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1.
通过块体集上限分析方法,研究锚板的抗拔承载力和破坏面特性,并将分析结果与Das[1]以及Rowe[2]的锚板模型试验结果进行详细对比,验证块体集上限法的有效性。分析斜坡地形条件下锚板抗拔承载特性,并与Khing等[3]的条形锚板抗拔承载力试验以及Rao和Prasad[4]的圆形锚板抗拔承载力试验进行详细对比,分析斜坡地形条件下锚板模型试验中采用拉杆加载的方式对于试验结果的影响。分析结果表明,斜坡地形条件下拉杆的存在对于锚板抗拔承载力影响较大,模型试验应优先采用Trapdoor模型。 相似文献
2.
为了研究最优含水率、流动上、下限含水率对轻量土性能的影响,通过密度、无侧限抗压强度试验研究了混合土的工程性质。结果表明：采用流动性指标 控制混合土的流动性基本可行。混合土处于流动性上、下限含水率时,无侧限应力-应变关系曲线几乎重合,流动性上、下限含水率范围内土壤性质较为接近。无侧限抗压强度随含水率增加而衰减,但流动上、下限含水率对应强度差别不大。不管含水率高低,强度随龄期增长,都可以采用双曲线模型进行预测,并且总结了7 d、90 d强度与28 d强度之间的经验关系。当含水率为最优含水率时,混合土基本不收缩;在流动性上、下限含水率范围内,线收缩率范围为1.53%～4.71%,体积收缩率范围为4.53%～13.46%,收缩性受含水率、水泥剂量等因素影响。理想密度模型可以近似预测混合土的湿密度,高含水率时预测值有一定误差,误差范围为3.834%～8.231%。 相似文献
3.
Using a two-component model for the structure of the circumstellar nebulae of WR and O stars, we predict that their emission may be variable on time scales from several months to several years. This variability should be manifest as an enhancement of the emission luminosities of separate compact regions in the hydrogen Balmer lines, HeII ion line, and nebular lines of the ions [OII], [OIII], [NeIII], and [NeIV]. In the model considered, this line variability reflects non-stationary ionization, cooling, and recombination behind a shock propagating inward in the cloud. The set of lines that are variable depends on the shock velocity, while the scale of the variability decreases with increasing cloud density. 相似文献
4.
Some mathematical models for permafrost 总被引：2，自引：0，他引：2
This paper contains a review of fundamental new results in mathematical theory of geocryological problems obtained in the Institute of Mechanics in Moscow State University [5]. The problems of temperature regime and phase state of permafrost [2, 8, 4], formation and evolution of thermokarst are analyzed [3, 6, 7, 11, 12]. In this paper the mathematical models of these problems, computer programs for the models and some numerical calculations for concrete objects and districts are suggested [3, 6, 8, 5]. 相似文献
5.
裂变径迹分析方法利用裂变径迹年龄及裂变径迹长度分布形态来反映随时间产生的裂变径迹积累及由温度控制的退火(裂变径迹缩短或消失)两种因素综合作用的结果。近几年来，有关磷灰石的退火特征进行了大量实验和野外研究，取得了较大进展。本文通过对80年代以来国内外裂变径迹研究状况的追踪调研结果，简要介绍裂变径迹定年方法的主要进展及应用情况。 相似文献
6.
In this paper, we are interested in the modeling of wave propagation in viscoelastic media. We present a family of models which generalize the Zeners model. We achieve its mathematical analysis: existence and uniqueness of solutions, energy decay and propagation with finite speed. For the numerical resolution, we extend a mixed finite element method proposed in [8]. This method combines mass lumping with a centered explicit scheme for time discretization. For the resulting scheme, we prove a discrete energy decay result and provide a sufficient stability condition. For the numerical simulation in open domains we adapt the perfectly matched layers techniques to viscoelastic waves [23]. Various numerical results are presented. 相似文献
7.
在有较厚沉积物覆盖的地洼盆地中，如何利用已有的重力资料研究被掩埋目的层的分布、厚皮等，是沉积盆地及能源研究等方面的一个重要任务。本文的电子计算机正、反演处理，正是这方面的一个尝试。 相似文献
8.
Open cast mining of lignite leads to dumps containing highly mineralised pore waters. To predict the impact of the dump waters on the undisturbed aquifers two steps are necessary. (1) The prediction of dump water quality at times when steady state flow conditions will be established. (2) The simulation of the dump ground water migration with a model that is able to handle the complexity of the homogeneous and heterogeneous interactions of the migration process.For the investigated site Jänschwalde, which is still dewatered, a chemical mass balance was performed. The predicted alkalinity potentials exceed acidity potentials for the dump as a whole. The distribution of these parameters show high alkalinity potentials for the northern part.In order to model the migration process the transport code PCGEOFIM® [Anwenderdokumentaion, IBGW Leipzig, (in German)] was coupled with the geochemical equilibrium code PHREEQC [USGS, Water-Resources Investigations Report]. This was done to simulate redox reactions, mineral dissolution and precipitation, and cation exchange in the ground water zone. The model is verified by a column flow test. The results of the simulations show a small effect of the migrating dump waters on the quartenary aquifer with respect to acidity changes. This results from calcite buffering and cation exchange. The impact on the quartenary aquifer by sulphate is much higher. 相似文献
9.
Chapman and Pollack (C and P)[2007, Int J Earth Sci] criticize Hamza et al. [2007, Int J Earth Sci] for using actual heat flux measurements in young oceanic crust instead of values from 1-D cooling models.
The rationalization of C and P and previous authors is that hydrothermal circulation causes the discrepancy between model
and measurement. However, the discrepancy between model values and measured heat flux exists over the entire ocean floor and
is opposite to the perturbations that hydrothermal circulation would superimpose on a conductive system [Hofmeister and Criss
(2005) Tectonophysics 409:199–203]. The error lies in force-fitting a 1-D cooling model to the 3-D oceanic crust [Hofmeister and
Criss (2005) Tectonophysics 395:159–177]. Shortcomings of the 1-D model include mathematical errors, such as use of volumetric rather
than linear thermal expansivity to describe contraction which, by assumption, is limited only to the Z
-direction [Hofmeister and Criss (2006) Tectonophysics]. This 3× error, traceable to McKenzie and Sclater [1969, Bull Vocanol 33–1:101–118], accidentally provides good agreement of model values with globally averaged seafloor depths
for young, but not old ages, and is the sole rationale for using the simplistic cooling model. There is no justification for
selective substitution of erroneous 1-D model values for measurements only for the younger half of the 3-D oceanic crust,
as stridently and arbitrarily promoted by C and P. Hamza et al. [2007, Int J Earth Sci], in contrast, use the scientific method, which calls for discarding models that do not well describe physical
phenomena.
The remainder of this report summarizes the shortcomings of cooling models, particularly the half-space cooling (HSC) model
touted by C and P, and explains how hydrothermal circulation affects heat flux. We focus on the basics, as these have been
misunderstood. With the key issues of C and P being erroneous, it is not necessary to address their remaining comments, many
of which enumerate the vote for an imagined, gargantuan circulation of hot fluid through oceanic basins that is somehow warmed
without removing heat from the rocks. The use of “consensus” to belittle valid challenge is the enemy of the scientific method. 相似文献
10.
Astronomy Reports - We search for observational evidence that is in agreement with the model of a binary star system in gamma-ray bursts (GRBs), as presented in [1–3]. The model predicts... 相似文献
11.
J. Kemeny E. Mofya R. Kaunda P. Lever 《Fragblast: International Journal for Blasting and Fragmentation》2002,6(3):311-320
One of the fundamental requirements for being able to optimise blasting is the ability to predict fragmentation. An accurate blast fragmentation model allows a mine to adjust the fragmentation size for different downstream processes (mill processing versus leach, for instance), and to make real time adjustments in blasting parameters to account for changes in rock mass characteristics (hardness, fracture density, fracture orientation, etc). A number of blast fragmentation models have been developed in the past 40 years such as the Kuz-Ram model [1]. Fragmentation models have a limited usefulness at the present time because: 1. The input parameters are not the most useful for the engineer to determine and data for these parameters are not available throughout the rock mass. 2. Even if the input parameters are known, the models still do not consistently predict the correct fragmentation. This is because the models capture some but not all of the important rock and blast phenomena. 3. The models do not allow for 'tuning' at a specific mine site. This paper describes studies that are being conducted to improve blast fragmentation models. The Split image processing software is used for these studies [2, 3]. 相似文献
12.
沉管隧道基槽爆破施工对既有堤岸稳定性影响的数值仿真分析 总被引：1，自引：0，他引：1
结合爆破数值模拟中爆破荷载的特点,分析了各种荷载施加方法的特点及爆破震动场模拟的要求,基于圣维南荷载等效原理,提出了爆破荷载的等效施加方法,即将作用在炮孔壁上的爆破荷载等效后,施加在同排炮孔中心线或者面上来模拟爆破荷载的作用。结果表明,等效施加方法在近区存在一定差异,但在中远区吻合得较好。利用该等效荷载施加方法,采用三维实体模型计算分析了某沉管隧道基槽爆破施工对既有堤岸稳定性影响,计算了周围不同位置、不同深度位置处的振动响应,并在此基础上,分析研究了减小爆破振动对既有结构物影响的减振措施,可为类似工程提供借鉴。 相似文献
13.
In this article, we propose to:
1. Establish most of the properties conjectured in [2] about the higher order finite difference approximation of the 1D Laplace
operator.
2. Generalize to any order the fourth-order accurate scheme in space and time of Shubin and Bell [20] and Cohen [6].
For this new family of 2m–2m schemes, we establish, via elementary mathematics, various stability and dispersion results that
are helpful to compare these schemes to the 2–2m schemes of Anné et al. [2].
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Generalized equations using fractional-flow dimensions were derived to estimate the Darcy and groundwater-flow velocities
obtained from the point-dilution and the single-well injection-withdrawal field tests. Flow velocities can only be estimated
from single-well tests if the kinematic porosity or the hydraulic conductivity and hydraulic gradient are known a priori.
A pumping test performed on the boreholes will yield an estimate of the fractional-flow dimension and the extent of the flow
region by applying the generalized radial flow (GRF) model of Barker [Barker JA (1988) A generalized radial flow model for
hydraulic tests in fractured rock. Water Resour Res 24(10):1796–1804]. These parameters are used in the generalised equations
for the single-well tracer tests to estimate the flow-through area and, therewith, the Darcy or flow velocity.
The generalized procedure, described in detail in Part 1 of this paper, is applied to two boreholes on the Campus Test Site
located at the University of the Free State, Bloemfontein, South Africa, and it is shown that the two independent tests (i.e.
the point-dilution and the single-well injection-withdrawal tests) yield similar estimates of the natural-seepage velocity
in the aquifer. The estimated natural-flow velocity obtained by using fractional dimensions is about two times higher than
the velocity estimated by using the standard method (i.e. flow dimension n=2, flow thickness equal to length of the sealed-off section of the borehole).
Electronic Publication 相似文献
15.
Chemical composition of the phases occurring as corona structures in the Thessaloniki gabbros are subjected to algebraic method of treatment following Korzhinskii [1]. The analysis reveals that the mineralogical reactions responsible for the growth of the corona structures were possibly allochemical in nature in regard to the non-volatile components. The chemical similarity of the pyroxenes occurring within and beyond the corona structures in the gabbros appears compatible with such a model. 相似文献
16.
The integral equations of the direct problem of magnetic prospecting with respect to demagnetization are derived for a two-layer medium model; a method of determining the intensity of a secondary magnetic field for the case of magnetizing by a static field, whose potential is a harmonic function, is described. The respective integral equations are written based on the theory of a simple layer potential. An iteration algorithm for solving the three-dimensional structural inverse problem of magnetic prospecting with respect to demagnetization for the sampled medium model is proposed based on the modified method of local corrections. Its numerical implementation is less computer-intensive than, for example, the gradient methods of nonlinear minimization, the sampling accuracy being equal. Note that problems of electric and magnetic prospecting with respect to demagnetization and thermometry are mathematically equivalent for stationary fields [1]. Therefore, the obtained results can be used in interpreting the data of these methods. 相似文献
17.
A combination of empirical and physically based hydrological models has been used to analyze historical data on rainfall and debris-flow occurrence in western Campania, to examine the correlation between rainfall and debris-flow events.
Rainfall data from major storms recorded in recent decades in western Campania were compiled, including daily series from several rain gauges located inside landslide areas, supplemented by hourly rainfall data from some of the principal storms.
A two-phase approach is proposed. During phase 1, soil moisture levels have been modelled as the hydrological balance between precipitation and evapotranspiration, on a daily scale, using the method of Thornthwaite [Geograph. Rev. 38 (1948) 55].
Phase 2 is related to the accumulation of surplus moisture from intense rainfall, leading to the development of positive pore pressures. These interactions take place on an hourly time scale by the “leaky barrel” (LB) model described by Wilson and Wiezoreck [Env. Eng. Geoscience, 1 (1995) 11]. In combination with hourly rainfall records, the LB model has been used to compare hydrological effects of different storms. The critical level of retained rain water has been fixed by the timing of debris-flow activity, related to recorded storm events.
New rainfall intensity–duration thresholds for debris-flow initiation in western Campania are proposed. These thresholds are related to individual rain gauge and assume a previously satisfied field capacity condition. The new thresholds are somewhat higher than those plotted by previous authors, but are thought to be more accurate and thus need less conservatism. 相似文献
18.
The yield vertex non-coaxial model is different from classical elastoplastic models, in that there is an additional plastic strain rate tangential to yield surfaces, as well as the plastic strain rate normal to yield surfaces, when orientations of principal stress change. This feature raises concerns on its finite element implementations. In nonlinear finite element numerical iterations, a large tangential plastic strain rate is likely to make the trial total strain rate direct inside a yield surface, which entails convergence difficulty. Some modifications are introduced on the non-coaxial model itself to make numerical convergence easier in the work published in Yang and Yu (2010) [20]. This paper is an extension of the previous work. Instead of modifying the non-coaxial model itself, this paper concerns the use of finite element explicit procedure, which is suitable for highly discontinuous problems. The simulations of shallow foundation load-settlement responses indicate that the finite element explicit procedure, assisted with a robust and explicit automatic substepping integration scheme of the non-coaxial model, does not encounter numerical difficulty. In addition, the overall trends of implicit and explicit simulations are similar. 相似文献
19.