Load-bearing behavior and interaction of rigid inclusion systems with granular load transfer platforms

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Rigid inclusions, are a relatively new method for soil improvement in Germany. An essential difference between rigid inclusions and conventional pile foundations is the load transfer platform (LTP) above the columns. The columns, the soil between the columns and the LTP interact and form a combined overall system which determines the load bearing behavior. The research project is focused on the type of wet mortar column. After the penetration of the partial or full displacement auger the concrete is injected. The diameter of the columns is usually approx. 20 to 40 cm. They are installed in a grid with a centre to centre distance of 3D to 5D. The load-bearing behavior of rigid inclusion systems is not yet fully understood and the models on which the design is based are simplified approaches. The influence of a change in the soil state parameters due to the grid-shaped installation process is not yet quantified. Furthermore, the influence of cyclic loading on the load transfer and the arching effect in the LTP has not been sufficiently researched. The main objective of the research project is therefore to clarify the load-bearing behavior of rigid inclusion systems, taking the installation effect, the group effect and the interaction between soil, column, load transfer layer and foundation under static monotonic and cyclic loading into account. For this purpose, numerical simulations are carried out, which are supplemented and validated by model tests. For the numerical calculations, continuum models are used. The corresponding equations are solved with FEM. For this purpose, the CEL approach is applied, which has proven itself in the preliminary investigations for the simulation of the drilling process.