This paper discusses an experimental study on the effects of soil plugging on the inner frictional resistance of bottom thick-walled open-ended piles. The piles were penetrated in both dense and loose sand, prepared by 60 and 30% of relatively densities respectively. Open-ended piles of 30 and 50mm outer diameters were used in the study. A sleeved and non-sleeved open-ended pile each were used in addition to the respective closed-ended piles. The sleeve height of the sleeved open-ended piles was designed as a 2D length (D is pile outer diameter). The degree of soil plugging is discussed using the incremental filling ratio. The results suggest that the loose ground is more effective to use the bottom thick-walled open-ended piles regardless of the pile diameter. The results also indicate that the larger diameter piles are more effective to use the bottom thick-walled open-ended piles. The results of soil plugging indicate that the influence of ground density is not significant in relatively smaller diameter piles than relatively larger diameter piles.