Civil engineers are faced with limitations using conventional methods in muddy basin sediments, which are frequently encountered in the lake regions of Southern Bavaria. Through unique field experiments and novel modeling approaches, essential foundations for a sustainable design of foundations in these particular soils are to be established.

Structurally sensitive fine-grained limnic soils, colloquially known as lacustrine clays, exhibit the peculiarity of significantly losing their already relatively low shear strength when disturbed from their natural state. Compared to other soft soils, lacustrine clays are particularly challenging: this applies both to exploration and soil mechanical characterization, as well as to the load-carrying behavior of foundations, which is significantly influenced by the intensity of construction-related interference.

Common field and laboratory methods, as well as modeling approaches that form the basis of foundation design, reach their limits. The functionality of foundation systems successfully applied in soft soils with high structural sensitivity cannot be assumed. This complicates the implementation of construction projects and can even call their feasibility into question.

In the past, in Southern Bavaria, the construction use of areas with such high ground construction risk could often be avoided. However, the demand for infrastructure for mobility, as well as the development of sites for commercial and residential use, makes sustainable utilization of all available areas, considering ecological, economic, and social aspects, unavoidable in the future.

On a test site of around 6,000 m² in Kolbermoor near Rosenheim, large-scale load tests will be carried out on twelve foundation systems and an additional shallow foundation which is unique in terms of design and scope worldwide. The results of the load tests and the accompanying advanced field and laboratory tests are used to validate novel modeling approaches. Subsequently, the efficiency and sustainability of the considered foundation methods concerning region-specific soils will be evaluated. The ecological footprint will be considered from the production to the possible dismantling of the foundation.

Current status - November 2023

Starting with two test fields - the shallow foundation and the mass-soil-mixing method from Kemroc/Division Kemsolid - the first load tests will take place soon. The dead loads and 5 m x 5 m foundation slabs for loading the foundations with a maximum of around 625 tons each are already on site. About 4,000 running meters of vertical drains have been installed for all 13 test fields. The measuring equipment for the test fields is currently being installed and calibrated. This includes extensometers, sliding deformeters, and inclinometers for measuring vertical and horizontal deformations over the foundation depth, pressure meters and pore water pressure transducers in several depths, as well as water levels for measuring  the settlement below the foundation edges.

For the past year, various campaigns for subsoil exploration have been carried out on an ongoing basis, which are evaluated in parallel. The field tests (in-situ) so far include plate load tests (static & dynamic), cone penetration tests with pore water pressure measurement (CPTu), vane shear tests, cross-hole tests, self-boring pressure meter tests, and a tomographic measurement. Extensive laboratory tests accompany these.

As part of the research project, two master theses are carried out regarding numerical simulations of settlement prediction and the classification of the lacustrine clay using advanced laboratory tests.