Study of the stresses below a raft founded on collapsible soil reinforced with rigid inclusions

The region of the Federal District of Brasilia has a superficial layer formed by clayey, porous and collapsible soil whose thickness varies from a few centimetres to several meters deep. It is due to the presence of this layer of collapsible porous soil that in the Federal District is common to use deep foundations. The inclusions have been studied and used for the purpose of controlling the settlements and reducing the cost in the foundations of low height buildings over soft soil. The authors have studied the use of foundations with rigid inclusions as an alternative for controlling the settlement in the collapsible soils of the Federal District, demonstrating its good performance. This paper studies, through axisymmetric modelling, the stress under raft induced by the top of the inclusions. For this, several models were developed, where the spacing between inclusions, the height of the distribution layer and the stratigraphy were varied. The results show the influence of the geometric characteristics of the foundation and the type of stratigraphy on the development of stress under the raft, as well as the geometric arrangement in which the stresses induced by the inclusion head are minimal, which constitutes an advantage of this type of foundation since it decreases the amount of structural reinforcement in the raft.