The problem of foundation of railway embankments on non-bearing soils and instability of existing embankments, upgraded to higher loads category, periodically returns on the desks of designers, inspectors and managers of the rail roads. According to the disposition ‘Id – 3’ – Technical conditions for maintaining railway subgrade’, it is necessary for the track to be sufficiently stable and durable for specific operational parameters of the railway and there were no permanent and elastic deformation, which considerably jeopardize railway traffic safety.
In order to meet these requiements, it is extremely important to carry out soil investigation. Field and laboratory tests allow us to select an appropriate method of improvement, and by the application of numerical models based on laboratory-confirmed ground parameters – soil improvement will be optimal both technically and economically.
Technologies for improvement in railway construction
From the geotechnical point of view, railway construction is a very challenging field of operation. The selection of improvement method, in addition to the conditions for a compressive capacity and acceptable settlement is justified by the technical capabilities of the execution of works while maintaining railway traffic and also abilities to bypass aby type of ground or sub-surface installations.
In the construction and modernization od railway embankments we use the following methods of soil improvement:
- Controlled Modulus Columns CMC – treated as soil improvement method, are characterized by relatively low susceptibility to impacts caused by the movements of trains. They are constructed to the level of load bearing soil layer;
- Combined Columns MCC – dedicated in particular to the places where below the layer of track substructure occur relatively favourable ground conditions, and where the weak soils that require improvement are deposited;
- Stone Columns SC – in addition to the improvement of soil parameters – primarily the modulus of elasticity and bearing capacity – SC can serve as vertical drains. Their application in wet cohesive soil accelerates the consolidation of soil, reducing subsidence and increasing the stability factor of road embankments;
- Bi-Modulus Columns BMC – combine the advantages of stone and concrete columns. On the one hand, the soil is not over-stiffen, and there is no risk of column buckling or bulging. The application allows for the optimization of transition layer thickness, transmitting the traffic load to the column shaft;
- Supple/Susceptible Columns MSC – are technologically advanced solution of cement ground columns, which due to their small equipment size can be successfully applied to improve the existing embankments whilst maintaining the free traffic flow on adjacent track;
- Deep Soil Mixing Columns DSM – the method of soil improvement using concrete-soil grout as a reinforcing material. Construction of these columns consists in mixing properly selected cement-ash slurry with the thickening soil.
The examples of our projects:
• Modernization of E-65 of the railway line, Warszawa-Gdynia section (area LCS Działdowo),
• Modernization of the railway line, Warszawa-Łódź section, Warszawa Włochy-Pruszków railway route;
• Modernization of E-30/C-E30 railway line, Kraków-Rzeszów section, stage III.