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Secant pile example with DeepXcav

A secant pile wall example will be analyzed with DeepXcav. The following data is available:

a) Soil properties: Sand, friction angle = 30 degrees, total unit weight 120 pcf, loading modulus of elasticity Eload= 300 ksf, reloading modulus of elasticity Eur = 900 ksf. Ultimate bond resistance for ground anchors 40 psi.

b) Excavation depth: 25 ft, cantilever stage 10ft, ground anchor at 8ft depth at 15 degrees. Reinforced piles spaced at 6ft off center, while pile diameter is 2.5ft. Include 600 psf traffic surcharge 1ft behind the wall for a length of 20ft.

Objective: Design the secant pile and the ground achors with allowable stress methodology and obtain a wall embedment safety factor of 1.5. Use reinforced concrete and steel rebars.

Secant pile excavation with DeepXcav

By double clicking on the wall and selecting edit properties we can change the wall type and other wall properties as shown in the following figure.

Secant pile wall properties

Secant pile wall reinforcement

Initial wall properties, with 8 bars #9, piles are spaced at 4 ft O.C.

Next we set the design code standards to US allowable (AISC ASD, and ACI with safety factor)

Select US allowable design settings

We then apply 50% wall friction as shown in the next figure:

Wall friction for secant pile wall

Tiebacks in secant pile wall with DeepXcav

Ground anchor data                                                  Surcharge data

We add a ground anchor and change the properties as shown above. A surface surcarge is also drawn and the vertical magnitude qZ is changed to 0.6 ksf.

Then we perform the analysis by selecting the calculation button. When the analysis is completed the summary tables appear (foollowing image contains snapshots).

Initial results of secant pile analysis

Here, we can see that the minimum obtained embedment safety factor is above 1.5. Since it is desired to have a smaller safety factor and realize savings on the wall length, we manually reduce the wall length to 42ft. We then re-analyze the model, and the obtained minimum wall embedment safety factor reduces to 1.532 which is deemed adequate.

Revised secant pile analysis results