Design of Ground Improvement by Inclined DSM Columns for Railway Embankment (TÃœRKEY)-PPT Presentation

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The study addresses settlement beneath the approach embankments of a bridge on the Ankara–Sivas Railway in Sivas, Türkiye. Deformations in reinforced-earth walls were observed in 2021. Site investigations identified soft, compressible clay and related sediments, with groundwater depths ranging from 4.3 to 18 m.<br /><br />Consolidation analyses estimated remaining settlements of 33.2 cm at Km 358800 and 13.6 cm at Km 358880—both exceeding the railway’s 5 cm target. To reduce settlement while working beneath an active railway, the project used inclined deep soil mixing (DSM) columns, installed at 45° to the horizontal. The columns were 0.6 m in diameter, arranged in three to four rows, and spaced 1 m horizontally and 1.5 m vertically. Cement–water grout was mechanically mixed into the soil.<br /><br />Settle 3D analyses predicted post-treatment settlements of 1.85 cm and 3.71 cm at the two critical sections, within the allowable limit. Core testing showed an average uniaxial compressive strength of 11.24 MPa, exceeding the design minimum. Slope stability analyses for short- and long-term static and seismic conditions also met the required safety limits.<br /><br />Construction was completed in November 2021. During six months of post-treatment monitoring, no further settlement changes were observed, and the railway continued operating safely. The authors conclude that inclined DSM columns provided an effective and practical solution for improving embankment settlement and stability under a live railway.

Keywords

Ankara–Sivas Railway

settlement

deep soil mixing

inclined DSM columns

embankment stabilization

soft clay

consolidation analysis

reinforced-earth walls

railway geotechnical engineering

slope stability