Regional-scale landslide activity and landslide susceptibility zonation in the Nepal Himalaya   总被引：1，自引：1，他引：0  

Ranjan Kumar Dahal 《Environmental Earth Sciences》2014,71(12):5145-5164

Landslide susceptibility zonation mapping is a fundamental procedure for geo-disaster management in tropical and sub-tropical regions. Recently, various landslide susceptibility zonation models have been introduced in Nepal with diverse approaches of assessment. However, validation is still a problem. Additionally, the role of various predisposing causative parameters for landslide activity is still not well understood in the Nepal Himalaya. To address these issues of susceptibility zonation and landslide activity, about 4,000 km² area of central Nepal was selected for regional-scale assessment of landslide activity and susceptibility zonation mapping. In total, 655 new landslides and 9,229 old landslides were identified with the study area with the help of satellite images, aerial photographs, field data and available reports. The old landslide inventory was “blind landslide database” and could not explain the particular rainfall event responsible for the particular landslide. But considering size of the landslide, blind landslide inventory was reclassified into two databases: short-duration high-intensity rainfall-induced landslide inventory and long-duration low-intensity rainfall-induced landslide inventory. These landslide inventory maps were considered as proxy maps of multiple rainfall event-based landslide inventories. Similarly, all 9,884 landslides were considered for the activity assessment of predisposing causative parameters. For the Nepal Himalaya, slope, slope aspect, geology and road construction activity (anthropogenic cause) were identified as most affective predisposing causative parameters for landslide activity. For susceptibility zonation, multivariate approach was considered and two proxy rainfall event-based landslide databases were used for the logistic regression modelling, while a relatively recent landslide database was used in validation. Two event-based susceptibility zonation maps were merged and rectified to prepare the final susceptibility zonation map and its prediction rate was found to be more than 82 %. From this work, it is concluded that rectification of susceptibility zonation map is very appropriate and reliable. The results of this research contribute to a significant improvement in landslide inventory preparation procedure, susceptibility zonation mapping approaches as well as role of various predisposing causative parameters for the landslide activity.  相似文献   

Prediction of load displacement response of single piles under uplift load     

Shubhra Goel  Nihar Ranjan Patra 《Geotechnical and Geological Engineering》2007,25(1):57-64

Load displacement response and ultimate resistance of piles in sand under uplift load are predicted by load transfer approach. The pile is divided into number of segments and assigned geometrical and material properties according to actual soil pile situation. The shaft resistance is obtained analytically in accordance with existing studies. The proposed method takes into account the length, diameter and relevant surface characteristics of pile and soil properties. The load displacement characteristics and the value of uplift capacity of vertical piles from field test have been predicted. Reasonable agreement has been found out between predicted and observed values of uplift capacity. Load transfer mechanism is capable of predicting the nonlinear variation of load-displacement response of piles.  相似文献   

Scattering Properties and Composition of Cometary Dust     

Ranjan Gupta  D. B. Vaidya  J. S. Bobbie  Petr Chylek 《Astrophysics and Space Science》2006,301(1-4):21-31

Composition of the Comet dust obtained by the dust impact analyzer on the Halley probes indicated that the comet dust is a mixture of silicate and carbonaceous material. The collected interplanetary dust particles (IDP's) are fluffy and composite, having grains of several different types stuck together. Using discrete dipole approximation (DDA) we study the scattering properties of composite grains. In particular, we study the angular distribution of the scattered intensity and linear polarization of composite grains. We assume that the composite grains are made up of a host silicate sphere/spheroid with the inclusions of graphite. Results of our calculations on the composite grains show that the angle of maximum polarization shifts, and the degree of polarization varies with the volume fraction of the inclusions. We use these results on the composite grains to interpret the observed scattering in cometary dust.  相似文献   

Causes of large-scale landslides in the Lesser Himalaya of central Nepal   总被引：1，自引：0，他引：1  

Shuichi Hasegawa  Ranjan Kumar Dahal  Minoru Yamanaka  Netra Prakash Bhandary  Ryuichi Yatabe  Hideki Inagaki 《Environmental Geology》2009,57(6):1423-1434

Geologically and tectonically active Himalayan Range is characterized by highly elevated mountains and deep river valleys. Because of steep mountain slopes, and dynamic geological conditions, large-scale landslides are very common in Lesser and Higher Himalayan zones of Nepal Himalaya. Slopes along the major highways of central Nepal namely Prithvi Highway, Narayangadh-Mugling Road and Tribhuvan Highway are considered in this study of large-scale landslides. Geologically, the highways in consideration pass through crushed and jointed Kathmandu Nappe affected by numerous faults and folds. The relict large-scale landslides have been contributing to debris flows and slides along the highways. Most of the slope failures are mainly bechanced in geological formations consisting phyllite, schist and gneiss. Laboratory test on the soil samples collected from the failure zones and field investigation suggested significant hydrothermal alteration in the area. The substantial hydrothermal alteration in the Lesser Himalaya during advancement of the Main Central Thrust (MCT) and thereby clay mineralization in sliding zones of large-scale landslide are the main causes of large-scale landslides in the highways of central Nepal. This research also suggests that large-scale landslides are the major cause of slope failure during monsoon in the Lesser Himalaya of Nepal. Similarly, hydrothermal alteration is also significant in failure zone of the large-scale landslides. For the sustainable road maintenance in Nepal, it is of utmost importance to study the nature of sliding zones of large-scale landslides along the highways and their role to cause debris flows and slides during monsoon period.  相似文献   

DEM-Based Analysis of Earthquake-Induced Shallow Landslide Susceptibility   总被引：3，自引：0，他引：3  

Shuichi Hasegawa  Ranjan Kumar Dahal  Toshiaki Nishimura  Atsuko Nonomura  Minoru Yamanaka 《Geotechnical and Geological Engineering》2009,27(3):419-430

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Automated classification of sloan digital sky survey (SDSS) stellar spectra using artificial neural networks     

Mahdi Bazarghan  Ranjan Gupta 《Astrophysics and Space Science》2008,315(1-4):201-210

Automated techniques have been developed to automate the process of classification of objects or their analysis. The large datasets provided by upcoming spectroscopic surveys with dedicated telescopes urges scientists to use these automated techniques for analysis of such large datasets which are now available to the community. Sloan Digital Sky Survey (SDSS) is one of such surveys releasing massive datasets. We use Probabilistic Neural Network (PNN) for automatic classification of about 5000 SDSS spectra into 158 spectral type of a reference library ranging from O type to M type stars.  相似文献   

Evaluation of groundwater resources in wide inundation areas of the Mekong River basin   总被引：2，自引：0，他引：2  

So Kazama  Terumichi Hagiwara  Priyantha Ranjan  Masaki Sawamoto 《Journal of Hydrology》2007,340(3-4):233-243

Severe floods can have disastrous impacts and cause wide ranging destruction in the Mekong River basin. At the same time groundwater resources are significantly influenced and extensively recharged by flood water in inundation areas of the basin. This study determines the variation of groundwater resources caused by flooding over inundated areas located in lower part of the Mekong River basin using numerical modeling and field observations. The inundation calculations have been evaluated using satellite image outputs. Comparing large, medium and small flood events, we conclude that flood control which reduces the area of inundation, results in a reduction of groundwater resources in the area. In 1993, a 19% reduction in inundation areas resulted in a 31% reduction in groundwater storage. In 1998, a 44% reduction in inundation areas led to a 42% reduction in groundwater storage. Thus, while flood control activities are vital to reduce negative flood impacts in the Mekong River basin, they also negatively impact groundwater resources in the area.  相似文献   

Performance of Counterfort Walls with Reinforced Granular and Fly Ash Backfills: Experimental Investigation     

Sutapa Hazra  Nihar  Ranjan Patra 《Geotechnical and Geological Engineering》2008,26(3):259-267

Experimental investigations on model counterfort retaining walls have been carried out to study the lateral movement of the walls and the nature of the failure modes. Mild steel plates of size 1,000 × 900 × 8 mm were used as model retaining walls and were placed in a tank of size 900 × 900 × 670 mm. Ennore sand, obtained from Madras India, and Fly ash, obtained from Panki Thermal Power Plant, India were used as backfill material. Tests were carried out both with and without reinforced backfill. Two types of loading conditions were applied: (i) line load and (ii) uniform surcharge. The shape and size of the failure wedge was studied by observing displacement of bands of colored through a Perspex plate fixed on one side of the tank. Plots of overturning moment against the rotation of a wall top show that with the increase in rotation of wall, the overturning moment decreases. The minimum value of overturning moment is taken as the limiting value. The failure surfaces obtained in different cases are linear and parabolic in shape.  相似文献   

Study of variation of aerosol optical properties over a high altitude station in Indian Western Himalayan region,palampur using raman lidar system     

Singh  Shishir Kumar  Radhakrishnan  S. R.  Jaswant  Mishra  Sumit Kumar  Shukla  Devesh Kumar  Ranjan  Ashish  Sharma  Chhemendra 《Journal of Atmospheric Chemistry》2022,79(2):117-139

A Raman lidar system was operated along with the Microtops sunphotometer measurements to carry out the study of the variation of the optical properties of aerosols over Palampur (32.11° N and 76.53° E), India from 17th April to 11th May 2019. The lidar system is furnished with Raman (N₂) channel and depolarization channel allowing independent measurement of Lidar Ratio (LR) and linear depolarization ratio. The study reveals that the majority of the aerosols approximately were restricted within the planetary boundary layer (PBL) and very less loading was present in the free troposphere over the study location. The particle loading over the study period was found to be very less with aerosol backscatter coefficient (at 355 nm) ranging from ～0.13 Mm^?1sr^?1 to ～7.25 Mm^?1sr^?1 with mean value of 2.67?±?0.82 Mm^?1sr^?1 and it is well supplemented by the mean aerosol optical depth (AOD) of 0.37?±?0.13 obtained from Microtops Sunphotometer. The average lidar ratio values for 0-1 km altitude (L1) 72?±?13sr, for 1-2 km (L2) altitude 55?±?8sr, for 2-3 km (L3) 54?±?15sr were observed as suggesting dominance of the biomass burning aerosols and anthropogenic aerosols. The particle depolarization ratio (355 nm) values were found from approximately 4.8?±?2.7% to 11.5?±?1.9% with the mean value of 7?±?1.3% suggesting the presence of non-spherical particles. To trace the sources of the pollution, we derived the HYSPLIT trajectory which shows the majority of the movement was from local sources.

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Assessment of chemical and microbial contamination in groundwater through leaching of sewage waste in Delhi,India     

Ashwani Kumar  Anuj Ranjan  Khushbu Gulati  Shalini Thakur  Tanu Jindal 《Environmental Earth Sciences》2016,75(3):275

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