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31.
This paper presents the analysis of creep settlement of pile groups for line pile groups, square pile groups, and rectangular pile groups undergoing creep settlements over a period of time. The soil is treated as a viscoelastic material and is modeled using a three-parameter viscoelastic model. The damping component (dashpot) takes care of the permanent time-dependent deformations in three-parameter viscoelastic model. An approach suggested by Mindlin has been employed to calculate the stress distribution along the pile length in a group. The viscoelastic problem is converted into an elastic problem by the application of Laplace transform. Results in the form of variation of interaction factors for parameters such as pile length to diameter ratio, pile spacing, Poisson's ratio, and modulus ratio have been presented. Comparison has been made between interaction factors for piles groups undergoing immediate settlements and creep settlements. Finally, a typical predictive example has been presented for a 3 × 3 pile group showing creep settlement. The load rearrangement due to creep settlements causes about 5% to 35% increase in base resistance over time. Interaction factors for pile groups (2 × 1, 3 × 1, 2 × 2, and 3 × 2) undergoing creep settlement is about 15% to 55% higher than the interaction factors considering only the immediate settlements for pile group spacing less than or equal to 5d. 相似文献
32.
Marcus Bursik Matthew Jones Simon Carn Ken Dean Abani Patra Michael Pavolonis E. Bruce Pitman Tarunraj Singh Puneet Singla Peter Webley Halldor Bjornsson Maurizio Ripepe 《Bulletin of Volcanology》2012,74(10):2321-2338
Data on source conditions for the 14 April 2010 paroxysmal phase of the Eyjafjallaj?kull eruption, Iceland, have been used as inputs to a trajectory-based eruption column model, bent. This model has in turn been adapted to generate output suitable as input to the volcanic ash transport and dispersal model, puff, which was used to propagate the paroxysmal ash cloud toward and over Europe over the following days. Some of the source parameters, specifically vent radius, vent source velocity, mean grain size of ejecta, and standard deviation of ejecta grain size have been assigned probability distributions based on our lack of knowledge of exact conditions at the source. These probability distributions for the input variables have been sampled in a Monte Carlo fashion using a technique that yields what we herein call the polynomial chaos quadrature weighted estimate (PCQWE) of output parameters from the ash transport and dispersal model. The advantage of PCQWE over Monte Carlo is that since it intelligently samples the input parameter space, fewer model runs are needed to yield estimates of moments and probabilities for the output variables. At each of these sample points for the input variables, a model run is performed. Output moments and probabilities are then computed by properly summing the weighted values of the output parameters of interest. Use of a computational eruption column model coupled with known weather conditions as given by radiosonde data gathered near the vent allows us to estimate that initial mass eruption rate on 14 April 2010 may have been as high as 108?kg/s and was almost certainly above 107?kg/s. This estimate is consistent with the probabilistic envelope computed by PCQWE for the downwind plume. The results furthermore show that statistical moments and probabilities can be computed in a reasonable time by using 94?=?6,561 PCQWE model runs as opposed to millions of model runs that might be required by standard Monte Carlo techniques. The output mean ash cloud height plus three standard deviations??encompassing c. 99.7?% of the probability mass??compares well with four-dimensional ash cloud position as retrieved from Meteosat-9 SEVIRI data for 16 April 2010 as the ash cloud drifted over north-central Europe. Finally, the ability to compute statistical moments and probabilities may allow for the better separation of science and decision-making, by making it possible for scientists to better focus on error reduction and decision makers to focus on ??drawing the line?? for risk assessment. 相似文献
33.
D. V. Phani Kumar A. K. Patra Y.-S. Kwak K.-H. Kim G. Yellaiah 《Astrophysics and Space Science》2009,323(3):225-233
In this paper, we attempt to identify the driving forces responsible for the generation of low-latitude E-region field-aligned
irregularities (FAIs). It is evident that the low-latitude E-region FAIs occur both during the day and night with preferential
occurrence being most during local sunrise period. Simultaneous measurements are made with Gadanki radar and nearby located
Ionosonde for understanding the low-latitude Es–FAIs relationship. The observations suggest that the occurrence and SNR of
FAIs have a close relationship with f
t
E
s
−−f
b
E
s
. Finally, using the past electron density profiles and reasonable values of electric field, we have shown that it is generally
difficult with the gradient drift instability to explain low-latitude E-region FAIs when electric field alone is considered
as driving agency. We hypothesize that neutral winds play important role for the generation of irregularities at low latitudes
outside the electrojet belt either by forming sharp Es layers or by enhancing the differential drift of electrons and ions
or by both. 相似文献
34.
Sankar Narayan Patra Gautam Bhattacharya Koushik Ghosh Probhas Raychaudhuri 《Astrophysics and Space Science》2009,324(1):47-53
The solar irradiance data plays a very important role for understanding of Solar internal Structure and the solar terrestrial
relationships. The Total Solar Irradiance (TSI) is integrated solar energy flux over the entire spectrum which arrives at
the top of the atmosphere at the mean sun earth distance. TSI has been monitored from several satellites, e.g. Nimbus 7, Solar
Maximum Mission (SMM), The NASA, Earth Radiation Budget Satellite (ERBS), NOAA9, NOAA10, Eureca and the Upper Atmospheric
Research Satellite (UARS) etc. From these observations it reveals that the total solar irradiance varies about a small fraction
of 0.1 over solar cycle being higher during maximum solar activity condition. In the present paper we have analysed the solar
irradiance data from ERBS during the time period from October 15, 1984 to October 15, 2003. First filtering the data by Simple
Exponential Smoothing we have applied the Rayleigh Power Spectrum Analysis on the processed data in order to search for its
time variation. Study exhibits multi-periodicities on these data around 7, 11, 42, 80, 104, 130, 160, 254, 536, 752, 1142,
1388, 2474 and 4951 days with very high confidence levels (more than 95%). Apart from these strong periods there are some
other weak periods around 22, 47, 53, 67, 69, 149, 167, 365, 489 and 683 days. These periods are significantly similar with
the periods of other solar activities which may suggest that solar irradiance may be associated with other solar activities. 相似文献
35.
An analytical method has been proposed to predict the ultimate uplift capacity of single vertical piles embedded in sand considering
arching effect. The present analysis takes into consideration of various pile and soil parameters such as length (L), diameter (d) of the pile, angle of internal friction of soil (ϕ), soil pile friction angle (δ) and unit weight of soil (γ). A modified value of coefficient of lateral earth pressure in uplift has been developed considering the arching effect of
soil. A comparative assessment of the uplift capacity of piles predicted by using proposed theory and the existing available
theories is made with the existing field and model test results. It has been observed that the present model considering the
arching effect predicts the results closer. 相似文献
36.
Natural Hazards - It has been found that the less care is shown while constructing the water retention structures as compared to the amount of care shown in designing for it. This is more often in... 相似文献
37.
Nihar Ranjan Patra Prabhakar Jagannath Pise 《Geotechnical and Geological Engineering》2006,24(2):265-282
Experimental investigations on model pile groups of configuration, 1 × 1(single pile), 3 × 1, 2 × 2 for embedment length to
diameter ratio, L/d = 38, were conducted in uniform dry medium dense Ennore sand. The spacing of piles in the groups varied from 3 to 6 pile
diameter. Soil–pile friction angles were δ = 16° and 28°. The pile groups were subjected to oblique pulling loads at angles θ = 0°, 30°, 60° and 90° with the vertical central axis of the groups. The load–displacement response, oblique ultimate pulling
resistances have been qualitatively and quantitatively studied. The inclinations of the load, at which maximum oblique resistance
for the groups were observed, have been reported. Predictions of ultimate resistance of pile groups under uplift, lateral
and oblique pulling loads have been carried out respectively by the methods of Patra and Pise (2002) (Electronic Journal of Geotechnical Engineering, 8, Bundle B), Patra and Pise (2001) (Journal of Geotechnical and Geoenvironmental Engineering ASCE, 127(6), 481–487) and Chattopadhyay and Pise (1986c) (Proceedings of IST East Asian Conference on Struct Engineering and Const., Vol. 1, pp. 1632–1641). A comparison of the measured values of the Writers and others with the predicted values showed
reasonable agreement. 相似文献
38.
P. Mishra S. K. Patra M. V. Ramana Murthy P. K. Mohanty U. S. Panda 《Natural Hazards》2011,59(2):1145-1159
A 97-day-long record on waves and currents was obtained using wave rider buoy and current meter moored at 2.5 km off Gopalpur
from 19 May to 23 August 2008 representing southwest monsoon months. A Valeport tide gauge was used to record water level
at Gopalpur port. Simultaneously, beach profiles at 4 transects were monitored using real-time kinematic (RTK) global positioning
system (GPS). A total of 636,167 waves were analyzed for the period; a range of 3,200–9,700 waves approach the coast in an
individual day. During the study, unusual characteristics of wave were observed on July 29, 2008, with a magnitude of significant
wave height, Hs = 2.85 m, maximum wave height, Hmax = 5.22 m, and peak wave period, Tp = 10.2 s, and on August 11, 2008, with Hs = 2.28 m, Hmax = 5.37 m, and Tp = 11.1 s. Significant beach loss was noticed during these periods, and severe erosion was recorded on August 1, 2008. Beach
profile data indicates that 18–58 cu. m/m sediment was lost during the study period. The paper provides an overview of the
statistical analysis of wave heights, periods, direction, and spectral energy density and explains the cause of coastal erosion
and loss of sediment. 相似文献
39.
We investigated the abundance of different picophytoplankton groups and the phytoplankton pigment ratio in relation to environmental factors such as nutrients and suspended solids along a salinity gradient in the Changjiang River Estuary. The average numbers of Synechococcus spp.(Syn) and picoeukaryotes(Euk) were(2.7 ±5.1) ×103 and(1.1±1.4) ×103 cells m L-1, respectively. Prochlorococcus spp.(Pro) was only found in the high-salinity brackish water with the concentration of 3.0×103 cells m L-1. Syn and Euk numbers both tended to increase offshore and Syn showed a larger variation in cell abundance than Euk. The contribution of picophytoplankton to total phytoplankton biomass increased with increasing salinity and decreasing nutrient concentrations from the estuary to the open ocean. The response of different picophytoplankton groups to environmental variables was different. Water temperature was more important in its control over Euk than over Syn, while nutrients were more important in their influence over Syn than over Euk. Phytoplankton pigment ratios were different in the three different ecological zones along the salinity gradient(i.e., freshwater zone with 0-5 range, fresh and saline water mixing zone with 5-20 range, and high-salinity brackish water zone with 20-32 range), where three different phytoplankton communities were discovered, suggesting that phytoplankton pigment ratios can be considered as a complementary indicator of phytoplankton community structure in the Changjiang River Estuary. 相似文献
40.
M. S. Ramayya A. K. Chaturvedi I. Patra D. Srinivas P. Yadagiri Reddy 《Journal of the Geological Society of India》2014,84(3):311-318
Present study examines the utility of gamma rays of energies 1.12 MeV and 1.76 MeV of uranium in estimation of uranium in airborne gamma ray spectrometric survey (AGRS) in comparison to the conventional 1.76 MeV alone used world wide. As a case study, the AGRS data of northern part of Cuddapah Basin is considered. Multi-channel processing is applied on this dataset to reduce the spectral noise and use of combined 1.12 MeV and 1.76 MeV has reduced the Poisson’s related statistical error. Uranium is estimated using above two energies individually and in combination, using multi-channel processing followed by standard corrections procedure. Result indicates that a combination of both energies has given best estimation due to a reduction in overall noise which helped in demarcating geological entities and litho-contacts. This indicates the efficacy of this technique which improved the radio-geochemistry of study area in understanding the radio-elemental variation. 相似文献