Taş Kolon

Zemin / Sondaj

STA · Neftaş Makina Turkey

Stone Column — Vibro Replacement

Installation of stone columns improves ground by reducing soil settlement. Due to their higher modulus of elasticity than that of soil, stone columns absorb more load and reduce overall settlement.

Since applied load distributes between soil and stone column in the ratio of their stiffness, the load carrying capacity of soil also increases. Content on this page is based on the STA Milano stone column technical overview. For project-specific design and equipment selection, contact Neftaş sales engineering.

How Stone Columns Improve the Ground

Stone aggregates are used to fill stone columns. Water can easily pass into the stone column, so stone columns help in excess pore water pressure mitigation and accelerate the consolidation process.

In this method, boring is done by displacing nearby soil. The soil is displaced laterally, due to which the engineering properties of the soil change. Stone columns act as stiff inclusions within soft ground, sharing structural loads with the surrounding soil and limiting differential settlement.

Neftaş Makina represents STA vibroflotation equipment in Turkey. With service points in İzmir, Istanbul, Ankara, Adana, Çanakkale and Gaziantep, we support stone column projects with VibroSTA equipment, spare parts and field expertise.

Two Installation Methods

Stone column construction can be performed using two distinct techniques, selected according to soil type, fines content and whether the borehole remains open during and after penetration.

Bottom feed method: Recommended when fines exceed 10–15% of soil volume and the hole does not stay open. Aggregate is discharged at the tip of the VibroSTA through a stone tube.
Top feed method: Recommended for cohesive saturated soils where an annular space remains open. Aggregate is added from the ground surface and compacted from the bottom of the hole upward.

Bottom feed

Bottom Feed Method

Used when the percentage of fines is higher than 10–15% of the soil volume. The soil collapses around the VibroSTA and the hole does not stay open during and after the perforation process.

Stones discharged at the bottom of the VibroSTA tip via stone tube
Column built from bottom to top to designed depth
Preferred perforation fluid: compressed air
Crane suspended · excavator mounted · piling rig application

Top feed

Top Feed Method

During and after the perforation process an annular space stays open around the VibroSTA and gravel can be provided into the hole from the top. A vibro-replacement technique recommended for cohesive saturated soils.

Columns built from coarse gravel, crushed stone or aggregate on a trial grid
Stones added from the ground surface into the VibroSTA hole
Same equipment as vibro compaction suspended from a crane
Backfill compacted and pushed into hole sides — column formed bottom to top

VibroSTA Equipment & Applications

Selected images from the STA Vibroflot brochure — crane-suspended, excavator-mounted and offshore stone column installations.

STA Vibroflot brochure — bottom-feed crane application

STA Vibroflot brochure — top-feed vibro replacement

STA Vibroflot brochure — VibroSTA suspended from crawler crane

STA Vibroflot brochure — stone column rig on site

STA Vibroflot brochure — vibroflot power unit and hoses

STA Vibroflot brochure — excavator-mounted application

STA Vibroflot brochure — offshore stone column from barge

STA Vibroflot brochure — marine vibro replacement operation

STA Vibroflot brochure — stone column grid pattern

STA Vibroflot brochure — VibroSTA tip and stone tube

STA Vibroflot brochure — completed stone column field

Technical Overview — Methods & Applications

Expanded summary based on STA Milano vibroflotation documentation. Soil investigation and trial columns determine the final grid, depth and aggregate specification.

Ground improvement benefits

Stone columns improve ground performance through a combination of stiff inclusion, load sharing and drainage enhancement:

Reduced total and differential settlement under structural loads
Increased load carrying capacity through stiffness ratio between column and soil
Accelerated consolidation via drainage paths within the aggregate column
Excess pore water pressure mitigation in saturated soils
Lateral soil displacement during installation changes in-situ soil properties

Bottom feed method — process & equipment

The bottom feed technique is selected when fines content exceeds 10–15% and the borehole cannot remain stable without continuous support from the bottom-up stone feed.

Once the perforation process is terminated, stones are discharged at the bottom of the VibroSTA tip through a stone tube that drives the gravel into the VibroSTA, building the stone column from the bottom to the top of the designed depth. Preferred perforation fluid is compressed air.

Crane suspended
Excavator mounted
Piling rig application
Compressed air flushing
Stone tube bottom discharge

Top feed method — process & equipment

Top feed stone columns are a vibro-replacement technique recommended for cohesive saturated soils. This technique consists in building and compacting in the ground columns made from coarse gravel, crushed stone or crushed aggregate, following a grid pattern previously determined by a test trial.

In the top feed method, the column is made with stones that are added from the ground surface into the hole created by the VibroSTA. This method requires the use of the same equipment as vibro compaction suspended from a crane. The backfill is compacted and pushed into the sides of the hole; the stone column is formed from the bottom of the hole to the top.

Cohesive saturated soils
Annular space remains open
Crane-suspended VibroSTA
Trial grid design
Surface aggregate supply

Method selection criteria

The choice between bottom feed and top feed depends primarily on soil behaviour during penetration:

Bottom feed: High fines content (>10–15%), collapsing borehole, unstable hole walls during and after penetration.
Top feed: Cohesive saturated soils where an open annulus is maintained; suitable for vibro-replacement with surface-fed aggregate.

A trial column programme on site confirms spacing, depth, stone gradation and production rates before full-scale installation.

Method

Soil condition

Key characteristics

Bottom feed

Fines > 10–15%, collapsing hole

Stone tube discharge · compressed air · crane / excavator / piling rig

Top feed

Cohesive saturated soils

Open annulus · surface aggregate · crane-suspended VibroSTA

Technical content sourced from STA Milano — Stone column. For VibroSTA equipment specifications and project support in Turkey, contact Neftaş Makina.