Behaviour of a CFA pile in a lateric clay

Lateritic clays are scarce in many parts of the world, but very common in tropical countries like Brazil. The stiffness of lateritic clays arc much higher than that of non lateritic, but otherwise similar clays, showing the same penetration resistance. For these lateritic soils the well established and reliable semi-empirical formulas for predicting bearing capacities of piles and footings, provide too conservative results. This paper presents the results of one investigation, carried out very recently, in a foundation of a building on CFA piles. Due to the high stiffness characteristics of these clays, it was considered that the contribution of the pile cap should not be neglected, in design, as it is usually done in routine jobs. A large number of in situ and laboratory tests were carried out. But the highlights of all in situ tests were the load tests. In order to properly assess the load-settlements characteristics of foundations in these soils, two load tests were carried out. One of them was a load test on a square shallow foundation, with a width of 0.60m. The other was a load test on a CFA pile. It must be emphasized that the knowledge of the high stiffness of these clays, together with proper consideration of the capacity of the pile caps were fundamental for the successful design of the foundations for this building.