ETL 1110-2-544
31 Jul 95
(2) To determine which factors have the greatest
water levels of 4.0, 6.0, 7.0, 8.0, and 9.0 ft. A
influence in the performance of the sheet-pile wall
second mesh was used in this study for the purpose of
through a parametric study with the finite element
performing a parametric analysis. This mesh,
method. Variations in soil properties, loadings, sheet-
presented in Figure 10 and based on the E-105 test
pile type, and depth of penetration were considered in
section, was used to investigate design implications of
this study.
soft foundation behavior.
(3) To develop recommendations for a sheet pile
f. Construction sequence modeling. The basic
design procedure that overcomes some of the incon-
construction/loading sequence employed in the finite
sistencies in the current methods.
element analyses of both the E-99 test section and in
the parametric studies was:
c. Material behavior model, property values,
and finite element code. The hyperbolic model
(1) Computation of the initial stresses based on
(Duncan and Chang 1970) implemented in
an elastic gravity turn on analysis.
SOILSTRUCT (Clough and Duncan 1969, and
Ebeling 1990) was selected for this problem. Soil
(2) Insertion of the sheet pile.
material properties were determined from laboratory
tests and back analysis of the observational data
(3) Application of water loads in 1-ft
retrieved from the E-99 test section. The sheet piles
increments.
were treated as linear elastic materials.
(4) Application of wave loads.
d. Modifications to finite element code. The
finite element code, SOILSTRUCT, was modified
The stresses determined in (1) were used to determine
during the course of the study to ease the input of
Su and the Ei for each element in the mesh. The
material parameters for soils and to improve the
insertion of the sheet-pile wall was accomplished by
means of computing the bending moments in the sheet-
changing the material of the elements representing the
pile wall. These modifications included:
sheet-pile wall from soil to steel during the first step.
Water loads were simulated through the application of
(1) Implementation of a (Su/p) model to ease the
the appropriate pressure to surface nodes in contact
input of shear strength parameters.
with the floodwaters.
(2) Determination of the initial tangent modulus
g. Results of the E-99 test section. Field data
of soils, Ei, as a function of the undrained shear
obtained from the E-99 test section was used to
strength of the soil using the relationship
establish and validate the FEM for the analysis of the
sheet-pile walls. A PZ-27 sheet pile was simulated in
the analysis. Water loads were applied to simulate
Ei ' K x Su
(1)
water levels of elevations 4.0, 6.0, 7.0, 8.0, and
9.0 ft. Soil material properties for analysis were ob-
tained from "Q-tests" and field classifications. Three
where K is a unitless parameter between 250 and
shear strength profiles obtained form test data, used in
1,000 as determined from previous experience.
design, and used in the finite element analysis are
shown in Figure 11. The soil stiffness in all finite
(3) Improving the bending elements representing
element runs of the E-99 test section were made on the
the sheet piles so that the bending moments could be
assumption that K was the same for all soils. Two
directly computed.
runs were made with K = 500 and K = 1,000.
Leavell et al. (1989) concluded from the
e. Mesh details. The mesh used to model the
SOILSTRUCT analysis that:
E-99 test section is shown in Figure 9. The mesh
consists of 281 solid elements and 322 nodes and
(1) Wall-versus-head relationship. The
models the foundation between elevations (el) +6.5 to
displacement at the top of the wall-versus-head
-35 ft. Sheet-pile elements are attached to soil
relationship is predicted fairly well as shown in
elements by 19 interface elements. Water loads are
Figure 12. The ability of the analysis to predict the
applied to the soil surface and pile as linearly varying
larger displacements as the head approached 8.0 ft is
distributed loads in increments corresponding to
particularly important because it implies that the limit
A-11
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