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 – December 2025:

Building on the geosynthetic trials, individual element and group load tests are currently being conducted simultaneously with at least two test fields. The dead loads and 5 m x 5 m mobile foundations are being gradually stacked by BKL through loading, unloading, and reloading phases of the foundations, with a maximum of about 640 tons each. For all 13 test fields (including one test field for uplift injections to investigate remediation options for serviceability issues), a total of approximately 4,000 linear meters of vertical drains were previously installed by Menard.

The first two test fields – shallow foundation (TUM Geotechnical Center) and milling-mixing method (Kemroc) – were loaded stepwise over a period of approximately 6 months each in 2024. The subsequent unloading cycle is equivalent to the loading of the next test fields. The loading cycles of the following test fields -  Ductile Driven Pile system (Kurt Motz with Tiroler Rohre) and Atlas Pile system (Porr Group, specializing in deep foundation engineering)  - have been also completed. The systems Dry mortar stabilization columns CSV (Laumer company) and  Centrum - precast reinforced concrete pile ( Aarsleff-Spezialtiefbau company ) - were constructed by July 2025 and are currently in the third load stage with approximately 640 tons of dead load each (average bearing pressure approximately 250 kPa).

From January 2026, the manufacturing-induced effects on the stressed test fields will be investigated using the following methods:

• Vibro compaction with a sluice vibrator ( Keller Grundbau company ) - from January 2026
• Concrete rammed columns ( Keller Grundbau company ) - from January 2026

Finally, in mid-2026, the last test fields will be carried out using the following methods and subsequently subjected to load tests:

• Vibro compaction with vibratory pipe and vibratory attachment ( Bauer Spezialtiefbau company)
• Hybridinjection ® ( Uretek ) 

Measurement Technology for Each Test Field – With the support of cooperation partners Glötzl and Solexperts:

• Extensometer in several depth steps
• Sliding former
• Inclinometers for measuring horizontal deformations and for seismic cross-hole tests
• Earth pressure and pore water pressure sensors at several depth steps
• Hose level sensors for settlement and inclination measurement, both below and at the foundation edges
• Geodetic measuring bolts
• Surface seismics
• Concrete deformation device
• Fiber optics DFOS (distributed fiber optic sensors)

Site Investigation – Conducted and supported by cooperation partners Geo-Bohrtechnik and Mull & Partner:

For more than two years, various geotechnical investigation campaigns have been continuously conducted and evaluated. The field tests (in-situ) include, among other things:

• Plate pressure tests (static & dynamic)
• Pressure soundings with measurement of pore water pressure (CPTu)
• Seismic pressure soundings (SCPT)
• Wing shear tests
• Cross-hole tests
• Novel self-boring pressure meter tests in Germany
• Menard Pressureometer
• Marchetti Medusa / SDMT
• Tomographic measurement

These field trials are accompanied by extensive and novel laboratory experiments (Bender Element, P-Rat, etc.) in addition to index trials.

Within the framework of the research project, theses are currently being prepared on numerical simulations of settlement prediction, on the classification of marine clay using advanced laboratory experiments, and on the sustainability assessment of foundation systems.

These field tests, along with index tests, are complemented by extensive and innovative laboratory tests (e.g., Bender Element, P-Rat, etc.).

As part of the research project, final work is also currently being carried out on numerical simulations of the settlement forecast, the classification of the lacustrine clay using advanced laboratory tests and the sustainability assessment of the foundation systems.

Current Status – December 2025:

• Vibro compaction with a sluice vibrator ( Keller Grundbau company ) - individual load tests from February 2026
• Concrete tamped columns ( Keller Grundbau company ) - individual load tests from approximately February 2026
• Vibro compaction with vibratory pipe and vibratory attachment ( Bauer Spezialtiefbau company) - individual load tests from approximately August 2026
• Hybridinjection® ( Uretek ) - Individual load tests from approximately August 2026

Preparations and implementation:

Based on two preliminary tensile tests conducted independently on the test site using ductile driven piles from Kurt Motz with Tyrolean pipes , the load-bearing capacities of the foundation variants implemented in the research project were estimated for their individual load tests. These are subjected to individual element load tests at conventional intervals after construction, in parallel with the group load tests. For each method, a total of three individual load tests are performed, some with varying boundary conditions of the manufacturing parameters, and loaded to the ultimate limit state (ULS). 

• Atlas pile (Porr Spezialtiefbau ) - Individual load tests completed October/November 2024
• Ductile iron driven pile ( Kurt Motz company with Tiroler Rohre ) - individual load tests completed October/November 2024
• Dry mortar stabilization columns CSV ( Laumer company ) - individual load tests completed April 2025
• Wet mortar columns CMC® ( Menard ) - Individual load tests completed April/May 2025
• Micropile TITAN ( Ischebeck company ) - Individual load tests completed September 2025
• Centrum - precast reinforced concrete pile ( Aarsleff Special Foundations ) - individual load tests completed December 2025

Test field and preparation – with the support of partners Zosseder und Naue

Prior to the load tests, geosynthetic tests were carried out in cooperation with the company Naue using trucks with stable tracks. Among other things, these serve to specifically examine the dimensioning of reinforced base layers.

• Geosynthetic overrun tests completed
• Geosynthetic tests to investigate the effects of manufacturing-induced dynamic stress caused by construction equipment completed
• Geosynthetic tests to investigate reinforced base layers under quasi-static crane loads - t.b.d.