Heave due to pile driving

Question

Hi all, 
 Anyone can tell how to make the soil heave due to unloading in the soil (because I need to see the soil heaving due to pile driving in soft clay layers)? how to use plaxis to make the soil heave after the removal of high pressure from the soil? 
 
 Load applied

but after load was removed I couldn't get a considerable amount of heave. 
 
 Thanks.

Dennis Waterman · Answer

Dear Nitharshan, 
 The heave is not caused by unloading, but because in the reality the pile doesn't replace the soil, but pushes the soil aside and that soil has to go somewhere. For the upper soil the soil will mostly go upwards which is the heave observed. In PLAXIS if a pile is modelled by replacing the soil (change material set from soil to the pile material) there is no side pushing of the soil, hence no heave. To get heave for instance a volume strain should be introduced to model the additional volume (of the pile) that is introduced by driving the pile. 
 With kind regards, 
 Dennis Waterman

Dennis Waterman · Answer

Dear Nitharshan, 
 You know the volume of the pile, dV. Make an estimate of the influence zone of the pile and the volume of the influence zone is V. Since the volume of the pile is added to the soil, the volume strain is dV/V. 
 With kind regards, 
 Dennis Waterman

Dennis Waterman · Answer

Dear Nitharshan, 
 Why would you fix the horizontal displacement along the pile? There is an undisturbed soil mass in which a pile is inserted. What would happen with the soil? Your model says that all soil is being pushed downwards... if that would be the case, how would you then get heave? 
 With kind regards, 
 Dennis Waterman