Steffen Leppla

Foundation Systems for High-Rise Structures

To view our full range of books and order online visit: The book deals with the geotechnical analysis and design of foundation systems for high-rise buildings and other complex structures with a distinctive soil-structure interaction. The basics of the analysis of stability and serviceability, necessary soil investigations, important technical regulations and quality and safety assurance are explained and possibilities for optimised foundation systems are given. Additionally, special aspects of foundation systems such as geothermal activated foundation systems and the reuse of existing foundations are described and illustrated by examples from engineering practice.

Aspects Regarding Management of Soil Risk

The geotechnical investigations of soil and groundwater conditions are an essential part of the design for almost every construction project. Especially at large and challenging projects, problems often occur during the construction works when the detected soil and groundwater conditions (structure, properties) differ from the result of the earlier geotechnical investigation. Time delay in the construction process, modifications of the construction, additional expenditure and in some cases even damages may be the consequences. The so-called “soil risk” occurs, when the soil and groundwater conditions are different to the results of the geotechnical investigation. In any case the soil risk is connected to the chosen construction process and type of construction (“system risk”). Most forensic geotechnical tasks deal with handling of the soil risk respectively system risk. In this paper the legal aspects of managing the soil risk respectively the system risks are explained with special focus to forensic geotechnical engineering and the qualification of publicly certified geotechnical experts. Standards are defined and the applications in engineering practice are shown through several prominent examples of retaining structures of deep excavations, foundations in organic soils and tunnel constructions in urban areas.

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.

Anforderungen an die bodenmechanische Modellbildung in der Baupraxis

Die Modellbildung ist fur jedwede Untersuchung der Standsicherheit und der Gebrauchstauglichkeit von Tragwerksstrukturen von entscheidender Bedeutung [1], da sie die qualitative und quantitative Zuverlassigkeit der Prognose bestimmt [2]. Dies gilt insbesondere, wenn den Untersuchungen zur Standsicherheit und Gebrauchstauglichkeit nicht mehr analytische, sondern numerische Verfahren zugrunde liegen. Zu diesen numerischen Verfahren zahlen z.B. die Finite-Element-Methode (FEM) oder die Diskrete-Element-Methode (DEM).