Advanced New Methodology for the Identification of Stiffness and Strength of Weak Rock as Basis for Economic Foundation Design

The most important aspects for the design of any foundation system are safety, optimisation and the sustainability. An optimised and safe design of foundation systems for high-rise structures in difficult soil and groundwater conditions is based on a reduction of construction material used, construction time spent, energy consumed and the adequate consideration of the soil-structure interaction. This is also important for the high-rise structures like skyscrapers and bridge piers in weak rock like in Dubai, UAE. Due to the large loads most of these structures are founded in the Dubai Sandstone and Dubai Siltstone. Up to now the rock mechanical parameters for these rock layers have been defined on the very conservative side which led to over-dimensioned foundations in many cases. In a large research program the bearing behaviour of Dubai Sandstone and Dubai Siltstone has been investigated by field and laboratory tests, by in-situ pile load tests and the numerical back-analysis using the Finite-Element-Method (FEM). The comprehensive research investigations show, that the stiffness of Dubai Sandstone and Dubai Siltstone is more than 20 times higher as it is assumed up to now. The paper presents the scope of research, the epoch-making results and the significance for the engineering practice.