Finite Element Analysis of Mixed-in-Place Columns (MIP) Supporting Excavations in Slopes Considering Tension Softening

The use of mixed-in-place (MIP) columns can be considered as attractive alternative to sheet pile, diaphragm or bored pile walls for supporting deep excavations, even when it comes to difficult ground conditions. In this paper results from a numerical study based on a case history are presented, where MIP-columns are used to support an excavation in a slope. The special feature of this project is that tied-back anchors were not feasible as additional support measure because it was not allowed to put any structural elements within the neighbouring ground. Thus the MIP-columns were placed in such a way that they formed an arch including buttresses capable to transfer the load acting on the backside of the wall into the ground. In this study an advanced constitutive model for the MIP-columns is applied to capture the development of possible cracking. Variations in geometry have been performed in order to investigate the potential for optimization. Finally some analyses have been conducted to show that a design of such structures compatible with EC7 requirements is perfectly feasible by means of the finite element method.