Vibro Stone Columns for Cost-Efficient, High-Quality Ground Improvement

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Vibro Stone Columns for Cost-Efficient, High-Quality Ground Improvement

Post  heroisthai12 on Sat Dec 11, 2010 3:16 am

Vibro stone columns (or VSCs) are columnar elements of highly compacted aggregate materials often installed in weak in-situ soils or fills. Vibro Stone columns extends the types of soils you can improve, prevents earthquake-induced lateral spreading, and provides these additional benefits for your next project:

increases bearing capacity
Reduces foundation settlement
Mitigates liquefaction
Greater slope stabilization
Allows construction on fills
Shallow footing construction is possible
Get your project analysis today from vibro stone column experts

Importance of Using Specialized Vibro Stone Column Contractors

Substantial savings in time and money – Subsurface can perform as the sole vendor for your site investigation, design, and installation.

Less risk, Greater flexibility – You receive ability to make necessary design changes in the field. Putting responsibility and risk with one subcontractor like Subsurface helps resolve problems quickly, minimizing impact on your schedule

Get Your Prompt Vibro Stone Column Project Analysis Today

Contact Subsurface Constructors today for an analysis with experienced ground improvement engineers. We will customize a design for your exact needs, and get your project on the fast-track to completion.

You may also discover more about the Vibro Stone Column process below, and download case studies or more detailed technical specifications.

The Vibro Stone Column Process

VSCs, sometimes called aggregate piers, are typically installed using a high-energy vibratory poker (called vibroflot) to penetrate the ground and displaces the soil laterally as it is advanced. This technique may also be called vibro-displacement. If the soils are too stiff to allow advancement of the vibroflot, pre-drilling may be necessary. This technique is called vibro-replacement.

We then add lifts of aggregate to the bottom of the hole. The vibroflot compacts each lift with high-frequency vibration and down pressure, resulting in very stiff, high density stone columns. The vibro stone columns are normally constructed directly beneath the main foundations, usually in single or multiple rows beneath strip foundations and in groups beneath pad/mat foundations.

Vibro stone columns apply to many different weak ground conditions, including soft, cohesive in-situ soils, poorly compacted fills (made ground), and loose granular soils in which seismic liquefaction is a concern. VSCs used in cohesive soils provide increased soil stiffness, mostly immediate settlements, reduced drainage paths, and reduction in pore water pressure. Typical design bearing pressures range from 4,000 to 6,000 pounds per square foot.

Vibro stone columns are installed to your project using different techniques which are highly-dependent on soil conditions. Methods for installation consist of:

dry top feed for soft but stable cohesive soils
dry bottom feed for unstable (collapsible) clays and silty soils
wet top feed for sands and silty sands.
DRY TOP FEED Vibro Stone Columns

In predominantly cohesive soils, Subsurface Constructors mounts a hydraulically-powered vibroflot to the ground improvement rig. This rig advances the vibroflot into the ground with significant down pressure, laterally displacing the soil and creating an open hole down to the design depth.

We dump Aggregate material from the ground surface into the hole in approximately one to two foot lifts. The lifts are compacted with vibration and down pressure from the vibroflot. This is called the Dry Top Feed Method.

DRY BOTTOM FEED Vibro Stone Columns

When soil conditions consists of unstable, fine grained soils such as silts and clays that may be below the water table, it may be necessary to bottom-feed the aggregate material, alleviating possibility of hole collapse.

With this technique, we attach a tremie to the vibroflot full-length which is used to carry stone from a rig-mounted hopper to the bottom of the hole. As we raise the vibroflot, stone empties into the hole. The stone compacts in lifts in a continuous process until the vibro stone column is complete.

WET TOP FEED Vibro Stone Columns

The Wet Top Feed method of vibro stone column installation is required for deep treatment of unstable soils consisting of silts and silty sands, often below the water table. With this technique, we either suspend the vibroflot from a crane or mount on a rig. It is then lowered into the ground and penetrates the soil with the combined action of water jetting from the tip and vibration.

After reaching the required depth, We reduce the water jetting volume until a small upward flow of water around the annulus of the vibroflot is observed. At this point, a small quantity of stone aggregate is introduced and the vibroflot is slightly lifted and lowered until the stone charge is fully compacted a the tip of the vibroflot. This action is repeated in one to two foot lifts until the vibro stone column is formed to the surface.

Get Your Prompt Vibro Stone Column Project Analysis Today

Contact Subsurface Constructors today for an analysis with experienced ground improvement engineers. We will customize a design for your exact needs, and get your project on the fast-track to completion.


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heroisthai12

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