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61.
Manish A. Mamtani V. Abhijith Sivaji Lahiri Virendra Rana Sandeep Bhatt Shalini Goswami A. R. Renjith 《Journal of the Geological Society of India》2017,89(1):5-11
Salem-Attur shear zone in the Southern Granulite Terrane demarcates the tectonic boundary between Archaean granulites of Dharwar craton and the Palaeoproterozoic granulites of Salem area. The shear zone marks a low angle thrust which has been steepened at places due to late stage folding. Static recrystallisation during late stage folding has removed the strain marker of mylonites to large extent. However, in a few places S-C angle and porphyroclasts are preserved and have been used to compute the strain. The strain shows apparent flattening by simple shear deformation with 35 % volume loss. A minimum displacement along the thrust has been computed to be 2.7 km. The strain k values increases with r suggesting the strain approaching towards prolate field with increase in strain intensity. The above study suggests the Salem-Attur shear zone is a thrust with low to moderate deformation and volume loss. 相似文献
62.
Model tests on steel piles embedded in sand were carried out in the laboratory to study the effects of compressive load (i.e.
0, 25, 50, 75, and 100% of their ultimate capacity in compression) on oblique pull-out capacity of piles. The model piles
were of 20 mm × 20 mm cross section, which had an embedded length of 400 and 600 mm. The pull was applied at an inclination
of 0°, 30°, 60° and 90° with vertical axis of the piles. The experimental results indicate that the net oblique pull-out capacity
of piles decreases with increase in % of compressive load and the decrease depends on the magnitude of the compressive load.
Semi-empirical methods, based on experimental results, have been suggested to determine the oblique pull-out resistance of
piles subjected to static compressive loads. A comparison of predicted values of the ultimate oblique resistance by proposed
methods of analysis with experimental values, and also with those reported by others, showed reasonably good agreement. 相似文献
63.
Digital elevation models (DEMs) used in geospatial analysis like the simulation of geophysical flows, such as floods, landslides, and block and ash flows, differ in resolution, acquisition time and generation methodology, which results in varied representation of topographic features. This study investigates the effects of DEMs on the output of a granular flow model, TITAN2D by comparing the output using different DEMs to that obtained with a “true” representation of the terrain, which is considered to be that obtained by using TOPSAR 5 m data. Seven DEMs at four resolutions from four sources were used for Mammoth Mountain, California, a cumulodome volcano. TITAN2D was run for seven different locations of an eruption of a potential dome and two different collapse volumes. The resulting outputs were subsequently compared with TOPSAR 5 m output, and qualitative and statistical inferences were drawn. DEMs with different resolutions and sources generated different outputs that led to different flow maps. For moderate and smaller scale flows ( $\mathcal{O}(10^4)$ m3 – $\mathcal{O}(10^5) \,\text{m}^3$ ), different representations can affect the computation of accurate footprint of the flow and fine DEM resolution is critical for correct characterization of these flows. 相似文献
64.
A. Markandeyulu I. Patra B. V. S. N. Raju A. K. Chaturvedi P. S. Parihar 《Journal of the Geological Society of India》2012,80(3):382-392
The Paleo-Meso Proterozoic Gwalior basin (E - W), lying to NW fringe of Bundelkhand massif is represented by litho-package of lower arenaceous Par Formation and upper chemogenic Morar Formation. It is bounded by Indo-Gangetic alluvium in north and east, Kaimur sediments in west and Bundelkhand granitoids in south. Gwalior Basin has been the exploration target for uranium mineralization right from early 60’s. Surface radioactivity anomalies due to uranium has been reported in both Par and Morar Formations of Gwalior Group and Vindhyan sediments. Besides presence of syngenetic uranium in the system, presence of post-depositional faults and fractures are the favorable factors. Aeromagnetic survey was carried out by AMD in 2002 with N-S lines of 500 m interval covering 9406 line km. The data with sampling interval of 0.1 sec was corrected for spikes, diurnal variation, IGRF, heading and lag. Final processed images are prepared after suitable leveling and gridding. First vertical derivative of TMI-RTP and tilt-angle derivative images are used to map the litho-contacts, lineaments and structural features. Numerous NE-SW trending low amplitude and NW-SE trending high amplitude magnetic linears corroborate with quartz reefs and basic dykes respectively. Besides, E-W to WNW-ESE and ENE-WSW trending fractures are also evident from the processed image maps. Further, the Euler’s depth solution of gridded aeromagnetic data calculated for structural indices of 0 and 1 are very consistent in locating the position of the causative sources. Based on the amplitude and textural character of processed aeromagnetic data, alteration zone is delineated well within the Morar Formation. Enhanced Thematic Mapper (ETM+) image with 30m resolution was merged with IRS PAN 1D (5.8 m resolution) for better spatial/radiometric resolution to extract litho-contacts and lineament patterns. Merged PAN band-4 after linear contrast and edge enhancement techniques deciphered detailed lineament pattern, which corroborate the magnetic data. Merged ETM+ (RGB 751) and PC (PC1-PC2-PC5) images depict litho-logical contrast. Integration of aeromagnetic and satellite imagery data helped in understanding the structural fabric of the Gwalior Basin and to identify favorable loci of uranium mineralization. 相似文献