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81.
Analysis of earth dams affected by the 2001 Bhuj Earthquake 总被引:3,自引:0,他引:3
An earthquake of magnitude of 7.6 (Mw 7.6) occurred in Bhuj, India on January 26, 2001. This event inflicted damages of varying extents to a large number of small to moderate size multi-zone earth dams in the vicinity of the epicenter. Some of the distress was due to the liquefaction of saturated alluvium in foundation. Liquefaction was relatively localized for the majority of these dams because the earthquake struck in the middle of a prolonged dry season when the reservoirs behind these dams were nearly empty and shallow alluvium soils underneath the downstream portions of the dams were partly dry. Otherwise, liquefaction of foundation soils would have been more extensive and damage to these dams more significant. Six such dams have been examined in this paper. Four of these facilities, Chang, Shivlakha, Suvi, and Tapar were within the 50 km of epicenter region. These dams underwent free-field ground motion with peak ground accelerations between 0.28g to 0.52g. Of these Chang Dam underwent severe slumping, whereas Shivlakha, Suvi, and Tapar Dams were affected severely especially over the upstream sections. Fatehgadh Dam and Kaswati Dam were affected relatively less severely. Foundation conditions underneath these dams were first examined for assessing liquefaction potential. A limited amount of subsurface information available from investigations undertaken prior to the earthquake indicates that, although the foundation soils within the top 2.0 to 2.5 m underneath these dams were susceptible to liquefaction, Bhuj Earthquake did not trigger liquefaction because of lack of saturation of these layers underneath the downstream portions of these dams. These dams were then analyzed using a simple sliding block procedure using appropriate estimates of undrained soil strength parameters. The results of this analysis for these structures were found to be in general agreement with the observed deformation patterns. 相似文献
82.
The strain developed due to creep is mainly proportional to the logarithm of the time under load, and is mostly proportional
to the stress and temperature. At higher temperature the creep rate falls slowly with respect to time, and the creep strain
is proportional to a fractional power of time, with the exponent increasing as the temperature increases and reaching a value
approximately one-third at temperatures of about 0.5°C. At these temperatures, the creep increases with stress according to
a power greater than unity and possibly exponentially. It increases with temperature as (−U/kT), where U is an activation energy and k is Boltzman’s constant. There are different methods to determine the creep strain and the energy of Jog (B) including experimental
methods, multivariate regression analysis, and by numerical simulation. These methods are less cumbersome and time consuming.
In the present investigation, artificial neural network technique has been used for prediction of the creep strain and energy
of Jog (B). Two different networks have been tested and validated. Both the networks have four input neurons and one hidden
layer with five neurons, and one output neuron. The data for different rocks at temperatures up to 750°C under conditions
of compressive or tortional stress are taken from the literatures. The training and testing data sets used were 163 and 14,
respectively. To deal with the problem of overfitting of data, Bayesian regulation has been used and network is trained with
suitable training epochs. The coefficients of correlation among the predicted and observed values are found high and they
improve the confidence of the users. The mean absolute percentage error obtained are also very low. 相似文献
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The Hammond Hill Research Catchment (HH) is a small (120 ha), temperate, second order tributary to Six Mile Creek, Cayuga Lake, and the Great Lakes (42.42°, −76.32°). The HH has been monitored since January 2017 for the purpose of understanding how recent infiltration mixes with antecedent soil water on hillslope forest floors and the spatial and temporal patterns of Root Water Uptake (RWU) by temperate northeastern US tree species (eastern hemlock [Tsuga canadensis], American beech [Fagus grandifolia], and sugar maple [Acer saccharum]). These data are informing us about the hydrologic consequences of anticipated tree species composition change and supporting the development of more refined ecohydrological models. The glaciated catchment is underlain by a shallow confining siltstone layer (1–1.5 m depth) and densely covered with an approximately 60 year old regrowth mixed species forest of hemlock, beech, and other deciduous tree species common to the northeastern US. Current datasets from the HH include precipitation snow water equivalent, discharge, and associated isotopic water compositions, δ2H & δ18O. Measurements of (top 10 cm) soil water content, as well as bulk soil water and hemlock and beech xylem isotopic compositions are made at several locations across a topographic wetness gradient. The near-term role of the HH is to support an understanding of the environmental and ecological drivers of plant RWU competition. All data from the HH are publicly available. 相似文献
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87.
Changes in dissolved organic matter (DOM) amount and composition along nested headwater stream locations during baseflow and stormflow
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Amount and composition of dissolved organic matter (DOM) were evaluated for multiple, nested stream locations in a forested watershed to investigate the role of hydrologic flow paths, wetlands and drainage scale. Sampling was performed over a 4‐year period (2008–2011) for five locations with drainage areas of 0.62, 3.5, 4.5, 12 and 79 ha. Hydrologic flow paths were characterized using an end‐member mixing model. DOM composition was determined using a suite of spectrofluorometric indices and a site‐specific parallel factor analysis model. Dissolved organic carbon (DOC), humic‐like DOM and fluorescence index were most sensitive to changes with drainage scale, whereas dissolved organic nitrogen, specific UV absorbance, Sr and protein‐like DOM were least sensitive. DOM concentrations and humic‐like DOM constituents were highest during both baseflow and stormflow for a 3.5‐ha catchment with a wetland near the catchment outlet. Whereas storm‐event concentrations of DOC and humic DOM constituents declined, the mass exports of DOC increased with increasing catchment scale. A pronounced dilution in storm‐event DOC concentration was observed at peak stream discharge for the 12‐ha drainage location, which was not as apparent at the 79‐ha scale, suggesting key differences in supply and transport of DOM. Our observations indicate that hydrologic flow paths, especially during storms, and the location and extent of wetlands in the catchment are key determinants of DOM concentration and composition. This study furthers our understanding of changes in DOM with drainage scale and the controls on DOM in headwater, forested catchments. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The concentration of dissolved and particulate Re have been measured in the Narmada, Tapi and the Mandovi estuaries in the Arabian Sea and the Hooghly estuary in the Bay of Bengal. Re concentration in water and particulate matter of these estuaries is highly variable. Re in river waters analysed varies from 1 to 41 pmol/kg, the lowest in the Mandovi and the highest in the Mahi river. Re concentrations in the rivers analysed except in the Mandovi river are higher than the average global riverine Re concentration of 2.1 pmol/kg. Based on this study and the available data, the contemporary global annual flux of dissolved riverine Re is estimated to be ~ 350 × 103 mol with an average concentration of ~ 9.2 pmol/kg, much higher than the earlier estimates. Residence time of Re in the oceans based on this estimate is 175,000 years, ~ 4 times lower compared to earlier estimates. Re behaves conservatively in all the estuaries studied. Re concentrations of seawater in the Bay of Bengal and in the Arabian Sea, estimated from the data of the Hooghly and the Mandovi estuaries respectively are ~ 40 pmol/kg, similar to the open ocean Re values of the Arabian Sea measured in this study and the values reported for in other oceanic regions. However, the dissolved Re in the Gulf of Cambay is 2 to 5 times higher, consistent with the high Re measured in the Mahi estuary and in the coastal waters of the Gulf of Cambay. The source of high Re in the Gulf of Cambay seems to be anthropogenic, measurements of Re in rivers and industrial waste waters draining into the Gulf supply amount to ~ 2300 mol of Re annually. This anthropogenic supply coupled with high residence time of water in the Gulf contribute to its high Re. Re concentration in suspended sediments of the Narmada estuary varies from 1 to 2 pmol/g, and does not show any discernible trend with salinity.The contemporary global riverine Re supply to the oceans estimated in this study is ~ 2–4 times higher compared to its removal in the reducing (anoxic/suboxic) sediments, indicating non-steady state of Re in the ocean. High dissolved riverine Re flux coupled with high Re content in the Gulf of Cambay highlights the need of a detailed study of Re in the various global rivers and in oceans including coastal regions and semi enclosed basins of the world to understand its behaviour in various reservoirs and to constrain the residence time of Re in the ocean. 相似文献
90.
Prasanta Kumar Behera Kripamoy Sarkar Ashok Kumar Singh A. K. Verma T. N. Singh 《Journal of the Geological Society of India》2016,88(6):725-735
In opencast mining operation, the stability of waste materials stands at high priority from the safety and economic perspective. Poor management of overburden (OB) dump results the instability of slope in an opencast mine. The present paper deals with the stability analysis of dump material of an opencast coal mine at Talcher coal field, Angul district, Odisha, by means of different geotechnical parameters and mineralogical composition affecting the dump slope. The prolonged rainfall in the mining area causes dump failure and loss of valuable life and property. A recent dump failure that occurred in 2013 at Basundhara mines of Mahanadi Coalfields Limited (MCL), Odisha, took 14 lives, and created problems for the mining industry. Most of the dump failure that occurs in the study area are mainly due to increase in pore water pressure as a result of rainfall infiltration. The stability of the waste dump was investigated using the limit equilibrium analysis to suggest an economical, sustainable and safe disposal of the dump in the study area. 相似文献