Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand?

Explanation

When a person stands on a pile of gravel, the area of contact between the feet of the person is large `(P=(F)/(A))`. On the other hand the area of contact between the feet and the sand is large and the pressure on the feet of the person is reduced. The pain felt by the person is related more to the pressure experinced by his feet and not so much to the force.