Qualified pile load testing concepts are an important tool for the technically and economically optimized design of piled foundations and consequentlyfor a sustainable design of deep foundations with reduced consumption of resources and a reduced carbon footprint. In this context, new and improved measuring devices like fibre optics and ultrasonic instruments can provide significantly more detailed knowledge about the bearing behaviour of test piles even for difficult geotechnical conditions. In this paper, two exceptional pile load testing campaigns for two infrastructure projects, a major bridge project and a cut-and-cover tunnel will be presented: For the construction 9.7 km long harbour passage in the course of the new A26 motorway south of Hamburg, Germany, the route crosses the river Elbe with a cable-stayed bridge. In conjunction with the adjoining elevated road and the foreland bridges, this approximately 5 km long section will form Germany's longest motorway bridge in future . Due to the challenging subsoil conditions, including thick organic material the foundation of this section is planned with more than 2,000 large bored piles, most of which are to be constructed with base expansion. As a basis for technically and economically optimised planning of the pile foundations, a total of 28 large bored piles were constructed in advance at four locations and static and dynamic axial as well as static horizontal pile loads tests were carried out on these test piles. The targeted variation of only one manufacturing parameter at a time makes it possible to determine its respective influence on the axial and lateral resistance deformation behaviour. At the same time, intensive instrumentation of the piles, includingfibre-optic measurement methods, allows a detailed analysis of the pile load-bearing behaviour. As part of the parameter variation, the influence of different pile diameters and pile lengths, the influence of a cased and suspension-supported execution, as well as the effect of a base widening of different geometries is analysed. For a 2km long adjacent cut-and-cover tunnel project another test campaign was planned and executed. In this context, the load-bearing behaviour of various drilled and driven deep foundation elements was investigated as basis for planning the foundations. For this purpose, conventional bored piles, partial and full displacement bored piles as well as in-situ concrete driven piles, sheet piles and diaphragm elements (barrets) were constructed. A total of more than 40 test loads were applied to these load-bearing elements and the load transfer behaviour was determined. Based on this the tests carried out and the results for the different types of load-bearing elements are presented and compared with each other. For both case studies the impact on the qualified pile load testing campaigns on the optimization of the piled foundations embracing sustainability and reducing CO2 production will be identified and quantified.
Christian Moormann (Thu,) studied this question.