Large Diameter Piles Technology Soilmec

Soilmec equipment is used everyday on jobsites all around the world for bridges, viaducts, motorways, tunnels, underground lines, railways and buildings of all types.
The large diameter bored piles are foundation structure characterized by a cylindrical shape with a diameter larger than 600 mm; manufactured by excavating ground through a rotary drilling equipment with a complete soil removal and cast in place by casting concrete into the borehole.
The bored piles construction entails two main steps, the drilling phase (Demolition - Removal - Stabilisation) and the construction phase (Reinforcing cage - Casting - Curing).
Excavation WITH DRILLING FLUIDS
When drilling through loose soil or very soft clay below the water table, special bentonite or polymer slurries are used to stabilise the borehole walls.
Thanks to the greater specific weight of bentonite slurry compared to water and its capacity to create a waterproof layer over the borehole walls, these slurries, when applied for more than at least metre above the water table, help make the shaft watertight, preventing the walls from collapsing.
Once drilling operations are complete, the bottom of the borehole is cleaned using a special “cleaning” tool and the slurry in the borehole is desanded.
This is carried out by lowering a centrifugal pump to the bottom of the hole and pumping the slurry to a special piece of equipment called “desander”.
At the desander, the slurry is fed through a series of vibrating screens and hydrocyclones which separate it from soil residues before conveying it back to the borehole. This process operates in a continuous cycle so the slurry in the borehole remains at the same level.
Excavation WITH CASING SUPPORT
Segmental casing is used as a temporary or permanent support for a bored piling system with deeper unstable soil conditions. It is utilised during the driling stage and can be installed and extracted by using a drilling rig or an oscillator attached to a rig, service crane or power pack. A large casing driving plate is fitted under the rotary to couple the first 1.5 m-casing section. The soil therein is removed by means of boring tools such as an auger or drilling buckets. The sections are joined using mechanical joints until the desired length is achieved.
During the concreting stage casings are withdrawn in segments, extracted by the piling rig and or oscillator. Segmental casing method can be applied to foundation piles, secant pile and contiguous retaining walls. Casing drilling is recommended in soils with rocks or boulders which tend to displace the kelly bar from the drilling axis, and thus cause serious damage to them.

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Обсадную трубу одновременно вращают и вдавливают в грунт. По мере погружения трубу наращивают следующими секциями. Грунт вынимают шнеком на телескопической штанге через каждые 1,5 - 2 м. После бурения и очистки внутренней полости обсадной трубы в скважину опускают каркас и заливают сваю бетоном. Глубина сваи может достигать - до 80 м.
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