The decrease in the stress at the bottom of a sandpile exhibits the preparation dependence known to occur for granular materials. By using a grid-based tactile pressure sensor, we carefully measured the progressive development of the pressure profile at the bottom of conical piles formed by funneling rice grains onto the sensor. A significant decrease in the stress was observed at small flow rates, but it gradually disappeared at greater flow rates. This result is helpful in understanding the stress distribution within sandpiles. (C) 2011 Elsevier B.V. All rights reserved.