Bayesian analysis for learning and updating geotechnical parameters and models with measurements - Risk and Reliability in Geotechnical Engineering - page 252

take advantage of the symmetry of the trench and model just one-half of the soil profile,
although this implies an approximation when randomness in the soil material is taken into
account. The material model used is an elasto-plastic model with a prismatic yield surface
according to the Mohr-Coulomb criterion and a nonassociated plastic flow. The sheet pile
is modeled using beam elements and the interaction between the retaining structure and the
surrounding soil is modeled using nonlinear interface elements. The corresponding finite
element (FE) model is implemented in the SOFiSTiK program (SOFiSTiK 2012). The finite-
element mesh used in the analysis is shown in Figure 5.14b .
The sheet pile dimension and profile is determined analytically using the conventional
method for the cantilever sheet pile design in granular soils, which requires equilibrium of
the active and passive lateral pressures (see, e.g., Tschebotarioff 1951). Applying a global
safety factor of 1.5, the design results in sheet piles of depth of 7.5 m and profile PZC 13.
Young's modulus of steel is 210 GPa. The pile is modeled using beam elements with an
equivalent rectangular cross section that behaves as the sheet pile under bending and axial
loading. The interaction between the retaining structure and the surrounding soil is mod-
eled using nonlinear interface elements. An elasto-plastic model with a yield surface defined
by the Mohr-Coulomb criterion is used to describe the interface behavior. The elastic prop-
erties of the interface elements are taken from the mean values of the adjacent soil, while the
strength properties are reduced by a factor 2/3 and a zero dilatancy is chosen.

(a) Stochastic finite-element mesh (b) Deterministic finite-element mesh

(c) Deformed configuration

Figure 5.14 (a) Stochastic and (b) deterministic finite-element mesh of the geotechnical site, shown for the
situation prior to the excavation; (c) deformed configuration at full excavation for the mean
values of the material properties. (From Straub, D. and I. Papaioannou. 2014. Doi: 10.1061/(asce)
em.1943-7889.0000839.)