Comparison of Large Plate Load Test Result with Predicted Deformation in Deep Vibro Techniques Treated Ground for Iron Ore Stockpile Yard in Vietnam-Paper

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The paper describes ground improvement for a 20-hectare iron ore stockpile yard in Quang Ngai, Vietnam, designed for stockpiles up to 14 m high. The reclaimed site contained 12–18 m of loose-to-medium-dense sand over 2–6 m of soft clay, with localized very dense sand. Heavy stockpiles could cause excessive settlement and lateral movement of nearby roof and reclaimer piles.<br /><br />The treatment combined vibro compaction to densify the sand with vibro replacement stone columns in the soft clay. Because the compacted silty sand could still be insufficiently stiff to limit pile movement, additional, smaller stone columns were installed in the sand. Pre-boring was used where dense sand obstructed installation of the larger columns, followed by vibro compaction to densify the sand and address disturbance from pre-boring.<br /><br />Settlement was predicted using finite element analysis, with stone-column-treated ground represented by composite soil properties calculated using Priebe’s method. The analysis predicted approximately 27 mm settlement at 90% consolidation under 140 kPa, and a maximum total settlement of about 30 mm.<br /><br />A reinforced 6 m by 12 m plate load test was conducted to assess performance. Earth pressure cells confirmed that the applied average stress of 140 kPa was distributed uniformly. The measured settlements averaged 21.8 mm, approximately 20% less than the predicted value. The authors attribute the difference potentially to the average soil modulus used and limitations of the Mohr–Coulomb model.<br /><br />The study concludes that combined vibro compaction and stone columns can effectively improve stockpile-yard ground, and that Priebe’s method provides a useful basis for estimating the properties of stone-column-treated soil. A stiffened large test plate helps achieve more uniform loading and reliable validation.

Keywords

ground improvement

iron ore stockpile yard

vibro compaction

stone columns

settlement prediction

Priebe method

finite element analysis

plate load test

soft clay

Vietnam