Vibro-replacement stone columns, has been one of the world's most popular methods over the past half century. The purpose of the stone column implementing is creating soil beds under the structure with new characteristics, as different structural foundations (strip, single or mat foundations, concrete slabs, embankment and etc.) show predictable and justifiable behavior consistent with the privacy and tolerance that is intended for building structures. During the process of construction of stone columns using vibro- replacement method, due to the water jet of the end of the probe, lead creation of wells with desired depth in the earth. Well get washed without casing with water jets, and then gravel materials which feed from the top or bottom of the well, by an electric or hydraulic vibrator, located at the bottom of the probe are dense in layers with 0.3-1.2 meters thick.
Vibro-replacement process is commonly used where the stability of walls is doubtful. Thus, it is useful for areas with loose to dense relative density (or soft to stiff) soil layers and high underground water level. Vibro-replacement process should be used in areas with too soft soil where the well without casing can be stable and underground water level is high. The columns can be made in regular or variable grid as row or group or even individually. Soil improvement with using stone columns contain one or a combination of the following effects:
_Increasing bearing capacity
_Reducing settlement
_Correcting uniformity of geotechnical properties
_Increasing the rate of consolidation with creation of drainage elements
_Increasing technical characteristics of the composite soil bed
