Pile reaction vs pile cap thickness

[dccd]

https://www.youtube.com/watch?v=imznVQh5QXQ&ab_channel=EngineeringWorld

In this video , at 22.00 to 24.00 minutes, the author assign different slab thickness to make the punchign shear design os slab pass. Just wondering, why when the author increased the thickenss of slab, the compression on the pile decrease ?

My thought is when thepile cap thickenss is increased, the selfweight of pile cap become higher, shouldnt the compression on the piles become higher?

 

[sticksandtriangles]

As the pile cap gets thicker, it is better able to distribute load to adjacent piles, e.g. it gets stiffer.

In typical small pile cap design, assuming an infinitely stiff pile cap, all pile reactions would be the same.

As you can see in this video, assuming an infinitely stiff pile cap would under-estimate the reaction force of the piles near the column, while over-estimating the pile reactions away from the column.

S&T