Construction over highly compressible soils can create excessive settlement and bearing capacity problems. To overcome these difficulties, deep foundation elements such as driven piles or drilled shafts have been traditionally used to transfer the surcharge loads exerted by the superstructures to a more competent layer at greater depths. Although deep foundation methods have proven to be effective in most cases, these methods are relatively expensive when constructed over large areas and may also cause unwanted delay during construction. As alternatives to deep foundation methods, ground improvement technologies have been widely used to improve the load-carrying capacity and stiffness of shallow soil layers located immediately underneath the superstructures. Over the past 70 years, soil improvement technologies have mainly focused on the development of vibratory methods for densification of cohesionless soils, injection and grouting materials and procedures, and new concepts of soil reinforcement. Among other soil reinforcement technologies, rammed aggregate pier systems have been emerging rapidly during the last two decades to become one of the most popular methods for stiffing and stabilizing soft soils in the United States. Rammed Aggregate Piers (also known as Geopier Soil Reinforcement) technology was developed in the early 1980s to provide an economical alternative to deep foundations and traditional methods of soil improvement, such a overexcavitation and replacement. Since the inception, rammed aggregate piers have been used to support a wide range of structures including column footings, highway embankments, heavily-loaded slabes, slopes, retaining walls, and industrial storage tanks. Typical application of rammed aggregate pier systems include settlement control, bearing capacity improvement, slope stabilization, uplift capacity enhancement, and liquefaction mitigation. Since rammed aggregate piers are relatively short and generally not intended to penetrate to a competent layer, the rammed aggregate piers system is essentially a floating system. Although this technique have been developed in many projects; studies due to understanding the behavior of rammed aggregate piers are not so much and have been focoused on full scale load tests on isolated piers or pier groups. So use of nummerical modeling of piers and parametric study in this aspect is necessary. Nummerical analyses which have been done in this aspect, in most cases don’t consider installation effects or considering it with not so much accuracy while with looking at studeies which have been done, it can be seen that exact modeling of installing process is so important and don’t considering it may cause mistake in results. In other hand recent progresses in aspects of analyses of problems with new nummerical methods which improve accuracy of analyses and make them reliable, have opened a new window for investigation geotechnical cases. The goal of this research is to modeling the construction of rammed aggregate piers using both distict element method and finite-element method. A parametric study also performed in different conditions of geometry and matrix soil properties. These studies not only help to better undrestanding the pier behavior but also it can be used as a tool for predecting the expansion of pier in different conditions. Key words: Nummerical methods, distict element, RAPs, construction process