Question

What is main mechanism of formation of soil plugs in marine driven steel piles with reinforced concrete infill?

Answer

Throughout initial driving process, open-ended steel piles are driven from side to side soils at their bases. Still, shaft friction will slowly develop between steel piles and soils inside piles at some time after pile driving. Hitting action of driving hammers induces forces to soil and later it comes to a stage when inertial forces of inside soils, together with inner frictional forces more than bearing capacity of soils at pile toes. As a result, soil plug formed is brought down by the piles.