Study of Unsaturated Soils by Coupled Numerical Analyses of Water Flow-Slope Stability
Por:
Patricia Lopez-Acosta, Norma, Alfredo Mendoza-Promotor, Jose
Publicada:
1 ene 2016
Resumen:
The geotechnical engineering, among the problems related to water flow,
is specifically interested in soil and water that it contains, and also
on the movement of water through their pores, in addition to the laws
governing this phenomenon. A very important subject is to quantify the
retention and filtration of water within the soil structure; however,
the emphasis should be not only on how much water flows through the soil
but also on the state of pore water pressures because this pressure,
either positive or negative, has a direct influence on the stress state
and changes in volume of soil. Several publications address the issue of
water flow in saturated state; however, only some of them consider the
flow under unsaturated conditions. In this chapter, the main emphasis is
focused on the study of water flow in unsaturated soils.
Initially, the basic concepts and the main equations applicable to the
study of water flow in unsaturated media are defined. Then, fitting and
estimation models of soil hydraulic functions (soil-water characteristic
curve and hydraulic conductivity function) necessary to solve this type
of problems are discussed. The importance of considering calculations in
the unsaturated zone of the flow region is demonstrated by the analysis
of a tailings dam. It is explained how to perform two-dimensional (2D)
and three-dimensional (3D) numerical analysis of water flow by finite
element method (FEM) under steady and transient-state conditions, whose
results are evaluated and coupled to study the stability of the
structure assuming the phi-b linear model for unsaturated soils. Special
attention to the analysis of the variations obtained in 2D and 3D models
constructed with extrusions and rough topography of the site is given.
Finally, important recommendations for engineering practice according to
the results obtained are issued.
Some concluding remarks and recommendations of the analyses presented in
this chapter are as follows:
The mathematical models for estimating soil-water characteristic curve
and hydraulic conductivity function are an important tool when
laboratory test results are not available because of the high costs of
these tests or the requirements of specialized equipment and personnel
to perform them.
3D models have important advantages over 2D models because they can
include irregular geometries of the structure under study, topographical
configuration of soil, unsaturated flow conditions, more realistic
boundary conditions representing the environment, among others.
To get more representative numerical analyses, the unsaturated soil
theory should be considered for all those situations where the material
is in this state.
In this chapter, it is demonstrated that the considerations exposed for
modelling, estimation, and fitting of hydraulic functions of soil
provide the necessary elements to carry out these analyses in a simple
way.
Computer programs facilitate the study of transient-state flow and
unsaturated soil condition, whose analytical solutions are generally
complicated and laborious.
Filiaciones:
Patricia Lopez-Acosta, Norma:
Nacl Univ Mexico UNAM, Inst Engn, Mexico City, DF, Mexico
Alfredo Mendoza-Promotor, Jose:
Nacl Univ Mexico UNAM, Inst Engn, Mexico City, DF, Mexico
Javaid, MS:
Lopez-Acosta, NP (Corresponding Author), Nacl Univ Mexico UNAM, Inst Engn, Mexico City, DF, Mexico
Patricia Lopez-Acosta, Norma Alfredo Mendoza-Promotor, Jose, Nacl Univ Mexico UNAM, Inst Engn, Mexico City, DF, Mexico
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