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排序方式: 共有345条查询结果,搜索用时 31 毫秒
71.
G. L. Sivakumar Babu Satyanarayana Murthy Dasaka 《Geotechnical and Geological Engineering》2008,26(1):37-46
The effect of directional behaviour of correlation structure of cone tip resistance on the bearing capacity of shallow strip
footing resting on cohesionless soil deposit in 2-D random field is analysed using probabilistic approach. The results obtained
from the analysis show that the assumption of perfect (or infinite) correlation of cone tip resistance data leads to lower
values of probability of failure. In contrast, the isotropic assumption of correlation behaviour based on vertical scale of
fluctuation leads to higher values of probability of failure. The results also show that the transformation model would play
a major role in the evaluation of variability of design property. In conclusion, the need for a proper evaluation methodology
for calculation of correlation lengths of soil properties and their influence in foundation design is highlighted. 相似文献
72.
V. Ramesh Babu J. S. Sastry V. V. Gopalakrishna D. V. Rama Raju 《Journal of Earth System Science》1991,100(1):55-68
The hydrographic structure in the east central Arabian Sea during premonsoon period undergoes significant temporal change
in the thermal field of upper 100 m, wherein temperature rises by about 0–5°C on an average from May to June. The major contribution
in increasing the surface layer temperature comes from surface heat exchange processes, while the horizontal advective process
tends to remove the heat from the upper layer. The geostrophic flow patterns are similar from May to June in the major part
of the study area while in the coastal areas off Goa a southerly current sets in June in response to coastal upwelling. 相似文献
73.
Lavkush Kumar Patel Parmanand Sharma Meloth Thamban Ajit Singh Rasik Ravindra 《Arabian Journal of Geosciences》2016,9(4):309
Complex factors such as climate, glacial geometry, topographical features and debris covers have significant influence on the dynamics of the Himalayan glaciers. Presence of debris covers on the surface of glaciers can significantly alter the surface energy balance and influence the climatic response of glaciers. In this study, the influence of debris covers and its impact on the ablation processes were analyzed from the in situ data collected over the surface of the Batal glacier in Chandra Basin, Western Himalaya. Almost 90 % of the ablation zone of the Batal glacier is covered by debris, 35 % of which is thick debris (>10 cm). Fourteen stakes (depth ~10 m) with increasing altitude and with varying debris thicknesses were installed to cover the whole ablation zone. Among them, four stakes represent thin debris (<2 cm), two stakes represent 2–5 cm debris thickness, two stakes represent 5–25 cm debris thickness, three stakes represent 25–50 cm debris thickness and three stakes represent >50 cm debris thickness. Our study has revealed high surface melting (?2.0 cm. w.e.d?1) in the debris free glacier while low surface melting observed in thick debris covered ice (?0.6 cm. w.e.d?1). Although limited to one season, this observation revealed a significant difference in the rate of surface melting as per the increasing debris thickness. Contrasting to normal ablation pattern over glaciers, Batal has experienced inverse retreat rate of ablation along with increasing altitude. A high degree of negative correlation (r = ?0.82, p < 0.05) between ablation rate and debris thickness in Batal suggest a significant control of debris thickness over ablation rate. 相似文献
74.
Natural Hazards - The Nirsa block, a coal mining area, and an industrial town lies in the southern part of Dhanbad district, at the border between the Indian states of Jharkhand and West Bengal.... 相似文献
75.
Suchandra Aich Bhowmick Rashmi Sharma K. N. Babu A. K. Shukla Raj Kumar R. Venkatesan 《Marine Geodesy》2015,38(3):193-205
The focus of this study is the validation of significant wave height (SWH) and sea surface height anomaly (SSHA) obtained from the first Ka-band altimeter AltiKa onboard SARAL (Satellite for ARGOS and Altimeters). It is a collaborative mission of the Indian Space Research Organization and Centre National d'Etudes Spatiales (CNES). This is done using in-situ observations from buoy and Jason-2 measurements. Validation using buoy observations are at particular locations while that using Jason-2 altimeter is an attempt towards global validation of Altika products. The results clearly indicate that the SARAL/AltiKa provide high-quality data and the errors are within a predefined range of accuracy. A parallel validation of SWH from other altimeters, which monitored ocean since last decade, like EnviSAT and Jason-2 was also performed with buoy observations. The results clearly show that the accuracy of AltiKa SWH is much better than EnviSAT and comparable to reference mission Jason-2. The accuracy is quite good for the calm sea while in the rough seas the accuracy degrades some. The inter-comparison of SARAL/AltiKa SSHA with Jason-2 indicates a fair match between them. These validation exercises demonstrate the high quality of AltiKa products, usable for practical applications. 相似文献
76.
2D Numerical Simulations of Soil Nail Walls 总被引:2,自引:1,他引:1
In practice, numerical simulations of soil nail walls are often carried out to assess the performance and stability. In the
present study, implications of the use of advanced soil models, such as hardening soil model and hardening soil with small-strain
stiffness model to simulate the behavior of in situ soil on the overall response of simulated soil nail wall have been studied,
and compared with respect to the analysis using conventional and most prevalently used Mohr-Coulomb soil model. Further, influence
of the consideration of bending stiffness of soil nails on the simulation results has been examined. Results of the simulations
indicated that the use of advanced models is desirable for cases of soil nail walls constructed in soft soils and when lateral
wall displacements are critical to the adjoining structures. Incorporation of bending stiffness of nails is found important
from the consideration of facing failure modes of soil nail walls. 相似文献
77.
Vladislav Babuška Jiří Fiala Jaroslava Plomerová 《International Journal of Earth Sciences》2010,99(4):891-907
We present model of the structure and development of the entire lithosphere beneath the western Eger Rift (ER). Its crustal
architecture and paths of volcanic products are closely related to sutures/boundaries of uppermost mantle domains distinguished
by different orientations of olivine fabric, derived from 3-D analysis of seismic anisotropy. Three different fabrics of the
mantle lithosphere belong to the Saxothuringian (ST), Teplá-Barrandian (TB) and Moldanubian (MD) microplates assembled during
the Variscan orogeny. Dipping fossil (pre-assembly) olivine orientations, consistent within each unit, do not support any
voluminous mantle delamination. The variable rift structure and morphology depend on the character of the pre-rift suture
between the northern ST unit and the TB/MD units in the southern rift flank. The proper rift with typical graben morphology
has developed above the steep lithosphere-scale suture between the ST and TB units. This subduction-related boundary originated
from the closure of the ST Ocean. Parts of the crust and mantle lithosphere were dragged there into asthenospheric depths
and then rapidly uplifted. The suture is marked by abrupt change in the mantle fabric and sharp gradients in regional gravity
field and in metamorphic grade. The secular TB-side-down normal movement is reflected in deep sedimentary basins, which developed
since the Carboniferous to Cenozoic and in topography. The graben morphology of the ER terminates above the “triple junction”
of the ST, TB and MD mantle lithospheres. The junction is characterized by offsets of surface boundaries of the tectonic units
from their mantle counterparts indicating a detachment of the rigid upper crust from the mantle lithosphere. The southwest
continuation of the rift features in Bavaria is expressed in occurrences of Cenozoic sediments and volcanics above an inclined
broad transition zone between the ST and MD lithospheres. Schematic scenario of evolution of the region consists mainly of
a subduction of the ST lithosphere to depths around 140 km, exhumation of HP-HT rocks and the post-tectonic granitoid plutonism. 相似文献
78.
A methodology for reliability based optimum design of reinforced soil structures subjected to horizontal and vertical sinusoidal excitation based on pseudo-dynamic approach is presented. The tensile strength of reinforcement required to maintain the stability is computed using logarithmic spiral failure mechanism. The backfill soil properties, geometric and strength properties of reinforcement are treated as random variables. Effects of parameters like soil friction angle, horizontal and vertical seismic accelerations, shear and primary wave velocities, amplification factors for seismic acceleration on the component and system probability of failures in relation to tension and pullout capacities of reinforcement have been discussed. In order to evaluate the validity of the present formulation, static and seismic reinforcement force coefficients computed by the present method are compared with those given by other authors. The importance of the shear wave velocity in the estimation of the reliability of the structure is highlighted. The Ditlevsen's bounds of system probability of failure are also computed by taking into account the correlations between three failure modes, which is evaluated using the direction cosines of the tangent planes at the most probable points of failure. 相似文献
79.
The Indian subcontinent has the largest semi-arid tropical (SAT) area among developing nations. The State of Andhra Pradesh
falls under the SAT region in India and is mostly covered by compact and hard rocks, characterized by seasonal rainfall of
a highly fluctuating nature, in both space and time. As a consequence of the green revolution and an increase in industrial
activity, there has been an increase in the utilization of groundwater resources during the last two decades in Andhra Pradesh.
The development has also caused a number of problems, such as water table decline, decrease in well yields and seawater intrusion.
Although major irrigation projects have contributed to improved agricultural production, the associated problems of waterlogging,
salinization and loss of valuable bioresources have led to the gradual degradation of the land, affecting agricultural productivity.
Surface water and groundwater have also been polluted in several parts of the State because of untreated discharge of effluents
from the industries into nearby streams or open lands. A brief account of the overall scenario of the hydrogeological framework
and geo-environmental effects on the groundwater regime in Andhra Pradesh is presented. Possible management practices and
conservation methods are suggested.
Received: 9 August 1999 · Accepted: 10 July 2000 相似文献
80.