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Krishna Kanta Panthi - One of the best experts on this subject based on the ideXlab platform.

  • a dynamic analysis of in situ stress state at the upper tamakoshi hydroelectric project area
    Hydro Nepal: Journal of Water Energy and Environment, 2018
    Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur Basnet
    Abstract:

    The in-situ stress condition in the rock mass is influenced by both tectonic and geological Environment, such as faulting and shearing in the rock mass. This influence is of considerable magnitude in the Himalayan region where the tectonic movement is active, resulting periodic dynamic earthquakes. Each large-scale earthquake causes both accumulation and sudden release of strain energy instigating changes in the in-situ stress Environment in the rock mass. This paper evaluates the influence of local shear fault on the in-situ stress state along the shot crete lined high pressure tunnel of Upper Tamakoshi Hydroelectric Project, 456 MW in Nepal. A detailed assessment of the in-situ stress state is carried out by using both; measured data and three-dimensional numerical analysis using FLAC3D. The analysis includes evaluation on the possible changes in the in-situ stress state in the rock mass caused by seismic activities (dynamic loading). HYDRO Nepal JournalJournal of Water, Energy and Environment Issue: 23Year: 2018

  • Methods Applied in the Prediction of Brittle Failure in Tunnels and Underground Caverns
    Hydro Nepal: Journal of Water Energy and Environment, 2018
    Co-Authors: Krishna Kanta Panthi
    Abstract:

    Tunnels and underground caverns located at greater depth (high rock cover or overburden) are subjected to high in-situ stress Environment. Those rock mass that are relatively unjointed and massive are exposed to the brittle failure, which is famously known as rock spalling/ rock bursting phenomenon. Establishing state of the stress and evaluating stress-induced instability in tunnels passing through such rock mass at relatively greater depth is therefore a challenge. The aim of this manuscript is to describes existing brittle failure (rock burst) prediction methods that are being practiced worldwide and propose necessary editions so that quality of assessment is enhanced. The methods described are very practical and the author is confident that professional engineers will use them to evaluate and predict potential rock burst/ rock spalling scenario in the tunnels during planning, design and construction phases. Each method of prediction is explained, applicability extent is highlighted and comparisons between the methods are made. HYDRO Nepal Journal Journal of Water Energy and Environment Issue No: 22 Page: 5-9 Uploaded date: January 14, 2018

  • 3D in-Situ Stress Model of Upper Tamakoshi Hydroelectric Project Area
    Hydro Nepal: Journal of Water Energy and Environment, 2017
    Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta Panthi
    Abstract:

    Reliable estimation of in-situ stress state is very important in implementing the shotcrete lined/ unlined tunnels and shafts. The in-situ stress state of the area of concern is mainly governed by the gravity-induced stress, tectonic activity of the earth’s crust and topographic condition of that area. The local tectonic and geological Environment such as faulting and shearing activities in general influences the magnitude of tectonic stress level. The Himalayan region is renowned with its active tectonic movement (earthquake activities), which causes accumulation and sudden release of strain energy instigating changes in the stress Environment. This paper aims to evaluate in-situ stress state at the Upper Tamakoshi Hydroelectric Project, where shotcrete lined/ unlined headrace tunnel with considerable hydrostatic head is being implemented. A detailed assessment of the in-situ stress state is carried out by using both measured data and three-dimensional numerical analysis using FLAC3D. HYDRO Nepal Journal Journal of Water Energy and Environment Issue: 21, July, 2017 Page: 34-41 Upload Date: July 18, 2017

  • estimating tunnel strain in weak and schistose rock mass under a state of in situ stress anisotropy
    Hydro Nepal: Journal of Water Energy and Environment, 2015
    Co-Authors: Pawan Kumar Shrestha, Krishna Kanta Panthi
    Abstract:

    Tunnels excavated in weak and schistose rock mass below high overburden (rock cover) are prone to instability in the form of tunnel deformation. The deformation in the tunnel takes place to such an extent that it is irreversible and of significant magnitude, which is often known as tunnel squeezing. In order to limit such plastic deformation in tunnels, it is desirable that the response of the rock mass to induced stresses is known so that requirement of rock support can be estimated. Contrary to the assumption of uniform in-situ stresses made in analytical solutions for elasto-plastic analyses, large degree of stress anisotropy condition prevails in most tunnelling conditions. The effect of such anisotropic stress condition leads to varying degrees of deformations around the tunnel contour. Therefore, stress anisotropy is also an important factor that needs to be addressed to ensure a proper support design for tunnels. This paper discusses the inter-relationship among rock mass property, in-situ stresses including horizontal to vertical stress ratio, tunnel support pressure and deformation. The study is based on the tunnel cases from the Nepal Himalaya. Three completed tunnel projects were selected, where moderate to large tunnel deformations had been recorded. Long term deformation records were analyzed to assess time independent and time dependent deformations. Results of the analyses of the tunnels in weak and schistose rock mass at stress anisotropy states show that a good correlation among tunnel strain, rock mass shear modulus, support pressure, vertical stress and stress ratio of horizontal to vertical stresses exists. Moreover, the study also shows that significant amount of time dependent deformation can occur in such weak rock mass. Such deformation was found to be high in schist and micaceous phyllite, moderate in graphitic phyllite and low in siliceous phyllite. The suggested relationships can be used as a basis for an early estimate of instantaneous and final deformations and the corresponding requirement of support pressures in tunnel walls in weak and schistose rock mass. DOI: http://dx.doi.org/10.3126/hn.v16i0.12212 HYDRO Nepal  Journal of Water Energy and Environment Issue. 16 , 2015 January Page: 7-13 Upload date: March 1, 2015

Chhatra Bahadur Basnet - One of the best experts on this subject based on the ideXlab platform.

  • a dynamic analysis of in situ stress state at the upper tamakoshi hydroelectric project area
    Hydro Nepal: Journal of Water Energy and Environment, 2018
    Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur Basnet
    Abstract:

    The in-situ stress condition in the rock mass is influenced by both tectonic and geological Environment, such as faulting and shearing in the rock mass. This influence is of considerable magnitude in the Himalayan region where the tectonic movement is active, resulting periodic dynamic earthquakes. Each large-scale earthquake causes both accumulation and sudden release of strain energy instigating changes in the in-situ stress Environment in the rock mass. This paper evaluates the influence of local shear fault on the in-situ stress state along the shot crete lined high pressure tunnel of Upper Tamakoshi Hydroelectric Project, 456 MW in Nepal. A detailed assessment of the in-situ stress state is carried out by using both; measured data and three-dimensional numerical analysis using FLAC3D. The analysis includes evaluation on the possible changes in the in-situ stress state in the rock mass caused by seismic activities (dynamic loading). HYDRO Nepal JournalJournal of Water, Energy and Environment Issue: 23Year: 2018

  • 3D in-Situ Stress Model of Upper Tamakoshi Hydroelectric Project Area
    Hydro Nepal: Journal of Water Energy and Environment, 2017
    Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta Panthi
    Abstract:

    Reliable estimation of in-situ stress state is very important in implementing the shotcrete lined/ unlined tunnels and shafts. The in-situ stress state of the area of concern is mainly governed by the gravity-induced stress, tectonic activity of the earth’s crust and topographic condition of that area. The local tectonic and geological Environment such as faulting and shearing activities in general influences the magnitude of tectonic stress level. The Himalayan region is renowned with its active tectonic movement (earthquake activities), which causes accumulation and sudden release of strain energy instigating changes in the stress Environment. This paper aims to evaluate in-situ stress state at the Upper Tamakoshi Hydroelectric Project, where shotcrete lined/ unlined headrace tunnel with considerable hydrostatic head is being implemented. A detailed assessment of the in-situ stress state is carried out by using both measured data and three-dimensional numerical analysis using FLAC3D. HYDRO Nepal Journal Journal of Water Energy and Environment Issue: 21, July, 2017 Page: 34-41 Upload Date: July 18, 2017

Katrin Vorkamp - One of the best experts on this subject based on the ideXlab platform.

  • an overlooked Environmental Issue a review of the inadvertent formation of pcb 11 and other pcb congeners and their occurrence in consumer products and in the Environment
    Science of The Total Environment, 2016
    Co-Authors: Katrin Vorkamp
    Abstract:

    Polychlorinated biphenyls (PCBs) are banned from production and use in most countries as they are persistent organic pollutants (POPs) of concern for Environment and health. Recent research has pointed at a new Environment Issue resulting from the inadvertent formation of PCBs in certain processes, in particular the pigment production. PCB-11 is a major by-product in these processes, but PCB-28, PCB-52, PCB-77 as well as the nonachlorinated PCBs and PCB-209 have been found in pigments and consumer products as well. In addition to Environmental emissions via point sources, in particular related to industrial and municipal wastewater, atmospheric transport seems to be important for the global distribution of PCB-11. Thus, PCB-11 has also been detected in the polar regions. Worldwide air concentrations appear relatively uniform, but maxima have been found in urban and industrialised areas. Data on the uptake and accumulation of PCB-11 in the food chain are still inconclusive: Although food web studies do not show biomagnification, PCB-11 has been detected in humans. The human exposure might originate from the direct contact to consumer products as well as from the omnipresence of PCB-11 in the Environment.

Helmut Volger - One of the best experts on this subject based on the ideXlab platform.

  • ICAO – International Civil Aviation Organization
    A Concise Encyclopedia of the United Nations, 2010
    Co-Authors: Helmut Volger
    Abstract:

    The International Civil Aviation Organization (ICAO) was established by the Convention on International Civil Aviation signed in Chicago on 7 December 1944, known as the Chicago Convention. The ICAO has dealt with Environmental Issues since the 1960s, when the growing number of jet aircraft caused severe noise problems for the people in the vicinity of the airports, and in the early 1970s the first ICAO noise standards were established. The Environmental impact of international aviation exhaust emissions came later into the focus of the ICAO: it was in the year 1981 that ICAO Standards were adopted setting limits for the emission of smoke and gaseous pollutants from aircraft engines. The Environment Issue reveals once again the conflict over values and methods between the more technically oriented and in economic terms neo-liberally minded specialized agencies and the UN funds representing a stronger value orientation in terms of common responsibility and solidarity. Keywords: international air navigation; International Civil Aviation Organization (ICAO); UN

  • icao international civil aviation organization
    2010
    Co-Authors: Helmut Volger
    Abstract:

    The International Civil Aviation Organization (ICAO) was established by the Convention on International Civil Aviation signed in Chicago on 7 December 1944, known as the Chicago Convention. The ICAO has dealt with Environmental Issues since the 1960s, when the growing number of jet aircraft caused severe noise problems for the people in the vicinity of the airports, and in the early 1970s the first ICAO noise standards were established. The Environmental impact of international aviation exhaust emissions came later into the focus of the ICAO: it was in the year 1981 that ICAO Standards were adopted setting limits for the emission of smoke and gaseous pollutants from aircraft engines. The Environment Issue reveals once again the conflict over values and methods between the more technically oriented and in economic terms neo-liberally minded specialized agencies and the UN funds representing a stronger value orientation in terms of common responsibility and solidarity. Keywords: international air navigation; International Civil Aviation Organization (ICAO); UN

Bhola Thapa - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of Sediment Samples and Erosion Potential: A Case Study of Upper Tamakoshi Hydroelectric Project
    Hydro Nepal: Journal of Water Energy and Environment, 2015
    Co-Authors: Ravi Koirala, Surya Nath Regmi, Manisha Khadka, Hari Prasad Neopane, Sailesh Chitrakar, Bhola Thapa
    Abstract:

    Hydropower can be an effective green solution for meeting the current energy demand in Nepal. However, despite having tremendous water resources, only 2% of Nepal’s hydroelectricity potential has been tapped. Of the challenges that Nepali hydro faces, sediment erosion is a major one. Sediment erosion refers to an erosive tendency of sediment particles flowing with water over the exposed turbine parts including the runner. This paper deals with a sample analysis of sediment particles from the Upper Tamakoshi Hydroelectric Project. In this paper, we test for particle size distribution, particle count, mineral composition, and erosion potential analysis. For the mineral and erosion potential analysis, the sand samples range from 75 im to 200 im because the Tamakoshi plant consists of sediment traping system for particles larger than 150 im. The sediment samples were collected from three different points in the headrace and the severity of the effect of erosion has been analyzed in terms of depending variables like particle size, concentration, and mineral composition. DOI: http://dx.doi.org/10.3126/hn.v16i0.12216 HYDRO Nepal  Journal of Water Energy and Environment Issue. 16, 2015, January Page: 28-31 Upload date: March 1, 2015

  • Optimized Design of Francis Turbine Runner for Sand Laden Water
    Hydro Nepal: Journal of Water Energy and Environment, 2014
    Co-Authors: Krishna Prasad Shrestha, Hari Prasad Neupane, Nikhel Gurung, Bhola Thapa, Ole Gunnar Dahlhaug, Aatma Ram Kayastha
    Abstract:

    Nepal has an enormous amount of water resources and the topography gives rise to a huge hydropower potential. Out of 83,000 MW, only about 43,000 MW is economically and technically feasible. However, rivers of Nepal contain heavy quantities of sand particles. This is why the hydropower plants of this region face severe sand erosion problem.      Erosion mechanism in hydropower is a complex phenomenon. It is a major technological challenge for R-O-R (Run off river) hydropower plants. There are several technologies to reduce erosion but none of them has proven to be economically viable. The hydraulic design of the turbine with a new design philosophy expected to reduce sand erosion considerably and this process is economic too. This paper describes the alternative optimized design of Francis turbine runner for large sediment load. The process involves optimization to obtain specific Francis runner blade using not defined ANSYS CFX parametric study. The process also includes analysis of the runner blade using CFX parametric study and Fluid structure interaction simulation for specific blade design. Design and drafting of the runner and part model design for FSI (Fluid Structure Interaction) analysis have also been described. DOI: http://dx.doi.org/10.3126/hn.v13i0.10038 HYDRO NEPAL Journal of Water, Energy and Environment Issue No. 13, July 2013 Page: 36-43 Uploaded date: 3/13/2014