Soldier Pile Wall

Soldierpilewall–LimitEquilibrium–Non‐linearAnalysis

CreatedbyDeepExcavationLLC,Astoria,NewYork Page1

Soldier pile wall excavation analyzed with limit equilibrium

and non‐linear analysis methods

DeepXcav software program (Version 2011)

(ParatiePlus within Italy)

Document Version 1.0

Issued: 2‐August‐2012

Deep Excavation LLC

www.deepexcavation.com



This example presents a 25 ft excavation on the right side of a soldier pile and lagging wall supported by

one level of tiebacks (Figure 1). A surcharge with the magnitude of 0.6 ksf is added near the wall. Tables

1 through 3 present the assumed soil, wall, and support properties respectively.

Figure 1: Model of the problem.

Table 1: Soil properties.

Soil Layer

Design parameter

φ’ (deg)

C’ (psf)

γ (pcf) γdry (pcf)

ELOAD (ksf)

ERELOAD (ksf)

F 30 0 120 120 313 939

Table 2: Wall parameters.

Soldier pile section HP 12x74

Soldier pile spacing 7 ft

Wall depth 25 ft

Steel A50

Lagging 2 in timber lagging



Table 3: Support parameters.

Tieback elevation on wall 92 ft

Tieback spacing 7 ft

Angle 20 deg

Free length 15 ft

Fixed length 20 ft

Tieback structural section 3 strand tieback

Prestress 60 kips

First we select to use English units. This can be defined from the list in the General tab (Figure 2).

Figure 2: Select to use English units.

Next, we press the button and we choose to set the general elevation to the elevation 100 ft

(Figure 3).

Figure 3: Set general elevation to 100 ft.



Next, we define the soil properties. By pressing the button in the Properties tab of DeepXcav, we

can define the soil type properties. Figure 4 displays the dialog where these parameters are edited.

DeepXcav provides some useful tools for the estimation of certain soil properties. By pressing the button

we have access to these tests and estimators (Figure 5).

Figure 4: Soil properties dialog.

Figure 5: Soil properties estimation tools.



The limit equilibrium method uses mainly the highlighted in yellow parameters presented in Table 4

below. The most important parameters are presented with bold letters. The vertical and horizontal

permeabilities Kz and Kx are used when a flownet analysis is performed, while Kz is solely used when a

1D simplified water flow analysis is performed.

Table 4: General soil parameters.

Symbol Description

γt Total unit weight of soil (used below the water table)

γdry Dry unit weight of soil (used above the water table)

c’ Effective soil cohesion

Su Undrained shear strength (used for clays when undrained modeling is selected). In the non‐linear analysis this is used as an upper limit strength

v Poisson’s ratio (used for loads calculated with theory of elasticity)

Φ’ Effective soil friction angle

Φcv’ Constant volume effective shearing soil friction angle used in the non‐linear analysis for clays

Φpeak’ Peak effective soil friction angle used in the non‐linear analysis for clays

Kx Soil permeability at horizontal direction

Kz Soil permeability at vertical direction

KoNC Coefficient of at‐rest lateral earth pressures for normally consolidated conditions

nOCR Exponent for calculating Ko with Ko=KoNC*[(OCR)^(nOCR)]

Parameters that are used in the non‐linear analysis method are presented in Table 5. The > buttons next

to each parameter can be used to estimate a soil property from available test data (SPT or CPT). For

soils, in general, the exponential soil model tends to offer the most realistic approach as it captures non‐

linear soil behavior.

Table 5: Elasto‐plastic soil parameters.

Symbol Description

Elastic‐plastic soil behavior

Evc Virgin compression modulus of elasticity

Eur Reloading elasticity modulus

Exponential soil behavior

Eload Loading elasticity modulus

exp Exponent

av Coefficient for vertical stress

ah Coefficient for horizontal stress

Pref Reference pressure

Eur Reloading elasticity modulus

Subgrade‐modulus soil behavior

Kvc Loading subgrade reaction modulus

kur Reloading subgrade reaction modulus



In order to define the wall properties and dimension, we double click on the wall on the model. Here we

can define the wall top elevation and the wall depth (Figure 6). In order to define the wall section, we

press the button (Figure 7).

Figure 6: Wall data dialog.

Figure 7: Edit wall section data dialog.



Next, we apply a surcharge with a magnitude of 0.6 ksf in Stage 1. This can be done by pressing the

button from the toolbar on the left side of the screen and by clicking on two points on the left side

of the wall. Then, the Edit distributed load dialog appears (Figure 8). In this dialog we can define the

exact coordinates of the load and the load magnitude.

Figure 8: Edit surcharge properties dialog.

In construction stage 2 we add a tieback support. This can be done by pressing the button from the

toolbar on the left side of the screen and by clicking first on the wall and next to the ground. Then, the

Edit support data dialog appears (Figure 9). In this dialog we can define the exact coordinates of the

tieback’s place on the wall, the tieback’s free and fixed length, the spacing between the tiebacks, the

installation angle and the prestress that will be used for this tieback only for this stage. Figure 10

presents the model as initially set up with our assumptions.



Figure 9: Edit support properties dialog.

Figure 10: Model of the program in DeepXcav.

Next, we choose to use wall friction as a percentage of available soil friction (50%). We apply this option

in the Analysis tab of DeepXcav (Figure 11a). In addition, we choose to apply US allowable code settings

in the available option in the Design tab of DeepXcav (Figure 11b).



Figure 11a: Wall friction.

Figure 11b: US allowable settings.

The following construction stages are created in the base design section first:

Stage 0: Initial stages. Here we set the wall and soil parameters.

Stage 1: Excavation on the right side of the wall to elevation 90 ft.

Stage 2: Tieback installation.

Stage 3: Excavation to Elevation 75 ft and surcharge application.

Finally, in the last stage (Stage 3) we choose to change the Drive pressures to Peck, from the analysis tab

of DeepXcav (Figure 12).



Figure 12: Use Peck 1969 Apparent for drive pressures in Stage 3.

By right‐clicking with the mouse in the design sections area on the left side of the screen we can choose

to Edit the section name. We change it to “Limit‐Equilibrium”. Next, by right‐clicking once again we

choose to add as new section, and rename it to “Non‐linear” (Figures 13a and 13b). Now, we have to

identical design sections.

Figure 13a: Rename and adding new design sections.

Figure 13b: The edit section name dialog.

In the Limit Equilibrium design section, we apply the limit equilibrium method from the analysis tab of

DeepXcav (Figure 14).



Figure 14: Limit Equilibrium method.

In the Non‐linear design section, we use the beam on elastoplastic foundation method from the analysis

tab of DeepXcav (Figure 15). A Mesh Delta of 0.25 ft will be used in this example for the non‐linear

analysis. The Mesh Delta controls the number of nodes created along the wall for the non‐linear

analysis.

Figure 15: Beam on elastoplastic foundations (non‐linear) method.

We calculate both design sections by pressing the button . After the calculation

is completed the Analysis and checking summary table appears (Figure 16). In the non‐linear analysis the

calculation shows in red as some design items appear to be underdesigned.

Figure 16: Analysis and checking summary table.



In the Results tab of DeepXcav we can see on the screen a variety of results for all design sections and all

design stages. The following Figures present the wall embedment safety factors, the wall moment and

shear diagrams, the wall displacements and the soil effective stresses as calculated with DeepXcav. The

red lines on the moment diagrams represent the design capacity of the wall.

17a. Limit Equilibrium 17b. Non‐linear

Figure 17: Wall embedment Safety Factors for both design sections, stage 3.

Stage 1 Stage 2

Figure 18: Wall moment diagrams for Limit Equilibrium analysis design section.

Stage 2 Stage 3

Figure 19: Wall moment diagrams for Non‐linear analysis design section.



Stage 1 Stage 3

Figure 20: Wall shear diagrams for Limit Equilibrium analysis design section.

Stage 2 Stage 3

Figure 21: Wall shear diagrams for Non‐linear design section.

Stage 1 Stage 3

Figure 22: Wall displacements for Limit Equilibrium analysis design section.



Stage 2 Stage 3

Figure 23: Wall displacements for non‐linear analysis design section.

Stage 1 Stage 3

Figure 19: Soil effective horizontal stresses for Limit Equilibrium analysis design section.

Stage 0 Stage 3

Figure 20: Soil effective horizontal stresses for Non‐linear analysis design section.



Stage 2 Stage 3

Figure 21: Soil effective vertical stresses for Non‐linear analysis design section.

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Soldier Pile Wall