Solution:

• Elementary profile is a theoretical profile.
• Only external forces acting on elementary profile is water pressure.
• Internal force is self weight.
• The shape of elementary profile of a gravity dam is right angled triangle.
• For full reservoir condition resultant passes through outer one third point and for empty (only self weight) reservoir condition resultant passes through inner one third point.
• By providing a top width for roadway and free board in elementary profile of a gravity dam, for full reservoir condition the resultant force will shift towards heel of the dam.