particle Size Distributions ◽  
Glacial Deposits ◽  
Parent Materials ◽  
Fine Grained ◽  
Soil Fractions ◽  
South West ◽  
Dominant Soil ◽  
Fine Grained Sand

Presents characteristic of the soil texture that formed at mixture of moraine and fluvial-glacial deposits, moraine that overlaid clay loam mantle, clay loam mantle in shelterbelt forest ranges at south-west areas of the Bryansk region that contaminate radioactive fallouts in conse-quence of the Chernobyl accident. Dominant soil fractions determined in soil horizonts, its formed at different parent rock materials. There is a growing number of fine-grained sand and silt soil fractions in the moraine overlaid clay loam mantle compared to fluvio-glacial deposits in the relief of parent materials.

scholarly journals An Experimental Study for Quantitative Estimation of Rebar Corrosion in Concrete Using Ground Penetrating Radar

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Md Istiaque Hasan ◽  
Nur Yazdani
Keyword(s):  
Reinforced Concrete ◽  
Quantitative Estimation ◽  
Salt Water ◽  
Water Solution ◽  
Maximum Amplitude ◽  
Accelerated Corrosion ◽  
Oil Emulsion ◽  
Steel Rebar ◽  
Ground Penetrating ◽  
The Relationship

Corrosion of steel rebar in reinforced concrete is one the most important durability issues in the service life of a structure. In this paper, an investigation is conducted to find out the relationship between the amount of reinforced concrete corrosion and GPR maximum positive amplitude. Accelerated corrosion was simulated in the lab by impressing direct current into steel rebar that was submerged in a 5% salt water solution. The amount of corrosion was varied in the rebars with different levels of mass loss ranging from 0% to 45%. The corroded rebars were then placed into three different oil emulsion tanks having different dielectric properties similar to concrete. The maximum amplitudes from the corroded bars were recorded. A linear relationship between the maximum positive amplitudes and the amount of corrosion in terms of percentage loss of area was observed. It was proposed that the relationship between the GPR maximum amplitude and the amount of corrosion can be used as a basis of a NDE technique of quantitative estimation of corrosion.

Sign in / Sign up

Export Citation Format

Share Document