Abstract: Micropiles are mainly used to increase the bearing capacity and reduce the settlements particularly for strengthening the existing foundations. Frictional resistance between the surface of the pile and its surrounding soil and the associated group/network effects of micropiles are considered as the possible mechanisms for improvement. This paper is mainly devoted to investigation a case study in which foundation of a drilling rig was retrofitted by constructing a thick concrete ring confining the existing foundation which was supported by micropiles. The modelling was conducted by GEO 5 software in two phases including and excluding micropiles, respectively. Both phases were done regarding the existence of cracks around the foundation. The obtained results show that this method enhanced the bearing capacity and flexural stiffness of foundation. Also, this study provides valuable information about the design and application of micropiles.