VIBRO COMPACTION

Vibrocompaction is probably the oldest dynamic deep compaction method in existence. It was introduced and developed in 1936 in Germany.

The method enables the compaction of non-cohesive soils to be give excellent results. A detailed description of the method may be found in literature.

The method is simply densifying the soil by a deep single or double vibration probes that are hung by a crane. The measure of densification may be the settlement gained at top of ground surface and the gain in bearing capacity may be assessed through a zone load test and the improvement in soil properties is assessed by performing CPT test prior and after compaction.

The Vibrocompaction is done on points chosen in a triangular or square pattern to cover the whole area needed to be improved.During operation, the cylindrical, horizontally vibrating depth vibrator is usually suspended from a crane or like equipment. It weighs 15–40 kN, with a diameter of 30–50 cm and a length of 2–5 m. The vibrator reaches application depth by means of extension tubes.

Supply pipes for water and air (optional) are also enclosed in the extension tubes. The pipes can deliver their payload through the vibrator tip as well as through special areas of the extension tubes to aid the ground penetration action of the vibrator.

It is possible for settlement of the surface to range from 5% to 15% of the compaction depth. This range depends on the density prior to compaction, as well as the targeted degree of compaction.

VIBROREPLACEMENT AND STONE COLUMNS

An advancement to the Vibrocompaction is the vibroreplacement method. That is pouring crushed stone or coarse graded sand or gravel into the hole made by the Vibrocompaction probes.

After the vibrator is lifted, the temporarily stable cylindrical cavity obtained is filled with coarse material. The coarse material is then compacted by repetitive use of the vibrator. This vibroreplacement procedure came to be known as the conventional dry method. Such technique allows to get dense stone column construction for a greater range of weak natural soils and man-made fills. Vibroreplacement getting wide attention and has good reputation in stabilizing foundation soils for many types of structures especially housing and low-rise buildings.

The conventional dry method utilizes the vibrator to displace the surrounding soil laterally, then the crushed stone is pressed laterally into the soil during both the cavity-filling stage and compaction stage. This produces stone columns that are tightly interlocked with the surrounding soil. The conventional dry method produces stone columns to depths of 8m in cohesive soils that have very low shear strengths.

This method is different than the conventional stone columns where the soil is drilled with boring machines and the borings filled with stones.Another way for vibroreplacement is that the replacing soil or stones may be fed from bottom during vibration with vibrators having deep feeding nozzles. In bottom feeding vibrators, the stones or sands are fed during lifting the vibrator so all cavities will be filled and it overcomes collapse as well.

On the other hand, the wet vibroreplacement method is used for cohesive soils where a heavy water jet flushes the soil and allows a room for the replacement.

APCC has great capacity in carrying out Vibrocompaction and Vibroreplacement works. With more than 50 probes and many well-trained personnel, the company can improve millions of square meters without outsourcing. The ground improvements for Palm Deira and Palm Jebel Ali in Dubai were carried out entirely by APCC.