[en] Excavation ; Inverse Analysis ; Optimization ; Soil behaviour ; Neural network material model
[en] Performance observation is a necessary part of the design and construction process in geotechnical engineering. For deep urban excavations, empirical and numerical methods are used to predict potential deformations and their impacts on surrounding structures. Two inverse analysis approaches are described and compared for an excavation project in downtown Chicago. The ﬁrst approach is a parameter optimization approach based on genetic algorithm (GA). GA is a stochastic global search technique for optimizing an objective function with linear or non-linear constraints. The second approach, self-learning simulations (SelfSim), is an inverse analysis technique that combines ﬁnite element method, continuously evolving material models, and ﬁeld measurements. The optimization based on genetic algorithm approach identiﬁes material properties of an existing soil model, and SelfSim approach extracts the underlying soil behavior unconstrained by a speciﬁc assumption on soil constitutive behavior. The two inverse analysis approaches capture well lateral wall deﬂections and maximum surface settlements. The GA optimization approach tends to overpredict surface settlements at some distance from the excavation as it is constrained by a speciﬁc form of the material constitutive model (i.e. hardening soil model); while the surface settlements computed using SelfSim approach match the observed ones due to its ability to learn small strain non-linearity of soil implied in the measured settlements.