Backanalysis of the behavior of props in strutted excavations
This article is a short abstract about the Master's Final Project of the Master's Degree in Geotechnical Engineering in the Universitat Politècnica de Catalunya. First, the applied case study is described, and then the results to be obtained using Backanalysis techniques in the Daarwin platform will be analyzed.
With the increasing complexity of geotechnical projects, the use of advanced and sophisticated tools has increased as well. As a result of finite elements such as calculation methods and to the constitutive models developed by experts on Geotechnics, it has been possible to deal with highly complex projects.
One of the limitations in geotechnical modeling is that the actual tests and the restriction of taking samples, do not represent the global behavior of the soil where the project is carried out. Consequently, in view of these uncertainties in preliminary designs and models, backanalysis methods have been developed.
The case study of interaction between a monitored deep excavation and existing buildings is presented in this thesis. The Saint-Agne subway station of Toulouse (France) has been realized with a diaphragm wall supported by up to three levels of steel struts and has been built in an overconsolidated molassic geological context.
Therefore, the principal purpose is analyzing the placement of the props, the moment and the shape of the loading into a deep excavation. From the knowledge of this case, a numerical model has been constructed by means of finite elements using Plaxis 2D and techniques of Backanalysis to incorporate the measures of displacement of the retaining walls and relate them to the loading of the props.
The methodology consists of identifying the parameters that govern the behavior of the soil from measurements of lateral displacements of the retaining walls, mainly, analyzing the props loading. With these calibrated parameters, the excavation model can be recalculated to validate the design hypothesis and predict the behavior of the props with the retaining walls.
To find the calibrated parameters and analyze the props behavior, the error between the displacements of the numerical model and the displacements of the measurements in situ must be reduced. To minimize this error, the adaptive genetic algorithms technique applied through the Daarwin platform is used. Finally, the efficiency and precision of the methodology used to find the prop’s behavior will be evaluated.