Geological and Geophysical Study in Udheri Khola Area, Nalgad Hydroelectric Project, Jajarkot District, Lesser Himalaya, Western Nepal

2020 ◽  
Vol 22 ◽  
pp. 11-16
Author(s):  
Indra Lamsal ◽  
Subesh Ghimire ◽  
Kamala Kant Acharya
Keyword(s):  
High Resistivity ◽  
Lesser Himalaya ◽  
Geophysical Investigation ◽  
Resistivity Tomography ◽  
Engineering Construction ◽  
Hydroelectric Project ◽  
Geophysical Study ◽  
Karst Feature ◽  
Very High ◽  
Surface Collapse

Subsidence in carbonate rock is one of common and challenging action in terms of engineering construction. Geological study and geophysical investigation carried out in the intake area of Nalgad Hydroelectric Project Jajarkot, western Nepal Lesser Himalaya. The main objective was to identify the cause of subsidence in the intake area of Nalgad Hydroelectric Project, Jajarkot. Geological study of the area was carried to understand the lithology, thickness and structure of the area. The study area comprises two distinct rock units, namely, Dolomite Unit followed up by the Slate Unit. The Dolomite Unit is composed of light grey to grayish white stromatolitic dolomite which is thrusted over the Slate Unit near to Laikham village and Sepu Khola area. The Slate Unit is made up of grayish black to graphitic slate. A thin prominent calcareous horizon wasconfined between Slate Unit. 2D-Electric Resistivity Tomography (ERT) measurements were deployed in four different lines to investigate the cause of the subsidence in the carbonate terrain. A concentric very high resistivity patch shown by Tomogram ER-D-01 survey line was identified and interpreted as dry cavity. The result of the 2D- ERT survey was correlated with core log data of geotechnical exploration in the suspicious point to ensure the presence of karst in the Dolomite Unit at right bank of Nalsyagu Khola near dam axis of Nalgad Hydroelectric Project. The 2D – ERT survey together with geotechnical investigation is capable of identifying subsurface karst feature as the cause of surface collapse in the area.

Marine resistivity tomography for coastal engineering applications in Greece

Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. B97-B105 ◽  
Author(s):  
G. Apostolopoulos
Keyword(s):  
Loose Material ◽  
Saline Water ◽  
Coastal Engineering ◽  
High Resistivity ◽  
Geophysical Investigation ◽  
Engineering Applications ◽  
Resistivity Tomography ◽  
Construction Company ◽  
Drilling Data ◽  
Tomography Method

The marine resistivity tomography method can be useful for coastal engineering applications through the use of immersion cables, laid on the water bottom, thus achieving a deeper and more detailed detection of the formations underneath. Careful positioning of the profiles related to the available geologic, geomorphological, bathymetric, and drilling data and to the requirements of engineers, can give thicknesses of loose material as well as the bedrock relief. The formations and their interfaces are clearly defined either by calibration with available drilling data or by high resistivity changes which indicate discontinuities with resistivity values related to permeability and saline water presence. Two case studies are under examination. The first concerns the preservation of an old iron bridge in Lavrion Port with reinforcement and new foundations. Here, the geophysical investigation detects the formation on which the bridge was founded, as well as the loose material above it. The second case study concerns geophysical investigation asked by a construction company for the marine excavation work needed in the new Mesta port. Here, the geophysical measurements with the detected formations give valuable information with respect to the volume of material, equipment, time and cost of excavation as well as where the foundations will be laid for new constructions.

scholarly journals The Primary Origin of Excellent Dielectric Properties of (Co, Nb) Co-Doped TiO2 Ceramics: Electron-Pinned Defect Dipoles vs. Internal Barrier Layer Capacitor Effect

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3230
Author(s):  
Theeranuch Nachaithong ◽  
Narong Chanlek ◽  
Pairot Moontragoon ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Properties ◽  
Loss Tangent ◽  
Barrier Layer ◽  
Dielectric Response ◽  
High Resistivity ◽  
Low Loss ◽  
Rutile Tio2 ◽  
Complex Defect ◽  
Very High ◽  
Co Doped

(Co, Nb) co-doped rutile TiO2 (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO2 phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO2 with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ » 36,105 and a low loss tangent of tanδ » 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoVoTi complex defect. On the other hand, the substitution of TiO2 with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.

scholarly journals Distribution of boron in the rocks of central Nepal Himalaya

2003 ◽  
Vol 28 ◽  
Author(s):  
Santa Man Rai
Keyword(s):  
Partial Melting ◽  
Boron Content ◽  
Lesser Himalaya ◽  
Main Central Thrust ◽  
Nepal Himalaya ◽  
Metasedimentary Rocks ◽  
Central Nepal ◽  
Very High

Boron content in the rocks of central Nepal Himalaya depends upon the lithology and the grade of metamorphism. The concentration of boron is abundant (up to 322 ppm) in the metasedimentary rocks of the Lesser Himalaya. There seems to be a rather good correlation between the boron content in the rocks and the grade of metamorphism. The boron content progressively increases from chlorite to garnet isograds, then it systematically decreases in the staurolite±kyanite, kyanite and sillimanite isograds, respectively. This trend may be related to the inverse metamorphism associated with movement along the Main Central Thrust. The Manaslu leucogranite contains very high amount of boron (950 ppm). The enrichment of boron in this rock may be due to the release of boron from the Lesser Himalayan rocks during the partial melting of the Higher Himalayan Crystallines (Tibetan Slab) as a result of the movement along the MCT. Tourmaline from the Manaslu Granite is also highly rich in boron (8460 ppm).

Deposition of Thin Films of Silicon Carbide on Fused Quartz and on Sapphire by Laser Ablation of Ceramic Silicon Carbide Targets

1992 ◽  
Vol 285 ◽  
Author(s):  
L. Rimai ◽  
R. Ager ◽  
J. Hangas ◽  
E. M. Loaothetis ◽  
Nayef Abu-ageel ◽  
...  
Keyword(s):  
Thin Films ◽  
Silicon Carbide ◽  
Room Temperature ◽  
Optical Band Gap ◽  
Energy Gap ◽  
Fused Silica ◽  
High Resistivity ◽  
Fused Quartz ◽  
Amorphous Sic ◽  
Very High

ABSTRACTAblation of ceramic silicon carbide with 351 nm excimer radiation was used to depositSIC films on fused silica and on sapphire. For deposition temperatures above 850° C, diffraction shows the films to be crystalline with the [111] axis preferentially oriented normally to the film. Optical spectra show an indirect energy gap at 2.2 eV, near that for the cubic polytype, although the 200 diffractions are absent. Room temperature resistivities range between .02 to .1 Ωcm. Deposition below 600° C yields amorphous SiC with no diffraction bands, low and variable optical band gap and very high resistivity.

scholarly journals Geophysical study on moraine dam of Imja Glacial Lake in Eastern Nepal using Electrical Resistivity Tomography Method

2018 ◽  
Vol 55 (1) ◽  
pp. 15-22
Author(s):  
Pushpa Raj Dahal ◽  
Kabi Raj Paudyal ◽  
Sudhir Rajaure
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Maximum Depth ◽  
Glacial Lake ◽  
Resistivity Tomography ◽  
Electrical Resistivity Survey ◽  
Geophysical Study ◽  
Glacier Ice ◽  
Tomography Method ◽  
Seepage Channel

Glacial Lake Outburst Flood (GLOF) is one of the potential disaster of Nepal. The Imja glacial lake is considered as one of the fastest growing glacial lake with high risk of GLOF. The internal structure of moraine dams, especially the distribution of buried ice blocks and permafrost materials is key factors in assessing GLOF risk. This study covers exploration and assessment of subsurface conditions of the moraine material such as quantification of buried ice, seepage channel and permafrost material distribution. The geophysical study of dam was carried out by using Dipole–dipole array of Electrical Resistivity Tomography (ERT) method. This study presents the results regarding use of electrical resistivity survey for assessment of the subsurface buried glacier ice and permafrost zones within the dam of the Imja glacial lake. The interpretation of resistivity data at end moraine of Imja glacial lake is based not only on specific resistivity values, but also with field observations and correlation with previous studies. The maximum depth of information obtained from the modeling is about 25 m and; highest and lowest values of resistivity ranges from 117 Wm to 2682240 Wm. The distribution of major subsurface materials from lowest resistivity value to highest resistivity values are classified as saturated moraine (<5000 Wm), frozen moraine (5000 Wm to 20000 Wm) and dead ice (>20000 Wm). The distribution of dead buried ice in moraine dam is found to be heterogeneous. The minimum and maximum depth of dead ice from surface is about 0 m to 20 m at various locations. Based on the information of this study, an open channel was cut through the lake to lower its level and the result is found to be successful. 

Growth of Large Diameter 6H SI and 4H n+ SiC Single Crystals

2010 ◽  
Vol 1246 ◽  
Author(s):  
Avinash Gupta ◽  
Ping Wu ◽  
Varatharajan Rengarajan ◽  
Xueping Xu ◽  
Murugesu Yoganathan ◽  
...  
Keyword(s):  
Single Crystals ◽  
Growth Process ◽  
Large Diameter ◽  
Commercial Production ◽  
High Resistivity ◽  
Steady Growth ◽  
Vanadium Doping ◽  
Low Capacitance ◽  
Very High

AbstractSiC single crystals are grown at II-VI by the seeded sublimation technique. The process has been scaled up and optimized to support commercial production of high-quality 100 mm diameter, Semi-Insulating (SI) 6H substrates and 100 mm 4H n+ substrates. The growth process incorporates special elements aimed at achieving uniform sublimation of the source, steady growth rate, uniform doping and reduced presence of background impurities.Semi-insulating 6H substrates are produced using precise vanadium compensation. Vanadium doping is optimized to yield SI material with very high resistivity and low capacitance.Crystal quality of the substrates is evaluated using a wide variety of techniques. Specific defects, their interaction and evolution during growth are described with emphasis on micropipes and dislocations. The current quality of the 6H SI and 4H n+ crystals grown at II-VI is summarized.

scholarly journals Electrical resistivity tomography applied to geologic, hydrogeologic, and engineering investigations at a former waste-disposal site

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. B231-B239 ◽  
Author(s):  
Jonathan E. Chambers ◽  
Oliver Kuras ◽  
Philip I. Meldrum ◽  
Richard D. Ogilvy ◽  
Jonathan Hollands
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Site Investigation ◽  
High Resistivity ◽  
Potential Zone ◽  
Resistivity Tomography ◽  
L2 Norm ◽  
Resistivity Model ◽  
2D And 3D ◽  
2D Resistivity

A former dolerite quarry and landfill site was investigated using 2D and 3D electrical resistivity tomography (ERT), with the aims of determining buried quarry geometry, mapping bedrock contamination arising from the landfill, and characterizing site geology. Resistivity data were collected from a network of intersecting survey lines using a Wenner-based array configuration. Inversion of the data was carried out using 2D and 3D regularized least-squares optimization methods with robust (L1-norm) model constraints. For this site, where high resistivity contrasts were present, robust model constraints produced a more accurate recovery of subsurface structures when compared to the use of smooth (L2-norm) constraints. Integrated 3D spatial analysis of the ERT and conventional site investigation data proved in this case a highly effective means of characterizing the landfill and its environs. The 3D resistivity model was successfully used to confirm the position of the landfill boundaries, which appeared as electrically well-defined features that corresponded extremely closely to both historic maps and intrusive site investigation data. A potential zone of leachate migration from the landfill was identified from the electrical models; the location of this zone was consistent with the predicted direction of groundwater flow across the site. Unquarried areas of a dolerite sill were imaged as a resistive sheet-like feature, while the fault zone appeared in the 2D resistivity model as a dipping structure defined by contrasting bedrock resistivities.

scholarly journals DC resistivity investigation in a fractured aquifer system contaminated by leachate from an old dump

2017 ◽  
Vol 56 (4) ◽  
Author(s):  
César Augusto Moreira ◽  
Carolina Gonçalves Leandro ◽  
Camila Trindade Lopes ◽  
Lenon Melo Ilha
Keyword(s):  
Federal Law ◽  
Fractured Aquifer ◽  
Geophysical Investigation ◽  
Resistivity Tomography ◽  
Aquifer System ◽  
Monitoring Wells ◽  
Sanitary Landfills ◽  
3D Processing ◽  
Environmental Agencies ◽  
2D And 3D

The dumps are areas of final disposal of solid wastes directly into the soil, with no technical criteria or collecting systems of gases or liquids. A large part of Brazilian municipalities have used this extreme damaging alternative to the environment up to the year 2010, when a federal law made compulsory the installation of sanitary landfills. However, large parts of the dumps were simply abandoned, although some eventually go through treatment after assessments of the state environmental agencies. This work presents the results of a geophysical investigation in a dump deactivated in 2004 in a small city in southern Brazil, where previous investigations have revealed contamination of soil and groundwater by leachate. Structural analyzes in the area of study combined to geological data from monitoring wells indicate the presence of contaminants in fractured granite, with a wide variation in the thickness of soil, saprolite and groundwater level. The integration of chemical analyses of the groundwater with electrical resistivity tomography (ERT) in 2D and 3D processing, revealed the existence of large contaminated areas within the limits of the dump flowing into the aquifer partially free up to 5m depth. Such areas may decrease gradually with the increase in depth and between 9m and 19m contaminated zones clearly predominate, associated with the flow in the fractured aquifer. The indication of restricted and oriented zones suggests the targeting and accumulation of contaminants in two systems of preferential fractures. The discovery of these zones is fundamental for planning and the installation of pumping and decontamination systems of groundwater, considering a declining production of leachate since the closure of the dump.

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