Abstract: Experiments were conducted to investigate themaximum static friction force on a dragged probing rod in the uniform granular pilecontained in a cylindrical vessel. It is observed that the forceobtained is greater than thatof Jassen Model, when the gap between the wall and the rod is smaller than50 times of the spheres diameter. When the diameter of vessel is small,the force is related to theshape of the detecting rod. This strange behavior is due to the factthat the scattered granular can not be approximated as a continuummedium when the diameter (D) is small. The force chain in the granularpile plays a major role.