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1.
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
2.
3.
Ilvaite, Ca(Fe2+,Fe3+)Fe2+Si2O8(OH) shows two magnetic phase transitions, which have been studied by Mössbauer spectroscopy within the temperature range 120–4 K. The continued charge localization between Fe2+ and Fe3+ ions in octahedral A-sites causes the Fe2+-Fe3+ interaction to be ferromagnetic, although the overall magnetic order is antiferromagnetic. The thermal evolution of the hyperfine fields at the Fe2+ (A) and Fe3+ (A) sites indicates B
hf: 328 and 523 kOe respectively at 0 K and T
N1= 116K. The corresponding values for Fe2+ (B) site are: B
hf 186 kOe and T
N2=36K. An additional hyperfine field exists at the Fe2+(B) site within the temperature range 116–36K due to short-range order induced by the spin ordering in A sites. The considerable difference between the two magnetic transition temperatures is due to spin frustration, because the Fe2+ (B) site occurs on a corner common between two triangles with respect to two sets of Fe2+ (A) and Fe3+ (A) sites with opposite spin directions. 相似文献
4.
Crystal field spectra and jahn teller effect of Mn3+ in clinopyroxene and clinoamphiboles from India
S. Ghose M. Kersten K. Langer G. Rossi L. Ungaretti 《Physics and Chemistry of Minerals》1986,13(5):291-305
Blanfordite (I), winchite (II), and juddite (III), all showing vivid colors and pleochroism, from highly oxidized parageneses of Indian gondites were studied by microprobe, Mössbauer, and microscope-spectrophotometric techniques and by X-ray structure refinements. The compositions of the Mn-bearing minerals were close to diopsideacmite (I) and magnesio-arfvedsonite to magnesio-riebeckite (II and III). Transition metal ions are located inM(1)-octahedra (I) or predominantlyM(2)-octahedra (II, III). Mössbauer spectra of57Fe(IS, ΔE Q) are typical of octahedral Fe3+ only. Polarized absorption spectra in the UV/VIS/NIR ranges explain color and pleochroism of the minerals. The position of the UV-“edge” is correlated with Fe3+-contents of the minerals, except for judditeE ∥Z, where the edge shows an unusual low energy position. This is most likely due to Mie-scattering of submicroscopic inclusions of braunite with nearly uniform dimensions. In the VIS range, the spectra are dominated by a complex band system between 15,000 and 20,000 cm?1. Energies and ?-values of component bands are compatible with those of Mn3+ d-d transitions in other Mn3+-bearing silicates. The polarization behavior of component bands can best be explained by aC 2(C2″) symmetry of the crystal field. The Jahn-Teller splitting (<9,000 cm?1) of the5 E g ground state of Mn3+ inO h crystal fields is appreciably smaller than in other Mn3+-silicates. Crystal field parameters 10Dq, (I) 13,650, (II) ca. 11,640, and (III) 11,925 cm?1, are near to that in piemontite. The crystal field stabilization energy of Mn3+, (I) 146, (II) ca. 140, (III) 142 \({{{\text{kJ}}} \mathord{\left/ {\vphantom {{{\text{kJ}}} {\text{g}}}} \right. \kern-0em} {\text{g}}}{\text{ - atom}}_{{\text{Mn}}^{{\text{3 + }}} } \) , is appreciably smaller than that found in other Mn3+-silicates (piemontites and manganian andalusites, viridines and kanonaite). 相似文献
5.
6.
Plagioclase in cataclastic anorthosite 67075 occurs as angular matrix grains and as recrystallized clasts of micro-anorthosite. Olivines are Fe-rich and fall into two compositional groupings. Large grains of pyroxene show exceptionally well-developed exsolution lamellae analogous to those observed in pyroxenes from layered complexes. The low-Ca component in both pigeonites and augites shows varying degrees of inversion to orthopyroxene. The lattices of host and lamellae may deviate slightly (up to 2°) from the ideal orientation. Very slow cooling from magmatic temperatures is required to produce the coarse exsolution textures and inversion features. Augite macrocrystals are distinctly subcalcic indicating crystallization at temperatures around1100 ± 50°C while host-lamellae pairs and small grains in lithic clasts and matrix indicate reequilibration on a micron scale to temperatures less than 800°C. Pyroxene compositions tend to cluster into two groups both of which are among the most Fe-rich reported for highland pyroxenes. Ti and Al contents of pyroxenes are very low and Ti, Cr, and Mn follow well-established magmatic differentiation trends. The high Cr content may reflect low?O2 conditions and/or early crystallization of olivine and plagioclase.The87Sr/86Sr ratios in lunar anorthosites are the lowest reported for any lunar rock. It is likely that anorthosites formed as cumulates during the major differentiation episode which occurred prior to~4.3AE. Recrystallization features are common and39Ar/40Ar ages cluster around 4.0 AE. This may be the result of the intense bombardment prior to 4.0 AE which caused repeated cycles of in-situ fracturing and granulation followed by recrystallization. The low siderophile element content and the inferred slow cooling indicate a plutonic source region (10km) not frequently plumbed by impact events. The Fe-rich silicates indicate crystallization from a melt at an advanced stage of fractionation. However, the low REE abundances are not consistent with late-stage crystallization. Plagioclase apparently crystallized relatively early and was concentrated by flotation and/or convection currents while the mafic minerals crystallized from a fractionated trapped liquid. The chemical, isotopic, and mineralogical data place stringent constraints on the nature of genetically related rocks and the relationship of anorthosites to other members of the ANT suite does not appear to be one ofsimple fractionation. The data presented in this paper are consistent with the Taylor-Jake?model of lunar evolution. 相似文献
7.
8.
The strength and deformability of rock mass primarily depend on the condition of joints and their spacing and partially on
the engineering properties of rock matrix. Till today, numerical analysis of discontinuities e.g. joint, fault, shear plane
and others is conducted placing an interface element in between two adjacent rock matrix elements. However, the applicability
of interface elements is limited in rock mechanics problems having multiple discontinuities due to its inherent numerical
difficulties often leading to non-convergent solution. Recent developments in extended finite element method (XFEM) having
strong discontinuity imbedded within a regular element provide an opportunity to analyze discrete discontinuities in rock
masses without any numerical difficulties. This concept is based on partition of unity principle and can be used for cohesive
rock joints. This paper summarizes the mathematical frameworks for the implementation of strong discontinuities in 3 and 6
nodded triangular elements and also provides numerical examples of the application of XFEM in one and two dimensional problems
with single and multiple discontinuities. 相似文献
9.
Benoy K. Ghose 《Mathematical Geology》1970,2(3):265-276
This paper outlines a procedure to analyze statistically a mixture of two populations that cannot be Separated by usual methods.
In such instances, frequency histograms of taxonomically important characters that are normally distributed show the presence
of two modes revealing the possible existence of two populations. As a first step in the analysis, the joint distribution
of a suitable character is resolved by one of the two, Pearson or Rao, methods of moments; this gives estimates of the mean
and standard deviation of that character for each of the two constituent populations. A numerical example explains the computational
procedure. Rao's method is easier to use but is applicable only if the two standard deviations are assumed equal. If the distribution
of the characters have less than 10-percent overlap, it is possible to make further statistical analysis on the basis of results
obtained by either of the two methods. In paleobiometrical work the problem of having a mixed population is fairly common.
The procedure outlined in this paper may be utilized in such situations for a better evaluation and interpretation of data. 相似文献
10.
Deyan Draganov Ranajit Ghose Elmer Ruigrok Jan Thorbecke Kees Wapenaar 《Geophysical Prospecting》2010,58(3):361-373
Seismic interferometry is the process of generating new seismic traces from the cross‐correlation, convolution or deconvolution of existing traces. One of the starting assumptions for deriving the representations for seismic interferometry by cross‐correlation is that there is no intrinsic loss in the medium where the recordings are performed. In practice, this condition is not always met. Here, we investigate the effect of intrinsic losses in the medium on the results retrieved from seismic interferometry by cross‐correlation. First, we show results from a laboratory experiment in a homogeneous sand chamber with strong losses. Then, using numerical modelling results, we show that in the case of a lossy medium ghost reflections will appear in the cross‐correlation result when internal multiple scattering occurs. We also show that if a loss compensation is applied to the traces to be correlated, these ghosts in the retrieved result can be weakened, can disappear, or can reverse their polarity. This compensation process can be used to estimate the quality factor in the medium. 相似文献