Two number 3 bars shall be provided as indicated in attached sketch. Respect your City Code. Cities are not in the sales business. This way there won't be any shirring or swell. Could be yellow, red, brown or white rock.
Piers work by skin friction.
The larger the shaft the greater the friction. We tried larger bells and they would shear, so we invented the Counter Balance Pier. This gives the same effect as a 6 foot bell. Counter balancing the pier increased the load bearing. All piers must go to second strata clay, which does not shrink or swell.