Vibro stone columns are used to improve the characteristics of shallow low strength and stiffness soils. Adopting a Vibro Stone Column approach allows the use of lightly reinforced ground bearing slabs, pads & strip foundations – offering significant cost efficiencies when compared against a traditional piled approach.
Through the combined effects of densification, and/or reinforcement Vibro Stone Columns can be successfully used to improve both fine grained (Clay) and coarse grained (Sand & Gravel) soils.
Columns are constructed using imported stone compacted in voids formed using a displacement process, resulting in zero spoil arisings. GeMech operate a fleet of top feed vibro stone column rigs, with fixed mandrels ranging in length from 4.5m up to 7.0m.
With prior approval Vibro Stone Columns can be formed using recycled aggregates, offering environmental sustainability benefits.
Vibro stone columns can be used on a wide range of construction projects, from low rise housing, commercial warehousing to large scale Civil Engineering.
Suitable for a wide range of soils profiles
More cost effective than most other piling methods, particularly when the whole foundation package cost is considered
Faster than other traditional methods of piling
Zero spoil arising
Minimal site preparation requirements in comparison to traditional piling methods
Recycled aggregates can be used in column construction, offering environmental sustainability benefits.
A lesser understood benefit of vibro stone columns in fine grained soils (Clays & Silts) is the improved consolidation rate of the host soil after column construction, as the columns work effectively as vertical drains, reducing the time period required for achieving primary consolidation. Vibro stone columns can be used in tandem with static surcharging to provide efficient solutions on sites with challenging ground conditions.
The Vibro Stone Column Process
Ahead of commencement on site GeMech will complete a detailed ground improvement design and prepare a stone column layout based on a set of construction issue foundation drawings – supplied to GeMech in DWG format by the Client.
Step 1 – Prior to the rig arriving to site the client surveys the area for serviclevel andes a suitable working platform at either top of foundation level or underside of slab level, and drives a numbered pin into the working platform at each pile position.
Step 2 – A health and safety briefing will take place, the rig will be prepared to work, and moved to the first pile position.
Step 3 – Stone is delivered to site and tipped on the working platform, in a stockpile positioned close to the piling rig. GeMech will move stone from the stockpile to the individual columns using a 360 excavator.
Step 4 – The fixed mandrel, with an appropriate length with respect to the ground improvement design requirements, will be set up over the numbered stone column position. The mandrel is then progressed to a predetermined design depth, or refusal at a maximum hammer pressure.
Step 5 – Stone is placed in the void formed by the mandrel in a series of layers, with each layer successively compacted by the vibro mandrel during the column construction process.
The near surface section of column receives least degree of compaction during the construction process, this is not a concern for stone columns below pad foundations, as this section of material is removed during excavation. For columns below slab areas, it is important that the surface of the improved soil is subjected to heavy compaction prior to slab construction, in order to compact the material at the head of the stone columns.
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