en Geotechnique Geotechnique Research Paper Research Paper In present research, 17 centrifuge tests have been conducted to study the effect of various parameters such as the number of piles, the distance between piles, gradation and thickness of the granular layer on the load-settlement behavior of a pile raft system. The results showed the importance of granular layer to reduce the settlement of non-connected pile raft system when the roles of piles are to reduce the settlement. In other words when the piles have major contribution on the bearing capacity of pile raft system, presence of a granular layer may increase the settlement. Piled raft foundation, Non-connected piled raft, Load-settlement behavior and settlement reduction. 114 123 http://ijce.iust.ac.ir/browse.php?a_code=A-10-3317-1&slc_lang=en&sid=1 A. Saeedi Azizkandi asaeedia@yahoo.com 180031947532846009521 180031947532846009521 Yes Assistant Professor, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran M.H. Baziar baziar@iust.ac.ir 180031947532846009522 180031947532846009522 No Professor, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran H. Rasouli Rasouli.habib@gmail.com 180031947532846009523 180031947532846009523 No MSc. Student, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran M. Modarresi modarresi@civileng.iust.ac.ir 180031947532846009524 180031947532846009524 No MSc. Student, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran H. Shahnazari hshahnazari@iust.ac.ir 180031947532846009525 180031947532846009525 No Associate Professor, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran