COMPUTATIONAL GEOTECHNICS

Project:
Stuttgart, Germany

Customer:
Smoltczyk & Partner, Stuttgart

Project description:
Within the project in the city center of Stuttgart high point loads have to be carried into the subsoil. A piled raft foundation is planned in this project and the performance of the raft had to be investigated.

Subsoil:
Triassic layers, mainly variably weathered Gypsum Marl and in some areas sediments and fill.

Scope of work:

• Preliminary studies on possible alternatives for the foundation
• Three-dimensional Finite Element analyses of the foundation
• Three-dimensional Finite Element analyses of different alternatives for the piled raft foundation underneath the columns
• Investigated alternatives:
  
  • 3x3 group of bored piles underneath the columns
  • 3x3 group of driven cast-in-place concrete piles underneath the columns
  • 4x4 group of driven cast-in-place concrete piles underneath the columns
  • 5x5 group of driven cast-in-place concrete piles underneath the columns
  • Three-dimensional Finite Element analysis of a section over the total width of the foundation slab with 57 bored piles
• Calibration of the soil parameters using results of static pile load tests
• Determination of bedding modulus for a classic design of the foundation slab

Used Finite Element Code:
PLAXIS 2D V8.6
PLAXIS 3D Foundations V2.1

Used constitutive laws:
Linear elasticity (generalized Hooke)
Hardening-Soil model (elasto-plastic) + Small-Strain-Stiffness

Typical domain size:

Model of the section with one column: 36 m  x  15 m  x  36 m 13,800 to 30,700 wedge elements with quadratic interpolation 39,600 to 84,700 nodes

Model of the complete section: 196 m  x  30 m  x  36 m 63,000 wedge elements with quadratic interpolation 185,000 nodes