Remediation of Rail Structures Impacted by Landslides Using Sleeved Bored Piles-Paper

Paper

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The South Coast Railway between Sydney and Wollongong crosses steep, landslide-prone terrain where colluvial soils, historic embankments, intense rainfall and inadequate drainage have contributed to long-term ground movement. Following major landslides in the late 1980s, Sydney Trains managed geotechnical hazards through risk assessment, monitoring and staged remediation.<br /><br />The paper presents two case studies using sleeved bored piles to protect rail structures from moving ground. At Otford Station, creep movement had displaced the footbridge foundations; inclinometer readings recorded 42 mm of horizontal movement between 1993 and 2006. Rather than use ground anchors, which raised durability concerns in a moving embankment, the design underpinned the bridge with bored piles socketed into rock and enclosed in permanent steel casings. The sleeves allow surrounding soil to move while isolating the structural piles.<br /><br />At Coledale, an overhead wiring structure on a high embankment continued to move despite an existing anchored pile wall. Monitoring indicated both deeper landslide movement and ongoing creep in fill and colluvium, likely worsened by poor drainage and rainfall infiltration. The OHWS was replaced on sleeved piles designed to accommodate ground movement while carrying structural loads.<br /><br />Both projects required careful construction planning to limit disruption to railway operations and protect existing infrastructure. Long-term monitoring informed the geotechnical models, helped guide the designs and verified performance. The case studies demonstrate that sleeved bored piles can effectively separate railway foundations from moving soil, addressing serviceability and safety risks where ground movement continues.

Keywords

South Coast Railway

Sydney to Wollongong

landslide-prone terrain

geotechnical hazards

colluvial soils

ground movement

sleeved bored piles

rail infrastructure

Otford Station

Coledale