The influence of flow rate on the decrease in pressure beneath a conical pile

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.