Application of Piezoceramic Elements for Determining Elastic Properties of Soils     

A. Patel  K. K. Singh  D. N. Singh 《Geotechnical and Geological Engineering》2012,30(2):407-417

Elastic modulus and Poisson’s ratio of soils are two important parameters required for safe design of various civil engineering structures. The elastic modulus and shear modulus of the soils are generally obtained from the resonant column, torsional shear tests and geophysical methods. Though, from these parameters the Poisson’s ratio can be determined, these tests are quite elaborate, cumbersome, time consuming and require skilled manpower particularly for data interpretation. Moreover, direct determination of the Poisson’s ratio by employing micro-strain gauges, which measure axial and lateral strains using Wheatstone bridge circuits, is difficult for soils due to the problems associated with their fixing on the surface of the sample. Under these circumstances, application of piezoceramic elements, which can generate shear and compression waves, seems to be an excellent alternative. Using these wave velocities, the Poisson’s ratio can be computed easily and precisely. However, how this (computed) value of the Poisson’s ratio compares vis-à-vis that obtained from the conventional triaxial tests (i.e., strain controlled uniaxial compression tests), which yield stress–strain relationship, needs to be established. With this in view, investigations were conducted on soils of different types (clays and sands) in their disturbed and undisturbed forms by resorting to piezoceramic tests and the triaxial tests. Details of the methodology are presented in this paper and it has been demonstrated that application of piezoceramic elements yields the Poisson’s ratio and the elastic modulus of the soils quite easily, particularly for the soft clays and sands.  相似文献   

Assessing landslide vulnerability from soil characteristics—a GIS-based analysis   总被引：1，自引：1，他引：0  

L. P. Sharma  Nilanchal Patel  P. Debnath  M. K. Ghose 《Arabian Journal of Geosciences》2012,5(4):789-796

Hilly regions are prone to landslides that cause heavy losses of life and properties every year. A number of researches and analyses are carried out in the GIS environment to identify landslide vulnerability in the region. The important conditioning factors identified by the researchers are slope, geological, geomorphologic features, and land use coupled with triggering factors like rainfall and a few of the anthropogenic activities. Soil forms the uppermost part of the earth crust, and it is expected that various soil characteristics like depth, surface texture, depth texture, soil erosion, hydraulic conductivity, stoniness, etc., play significant roles in causing landslide in the area. These factors have been ignored so far by most researchers while identifying landslide hazard-prone areas. This paper attempts to assess the vulnerability status in parts of East Sikkim, India, by integrating the influence of the various soil attributes. A composite index called soil stability value was determined by aggregating the weights assigned to different soil parameters. Finally, based on the soil stability values, the study area was classified into least vulnerable, moderately vulnerable, and most vulnerable zones of landslide occurrences. Comparison between the vulnerability zones and the actual landslide occurrences yielded a 90% agreement with the density of landslides in the most vulnerable zone, demonstrating the efficacy of soil characteristics as potential indicators of landslide events.  相似文献   

Basin provenance and post-depositional thermal history along the continental P/T boundary of the Raniganj basin,eastern India: Constraints from apatite fission track dating     

R. C. Patel  H. N. Sinha  Bhaiya Anupam Kumar  Paramjeet Singh 《Journal of the Geological Society of India》2014,83(4):403-413

Apatite fission-track analysis has been applied to the Raniganj and Panchet formations of Raniganj basin of Gondwana Supergroup to unravel its thermal and provenance history. Apatite fission track age population from both Raniganj and Panchet formations indicate partial annealing and point to a maximum temperature of around ～100-110°C during their post depositional evolution. The sandstone of Raniganj Formation has five peak ages at 26.3, 59.3, 109.7, 173.7 and 299.9 Ma, while Panchet Formation has three peak ages at 25.4, 143.5 and 281.3 Ma. This implies that the provenance of the Raniganj Formation of late Permian and Panchet Formation of early Triassic changed obviously. According to thermotectonic evolution of the Gondwana basin, these apatites with different FT ages possibly represent different source components, although partial annealing had occurred to these apatites. Possibly all the apatites had transported from the Precambrian basement which was undergoing deformation due to Gondwana rifting initiated during Carboniferous period. Due to this, the basement was undergoing inhomogeneous thermal history which became source of sediments for Raniganj basin. Apatite FT ages of both Raniganj and Panchet formations have peak ages between 25 and 60 Ma, which perhaps recorded the cooling/uplift history during Cenozoic Alpine-Himalayan orogeny. Given a palaeo-thermal gradient of 40° C/km, it can be deduced that the Raniganj basin has uplifted about 3km at an average rate of about 0.09mm/a since 25–60 Ma.  相似文献   

A polarimetric study of the B[e] star HD 45677     

M. Patel  R. D. Oudmaijer  J. S. Vink  J. C. Mottram  B. Davies 《Monthly notices of the Royal Astronomical Society》2006,373(4):1641-1647

We aim to characterize the current status of knowledge on the accuracy of open-cluster parameters such as the age, reddening and distance. These astrophysical quantities are often used to study the global characteristics of the Milky Way down to the very local stellar phenomena. In general, the errors of these quantities are neglected or set to some kind of heuristic standard value. We attempt to give some realistic estimates for the accuracy of available cluster parameters by using the independently derived values published in the literature. In total, 6437 individual estimates for 395 open clusters were used in our statistical analysis. We discuss the error sources depending on theoretical as well as observational methods and compare our results with those parameters listed in the widely used catalogue by Dias et al. In addition, we establish a list of 72 open clusters with the most accurate known parameters which should serve as a standard table in the future for testing isochrones and stellar models.  相似文献   

FRACTAL ANALYSIS APPLIED TO SPATIAL STRUCTURE OF CHINA''''S VEGETATION     

Patel NILANCHAL 《中国地理科学(英文版)》2006,(1)

1INTRODUCTIONMandelbrot stated the uncertainty of the length of a coastline in his paper "How long is the coast of Britain? Statistical self-similarity and fractional dimension" pub- lished in Science in 1967 (MANDELBROT, 1967). The concepts of fractal and fractal dimension were presented for the first time in that paper and have been applied to quantitatively describing the difference of crooked coastlines of British and South Africa. Compared with the Euclidean geometry with more…  相似文献   

An imaging survey of a uniform sample of brightest cluster galaxies and intracluster light     

Parimal Patel  S. Maddox  Frazer R. Pearce  A. Aragón-Salamanca  E. Conway 《Monthly notices of the Royal Astronomical Society》2006,370(2):851-883

  相似文献   

Measurement and Scaling of Carbon Dioxide (CO<Subscript>2</Subscript>) Exchanges in Wheat Using Flux-Tower and Remote Sensing     

N. R. Patel  V. K. Dadhwal  S. K. Saha 《Journal of the Indian Society of Remote Sensing》2011,39(3):383-391

The present study investigates the characteristics of CO₂ exchange (photosynthesis and respiration) over agricultural site dominated by wheat crop and their relationship with ecosystem parameters derived from MODIS. Eddy covariance measurement of CO₂ and H₂O exchanges was carried out at 10 Hz interval and fluxes of CO₂ were computed at half-hourly time steps. The net ecosystem exchange (NEE) was partitioned into gross primary productivity (GPP) and ecosystem respiration (R _e) by taking difference between day-time NEE and respiration. Time-series of daily reflectance and surface temperature products at varying resolution (250–1000 m) were used to derive ecosystem variables (EVI, NDVI, LST). Diurnal pattern in Net ecosystem exchange reveals negative NEE during day-time representing CO₂ uptake and positive during night as release of CO₂. The amplitude of the diurnal variation in NEE increased as LAI crop growth advances and reached its peak around the anthesis stage. The mid-day uptake during this stage was around 1.15 mg CO₂ m⁻² s⁻¹ and night-time release was around 0.15 mg CO₂ m⁻² s⁻¹. Linear and non-linear least square regression procedures were employed to develop phenomenological models and empirical fits between flux tower based GPP and NEE with satellite derived variables and environmental parameters. Enhanced vegetation index was found significantly related to both GPP and NEE. However, NDVI showed little less significant relationship with both GPP and NEE. Furthemore, temperature-greenness (TG) model combining scaled EVI and LST was parameterized to estimate daily GPP over dominantly wheat crop site. (R ² = 0.77). Multi-variate analysis shows that inclusion of LST or air temperature with EVI marginally improves variance explained in daily NEE and GPP.  相似文献   

Geology,structural and exhumation history of the Higher Himalayan Crystallines in Kumaon Himalaya,India     

R. C. Patel  Vikas Adlakha  Paramjeet Singh  Yogesh Kumar  Nand Lal 《Journal of the Geological Society of India》2011,77(1):47-72

The crystallines in the Kumaon Himalaya, India are studied along Goriganga, Darma and Kaliganga valleys and found to be composed of two high-grade metamorphic gneiss sheets i.e. the Higher Himalayan Crystalline (HHC) and Lesser Himalayan Crystalline (LHC) zones. These were tectonically extruded as a consequence of the southward directed propagation of crustal deformation in the Indian plate margin. The HHC and its cover rocks i.e. the Tethyan Sedimentary Zone (TSZ) are exposed through tectonic zones within the hinterland of Kumaon Himalaya. The HHC records history of at least one episode of pre-Himalayan deformation (D₁), three episodes of Himalayan deformation (D₂, D₃, D₄). The rocks of the HHC in Kumaon Himalaya are thoroughly transposed by D₂ deformation into NW-SE trending S_m (S₁+S₂). The extent of transposition and a well-developed NE-plunging L₂ lineation indicate intense strain during D₂ throughout the studied portion of the HHC. Ductile flow continued, resulting in rotation of F₁ and F₂ folds due NE-direction and NW-SE plunging F₃ folds within the HHC. The over thickened crystalline was finally, superimposed by late-to-post collisional brittle-ductile deformation (D₄) and exposed the rocks to rapid erosion.  相似文献   

Extracting Regional Pattern of Wheat Sowing Dates Using Multispectral and High Temporal Observations from Indian Geostationary Satellite     

Swapnil Vyas  Rahul Nigam  N. K. Patel  Sushma Panigrahy 《Journal of the Indian Society of Remote Sensing》2013,41(4):855-864

Monitoring of Agricultural crops using remote sensing data is an emerging tool in recent years. Spatial determination of sowing date is an important input of any crop model. Geostationary satellite has the capability to provide data at high temporal interval to monitor vegetation throughout the entire growth period. A study was conducted to estimate the sowing date of wheat crop in major wheat growing states viz. Punjab, Haryana, Uttar Pradesh (UP), Madhya Pradesh (MP), Rajasthan and Bihar. Data acquired by Charged Couple Detector (CCD) onboard Indian geostationary satellite INSAT 3A have continental (Asia) coverage at 1 km?×?1 km spatial resolution in optical spectral bands with high temporal frequency. Daily operational Normalized Difference Vegetation Index (NDVI) product from INSAT 3A CCD available through Meteorological and Oceanographic Satellite Data Archival Centre (MOSDAC) was used to estimate sowing date of wheat crop in selected six states. Daily NDVI data acquired from September 1, 2010 to December 31, 2010 were used in this study. A composite of 7 days was prepared for further analysis of temporal profile of NDVI. Spatial wheat crop map derived from AWiFS (56 m) were re-sampled at INSAT 3A CCD parent resolution and applied over each 7 day composite. The characteristic temporal profiles of 7 day NDVI composite was used to determine sowing date. NDVI profile showed decreasing trend during maturity of kharif crop, minimum value after harvest and increasing trend after emergence of wheat crop. A mathematical model was made to capture the persistent positive slope of NDVI profile after an inflection point. The change in behavior of NDVI profile was detected on the basis of change in NDVI threshold of 0.3 and sowing date was estimated for wheat crop in six states. Seven days has been deducted after it reached to threshold value with persistent positive slope to get sowing date. The clear distinction between early sowing and late sowing regions was observed in study area. Variation of sowing date was observed ranging from November 1 to December 20. The estimated sowing date was validated with the reported sowing date for the known wheat crop regions. The RMSD of 3.2 (n?=?45) has been observed for wheat sowing date. This methodology can also be applied over different crops with the availability of crop maps.  相似文献   

Geospatial Approach in Assessing Agro-Climatic Suitability of Soybean in Rainfed Agro-Ecosystem     

Suresh Kumar  N. R. Patel  Aditi Sarkar  V. K. Dadhwal 《Journal of the Indian Society of Remote Sensing》2013,41(3):609-618

The present study demonstrated the methodology to assess agro-climatic suitability of the soybean crop through integration of crop suitability based on FAO framework of land evaluation and biophysical (water limited) yield potential in the rainfed agro-ecosystem. A long term climatic database (1980–2003) was prepared to compute decadal rainfall and temperature variations of 13 IMD stations in part of Madhya Pradesh state. The climatic database was used in soil water balance software–BUDGET to compute crop specific length of growing period (LGP) and biophysical production potential such as water limited crop yield potential of each soil types for soybean crop. Water limited crop yield potential of soils were found to be varied from 33 to 100 and LGP ranged from 65 to 180 days in the area. FAO based land suitability was analyzed in association with the water limited yield potential for better appraisal of land potential and assess their suitability in rainfed area. FAO based land suitability indicated 2.45 % area as highly suitable and 57.49 % area as moderately suitable. However, integration of water limited crop yield potential with FAO based land suitability lead to agro-climatic suitability analysis indicated 17.60 % and 40.03 % area, respectively as highly suitable and moderately suitable. FAO based land evaluation showed 88.13 % of plains as moderately suitable whereas agro-climatic suitability indicated only 47.79 %. Agro-climatic suitability analysis revealed undulating plateau and undulating plains as most suitable for soybean crop.  相似文献