Three-dimensional analysis of water infiltration into the Gouhou rockfill dam using saturated–unsaturated seepage theory

2006 ◽  
Vol 43 (5) ◽  
pp. 449-461 ◽  
Author(s):  
Qun Chen ◽  
L M Zhang
Keyword(s):  
Three Dimensional ◽  
Water Infiltration ◽  
Internal Erosion ◽  
Seepage Water ◽  
Two Dimensional ◽  
Material Anisotropy ◽  
Seepage Failure ◽  
Rockfill Dam ◽  
Seepage Theory ◽  
Unsaturated Seepage

The Gouhou Dam was a concrete-faced rockfill dam built in a steep canyon that collapsed in 1993 due to internal erosion during the initial reservoir filling. In this paper, the process of water infiltration into the originally unsaturated rockfill dam is studied using three-dimensional saturated–unsaturated seepage theory. The three-dimensional characteristics of seepage through the dam bounded by steep abutments, the effect of material anisotropy, and the effect of rockfill stratifications are studied. The three-dimensional results are compared with those from two-dimensional analyses. The three-dimensional simulations show that seepage water flows faster and the hydraulic gradients are greater near the abutment boundary in the dam. As such, the evolution of the seepage failure in the three-dimensional cases is faster than that in the two-dimensional analyses, and the two-dimensional analyses will underestimate the risk of seepage failure, particularly near the abutment boundary. If the materials in the dam were uniform, the reservoir water would infiltrate into the dam along a downward flow path towards the riverbed, and not exit from the surface on the downstream slope. Increasing the horizontal coefficient of permeability of the rockfill increases the infiltration velocity, but the material anisotropy does not appreciably change the infiltration pattern. Stratifications in the rockfill, however, cause the seepage water to advance more quickly in the horizontal direction along the interface between the sandwich layer and the rockfill, thus increasing the possibility of seepage failure.Key words: seepage, seepage failure, rockfill dam, unsaturated soils, wetting front, numerical analysis.

scholarly journals A QUANTITATIVE EVALUATION OF THE WATER DISTRIBUTION IN A SOIL SAMPLE USING NEUTRON IMAGING

2016 ◽  
Vol 56 (5) ◽  
pp. 388-394 ◽  
Author(s):  
Jan Šácha ◽  
Michal Sněhota ◽  
Jan Hovind
Keyword(s):  
Water Content ◽  
Soil Sample ◽  
Neutron Radiography ◽  
Three Dimensional ◽  
Neutron Imaging ◽  
Water Infiltration ◽  
Water Volume ◽  
Two Dimensional ◽  
Total Water ◽  
Beam Hardening

This paper presents an empirical method by Kang et al. recently proposed for correcting two-dimensional neutron radiography for water quantification in soil. The method was tested on data from neutron imaging of the water infiltration in a soil sample. The raw data were affected by neutron scattering and by beam hardening artefacts. Two strategies for identifying the correction parameters are proposed in this paper. The method has been further developed for the case of three-dimensional neutron tomography. In a related experiment, neutron imaging is used to record ponded-infiltration experiments in two artificial soil samples. Radiograms, i.e., two-dimensional projections of the sample, were acquired during infiltration. A calculation was made of the amount of water and its distribution within the radiograms, in the form of two-dimensional water thickness maps. Tomograms were reconstructed from the corrected and uncorrected water thickness maps to obtain the 3D spatial distribution of the water content within the sample. Without the correction, the beam hardening and the scattering effects overestimated the water content values close to the perimeter of the sample, and at the same time underestimated the values close to the centre of the sample. The total water content of the entire sample was the same in both cases. The empirical correction method presented in this study is a relatively accurate, rapid and simple way to obtain the quantitatively determined water content from two-dimensional and three-dimensional neutron images. However, an independent method for measuring the total water volume in the sample is needed in order to identify the correction parameters.

The three-dimensional stability of boundary-layer flow over compliant walls

1992 ◽  
Vol 238 ◽  
pp. 537-577 ◽  
Author(s):  
K. S. Yeo
Keyword(s):  
Boundary Layer ◽  
Eigenvalue Problem ◽  
Growth Rates ◽  
Isotropic Material ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Material Anisotropy ◽  
Compliant Walls ◽  
Tollmien Schlichting ◽  
Disturbance Growth

This paper examines the linear stability of the Blasius boundary layer over compliant walls to three-dimensional (oblique) disturbance wave modes. The formulation of the eigenvalue problem is applicable to compliant walls possessing general material anisotropy. Isotropic-material walls and selected classes of anisotropic-material walls are studied. When the properties of the wall are identical with respect to all oblique wave directions, the stability eigenvalue problem for unstable three-dimensional wave modes may be reduced to an equivalent problem for two-dimensional modes. The results for isotropic-material walls show that three-dimensional Tollmien–Schlichting instability modes are more dominant than their two-dimensional counterparts when the walls are sufficiently compliant. The critical Reynolds number for Tollmien-Schlichting instability may be given by three-dimensional modes. Furthermore, for highly compliant walls, calculations based solely on two-dimensional modes are likely to underestimate the maximum disturbance growth factor needed for transition prediction and correlation. However, because the disturbance growth rates on highly compliant walls are much lower than those on a rigid wall, significant delay of transition may still be possible provided compliance-induced instabilities are properly suppressed. Walls featuring material anisotropy which have reduced stiffness to shear deformation in the transverse and oblique planes are also investigated. Such anisotropy is found to be effective in reducing the growth rates of the three-dimensional modes relative to those of the two-dimensional modes.

Modeling of low-cement extruded curb of concrete-faced rockfill dam

2011 ◽  
Vol 48 (1) ◽  
pp. 89-97 ◽  
Author(s):  
Ga Zhang ◽  
Jian-Min Zhang
Keyword(s):  
Numerical Simulation ◽  
Damage Model ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Direct Simulation ◽  
Construction Technique ◽  
Displacement Analysis ◽  
Rockfill Dam ◽  
The Face ◽  
Cushion Layer

As the key structure of a practical construction technique, the low-cement extruded curb has been widely used in recent concrete-faced rockfill dams (CFRDs). The extruded curb exhibits significant interactions with the neighboring gravels and with the face slab. These interactions were investigated using element tests, and a new model was proposed. This model is composed of three parts: (i) the equivalent slab that is described using an ideal elastoplasticity model, (ii) the equivalent interface between the curb and the gravel cushion layer that is described using an elastoplasticity damage model, and (iii) the interface between the curb and the face slab that is described using a modified ideal elastoplasticity model. This model was verified via a two-dimensional numerical simulation of an ideal CFRD to capture the main behavior of the extruded curb with interactions between the extruded curb and the neighboring soil – face slab, employing a significantly smaller number of elements and a shorter calculation than direct simulation. The model was used to perform a three-dimensional stress–displacement analysis of the Bakun CFRD (205 m in height), and the results showed that the extruded curb causes a change in the stress of the face slab.

Numerical Simulation of Geomembrane Defect Leakage by Saturated-Unsaturated Seepage Method

2014 ◽  
Vol 904 ◽  
pp. 474-478 ◽  
Author(s):  
Lei Gan ◽  
Zhen Zhong Shen ◽  
Zhong Qi Yan ◽  
Hua Chun Ren
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
Seepage Field ◽  
Galerkin Finite Element ◽  
Dimensional Finite Element ◽  
Seepage Theory ◽  
Three Dimensional Finite Element ◽  
Unsaturated Seepage ◽  
Element Method

For the leakage problem caused by geomembrane defect, the unstable saturated-unsaturated seepage theory and Galerkin finite element method have been adopted. So a three-dimensional finite element numerical model of an earth-rock dam with geomembrane anti-seepage system is simulated by the unstable saturated-unsaturated seepage finite element method. The influnence on seepage field for the varying degrees of geomembrane damage is analyzed, and the overall and local seepage field characteristics of the dam for geomembrane defect leakage are discussed. The results show that the numerical method provides an effective way to study the leakage problem of geomembrane defect.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

A linearity test for thick specimens imaged by HVEM over a 180° angular range

1991 ◽  
Vol 49 ◽  
pp. 552-553
Author(s):  
Yu Liu
Keyword(s):  
Phase Contrast ◽  
Three Dimensional ◽  
Angular Range ◽  
Two Dimensional ◽  
Back Projection ◽  
Line Integral ◽  
Exponential Law ◽  
Transmission Electron ◽  
Absorption Law ◽  
Linearity Test

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.

An Image Reconstruction System Applied to High Voltage Microscopy

1975 ◽  
Vol 33 ◽  
pp. 292-293
Author(s):  
D. E. Johnson
Keyword(s):  
High Voltage ◽  
Prior Information ◽  
Block Diagram ◽  
Three Dimensional ◽  
Real Space ◽  
Two Dimensional ◽  
Efficient Manner ◽  
Fourier Methods ◽  
Tilt Series ◽  
Methods Of Reconstruction

Increased specimen penetration; the principle advantage of high voltage microscopy, is accompanied by an increased need to utilize information on three dimensional specimen structure available in the form of two dimensional projections (i.e. micrographs). We are engaged in a program to develop methods which allow the maximum use of information contained in a through tilt series of micrographs to determine three dimensional speciman structure.In general, we are dealing with structures lacking in symmetry and with projections available from only a limited span of angles (±60°). For these reasons, we must make maximum use of any prior information available about the specimen. To do this in the most efficient manner, we have concentrated on iterative, real space methods rather than Fourier methods of reconstruction. The particular iterative algorithm we have developed is given in detail in ref. 3. A block diagram of the complete reconstruction system is shown in fig. 1.

Computer Assisted Image Reconstruction of Oligomer Structure

1976 ◽  
Vol 34 ◽  
pp. 472-473
Author(s):  
A.M. Jones ◽  
A. Max Fiskin
Keyword(s):  
Three Dimensional ◽  
Depth Of Field ◽  
Computer Assisted ◽  
Projection Data ◽  
Two Dimensional ◽  
Single Particles ◽  
Dimensional Reconstruction ◽  
Computer Assisted Image ◽  
The Fourier Transform ◽  
Space Approach

If the tilt of a specimen can be varied either by the strategy of observing identical particles orientated randomly or by use of a eucentric goniometer stage, three dimensional reconstruction procedures are available (l). If the specimens, such as small protein aggregates, lack periodicity, direct space methods compete favorably in ease of implementation with reconstruction by the Fourier (transform) space approach (2). Regardless of method, reconstruction is possible because useful specimen thicknesses are always much less than the depth of field in an electron microscope. Thus electron images record the amount of stain in columns of the object normal to the recording plates. For single particles, practical considerations dictate that the specimen be tilted precisely about a single axis. In so doing a reconstructed image is achieved serially from two-dimensional sections which in turn are generated by a series of back-to-front lines of projection data.

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