Glennie K.W.,University of Aberdeen |
Fryberger S.G.,Petroleum Development Oman |
Hern C.,Royal Dutch Shell |
Lancaster N.,Desert Research Institute |
And 4 more authors.
Geochronometria | Year: 2011
In the Wahiba Sands of eastern Oman, luminescence dating of sands enables us to relate wind activity to climatic variations and the monsoon cycle. These changes resulted from Polar gla-cial/interglacial cyclicity and changes in global sea levels and wind strengths. Luminescence dates show that development of the Sands began over 230 ka ago when the sand-driving winds were the lo-cally arid, northward-blowing SW Monsoon. During late Quaternary low sea levels, the Tigris-Euphrates river system flowed across the floor of the Persian/Arabian Gulf to the Gulf of Oman SE of the Strait of Hormuz. OSL-dated sands contain-ing calcareous bioclastic fragments deflated from the exposed Gulf floor during glacial low-water pe-riods indicate that during the last glacial cycle, and at least one earlier cycle (~120-200 ka and possi-bly as far back as 291 ka), the floor of the Arabian Gulf was exposed. This is deduced from the pres-ence of aeolian dune sands containing bioclastic detritus on the coastal plain of the Emirates and south into Al Liwa (Abu Dhabi), which were built by northern "Shamal" winds. Those calcareous sands now locally overlie sabkhas formed during interglacial high sea levels. Within the present in-terglacial, marine flooding of the Gulf occurred between about 12 and 6 ka. © 2011 Silesian University of Technology, Gliwice, Poland. All rights reserved.
Madan M.M.,NHPC Ltd
Water and Energy International | Year: 2015
During tunnel execution encountering of thrust zones, shear zones, fracture zones, fluvioglacial material, sandy, silty or clayey strata, overburden material is very common. This type of strata makes tunnelling extremely challenging. Over and above encountering of seepage water creates flowing ground conditions and makes worst tunnelling conditions for excavation of underground structures. Tunnelling becomes very difficult and slow. By adopting new methods like Ground Freezing, Pre Grouting of Face with New Materials, Fibre Shotcreting with new materials and roof protection the weak strata can be strengthened inherently. The Paper deals with various new methods and new materials for controlling the weak zones and successful tunnelling. © 2015, Central Board of Irrigation and Power. All rights reserved.
Kumar R.,NHPC Ltd
Water and Energy International | Year: 2015
In a span of more than 100 years since the first hydro project was commissioned in India, phenomenon progress has been made on exploitation of water power potential. As a part of national policy on hydro development, renovation, modernization and operation of old hydro power plants is being accorded priority. This being a faster and cheaper way of capacity addition than installing new capacity. As per global experience, 10-15% capacity addition can be achieved by simply encroaching upon overload margins, safety factors. Capacity addition up to 30% is achievable by changing the F-class insulation of the stator and by changing the Hydraulic profile of the runner and capacity addition up to 50% is achievable by changing the complete unit and retaining only embedded parts and some major foundation components of the generator. In India, 150 such hydro schemes with an aggregate capacity of 27000.3 MW having expected benefit of 7282.76 MW already been identified for renovation, modernization and capacity addition. Out of these 95 hydro schemes with an aggregate capacity of 17247.9 MW have been completed providing a benefit of 3317.4 MW, 11 hydro schemes with an aggregate capacity of 1665.9 MW having expected benefit of 965.3 MW is under implementation, 17 hydro schemes with an aggregate capacity of 2981.75 MW having expected benefit of 1319.95 MW is under tendering, 13 hydro schemes with an aggregate capacity of 2225.75 MW having expected benefit of 1206 MW is under DPR preparation/finalization & approval and 10 hydro schemes with an aggregate capacity of 905 MW having expected benefit of 60 MW is under RLA studies. The paper attempts to discuss about the need of renovation, modernization and capacity addition of hydropower units in Indian context. The paper sets an over all attention to highlight major concept in regard to phenomenon leading to renovation, refurbishment and quick capacity addition cost effectively. © 2015, Central Board of Irrigation and Power. All rights reserved.
Dhawan G.,NHPC Ltd |
Patni B.D.,NHPC Ltd
Water and Energy International | Year: 2012
The understanding of hill slope stability in the construction of hydro project depends upon the realistic approach of Geological investigation & cautious construction procedure. The careful appraisal and analysis of geotechnical data helps to chalk out the strategies for coping with various slope failures. Excavation of 150m high spillway cut slope of Dhauliganga project experienced various geotechnical problems due to complex geological setup and adverse topographical conditions. With successful application of state of the art technology, the problems were conquered with success. The high angle spillway cut slope necessitated with progressive change in the design of spillway by reducing its width and utilization of diversion tunnel as spillway tunnel. For the first time in Himalayan terrain, a reinforced anchored drift was constructed to stabilize the vulnerable spillway cutslope. The present paper deals with the several geological problems faced during the excavation of 150m high spillway cut slope of 280 MW Dhauliganga Project, St-I (Uttarakhand) and its remedial measures.
Patni B.D.,NHPC Ltd |
Walvekar A.S.,NHPC Ltd |
Chakraborty A.,NHPC Ltd
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014
With the rapid growth of urbanization, the wide gap between demand and supply of power in the country has necessitated putting an increased thrust towards development of hydroelectric projects particularly in geologically complex Himalayan terrain. Tunnelling in Himalaya is undoubtedly the most challenging activity in hydro power construction. The hydropower tunnelling works in India were mostly accomplished by conventional drilling and blasting methods resulting in time and cost overruns. Now, while the focus is on faster completion of projects, need for an advanced technology more particularly in tunnelling is being felt. As a consequence, use of TBM has gained importance in hydropower tunnelling for being a more dependable alternative to drill & blast method. However, the ability of TBM to cope with varying ground conditions in Himalaya has posed a question mark in utility of this machine. The weak, jointed, sheared/fractured rock mass of Himalaya, under high stresses and potential confined aquifers, pose a major challenge to tunnelling engineers. The initial experience with TBM in Dulhasti Project (India) was not encouraging as TBM got submerged and ultimately buried which was partly attributed to unexpected ingress of water. Similarly, in Parbati-II and Tapovan Vishnugad Projects (India), excavation of HRT by TBM faced severe difficulties. However, success was achieved in excavation of inclined pressure shaft by a double shield TBM in Parbati-II Project. Presently, successful construction of 14.7km of HRT in Kishanganga Project (India) by double shield TBM has established TBM technology as a viable alternative for execution of long tunnels in Himalayas. The paper presents a brief account of the geological and geohydrological problems faced in some of the TBM driven hydropower tunnels in India, lessons learnt from them and prospects and the future challenges to be faced in TBM driven Himalayan tunnels. © 2014 by Japanese Committee for Rock Mechanics.
Sen A.,NHPC Ltd |
Nagar V.,NHPC Ltd |
Singh M.P.,NHPC Ltd
Water and Energy International | Year: 2011
Presence of palaeochannels pose serious concern in development of hydropower schemes. The foreknowledge of existence of such buried channels is important in establishing secure and economic projects. Accordingly, it necessitates initiating a well-considered subsurface investigation plan, involving application of indirect technique of engineering geophysics towards optimizing the direct exploration program in view of restricted time-frame and finance. Of the various engineering geophysical methods, the seismics refraction is a prime cost-effective exploration technique in furnishing continuous profile of the underground status. The paper aims to highlight utility of seismic refraction technique as an efficient subsurface exploratory tool for delineation of palaeochannel in a hydropower project. Detailed account of utilization of seismic refraction survey in delineating palaeochannels through generation of 2-D/ 3-D model defining the bedrock disposition is presented herein, citing a couple of case studies demonstrating its advantageous usage.
Dabral S.,NHPC Ltd. |
Bhatt B.,M. S. University of Baroda |
Joshi J.P.,M. S. University of Baroda |
Sharma N.,M. S. University of Baroda
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2014
Groundwater quality in Gujarat state is highly variable and due to multiplicity of factors viz. influenced by direct sea water encroachment, inherent sediment salinity, water logging, overexploitation leading to overall deterioration in ground water quality, coupled with domestic and industrial pollution etc. The groundwater scenario in the state is not very encouraging due to imbalance between recharge and groundwater exploitation. Further, the demand for water has increased manifold owing to agricultural, industrial and domestic requirement and this has led to water scarcity in many parts of the state, which is likely to become more severe in coming future due to both natural and manmade factors. Therefore, sustainable development of groundwater resource requires precise quantitative assessment based on reasonably valid scientific principles. Hence, delineation of groundwater potential zones (GWPZ), has acquired great significance. The present study focuses on the integrated Geospatial and Multi-Criteria Decision Making (MCDM) techniques to determine the most important contributing factors that affect the groundwater resources and also to delineate the potential zones for groundwater recharge. The multiple thematic layers of influencing parameters viz. geology, geomorphology, soil, slope, drainage density and land use, weightages were assigned to the each factor according to their relative importance as per subject experts opinion owing to the natural setup of the region. The Analytical Hierarchy Process (AHP) was applied to these factors and potential recharge zones were identified. The study area for the assessment of groundwater recharge potential zones is Mahi-Narmada inter-stream region of Gujarat state. The study shows that around 28% region has the excellent suitability of the ground water recharge.
Sen A.,NHPC Ltd
Water and Energy International | Year: 2013
In view of restricted time-frame and finance, establishing safe and economic hydropower schemes necessitates a planned approach towards a comprehensive investigation program involving both direct and indirect techniques. Besides the involvement of drilling, drifting as well as geological, geotechnical studies and other allied studies, it is important to apply state-of-the-art geophysical techniques during various stages of the project. The paper elaborates planned utility of the prime techniques of engineering geophysics in subsurface exploration and site characterization during Pre-feasibility, Feasibility, Detailed Investigation (DPR) and Pre-construction stages of the project towards minimizing geological uncertainties: The proposed extensive application of engineering geophysics during the various stage, with intent of avoiding the practice of carrying forward the application of geophysics to the Construction stage, shall facilitate the project execution with due level of confidence, within schedule and optimum involvement of direct exploration.
Singh N.,NHPC Ltd. |
Kumar R.,NHPC Ltd. |
Chaudhary J.,NHPC Ltd.
Water and Energy International | Year: 2010
Generator step up transformers are used for voltage transformation at generating power stations. Special care is to be given in designing and manufacturing of generator step up transformers of hydroelectric power stations due to location of these transformers at the remote end of long transmission lines where system voltage drops down upto 20-25% of normal system voltage during peak hours. At one of NHPC's Power Station four generator step up transformers failed in the year of 2004. This paper deals on the technical aspects that are to be considered while designing and manufacturing of generator step up transformers for hydroelectric power stations on the basis of reasons of failure of transformers to avoid failure of transformers in future.
Gahalaut V.K.,National Center for Seismology |
Martin S.S.,Nanyang Technological University |
Srinagesh D.,CSIR - Central Electrochemical Research Institute |
Kapil S.L.,NHPC Ltd |
And 11 more authors.
Tectonophysics | Year: 2016
The 2016 Mw 6.7 Tamenglong earthquake (in the state of Manipur in northeastern India) on 4 January 2016 at 04:35 Indian Standard Time (3 January, 23:05 UTC) was the strongest earthquake to strike Manipur since 1988. Using data from Indian stations, we constrain the hypocentral depth of the mainshock at 59 ± 3.8 km and determine a strike-slip mechanism with a moderate reverse component on a steeply dipping plane. Though coseismic offsets from GPS measurements from four nearby sites were inadequate to provide further constraints on the focal mechanism, they were consistent with the magnitude and hypocentral depth of the earthquake. The epicentre of the mainshock was located 15-km west of the Churachandpur Mao Fault (CMF) but it was unrelated to this structure and was instead a typical intra-slab earthquake within the Indian plate. A strong motion instrument at the Loktak Power Station (LOK), 56-km from the epicentre, recorded a peak ground acceleration (PGA) of 0.027g while a PGA of 0.103g was recorded at Shillong (SHL) at an epicentral distance of 111-km. We also present macroseismic observations from 461 locations in north-eastern India and the adjacent areas for this earthquake. The highest intensities (~7 EMS) were observed in the Manipur Valley and in the hills to the west while shaking was perceptible as far as Delhi and Jaipur. Lastly, we present a catalogue of 333 felt earthquakes in Manipur from 1588 ± 1 CE to 1955 derived from the royal chronicle of the kings of Manipur known as the Cheitharon Kumpapa, discuss important historical earthquakes in the region, and also estimate intensity magnitudes for the 1852 (MI 6.5 ± 0.8), 1869 (MI 7.1 ± 0.7), 1880 (MI 6.3 ± 0.7) and 2016 (MI 6.8 ± 0.8) earthquakes. © 2016 Elsevier B.V.