Case study: Tailings storage facility ground improvement stabilisation – from options to implementation

Joe Rola

Recent catastrophic tailings dam failures have driven the identification and need for TSF stabilisation solutions worldwide in an effort to improve factors of safety under a post-seismic loading condition, where contractive materials are present within the structural foundation zone. Although not common place, specific circumstances (i.e. limited available footprint, lack of buttress material, etc.) may drive the use of ground improvement (GI) as part of a wider stabilisation solution.

A case study is presented, which spans a near 7-year long journey from concept through to design and construction, where circumstance drove the stabilisation solution to include GI.  The 26 m high TSF embankment was founded on both weak and liquefiable units up to about 18 m below ground surface where the FoS was assessed to be below acceptable levels under both peak undrained and post-seismic loading conditions.  A variety of GI options were assessed, with stone columns (SC) selected as the preferred option due to drainage considerations.  A fully instrumented field trail (>180 SCs/~160 wick drains with more than 60 monitoring instruments) was implemented with post in situ testing (>80 in situ tests – CPT/VST/BPT/DMT/PMT) to inform detailed design of the stabilisation solution.  In parallel to the staged design phase, detailed design of early works packages were progressed to instrument the area in preparation for construction and increase the FoS to > 1.3 prior to commencement of GI.  Analyses increased in both quantity and complexity across the staged design phases, including 2D limit equilibrium modelling, 2D/3D seepage modelling and 2D/3D finite element modelling.  The end solution comprised the installation of ~6,500 SCs to a maximum depth of 18 m (~100 km of lineal depth), construction of linear drainage elements at depths of up to 5 m within shored excavation and the placement of ~390,000 m³ of buttress fill. 

In addition to presenting the design/construction of the stabilisation solution, a firsthand account of the challenges/solution and stresses encountered along the journey will be shared with a variety of construction photos show casing each stage of works.

About the speaker

Joe Rola Principal Geotechnical Engineer, SRK

Joe Rola is a civil/geotechnical engineer with over 20 years’ experience working on mine and power generation wastes, heap leach and land/infrastructure development projects across Australia, Southeast Asia and North America. Joe has extensive experience in design, analysis, reporting, construction support/quality assurance, field and laboratory investigations, project management, and geotechnical instrumentation design/installation. Joe specialises in tailings and mine waste related projects, providing review, project direction and/or lead engineering from concept stage through to detailed design, construction, operations and closure.

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