共查询到20条相似文献，搜索用时 15 毫秒
1.
Pai-Hsiang Tsai Der-Her Lee Gordon Tung-Chin Kung C. Hsein Juang 《Engineering Geology》2009,103(1-2):13-22
This paper presents simplified dilatometer test (DMT)-based methods for evaluation of liquefaction resistance of soils, which is expressed in terms of cyclic resistance ratio (CRR). Two DMT parameters, horizontal stress index (KD) and dilatometer modulus (ED), are used as an index for assessing liquefaction resistance of soils. Specifically, CRR–KD and CRR–ED boundary curves are established based on the existing boundary curves that have already been developed based on standard penetration test (SPT) and cone penetration test (CPT). One key element in the development of CRR–KD and CRR–ED boundary curves is the correlations between KD (or ED) and the blow count (N) in the SPT or cone tip resistance (qc) from the CPT. In this study, these correlations are established through regression analysis of the test results of SPT, CPT, and DMT conducted side-by-side at each of five sites selected. The validity of the developed CRR–KD and CRR–ED curves for evaluating liquefaction resistance is examined with published liquefaction case histories. The results of the study show that the developed DMT-based models are quite promising as a tool for evaluating liquefaction resistance of soils. 相似文献
2.
Puri Nitish Jain Ashwani Nikitas George Dammala Pradeep Kumar Bhattacharya Subhamoy 《Natural Hazards》2020,103(1):447-478
The paper highlights the importance of using site-specific shear modulus reduction (G/Gmax versus shear strain, γ) curves and damping ratio (D versus shear strain, γ) curves for ground response analysis. In order to develop comprehensive G/Gmax–γ and D–γ curves (i.e. over a wide range of strain level), two types of apparatus, viz. resonant column and cyclic simple shear, have been used. The case study considered the geological deposits from the river beds of Yamuna River originating from the Himalayan seismic zone of North India. The tests results have been analysed to develop G/Gmax–γ and D–γ curves and compared with standard curves. It has been observed that upper and lower boundaries for the standard curves are remarkably different for the geological deposit under consideration. In order to assess the impact of using standard curves rather than site-specific curves, ground response analysis has been carried out at five sites along the Yamuna River using two types of curves (standard and site-specific developed in this study). The study showed that the amplification of shear waves at these sites based on the experimentally derived curves is much higher as compared to the standard curves. The proposed curves better represent dynamic behaviour of the soil deposits of the region and will provide a realistic response as far as practically possible, for the structures constructed in the states of Haryana and Delhi and nearby areas. It is anticipated that the data presented in this paper will have wide application and usage.
相似文献3.
Threshold of sediment motion under unidirectional currents 总被引：40，自引：1，他引：40
Carefully selected data for the threshold of sediment movement under unidirectional flow conditions have been utilized to re-examine the various empirical curves that are commonly employed to predict this threshold. After a review of the existing data, we employed only that data obtained from open channel flumes with parallel sidewalls where flows were uniform and steady over flattened beds of unigranular, rounded sediments. Without these restrictions, an unmanageable amount of scatter is introduced. This selected data is used to develop a modified Shields-type threshold diagram that extends the limits of the original diagram by three orders of magnitude in the grain-Reynolds number. The equally general but more easily employed Yalin diagram for sediment threshold is also examined. Although the Shields and Yalin diagrams are general in that they apply to a wide range of different liquids, in both cases somewhat different curves are obtained for threshold under air than for the liquids. The often used empirical curves of the friction velocity u*, the velocity 100 cm above the bed u100, the bottom stress θt, and Shields’ relative stress θt, all versus the grain diameter D, are limited in their ranges of application to certain combinations of grain density, fluid density, fluid viscosity and gravity. These conditions must be selected before the curves are generated from either the more general Shields or Yalin curves. For example, on the basis of the data selected for use in this paper, empirical threshold relationships for quartz density material in water are where the velocity u100 measured 100 cm above the sediment bed is given in cm/sec and the grain diameter D is in cm. The limitations on any of the threshold relationships are severe. These limitations should be properly understood so that the empirical curves and relationships are not improperly employed. 相似文献
4.
N. A. Terekhova 《Astronomy Reports》2012,56(7):504-511
We test the hypothesis put forward by Bosma (1981) that the surface density of dark matter is proportional to the surface density of HI, using decompositions of the rotation curves of a number of galaxies according to the THINGS, along with data for the galaxy NGC 6822. The rotation curves of these galaxies can be explained by assuming the existence of a massive gaseous disk in the absence of a dark halo, although the proportionality factor ??dark/??HI between the surface densities of dark matter and HI is different for different galaxies. However, there emerges the problem of the gravitational stability of galaxies whose stellar-velocity dispersions have been estimated, if the thickness of the dark-matter disk is similar to or less than the thickness of the stellar disk. The proportionality between ?? dark and ??HI is probably due to the fact that the radial profiles of ??HI for galaxies with flat rotational curves are close to the critical density of a gravitationally stable gaseous layer (??HI ?? R ?1), and ??dark(R) for a pseudo-isothermal halo obeys the same law. 相似文献
5.
内陆湖泊沉积物的易溶盐含量与湖水化学组成密切相关，因此通过测试沉积物钻心的易溶盐含量可以重建古湖水化学演化过程。在安固里淖湖心区钻取沉积剖面，以1cm为间隔分样，测试剖面八大离子的含量（即K+、Na+、Ca2+、Mg2+、CO32-、HCO3-、Cl-和SO42-）和其他有关的地球化学特征，并且对各项离子含量进行相关分析，得到剖面易溶盐组成变化曲线和和易溶盐指标变化曲线。根据易溶盐曲线变化情况，结合钻心纹层纪年得到的的纹层年代，将安固里淖8507aB.P.以来的湖水化学演化过程分为以下几个阶段：8507~7600aB.P.，湖水化学类型为Na+-Cl- 型，盐度较高；7600~4724aB.P.，湖水化学类型为Na+-Cl--SO42- 型，盐度最高；4724~3057aB.P., 湖水化学类型为Na+-Cl- 型，3057~574a B.P湖水化学类型为Na+-CO32--HCO3-，盐度较低；574aB.P.以来湖水化学类型为Na+-Cl- 型，盐度较低但是呈现快速增加趋势。同钻心的粒度分析结果相比较，易溶盐变化曲线的转折早于粒度变化曲线，反映易溶盐沉积对气候变化的反应比粒度特征更敏感，是一个较好的反映气候变化的替代性指标，有待于推广应用。 相似文献
6.
The method of “p–y” curves has been extensively used, in conjunction with simplified numerical methods, for the design and response evaluation of single piles. However, a straightforward application of the method to assess the response of pile groups is questionable when the group effect is disregarded. For this reason, the notion of p-multipliers has been therefore introduced to modify the “p–y” curves and account for pile group effect. The values proposed for p-multipliers result from pile group tests and are limited to the commonly applied spacing of 3.0 D and layout less than 3 × 3, restricting the applicability of the method to specific cases. With the aim of extending the applicability of the “p–y” method to pile groups, the authors have already proposed a methodology for estimating the “p G–y G” curves of soil resistance around a pile in a group for clayey soils. A complementary research allowing for the estimation of the “p G–y G” curves for sandy soils is presented in this paper. The well-known curves of soil resistance around the single pile in sandy soils are appropriately transformed to allow for the interaction effect between the piles in a group. Comparative examples validate the applicability and the effectiveness of the proposed method. In addition, the method can be straightforwardly extended to account for varying soil resistance, according to the particular location of a pile in a group. It can therefore be used in a most accurate manner in estimating the distribution of forces and bending moments along the characteristic piles of a group and therefore to design a pile foundation more accurately. 相似文献
7.
Although simplified numerical methods are reliable for evaluating the response of a single pile under horizontal load, their application is questionable for assessing the response of pile groups. The notion of “p–y” curves has been considered with the aim of establishing a transformation relationship able to provide the “pG–yG” curves of soil resistance around a pile in a group from the well-known curves of soil resistance around the single pile.This transformation extends the applicability of the “p–y” method to pile groups, without the need for time consuming numerical computations, rendering the proposed method efficient and attractive. Comparative examples demonstrated the applicability and the effectiveness of the proposed method. In addition, the method can be straightforwardly extended to account for varying soil resistance, according to the particular location of a pile in a group. It can therefore be used to estimate accurately force and bending moment distributions along the characteristic piles of a group, which are required for the efficient design of foundations. 相似文献
8.
R-band photometric light curves of the eruptive eclipsing binary SDSS J090350.73+330036.1 obtained during a superoutburst in May 2010 (JD 2455341-2455347) are analyzed. Observations covering an interval near the outburst maximum and the post-maximum decrease by 0.7 m are presented. Oscillations (superhumps) whose period differs from the orbital period by several percent are observed in the light curve together with eclipses, suggesting that the studied system is a SU UMa dwarf nova. A ??spiral arm?? model is used to fit the light curves and determine the parameters of the accretion disk and other components of the binary system. Together with a hot line, this model takes into account, geometrical inhomogeneities on the surface of the accretion disk, namely, two thickenings at its outer edge that decrease exponentially in the vertical direction with approach toward the white dwarf. The increase in the R-band flux from the system during the superoutburst mainly results from the enhanced luminosity of the accretion disk due to the increase in its radius by up to ??0.44a 0 at the outburst maximum (a 0 is the component separation), as well as a shallower radial temperature decrease law than in the canonical case. As the superoutburst faded, the disk radius decreased smoothly at the end of our observation (to ??0.33a 0), the thickness of its outer edge and temperature of its boundary layer decreased, and the parameter ?? g approached its canonical value. Deviations from the mean brightness of the system as a function of the superhump period P sh are analyzed for each out-of-eclipse set of observations. Various factors affecting the appearance and amplitudes of superhumps in the orbital light curves are considered. 相似文献
9.
Analytical solutions for the steady‐state response of an infinite beam resting on a visco‐elastic foundation and subjected to a concentrated load moving with a constant velocity are developed in this paper. The beam responses investigated are deflection, bending moment, shear force and contact pressure. The mechanical resistance of the foundation is modeled using two parameters ks and ts — ks accounts for soil resistance due to compressive strains in the soil and ts accounts for the resistance due to shear strains. Since this model represents the ground behavior more accurately than the Winkler spring model, the developed solutions produce beam responses that are closer to reality than those obtained using the existing solutions for Winkler model. The dynamic beam responses depend on the damping present in the system and on the velocity of the moving load. Based on the study, dynamic amplification curves are developed for beam deflection. Such amplification curves for deflection, bending moment, shear force and contact pressure can be developed for any beam‐foundation system and can be used in design. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
Theoretical absorption-line profiles and radial-velocity curves for tidally deformed optical stars in X-ray binary systems are calculated assuming LTE. The variations in the profile shapes and radial-velocity curve of the optical star are analyzed as a function of the orbital inclination of the X-ray binary system. The dependence of the shape of the radial-velocity curve on the orbital inclination i increases with decreasing component-mass ratio q = m x /m v . The integrated line profiles and radial-velocity curves of the optical star are calculated for the Cyg X-1 binary, which are then used to estimate the orbital inclination and mass of the relativistic object: i < 43° andm x = 8.2–12.8 M⊙. These estimates are in good agreement with earlier results of fitting the radial-velocity curve of Cyg X-1 using a simpler model (i < 45°, m x = 9.0–13.2 M⊙). 相似文献
11.
Ian Parsons 《Physics and Chemistry of Minerals》1978,2(3):199-213
Variation in published alkali-feldspar solvus curves is discussed in the light of the concept of complete (crystal-crystal) and exchange (crystal-fluid-crystal) equilibrium. Exchange equilibrium may lead to very regular solvus-like two-phase curves differing substantially from the true binodal solvus; certain experimental strategies tend to favour the attainment and persistence of the exchange equilibrium condition. New long duration experiments under “alkali excess” and “alkali+silica excess” conditions did not yield fledspar pairs significantly off the bracketed binodal obtained by Smith and Parsons (1974) but exchange equilibrium behaviour is shown to influence the course of equilibration in peralkaline experiments. Agreement in solvus curves obtained by bracketing experiments by several workers is excellent (±2 mol. % Or) with a straight linear relationship between T crit and P such that dT crit/dP≈16°/Kbar. These curves do not exhibit breaks or sensitivity to chemical environment, and there is no evidence that the solvus changes shape with increasing P. 相似文献
12.
Estimation of velocity function parameters in unconsolidated sands using semblance velocity analysis
Abdullatif A. Al-Shuhail 《Arabian Journal of Geosciences》2013,6(2):549-556
To properly understand seismic wave propagation in unconsolidated sand layers, it is important to estimate the parameters of their continuous velocity–depth functions. This study proposes a procedure to estimate the V 0 and k parameters of a specific velocity function, where V 0 is the direct P-wave velocity at the ground surface and k is the velocity gradient. The V 0 and k parameters are generally independent of each other. However, it is possible to relate them numerically because both depend strongly on the porosity (?) and water saturation (S w). The proposed procedure starts by tabulating V 0 and k for 0.05?≤???≤?0.5 sampled at Δ??=?0.05 and S w?=?0.6, so that only V 0 is needed for fitting. Then, time–distance (T-X) type curves of the direct arrival are calculated for the corresponding values of V 0 and k parameters values. The type curves are fitted then to the observed shot gather through a modification of the classic semblance velocity analysis method. Once the best-fit V 0 value is found, the corresponding k, ?, and S w values are picked from a V 0–k–? lookup table. The procedure is applied on synthetic shot gathers with various amounts of additive Gaussian random noise. Results show that the method is robust and tolerant to low to moderate amounts of noise. 相似文献
13.
14.
The mean 1983–1996 UBV light curves of the dwarf nova SS Cyg are used to derive the binary parameters in the quiescent state. Solutions are obtained for a classical hot-spot model and a model with an energy source lying outside the accretion disk. Photometric and spectroscopic data are combined to infer the masses and radii of the binary components. The white dwarf in SS Cyg is one and a half times as massive as the red dwarf, q=M wd /M rd ～1.45, M rd ～0.46M ⊙ and M wd ～0.66M ⊙. The orbital inclination of the system is i?51°–54°. The contribution of the accretion disk to the total flux in the quiescent state is estimated to be ～47–49% and ～54% in the VU and B filters, respectively. The hot spot contributes less than ～3% to the total optical flux. In the “non-classical” hot-spot model, the disk and bulge contributions are 27 and 2–8%, respectively, depending on the orbital phase. The shape of the mean light curves of SS Cyg suggests asymmetric heating of the red-dwarf surface in the quiescent state by high-temperature radiation generated in the hot-spot region. 相似文献
15.
Study of the concentration of major, trace, and rare earth elements (REE) in the Shahindezh karst bauxite deposit, northwestern Iran clarifies the relationship of the tetrad effect with geochemical parameters in the bauxite ores. The existence of irregular curves in the chondrite-normalized REE patterns as well as non-CHARAC behavior of geochemically isovalent pairs (Y/Ho) are related to the tetrad effect. The meaningful positive correlation between the sizes of the calculated T3 tetrad effect and some geochemical factors such as Y/Ho, ΣREE, La/Y, (La/Yb)N, and (LREE/HREE)N as well as some major oxides-based parameters like Al2O3 + LOI/SiO2 + Fe2O3, Al2O3/Fe2O3, Al2O3 + LOI, IOL, and SiO2 + Fe2O3 indicate that the studied bauxite horizon was likely deposited by different (acidic and/or alkalic) solutions at different stages. The lower part of the studied horizon with a thickness of ~4.7 m displays alkali characteristics whereas the upper parts of the horizon with a thickness of ~5.3 m are characterized by more acidic conditions. These results are fully supported by the co-occurrence of convex-concave tetrad effect curves in the chondrite-normalized REE patterns. Therefore, the tetrad effect phenomenon used in this study has proved to be a good and reliable geochemical proxy to assess the conditions of the depositional environment in the Shahindezh bauxite ores. 相似文献
16.
The first high-accuracy CCDUBV RI light curves for the recently discovered eclipsing system V1176 Cas (P = 6 . d 33, V = 11 . m 1) have been obtained. A photometric solution for the light curves and physical characteristics of the component stars are derived. The orbital eccentricity is negligible, e = 0.009; both components have physical parameters similar to the Sun, but they are younger and may have an overabundance of metals. The orientation of the orbital ellipse and the low eccentricity make studies of the apsidal motion difficult. Nevertheless, the high accuracy of the available measurements of the timings of minima has enabled derivation of an upper limit for the rate of apsidal rotation, which agrees with a theoretical estimate of this effect. 相似文献
17.
Heterogeneous equilibria in the system Ca(HSiUO6)2 · 5H2O(c)–aqueous solution were studied over broad ranges of pH, ionic strength, and ionic composition of the solution, and the pH range of stability of Ca uranyl silicate is determined. Hydrolysis products of Ca uranyl silicate are identified, and their solubility is determined. The equilibrium constant of the dissolution reaction and the standard Gibbs function of formation of Ca(HSiUO6)2 · 5H2O are calculated from experimental data, and solubility curves of uranophane and equilibrium speciation diagrams for U(VI), Si(IV), and Ca(II) in coexisting aqueous solutions and solid phases are calculated. 相似文献
18.
The chemical composition of unaltered greywacke-argillite sequences varies both abruptly and gradationally across short distances of a few centimeters to meters. These original variations are sufficient to mask changes in K2O (and other oxides) resulting from hydrothermal alteration. Sorting curves for unaltered samples present K2O contents in terms of two relatively immobile oxides SiO2 and Al2O3. This allows an estimated of the original pre-alteration K2O content of altered samples, from which gains and losses can then be calculated. 相似文献
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20.
T. S. Khruzina A. M. Cherepashchuk D. V. Bisikalo A. A. Boyarchuk O. A. Kuznetsov 《Astronomy Reports》2003,47(8):621-636
We have analyzed optical and infrared light curves of GU Mus obtained during the system's quiescent state and carried out computations for “hot-line” and “hot-spot” models. The hot-line model describes the optical variability of GU Mus better than the hot-spot model. Season-to-season variations of the shape, amplitude, and mean levels of the optical and infrared light curves of GU Mus are due to changing parameters of the hot line and, to a lesser degree, of the accretion disk. Taking into account the contribution of the variability of the disk + hot line system to the variability of the system as a whole, we are able to reliably estimate the orbital inclination, \(i = 54^\circ \pm 1^\circ .3\), and the mass of the black hole, M X =(6.7–7.6)M⊙. 相似文献