| Summary: | So far insufficient research has been done on the long-term behavior of micropiles embedded in a clay medium, even though this has a significant influence on the expected total settlement. This paper considers a square foundation placed on a clay bed and tested under vertical loads until the clay reached its bearing capacity. Subsequently, the plate was underpinned with four micropiles, and the load test was repeated. These test data were used to validate the coupled hydraulic-mechanical three-dimensional finite difference model presented in this paper. In the numerical modelling, four different load transfer scenarios were considered to simulate different approaches to adding floors to an existing building. Consolidation periods of zero months, six months, and five years between the application of the load due to the existing building, and the application of loads due to additional storeys were considered. The six-month period represents a short-term, and the five-year period a long-term scenario. Following the first consolidation period and the application of loads representing additional storeys, a second consolidation period was implemented, such that the combined length of the two consolidation periods was five years. In this study, the results showed that the installation of micropiles immediately after the completion of existing floors is most successful in controlling the settlement of additional floors later on.
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