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1.
In recent years, spatial variability modeling of soil parameters using random field theory has gained distinct importance in geotechnical analysis. In the present study, commercially available finite difference numerical code FLAC 5.0 is used for modeling the permeability parameter as spatially correlated log-normally distributed random variable and its influence on the steady state seepage flow and on the slope stability analysis are studied. Considering the case of a 5.0 m high cohesive–frictional soil slope of 30°, a range of coefficients of variation (CoV%) from 60 to 90% in the permeability values, and taking different values of correlation distance in the range of 0.5–15 m, parametric studies, using Monte Carlo simulations, are performed to study the following three aspects, i.e., (i) effect of stochastic soil permeability on the statistics of seepage flow in comparison to the analytic (Dupuit′s) solution available for the uniformly constant permeability property; (ii) strain and deformation pattern, and (iii) stability of the given slope assessed in terms of factor of safety (FS). The results obtained in this study are useful to understand the role of permeability variations in slope stability analysis under different slope conditions and material properties. 相似文献
2.
Traditionally seismic design of structures supported on piled raft foundation is performed by considering fixed base conditions, while the pile head is also considered to be fixed for the design of the pile foundation. Major drawback of this assumption is that it cannot capture soil-foundation-structure interaction due to flexibility of soil or the inertial interaction involving heavy foundation masses. Previous studies on this subject addressed mainly the intricacy in modelling of dynamic soil structure interaction(DSSI) but not the implication of such interaction on the distribution of forces at various elements of the pile foundation and supported structure. A recent numerical study by the authors showed significant change in response at different elements of the piled raft supported structure when DSSI effects are considered. The present study is a limited attempt in this direction, and it examines such observations through shake table tests. The effect of DSSI is examined by comparing dynamic responses from fixed base scaled down model structures and the overall systems. This study indicates the possibility of significant underestimation in design forces for both the column and pile if designed under fixed base assumption. Such underestimation in the design forces may have serious implication in the design of a foundation or structural element. 相似文献
3.
This study presents the response of a vertically loaded pile in undrained clay considering spatially distributed undrained
shear strength. The probabilistic study is performed considering undrained shear strength as random variable and the analysis
is conducted using random field theory. The inherent soil variability is considered as source of variability and the field
is modeled as two dimensional non-Gaussian homogeneous random field. Random field is simulated using Cholesky decomposition technique within the finite difference program and Monte Carlo simulation approach is considered for the probabilistic analysis.
The influence of variance and spatial correlation of undrained shear strength on the ultimate capacity as summation of ultimate
skin friction and end bearing resistance of pile are examined. It is observed that the coefficient of variation and spatial
correlation distance are the most important parameters that affect the pile ultimate capacity. 相似文献
4.
Resource prediction is necessary for allocation of exploration efforts to keep pace with future demand and the growth pattern of a commodity. Zipf's law, a mathematical relationship between size and rank of discrete phenomena, has been used for resource prediction of oil in Western Canada, uranium, gold, tin, and lead-zinc deposits in Australia, and copper deposits in Zambia. The model, applied to lead-zinc metal accumulation of 24 known precambrain deposits in India, indicates that about 75% of the lead-zinc metal is yet to be discovered. The probability of occurrence of 14 deposits of larger dimensions based on the cumulative percentage frequency for different accumulations lies between 5 and 30%. In future exploration, preference should be given to more effort in the Banded Gneissic Complex of Rajasthan in comparison to Aravalilis of Rajasthan, followed by similar environments throughout the country and Palaeozoic strata of the Himalayas. 相似文献
5.
Dipak Ghosh Argha Deb Swarup Ranjan Sahoo Subrata Haldar Rosalima Sengupta 《Natural Hazards》2011,58(3):877-889
This paper reports the measurement of radon concentration in well water at the site of Jalpaiguri (26°32′N, 88°46′E) near
the active fault zone of West Bengal, India. Radon concentration has been measured in well water with the help of solid-state
nuclear track detectors (SSNTD). The study indicates a positive correlation between radon anomaly and earthquake. The data
of radon content in well water have been compared with that in soil gas at the same site. 相似文献
6.
S. S. De Suman Paul S. Barui P. Hazra D. Kala D. K. Haldar A. Ghosh G. Guha 《Earth, Moon, and Planets》2013,111(1-2):79-87
The effect of solar eclipse of July 22, 2009, obscuring up to 91 %, upon the value of point discharge current (PDC) has been reported in this paper. The observation had been taken from Kolkata (Lat. 22.56°N, Long. 88.5°E). During the eclipse period, significant variations in the magnitude of PDC were observed than their average value for the same period in other days. The average value of the PDC for the successive ±10 days adjacent to the solar eclipse day was about 2.253 A.U. (Arbitrary Unit), while the minimum value showed about 2.242 A.U. at the time of greatest phase at 06:26.4 IST (Indian Standard Time). The results are mainly interpreted in terms of changes of the conductivity of the medium during the solar eclipse. 相似文献
7.
S. S. De B. K. De Pinaki Pal B. Bandyopadhyay S. Barui D. K. Haldar Suman Paul Minu Sanfui Goutami Chattopadhyay 《Astrophysics and Space Science》2011,332(2):353-357
The detection of 2009 Leonid, Perseid and Geminid meteor showers over Agartala, Tripura, India (Lat: 23.0° N, Long: 91.4° E)
will be reported here by using two VLF receivers tuned to subionospheric transmitted VLF signals at the frequency 16.4 kHz
from Aldra Island, Norway (Lat: 66.42° N, Long: 13.13° E) and the other at 18.2 kHz from Vijayananarayanam, India (Lat: 8.4° N;
Long: 77.7° E). The received signals exhibited their peak values on November 17, 2009 when ZHR (Zenithal Hourly Rate) was
highest. Some typical variations which are observed in the records of amplitude during the 2009 Leonid, Perseid and Geminid
meteor showers will be presented in this paper. 相似文献
8.
S. S. De B. Bandyopadhyay S. Barui Suman Paul D. K. Haldar D. De B. K. De S. Chattopadhyay A. K. Kundu 《Earth, Moon, and Planets》2012,108(2):111-121
The effects of 2009 Leonid Meteor Shower upon the two VLF subionospheric transmitted signals and vertical electric potential
gradient from the ground surface have been studied from Kolkata (Lat: 22.56°N, Long: 88.5°E) on November 17, 2009. The received
signals showed their peak values when ZHR (Zenithal Hourly Rate) was highest. Some typical variations in the outcome of these measurements during the meteor showers
will be presented in this paper. 相似文献
9.
S.S. De B.K. De B. Bandyopadhyay Suman Paul D.K. Haldar S. Barui 《Journal of Atmospheric and Solar》2010,72(11-12):829-836
The variation of the first Schumann resonance (SR) frequency spectra observed from the recorded data over Kolkata (22.56°N, 88.5°E) during a solar proton event (SPE) on July 14, 2000 has been presented. It shows increase in frequency during X-ray bursts and decrease during the period of occurrence of an SPE. The results from some other locations for the same event are also reported. The severe X-ray bursts recorded just before the proton event exhibit enhancement in frequency of the first mode due to enhancement of ionization in the D-region of the ionosphere. Some attempts are made to explain the observed variation during solar proton events in terms of the perturbations within the Earth–ionosphere waveguide on the basis of two-layer-model. 相似文献
10.
R. K. Lal D. Ackermand F. Seifert S. K. Haldar 《Contributions to Mineralogy and Petrology》1978,67(2):169-187
Silica-deficient rocks in which sapphirine coexists with cordierite, gedrite, chondrodite, spinel, corundum and phlogopite in various parageneses, occur in association with cordierite-garnet-sillimanitebearing granulitic gneisses in a Precambrian metamorphic terrain displaying amphibolite-granulite transition facies. Brucite coexists with spinel and corundum and its unusual stability in this environment has been attributed to its significant fluorine content. Kornerupine occurs as armoured relics within cordierite in one sample of the sapphirine-spinel-cordierite-phlogopite-bearing rock. Sapphirines (X Mg 0.77 to 0.92) plot near the 793 composition.X Mg varies in the order: chondrodite and brucite>gedrite>cordierite >phlogopite>sapphirine>spinel.The consistent topology of the observed mineral assemblages with reference to the system MgO-FeO-Al2O3-SiO2-H2O, systematic partitioning of Mg and Fe in the coexisting phases, and textural relations are in accord with attainment of chemical equilibrium during the regional metamorphism. The sequence of metamorphic reactions has been deduced as a function of changing MgO/(MgO+FeO) ratio in the bulk composition and it has been shown that the topology in the SiO2-(FeO+MgO)-Al2O3 diagram for more magnesian compositions is consistent with experimental data in the system MgO-SiO2-Al2O3-H2O. The stable occurrence of the spinel-cordierite and spinel-sillimanite joins in less magnesian bulk compositions suggests that these tie lines are stable to higher pressures and lower temperatures respectively as compared to the Fe-free synthetic system.Using experimental and theoretical data on garnet-cordierite, garnet-biotite, garnet-plagioclase and orthopyroxene-clinopyroxene equilibria, PT conditions have been estimated to be 750 °±50 °C/ 5±0.5 Kb for the thermal peak of metamorphism.It is suggested that the unusual bulk composition of the sapphirine-bearing rocks viz. higher Al2O3, MgO and MgO/(MgO+FeO) and lower SiO2, Na2O and CaO compared to the parent cordierite-bearing granulitic gneisses may be attributed to partial melting and removal of granitic melt. This is in agreement with the variation of oxides in the restites and parent rock. The restites consisted of the assemblage cordierite-spinel—corundum which then reacted to form sapphirine. This reaction, which in the synthetic Fe-free system is confined to extremely low-pressures (300 bars), is likely to occur at higher pressures with MgFe substitution. 相似文献