embankment-foundation system based on data

collected from settlement gages, slope indicators,

pore pressure transducers, etc.

The analysis of embankment construction involves the

estimation of stresses and movements in embank-

ments and their foundations both during and after

The following paragraphs describe several items and

construction. The construction of embankments

considerations necessary for the performace of a good

generally involves both excavation and filling in

finite element model for embankment construction:

some specified order. The finite element method

offers an ideal way to perform such an analysis

because of its ability to handle complex geometries,

primary material of construction in embankment

construction sequences, and nonlinear soil behavior.

construction problems. As described in the

Some examples of embankment construction

introduction of this ETL, the stress-strain behavior

problems include those in embankment dams,

of soil is nonlinear and inelastic. For all cases

levees, and highway embankments. Additionally, a

except saturated soil under undrained conditions,

static finite element analysis is often performed as

the stress-strain behavior of soil is dependent on

part of the evaluation of liquefaction potential of

confining pressure. These aspects of soil behavior

foundation soils beneath an embankment as the

are encountered in most geotechnical engineering

cyclic strength of soil depends on the state of stress

projects, including projects involving the

in the soil (Wahl et al. 1987).

construction of embankments. Consequently, it is

important that the material model be capable of

tracking these aspects of soil behavior. Many

material models, such as the hyperbolic model of

Duncan and Chang (1970) and the Cam-Clay model

(Roscoe and Burland 1968), do capture these

characteristics of soils. The hyperbolic model uses

stresses and movements obtained from the analysis

a confining pressure-dependent, nonlinear elastic

can be used to evaluate the expected performance of

formulation, with an inelastic component

the embankment-foundation system against pre

introduced, because the value of the unload-reload

determined performance standards. The finite

modulus is larger than the value of the virgin

element analysis should be used in conjunction with

loading modulus. The Cam-Clay model uses a

a conventional slope stability stability program to

plasticity formulation that also yields reduced

ensure that both give the same results with respect

modulus values as the soil strength becomes

to the stability of the system.

mobilized and increased modulus values as the

confining pressure increases. One of the key

benefits of plasticity is that it can model plastic

analysis can be a useful tool during the design

strains that occur in directions other than the

process of an embankment. Parametric studies can

direction of the applied stress increment. This

be performed for the purpose of dealing with

feature becomes especially important when a soil

uncertainty in the foundation conditions and

mass is near failure. In such a case, the application

material properties. The results of these studies can

of a load increment in one direction can cause large

provide a range of values for stresses and

displacements of the soil in another direction if

movements which can be compared with allowable

large forces had been previously applied in that

values to help ensure the adequacy of the design.

other direction. For well-designed structures, in

which failure of large masses of soil is not

imminent, modeling this aspect of failure can

analysis of an embankment can also be useful in the

become less important.

construction process, since it can serve as an aid in

the selection of the types and locations of in-

stumentation systems that monitor performance both

Selection of appropriate stress-strain material

during and after construction. This type of analysis

property values is often the most important step in

can also provide insight into the interpretation of

performing SSI analyses. There are four methods

movements and distribution of stress in the

to obtain material property values:

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