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Evidence for anisotropy in the super-thick sedimentary basin under the northern Bay of Bengal is presented. Surface wave group
velocity data given by Brune and Singh (1986) is better fit by an anisotropic model than an isotropic one. This lends support
to the hypothesis that the mid-crustal rocks are metasediments and that the section of sediments and metasediments is more
than 20 km thick. 相似文献
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V Govardhan 《Journal of the Indian Society of Remote Sensing》1991,19(3):175-185
Spectral reflectance of different soil subgroups from different soil orders were measured using a field radiometer. The results showed that, on the basis of spectral signatures, different soils can be delineated. The physico-chemical characteristics including moisture content showed a definite bearing on the spectral reflectance. The plant cover, tillage and crop residue content influenced greatly spectral reflectance as compared to bare soil. The spectral reflectance on soil aggregate size showed that reflectance decreased with increase in the aggregate size. The saline and sodic soils also recorded greater spectral reflectance in relation to normal soils. 相似文献
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Chennarapu Hariprasad Mekala Rajashekhar Balunaini Umashankar 《Geotechnical and Geological Engineering》2016,34(6):1909-1922
Relative density is an important state parameter that influences the soil behavior. Preparation of sand specimens with uniform density is critical during large-scale laboratory testing in geotechnical engineering. In this study, the details of a stationary air pluviation device used to prepare uniform sand specimens in a large-size test chamber with dimensions equal to 900 mm × 900 mm × 1000 mm (in length, width, and depth) are provided. The proposed device is found to be simple to construct due to presence of only two diffuser sieves with an ability to produce uniform sand beds in a reasonably quick time. Prior to construction of full-scale pluviation device, a scaled-down model of the device with plan dimensions equal to 300 mm × 300 mm is fabricated to perform calibration studies. The range of densities of two gradations of Indian Standard sand (IS Grade II and IS Grade III) obtained using this device for various heights of fall of sand particles and passing through different opening sizes are provided. Relative density in the range of 53–99 % and 74–99 % is achieved for IS Grade II and III sands, respectively. The spatial uniformity in densities is also assessed, and the coefficient of variation (COV) in the density is found to be less than about 7 %. In addition to pluviation method, uniform sand beds are also prepared using pneumatically-operated vibratory method. The target relative density of sand bed is achieved by adjusting the pressure of compressed air inside the vibrator, and the maximum relative density of IS Grade II and Grade III sands from vibratory method is found to be higher than that from pluviation method for the range of pressures chosen in the study. 相似文献
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