Anchored Wall Example Secant Pile Wall with Tiebacks (SI ... · DEEPEX EXAMPLE: SECANT PILES WITH TIEBACKS DEEP EXCAVATION 2 A. Project description In this example we will design

DEEPEX EXAMPLE: SECANT PILES WITH TIEBACKS

DEEP EXCAVATION 1

Anchored Wall Example – Secant Pile Wall with Tiebacks (SI units)

Deep Excavation LLC Software program: DeepEX 2018

Document version: 1.0 September 3, 2018

www.deepexcavation.com www.deepex.com


DEEP EXCAVATION 2

A. Project description In this example we will design an anchored secant pile wall with 3 tieback rows, supporting a 12m excavation. The Figure below presents the project model. Tables 1 and 2 present the soil properties and the stratigraphy respectively. Table 3 presents the external loads. Tables 4 and 5 present the wall and support properties respectively. The general ground surface is at El. 0m and the general water table is at El. -15m.

Figure: Project model.

Table 1: Soil properties.

Soil Layer Soil Type Design parameter

φ’ (deg)

C’/Su (kPa)

γ (kN/m3)

γdry (kN/m3)

ELOAD

(kPa) ERELOAD

(kPa)

F Fill 25 0 19 19 15000 45000

C Clay 29 65 18.5 18.5 20000 60000

S1 Sand 32 0 20.5 20.5 30000 90000

S2 Sand 34 5 21 21 45000 90000

Table 2: Stratigraphy.

Soil Layer Elevation (m) OCR Ko

F -0 1 0.577

C -2 1 0.515

S1 -8 1 0.47

S2 -13 1 0.441

Table 3: External loads.


DEEP EXCAVATION 3

Load Load Type Start Point End Point Load Magnitude

Load 1 Strip Surcharge (-15.5,0) (-0.5,0) 25 kPa

Table 4: Wall parameters.

Pile width 0.23 m

Steel pile section IPE 180

Secant pile spacing 0.3 m

Steel Fe510

Wall depth 18 m

Table 5: Support parameters.

Tieback 1 Tieback 2 Tieback 3

Tieback elevation on wall

-3 m -6 m -9 m

Tieback spacing 2 m 2 m 2 m

Angle 20 deg 20 deg 20 deg

Free length 5 m 5 m 5 m

Fixed length 11 m 11 m 11 m

Support section 4 Strands x 0.525in 4 Strands x 0.525in 4 Strands x 0.525in

Prestress 310 KN 310 KN 310 KN


DEEP EXCAVATION 4

B. Modeling with DeepEX

The model will be created using the DeepEX Model Wizard:

• Define Analysis Methods:

Figure: Analysis Methods in DeepEX Wizard.

In this dialog, we choose to apply Limit Equilibrium Analysis method to our model. For the classical earth pressures in design stages with multiple support levels we define FHWA apparent pressures and for the beam analysis we choose CALTRANS method.


DEEP EXCAVATION 5

• Define project type and dimensions

Figure: Project Type and Dimensions in DeepEX Wizard.

In this dialog we select the project type (in this case we select the option to create an anchored wall model). Next, we define the project dimensions (final excavation depth, walls depth, excavation width, top of the wall elevation and water table). Finally, we define the support properties (in this case tieback spacing and the tieback structural section). The software will use the same properties (spacing, structural sections etc) for all created supports. Later we can access each support on the model area (double-click on the support) and edit the specific support properties.


DEEP EXCAVATION 6

• Define soil types and stratigraphy

Figure: Soil Properties and Soil Layers in DeepEX Wizard.

Figure: Soil Properties and Soil Layers dialogs in DeepEX.

In these dialogs we can define the required soil types and the properties for each created soil, as well as, the model stratigraphy by defining the top of the soil layer elevation and the soil type in each layer.


DEEP EXCAVATION 7

• Define wall type and wall section properties

Figure: Wall types in DeepEX Wizard.

Figure: Wall Sections dialog in DeepEX.

In these dialogs we select the wall section type (in this case secant pile wall), the steel beam section, the wall spacing and the concrete – steel materials.


DEEP EXCAVATION 8

• Define Stages – Support Elevations

Figure: Support Elevations in DeepEX Wizard.

In this dialog, we define the depth from the surface or each support level, as well as, the depth below each support level where we wish to excavate in the stages, before the support is installed. The software automatically calculates all elevations (excavations and support installation levels) of these defined depths and generates all intermediate construction stages.


DEEP EXCAVATION 9

• Define Surcharge

Figure: Support Elevations in DeepEX Wizard.

In this dialog we define the surcharge type and properties, as well as the surcharge modeling options. In this case we will use a 25KN strip surcharge, developed for 15m, starting 0.5m behind the left wall. After the model is automatically generated by the software wizard, we can access the stages in the model area and add any required additional loads graphically, using the Draw Loads options in the General tab of DeepEX.


DEEP EXCAVATION 10

• Define structural codes:

Figure: Structural Codes in DeepEX Wizard.

In this dialog, we can define the structural and geotechnical design codes that we wish to assign to this model. In this case, we will use Eurocode 2 and Eurocode 3 specifications for concrete and steel design.


DEEP EXCAVATION 11

The software automatically creates all project construction stages, according to our selections in the Model Wizard. The following Figures present the models in Stages 5 and 7 respectively:

Figure: Generated Model – Stage 5.

Figure: Generated Model – Stage 7.


DEEP EXCAVATION 12

C. Results in DeepEX

Since the model is ready, we can choose to calculate the design section, pressing on the

button . After the analysis is succeeded, the Summary table appears. The table below includes some critical checks and values for each construction stage. The following figures present some graphical results from the results tab of DeepEX.

Table: DeepEX critical results/stage

Figure: Wall moment and shear diagrams, Stage 7.


DEEP EXCAVATION 13

Figure: Wall deflections and soil pressures diagrams, Stage 7.

Figure: Wall embedment safety factors, Stage 7.

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Anchored Wall Example Secant Pile Wall with Tiebacks (SI ... · DEEPEX EXAMPLE: SECANT PILES WITH TIEBACKS DEEP EXCAVATION 2 A. Project description In this example we will design