Geotechnical characterization and ground improvement of soft glaciolacustrine clays along the Rail Baltica high-speed railway in Estonia

Verston Eesti OÜ, Tallinn, Estonia

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Abstract

The construction of the Rail Baltica high-speed railway in Estonia encounters significant geotechnical challenges where the alignment crosses deep deposits of very soft to soft Quaternary glaciolacustrine clays. These soils, characterized by low shear strength, high compressibility, and high sensitivity, pose critical risks to embankment stability and long-term serviceability. This paper presents an in-depth geotechnical characterization of these problematic clays across four key construction sections. The study integrates a comprehensive suite of advanced in-situ testing data, including Multichannel Analysis of Surface Waves (MASW) to establish small-strain stiffness profiles, Piezocone Penetration Tests (CPTU) for detailed stratigraphic delineation and consolidation parameter assessment, and Field Vane Tests (FVT) to determine the undrained shear strength profile. Analysis of this data provides robust, site-specific geotechnical models and establishes the key design assumptions for high-speed railway embankments. The primary design concerns embankment stability (both short- and long-term) and the prediction of total and differential settlements under strict serviceability limits are addressed. Furthermore, the paper discusses and evaluates a range of soil improvement solutions implemented to ensure the railway's long-term performance. These solutions include basal reinforcement with high-strength geosynthetics, accelerated consolidation using surcharge and Prefabricated Vertical Drains (PVDs), and load transfer platforms supported by rigid inclusions or stone columns. The findings offer validated design parameters and practical insights for constructing critical infrastructure on the complex soft clays of the Baltic region.