Imprints of long-range-transported pollution on high-altitude Eastern Himalayan lake water chemistry     

Jyoti Prakash Deka  Sangeeta Singh  Pawan Kumar Jha  Umesh Kumar Singh  Manish Kumar 《Environmental Earth Sciences》2016,75(4):285

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Study of Strain Rate and Thermal Damage of Dholpur Sandstone at Elevated Temperature   总被引：1，自引：0，他引：1  

P. K. Gautam  A. K. Verma  M. K. Jha  K. Sarkar  T. N. Singh  R. K. Bajpai 《Rock Mechanics and Rock Engineering》2016,49(9):3805-3815

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A locally conservative finite element framework for the simulation of coupled flow and reservoir geomechanics     

Birendra Jha  Ruben Juanes 《Acta Geotechnica》2007,2(3):139-153

In this paper, we present a computational framework for the simulation of coupled flow and reservoir geomechanics. The physical model is restricted to Biot’s theory of single-phase flow and linear poroelasticity, but is sufficiently general to be extended to multiphase flow problems and inelastic behavior. The distinctive technical aspects of our approach are: (1) the space discretization of the equations. The unknown variables are the pressure, the fluid velocity, and the rock displacements. We recognize that these variables are of very different nature, and need to be discretized differently. We propose a mixed finite element space discretization, which is stable, convergent, locally mass conservative, and employs a single computational grid. To ensure stability and robustness, we perform an implicit time integration of the fluid flow equations. (2) The strategies for the solution of the coupled system. We compare different solution strategies, including the fully coupled approach, the usual (conditionally stable) iteratively coupled approach, and a less common unconditionally stable sequential scheme. We show that the latter scheme corresponds to a modified block Jacobi method, which also enjoys improved convergence properties. This computational model has been implemented in an object-oriented reservoir simulator, whose modular design allows for further extensions and enhancements. We show several representative numerical simulations that illustrate the effectiveness of the approach.  相似文献   

Assessment of Ground Water Quality with Respect to Bacteriological Contamination in Bhavnagar,Gujarat, India          下载免费PDF全文

Mittal Patel  Krushnakant Baxi  Paras Dayma  Devang Upadhyay  Navalsang Parmar  Soumya Haldar  Bhavanath Jha 《洁净——土壤、空气、水》2014,42(10):1351-1362

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Detection and delineation of glacial lakes and identification of potentially dangerous lakes of Dhauliganga basin in the Himalaya by remote sensing techniques     

Lalan Kumar Jha  Deepak Khare 《Natural Hazards》2017,85(1):301-327

Glaciers are retreating and thinning in the high altitude of the Himalayas due to global warming, causing into formation of numerous glacial lakes. It is necessary to monitor these glacial lakes consistently to save properties and lives downstream from probable disastrous glacial lake outburst flood. In this study, image processing software ArcGIS and ERDAS Imagine have been used to analyse multispectral image obtained by Earth resource satellite Landsat for delineating the glacial lakes with the help of image enhancement technique like NDWI. Landsat data since 1972 through 2013 have been used and maximum seven glacial lakes (L1–L7) have been detected and delineated in Dhauliganga catchment, they are situated above 4000 masl. The Glacial Lake L2 (Lat 30°26′45″E and Long 80°23′16″N) is the largest whose surface area was 132,300 m² in Sept 2009, and L6 (Lat 30°23′27″E and Long 80°31′52″N) is highly unstable with variation rate ?55 to +145 % with increasing trend. Additionally, glacial lakes L2 (Lat 30°26′45″E and Long 80°23′16″N) and L6 (Lat 30°23′27″E and Long 80°31′52″N) have been identified as potentially hazardous. These lakes may probably burst; as a result, huge reserve of water and debris may be released all on a sudden. This may transform into hazardous flash flood in downstream causing loss of lives, as well as the destruction of houses, bridges, fields, forests, hydropower stations, roads, etc. It is to note that Dhauliganga river considered in this study is a tributary of Kaliganga river, and should not be confused with its namesake the Dhauliganga river, which is a tributary of Alaknanda river.  相似文献   

Study of mechanical properties of Vindhayan shaly rocks at elevated temperature     

Manish Kumar Jha  A. K. Verma  Pradeep Kumar Gautam  Anil Negi 《Journal of the Geological Society of India》2017,90(3):267-272

Shale is an important rock due to its suitability for different engineering and scientific applications. Elevated temperature may cause major deformation or damage in shale rock and it may be of irreversible in nature. Such damage have adverse effect on the physicomechnical properties of shale rock. The uniaxial compressive strength and tensile strength of two shales (upper Vindhyan basin, India) have been estimated at elevated temperature using point load strength index method. The rock samples have been analyzed at various temperatures starting from room temperature to 900 °C. The effect of elevated temperature on the physicomechanical properties and their influence on the uniaxial compressive strength has been studied in detail. Damage induced, in both shale have been estimated using compressional wave velocity. The analysis of the experimental result shows that the uniaxial compressive strength decreases from 63.45 to 18.45 MPa and 60.94 to 22.22 MPa, for Jhiri and Ganurgarh shale respectively. Tensile strength of shales have been also estimated. The value of tensile strength decreases from 3.65 to 1.05 MPa and 3.46 to 1.26 MPa respectively for Jhiri and Ganurgarh shale. Multivariate regression analysis has been carried out to obtain the correlation between physicomechanical properties and uniaxial compressive strength of Jhiri and Ganurgarh shale.  相似文献   

Evaluation of the Soil Conservation Service curve number methodology using data from agricultural plots   总被引：1，自引：0，他引：1  

Mohan Lal  S. K. Mishra  Ashish Pandey  R. P. Pandey  P. K. Meena  Anubhav Chaudhary  Ranjit Kumar Jha  Ajit Kumar Shreevastava  Yogendra Kumar 《Hydrogeology Journal》2017,25(1):151-167

The Soil Conservation Service curve number (SCS-CN) method, also known as the Natural Resources Conservation Service curve number (NRCS-CN) method, is popular for computing the volume of direct surface runoff for a given rainfall event. The performance of the SCS-CN method, based on large rainfall (P) and runoff (Q) datasets of United States watersheds, is evaluated using a large dataset of natural storm events from 27 agricultural plots in India. On the whole, the CN estimates from the National Engineering Handbook (chapter 4) tables do not match those derived from the observed P and Q datasets. As a result, the runoff prediction using former CNs was poor for the data of 22 (out of 24) plots. However, the match was little better for higher CN values, consistent with the general notion that the existing SCS-CN method performs better for high rainfall–runoff (high CN) events. Infiltration capacity (fc) was the main explanatory variable for runoff (or CN) production in study plots as it exhibited the expected inverse relationship between CN and fc. The plot-data optimization yielded initial abstraction coefficient (λ) values from 0 to 0.659 for the ordered dataset and 0 to 0.208 for the natural dataset (with 0 as the most frequent value). Mean and median λ values were, respectively, 0.030 and 0 for the natural rainfall–runoff dataset and 0.108 and 0 for the ordered rainfall–runoff dataset. Runoff estimation was very sensitive to λ and it improved consistently as λ changed from 0.2 to 0.03.  相似文献   

Pattern recognition in lithology classification: modeling using neural networks,self-organizing maps and genetic algorithms     

Sasmita Sahoo  Madan K. Jha 《Hydrogeology Journal》2017,25(2):311-330

Effective characterization of lithology is vital for the conceptualization of complex aquifer systems, which is a prerequisite for the development of reliable groundwater-flow and contaminant-transport models. However, such information is often limited for most groundwater basins. This study explores the usefulness and potential of a hybrid soft-computing framework; a traditional artificial neural network with gradient descent-momentum training (ANN-GDM) and a traditional genetic algorithm (GA) based ANN (ANN-GA) approach were developed and compared with a novel hybrid self-organizing map (SOM) based ANN (SOM-ANN-GA) method for the prediction of lithology at a basin scale. This framework is demonstrated through a case study involving a complex multi-layered aquifer system in India, where well-log sites were clustered on the basis of sand-layer frequencies; within each cluster, subsurface layers were reclassified into four depth classes based on the maximum drilling depth. ANN models for each depth class were developed using each of the three approaches. Of the three, the hybrid SOM-ANN-GA models were able to recognize incomplete geologic pattern more reasonably, followed by ANN-GA and ANN-GDM models. It is concluded that the hybrid soft-computing framework can serve as a promising tool for characterizing lithology in groundwater basins with missing lithologic patterns.  相似文献   

Elevational distribution of butterflies in the Himalayas: a case study from Langtang National Park,Nepal     

Ranjit Pandey  Kapil K. Khadka  Anuj Ghimire  Puja Jha  Umesh Pathak 《山地科学学报》2017,14(7):1384-1390

Mountain ecosystems are relatively more vulnerable to climate change since human induced climate change is projected to be higher at high altitudes and latitudes. Climate change induced effects related to glacial response and water hazards have been documented in the Himalayas in recent years, yet studies regarding species’ response to climate change are largely lacking from the mountains and Himalayas of Nepal. Changes in distribution and latitudinal/altitudinal range shift, which are primary adaptive responses to climate change in many species, are largely unknown due to unavailability of adequate data from the past. In this study, we explored the elevational distribution of butterflies in Langtang Village Development Committee (VDC) of Langtang National park; a park located in the high altitudes of Nepal. We found a decreasing species richness pattern along the elevational gradient considered here. Interestingly, elevation did not appear to have a significant effect on the altitudinal distribution of butterflies at family level. Also, distribution of butterflies in the area was independent of habitat type, at family level. Besides, we employed indicator group analysis (at family level) and noticed that butterfly families Papilionidae, Riodinidae, and Nymphalidae are significantly associated to high, medium and low elevational zone making them indicator butterfly family for those elevational zones, respectively. We expect that this study could serve as a baseline information for future studies regarding climate change effects and range shifts and provide avenues for further exploration of butterflies in the high altitudes of Nepal.  相似文献   

Reliability analysis of soil liquefaction based on standard penetration test   总被引：1，自引：0，他引：1  

Sanjay K. Jha  Kiichi Suzuki 《Computers and Geotechnics》2009

A review of probabilistic and deterministic liquefaction evaluation procedures reveals that there is a need for a comprehensive approach that accounts for different sources of uncertainty in liquefaction evaluations. For the same set of input parameters, different models provide different factors of safety and/or probabilities of liquefaction. To account for the different uncertainties, including both the model and measurement uncertainties, reliability analysis is necessary. This paper presents a review and comparative study of such reliability approaches that can be used to obtain the probability of liquefaction and the corresponding factor of safety. Using a simplified deterministic Seed method, this reliability analysis has been performed. The probability of liquefaction along with the corresponding factor of safety have been determined based on a first order second moment (FOSM) method, an advanced FOSM (Hasofer–Lind) reliability method, a point estimation method (PEM) and a Monte Carlo simulation (MCS) method. A combined method that uses both FOSM and PEM is presented and found to be simple and reliable for liquefaction analysis. Based on the FOSM reliability approach, the minimum safety factor value to be adopted for soil liquefaction analysis (depending on the variability of soil resistance, shear stress parameters and acceptable risk) has been studied and a new design safety factor based on a reliability approach is proposed.  相似文献