ETL 11102544
31 Jul 95
APPENDIX A: GEOTECHNICAL ANALYSIS BY THE FINITE
ELEMENT METHOD
(1) The geometry can be changed from one step
Chapter 1
to the next to simulate excavation or fill placement,
Introduction
by removing elements or adding elements to the
mesh.
11. Background
(2) The properties of the soil can be changed
from one step to the next to simulate the changes in
a. Purpose. The purpose of this engineering
behavior that result from changes in the stresses
technical letter (ETL) is to provide guidance to engi
within the soil mass.
neers who are unfamiliar with the finite element
method, but who are interested in understanding its
b. Types of problems. The finite element
potential for use in geotechnical engineering. The
method has been applied to a wide variety of geo
emphasis is on practical applications. The objective
technical engineering problems where stresses,
is to provide a basis for understanding what can be
learned from finite element analyses, what skills are
were of interest. The types of problems analyzed
required for its application, and what resources in
include:
terms of time, effort, and cost are involved.

Anchored walls used to stabilize landslides
b. Use of finite element method. Use of the

Building foundations
finite element method for geotechnical engineering

Cellular cofferdams
began in 1966, when Clough and Woodward used it

Embankment dams
to determine stresses and movements in embank

Excavation bracing systems
ments, and Reyes and Deer described its application

Longspan flexible culverts
to analysis of underground openings in rock. Many

Offshore structures
research studies and practical applications have taken

Plastic concrete seepage cutoff walls
place in the intervening 30 years. During this period,

Reinforced embankments
considerable advances have been made in theory and

Reinforced slopes
practice, and the cost of computers has diminished to a

Retaining walls
small fraction of the cost 30 years ago. This report

Seepage through earth masses
emphasizes the practical lessons learned in the past

Slurry trench seepage barriers
30 years, that together define the current state of

Tunnels
practice with regard to finite element analyses.

Uframe locks

c. Emphasis. The theory of the
finite element
method is not covered in this report. Instead, emph
This list is representative, but not exhaustive. It is
asis is placed on the types of geotechnical problems to
clear that the finite element method can be used to
which the method has been applied and the options
available to engineers who wish to use it for analysis
flow in virtually any conditions that arises in geo
of their problems.
technical engineering practice. Limitations on the
use of the method usually stem from limitations on
resources to define problems and to perform
12. Types of Problems
analyses, rather than inherent limitations of the
method itself.
a. Sequence of real events. Almost all geo
technical finite element analyses are performed in
steps that simulate a sequence of real events, such as
13. What Can Be Learned from Finite
the successive stages of excavation of a braced or
Element Analyses?
unbraced cut, or placement of fill on an embankment.
Performing the analyses in steps has two important
a. Analysis by finite element methods. For
advantages for geotechnical problems:
analysis by the finite element method, the region to
A1