Q. False set in pile driving?

For pile driving in certain soils such as dense silt and weathered rock, occurrence of false set phenomenon isn't uncommon. During the driving process, negative pore water pressure is developed and driven piles appear to have sufficient capacity during pile driving as the built-up of negative pore water pressure results in an apparent temporary increase in driving strength andresistance. Though sometime after the pile driving, dissipation of this negative pore water pressure will decrease the bearing strength in resisting the design loads. Occasionally the presence of cracks along pile sections can bring about the problem of false set by dampening effect of stress wavesby these cracks. To evade the problem of false set, a specific percentage of constructed piles must be chosen to perform re-driving to check for false set phenomenon.