Best Approach to Model Displacement of Caisson with Stepped Retaining Walls

[Geotech_Pavement]

Hi everyone,

I’m working on evaluating the displacement of the top of a caisson foundation that is part of a permanent shoring system designed by a structural engineer using Enercalc software. As the geotechnical engineer, our role was to provide the structural engineer with equivalent active and passive earth pressures for their design.

The project features:

• Caisson Depth: 48 ft below grade
• Stepped Retaining Wall Sections: These may provide passive resistance, and I’m unsure how to account for their contribution in displacement analysis.
• Backfill and Surcharge Loads: Various loading conditions at different elevations
• Soil Profile: Includes layered strata with varying stiffness

Since the shoring was analyzed in Enercalc, which primarily uses traditional limit equilibrium methods, I’m now looking for the best way to independently estimate the lateral displacement at the top of the caisson.

I'm considering the following approaches and would appreciate any guidance:

1. Beam on Elastic Foundation (P-Y Analysis):
   • Using software such as PYWall or LPILE to model soil-structure interaction with P-Y curves.
   • How should I incorporate the passive resistance from the stepped retaining walls in this approach?
2. Finite Element Analysis (FEA):
   • Utilizing PLAXIS 2D/3D to capture soil-structure interaction and staged construction effects.
   • Would this provide a more accurate displacement estimate considering the complexity of the system?
3. Validation Against Enercalc Results:
   • Are there ways to reconcile simplified Enercalc limit equilibrium methods with more advanced displacement-based analyses?

My goal is to determine the anticipated lateral displacement of the caisson top under the expected loading conditions and to compare it with the structural design assumptions.

Thanks

 

[EireChch]

You are essentially doing a retaining wall design. Check out Ciria C760 which has all the answers you need.

The tiered retaining walls will offer support like a berm. Draw a slope line to average out the two tiers. C760 then has guidance as how to analysis a wall with berms.

Ps your 'Soil profile' sections is missing some info. Layered strata with varying stiffness is hardly a soil profile description.