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G.h. Lei - One of the best experts on this subject based on the ideXlab platform.
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A general solution for vertical-drain consolidation with Impeded Drainage boundaries
Journal of Central South University, 2016Co-Authors: G.h. LeiAbstract:An analytical solution is derived from the generalized governing equations of equal-strain consolidation with vertical drains under multi-ramp surcharge preloading. The hydraulic boundary conditions at both top and bottom of the consolidating soil are modelled as Impeded Drainage. The Impeded Drainage is described by using the third type boundary condition with a characteristic factor of Drainage efficiency. Fully drained and undrained boundary conditions can also be modelled by applying an infinite and a zero characteristic factor, respectively. Simultaneous radial and vertical flow conditions are considered, together with the effects of drain resistance and smear. An increase in total stress due to multi-ramp loading is reasonably modelled as a function of both time and depth. A solution to calculate excess pore-water pressure at any arbitrary point in soil is derived, and the overall average degree of consolidation is obtained. It shows that the proposed solution can be used to analyze not only vertical-drain consolidation but also one-dimensional consolidation under either one-way or two-way vertical Drainage conditions. The characteristic factors of Drainage efficiency of top and bottom boundaries have a potentially important influence on consolidation. The boundary may be considered fully drained when the characteristic factor is greater than 100 and fully undrained when the characteristic factor is less than 0.1. The stress distribution along depth induced by the surcharge loading has a limited effect on the overall average degree of consolidation. However, it has a significant effect on the dissipation of excess pore-water pressure.
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Vertical-drain consolidation using stone columns: An analytical solution with an Impeded Drainage boundary under multi-ramp loading
Geotextiles and Geomembranes, 2016Co-Authors: G.h. LeiAbstract:Abstract An analytical solution is derived to predict consolidation with vertical drains under Impeded Drainage boundary conditions and multi-ramp surcharge loading. The Impeded Drainage is modelled by adopting the third type boundary condition with a dimensionless characteristic factor of Drainage efficiency developed by Gray (1945) for one-dimensional consolidation. Fully drained and undrained boundary conditions can also be modelled by applying an infinite and a zero characteristic factor, respectively. The combined effects of drain resistance and smear are taken into account fully. An explicit, rigorous analytical solution is derived using the method of separation of variables to calculate excess pore-water pressure at any arbitrary point in soil and to derive the overall average degree of consolidation. The proposed solution can also be used to analyse one-dimensional consolidation without vertical drains but with an Impeded Drainage boundary. Its validity and accuracy are verified by comparing the proposed solution with the solutions developed by Gray (1945) and Terzaghi (1943). Its practical applicability is also evaluated by analysing a case history involving a fill embankment, which was constructed over a crust layer of hard soil overlying soft clay improved with stone columns. The crust layer is modelled as an Impeded Drainage. Reasonably good agreement is obtained between the consolidation results obtained from the proposed analytical solution and available three-dimensional finite-element predictions. With the further consideration of smear effects, good agreement is achieved between the consolidation results obtained from the proposed analytical solution and field measurements.
Minghua Huang - One of the best experts on this subject based on the ideXlab platform.
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A general analytical solution for two-dimensional plane strain consolidation of unsaturated soil incorporating lateral and vertical Impeded Drainage boundaries
Computers and Geotechnics, 2021Co-Authors: Minghua Huang, Minghua ZhaoAbstract:Abstract In most practical consolidation problems, Impeded Drainage boundaries are a great concern. By simultaneously introducing the Impeded Drainage boundaries in the horizontal and vertical directions, this study attempts to constitute a general two-dimensional (2D) plane strain consolidation system of unsaturated soil. A newly analytical solution is developed to calculate the excess pore-air and pore-water pressures and average degree of consolidation. On the basis of the eigenfunction expansion method, the developed analytical solution is given as a product of three functions, including one variable of time, horizontal and vertical dimensions only. For the Impeded Drainage boundaries, the eigenfunctions and eigenvalues are derived in the horizontal and vertical dimensions. The Laplace transform technique is further adopted to solve the ordinary differential system in the time domain. The developed analytical solution is verified with the existing analytical/semi-analytical solutions and finite difference solution for several typical cases. Excellent agreements are obtained so that the correctness of the developed analytical solution is validated. Moreover, two worked examples are presented to show the superiority of the developed analytical solution and to assess the influences of the Drainage parameters on the 2D plane strain consolidation behavior of unsaturated soil.
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One-Dimensional Consolidation of Multi-Layered Unsaturated Soil with Impeded Drainage Boundaries
Applied Sciences, 2020Co-Authors: Suhua Zhou, Jiatao Kang, Minghua HuangAbstract:In geotechnical engineering, the consolidation of unsaturated soil is a common issue of great interest. Considering the multi-layered property and Impeded Drainage boundary condition of the soil stratum in real engineering, this study aimed to develop a general semi-analytical solution for assessing the one-dimensional (1D) consolidation behavior of multi-layered unsaturated soil that is subjected to a general Impeded Drainage boundary condition and a time-dependent loading. To achieve the final solution, the proposed consolidation system is firstly decoupled and solved in the Laplace domain. Then, the semi-analytical solutions for the excess pore-air pressure and excess pore-water pressures as well as the soil settlement are formulated. The Crump method is employed to provide their final results in the time domain. The correctness of the derived solutions was verified against the available analytical and numerical solutions, and excellent agreements were found for the two comparisons. Moreover, two studied examples are presented to illustrate the 1D consolidation behavior of multi-layered unsaturated soil and the influences stemming from the Impeded Drainage parameters are discussed.
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A general analytical solution for one dimensional consolidation of unsaturated soil incorporating Impeded Drainage boundaries
Computers and Geotechnics, 2020Co-Authors: Minghua Huang, Minghua ZhaoAbstract:Abstract This paper presents a novel analytical solution for one dimensional consolidation system of unsaturated soil incorporating Impeded Drainage boundary conditions. Through diagonalizing the coefficient matrix, the consolidation system is firstly transformed into a diagonal one with respect to a new variable vector. Then, using the methods of eigenfunction expansion and undetermined coefficients, the analytical solution is developed through deriving the eigenvalues, corresponding eigenfunctions and undetermined coefficients. Its orthogonality and convergence are proven, and several comparisons against existing solutions and two typical experimental data are performed to verify its validity. Finally, two typical examples are provided to illustrate the consolidation behavior of unsaturated soil with different Drainage parameters. The results indicate that the present analytical solution converges rapidly, and it is consistent with existing analytical, semi-analytical and numerical solutions for various Drainage boundary conditions. The proposed analytical solution achieves an overall better agreement with experimental data, and the Impeded Drainage boundary condition is more reasonable to describe the consolidation phenomenon of unsaturated soil. In general, larger Drainage parameter accelerates excess pore-pressure dissipation and soil settlement.
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2D Plane Strain Consolidation Process of Unsaturated Soil with Vertical Impeded Drainage Boundaries
Processes, 2018Co-Authors: Minghua HuangAbstract:The consolidation process of soil stratum is a common issue in geotechnical engineering. In this paper, the two-dimensional (2D) plane strain consolidation process of unsaturated soil was studied by incorporating vertical Impeded Drainage boundaries. The eigenfunction expansion and Laplace transform techniques were adopted to transform the partial differential equations for both the air and water phases into two ordinary equations, which can be easily solved. Then, the semi-analytical solutions for the excess pore-pressures and the soil layer settlement were derived in the Laplace domain. The final results in the time domain could be computed by performing the numerical inversion of Laplace transform. Furthermore, two comparisons were presented to verify the accuracy of the proposed semi-analytical solutions. It was found that the semi-analytical solution agreed well with the finite difference solution and the previous analytical solution from the literature. Finally, the 2D plane strain consolidation process of unsaturated soil under different Drainage efficiencies of the vertical boundaries was illustrated, and the influences of the air-water permeability ratio, the anisotropic permeability ratio and the spacing-depth ratio were investigated.
Martin Funk - One of the best experts on this subject based on the ideXlab platform.
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Water storage and subglacial Drainage conditions inferred from borehole measurements on Gornergletscher, Valais, Switzerland
Journal of Glaciology, 1996Co-Authors: Almut Iken, Kristian Fabri, Martin FunkAbstract:Measurements of change in length of a borehole, or displacements of poles and of subglacial water pressure were combined with Drainage tests and electrode tests in boreholes, in experiments near the northern margin of Gornergletscher, Valais, Switzerland, at the upstream side of an overdeepening. The measurements suggest that the subglacial Drainage system consisted of discrete conduits at that location, presumably linked cavities on clean bedrock. Changes in subglacial water pressure were followed by variations in subglacial water storage, together with similar variations in elevation of a pole. The variations in subglacial water storage caused changes in cross-sections of subglacial passageways and thereby changed the frequencies of slug-test oscillations. Similar experiments conducted near the center line of the glacier revealed different subglacial conditions: Impeded Drainage through a sediment layer, and different depths of water levels in different boreholes. These results are discussed in relation to previous studies.
Minghua Zhao - One of the best experts on this subject based on the ideXlab platform.
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A general analytical solution for two-dimensional plane strain consolidation of unsaturated soil incorporating lateral and vertical Impeded Drainage boundaries
Computers and Geotechnics, 2021Co-Authors: Minghua Huang, Minghua ZhaoAbstract:Abstract In most practical consolidation problems, Impeded Drainage boundaries are a great concern. By simultaneously introducing the Impeded Drainage boundaries in the horizontal and vertical directions, this study attempts to constitute a general two-dimensional (2D) plane strain consolidation system of unsaturated soil. A newly analytical solution is developed to calculate the excess pore-air and pore-water pressures and average degree of consolidation. On the basis of the eigenfunction expansion method, the developed analytical solution is given as a product of three functions, including one variable of time, horizontal and vertical dimensions only. For the Impeded Drainage boundaries, the eigenfunctions and eigenvalues are derived in the horizontal and vertical dimensions. The Laplace transform technique is further adopted to solve the ordinary differential system in the time domain. The developed analytical solution is verified with the existing analytical/semi-analytical solutions and finite difference solution for several typical cases. Excellent agreements are obtained so that the correctness of the developed analytical solution is validated. Moreover, two worked examples are presented to show the superiority of the developed analytical solution and to assess the influences of the Drainage parameters on the 2D plane strain consolidation behavior of unsaturated soil.
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A general analytical solution for one dimensional consolidation of unsaturated soil incorporating Impeded Drainage boundaries
Computers and Geotechnics, 2020Co-Authors: Minghua Huang, Minghua ZhaoAbstract:Abstract This paper presents a novel analytical solution for one dimensional consolidation system of unsaturated soil incorporating Impeded Drainage boundary conditions. Through diagonalizing the coefficient matrix, the consolidation system is firstly transformed into a diagonal one with respect to a new variable vector. Then, using the methods of eigenfunction expansion and undetermined coefficients, the analytical solution is developed through deriving the eigenvalues, corresponding eigenfunctions and undetermined coefficients. Its orthogonality and convergence are proven, and several comparisons against existing solutions and two typical experimental data are performed to verify its validity. Finally, two typical examples are provided to illustrate the consolidation behavior of unsaturated soil with different Drainage parameters. The results indicate that the present analytical solution converges rapidly, and it is consistent with existing analytical, semi-analytical and numerical solutions for various Drainage boundary conditions. The proposed analytical solution achieves an overall better agreement with experimental data, and the Impeded Drainage boundary condition is more reasonable to describe the consolidation phenomenon of unsaturated soil. In general, larger Drainage parameter accelerates excess pore-pressure dissipation and soil settlement.
Ch. Siebe - One of the best experts on this subject based on the ideXlab platform.
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Effects of land application of waste water from Mexico City on soil fertility and heavy metal accumulation: a bibliographical review
Environmental Reviews, 1995Co-Authors: Margarita Gutiérrez-ruiz, Iris E. C. Sommer, Ch. SiebeAbstract:Waste water from Mexico City metropolitan area has been used to irrigate the Mezquital Valley since 1912. This zone is nowadays the largest area under this situation. Mexico City's Drainage is a water mixture emanating from different sources: household, industries, commerce, rain, and runoff. Waste waters used in the valley have greatly increased crop yields. Owing to the increase in the country's industrial development, since the seventies several studies have been carried out in this area, especially related to metal content in water, soils, and crops. The aim of this paper is to present a bibliographical review of the effects of Mexico City's waste water land application on soil fertility and heavy metal accumulation. Pb, Cd, Cu, and Zn levels in soils and crops at present do not represent risks, but there is a clear tendency for these metals to accumulate in the upper layers of soils. Salt content in waste water is intensifying soil salinization in Impeded Drainage areas. The local conditions of soil,...
