Design of Ground Improvement by Inclined DSM Columns for Railway Embankment (TÃœRKEY)-Technical Paper Upload

Technical Paper Upload

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This case study describes ground improvement beneath the approach embankments of a live railway bridge in Sivas, Türkiye. The embankments, up to 13 m high, were founded on soft clay and weak claystone. Site investigations and settlement analyses identified substantial remaining consolidation settlement at critical sections—33.2 cm and 13.6 cm—exceeding the railway’s 5 cm limit.<br /><br />The project used deep soil mixing (DSM), in which cement-water slurry is mixed into the ground to form soil-cement columns. To target the deepest soft-clay layers beneath the embankments, the columns were installed at a 45° inclination. They were 0.6 m in diameter, arranged in three to four rows, with 1.5 m vertical and 1 m horizontal spacing. Analyses predicted post-treatment settlements of 1.85 cm and 3.71 cm at the critical sections.<br /><br />Laboratory tests on 12 column cores gave an average unconfined compressive strength of 11.24 MPa, exceeding the design minimum. Stability analyses also met the applicable requirements for short- and long-term static and seismic conditions. Following construction, completed in November 2021, six months of monitoring recorded no further settlement, and railway operations continued safely. The study concludes that inclined DSM columns provided an effective and practical solution to settlement and stability problems beneath an existing railway embankment.

Keywords

deep soil mixing

railway embankment

ground improvement

settlement control

soil-cement columns

inclined columns

soft clay

stability analysis

Sivas Türkiye

consolidation settlement