1 INTRODUCTIONThat the radar data are reasonably ingested into theassimilation analysis system to improve the analysisquality and prediction precision is one of the problemsmeteorologists currently try to resolve. Many scholarshave already obtained some r… 相似文献
1 INTRODUCTION China is rich in mountains. The mountainous area occupies 69% of the total land of the country. Thus, landslides frequently occur in the mountain areas of China. Landslides originating in subsurface soils are typical, and constitute approxi… 相似文献
Upscaling is a major issue regarding mechanical and transport properties of rocks. This paper examines three issues relative
to upscaling. The first one is a brief overview of Effective Medium Theory (EMT), which is a key tool to predict average rock
properties at a macroscopic scale in the case of a statistically homogeneous medium. EMT is of particular interest in the
calculation of elastic properties. As discussed in this paper, EMT can thus provide a possible way to perform upscaling, although
it is by no means the only one, and in particular it is irrelevant if the medium does not adhere to statistical homogeneity.
This last circumstance is examined in part two of the paper. We focus on the example of constructing a hydrocarbon reservoir
model. Such a construction is a required step in the process of making reasonable predictions for oil production. Taking into
account rock permeability, lithological units and various structural discontinuities at different scales is part of this construction.
The result is that stochastic reservoir models are built that rely on various numerical upscaling methods. These methods are
reviewed. They provide techniques which make it possible to deal with upscaling on a general basis. Finally, a last case in
which upscaling is trivial is considered in the third part of the paper. This is the fractal case. Fractal models have become
popular precisely because they are free of the assumption of statistical homogeneity and yet do not involve numerical methods.
It is suggested that using a physical criterion as a means to discriminate whether fractality is a dream or reality would
be more satisfactory than relying on a limited data set alone. 相似文献
Low-frequency current fluctuations in the deep central equatorial Atlantic are analyzed using current meter measurements recorded
from November 1992 to November 1994. Current meters were located at about 14°W of longitude and 1° of latitude on both sides
of the equator between 1,700 m depth and the ocean bottom. At all sampling depths, the velocity fluctuations are dominantly
zonal and symmetrical with respect to the equator. At 1,700 and 2,000 m, the flow is dominated by annual period fluctuations,
at 3,000 m, the velocity field amplitude presents a minimum, and at 3,750 and 3,950 m, the flow is modulated by annual and
semiannual period variability. The annual signal exhibits an apparent upward phase propagation. When considering the phase
and the amplitude of the seasonal fluctuations, the data compare well with the outputs of a realistic numerical simulation
of the Atlantic Ocean. Together with a previous analysis of the model simulations, this supports the idea that the observed
annual fluctuations are due to wind-forced vertically propagating Kelvin and Rossby waves. Data and model do not provide deciding
evidences of the presence of semiannual equatorial waves deeper than 3,500 m depth in the central equatorial Atlantic Ocean. 相似文献
The application of numerical models for the simulation of coastal hydro-and sediment dynamics requires model verification, calibration and validation with field data. Yet, no commonly accepted rules for the evaluation of sediment transport models exist. This paper discusses the significance of statistical parameters and their limitations considering common time lags in tidal environments. It is shown that the occasionally used discrepancy ratio lacks quantitative and qualitative information on model performance, as the time context information on time series characteristics is lost. As an initial measure of association, the simple linear correlation coefficient r2 is proposed. To account for time lag errors in suspended transport models, a separate cross-correlation analysis for the flood and ebb tidal phase is proposed. For a comparison with other model applications, a concluding rating of model performance can be expressed by a dimensionless error definition which takes into account the quality of field data. 相似文献
Stability conditions in an area located NW of Barcelona (Spain) are discussed. Here, several mass movements were observed, mainly affecting weathered Paleozoic slates. Many of these failures involved slopes cut along recent infrastructures: debris flows, wedge and plane failures, generally surficial, occurred more frequently. After a detailed geological and geomorphologic survey, geomechanic characterization was carried out, according to RMR and SMR classifications. This rating gave a prediction of slope behaviour, in fairly good agreement with the real observed one.
Stability numerical analysis was carried out for the main cut slopes, based upon the Limit Equilibrium Method. First of all, the deterministic factor of safety was computed using the mean values of parameters. After that, a simulation technique based upon the Monte Carlo Method was applied in order to obtain factor of safety distributions. The probability of failure was estimated as P(F<1).
Finally, results from deterministic and probabilistic approaches were compared. The effectiveness of different possible remedial measures was highlighted by means of a sensitivity analysis, which showed that the more important parameters in the study area are the geometrical ones (height, slope and failure plane angles). The final technical solutions adopted are briefly outlined. 相似文献
A DDM (displacement discontinuity method) program coupled with a modified energy criterion is used to simulate the development of cracks and chips by indentation tools. In our analysis a cavity model is applied to represent the expansion of crushed rock to the surrounding rock and the cracks are formedin two-dimensional and quasi-static conditions. The model parameters, rock properties and load magnitudes are varied in the numerical calculations. The results show that chips are formed by multiple mechanisms of either tension or shear, or their combinations. The cracks may either propagate to the free surface to form chips or rest in the rock subsurface. The crack development is dependent upon rock and fracture properties, loading force and tool characteristics. The DDM is a convenient tool in the study of rock fragmentation and cracks. 相似文献
A hybrid discrete-continuum approach has been presented in this paper to simulate water flow in the near and far fields of deformable fractured rocks. In the near field, the discrete model is used; while in the far field, the equivalent continuum model is employed. The discrete element method (with the static relaxation algorithm) is used in the near field and the boundary integral equation method in the far field. Along the interface of these two domains, both mechanical and hydraulic compatibility conditions are satisfied. Fully coupled hydro-mechanical analysis can be conducted in the combined near and far fields. Application to a dam foundation problem has demonstrated the capability of the developed approach. 相似文献