This is called a train kiln and was designed by John Neely at Utah State University. The pottery fired in this kiln resembles pottery fired in an anagama kiln, with thick deposits of ash.
I purchased my kiln's design plans from Judith Duff, who built a similar train kiln in North Carolina. My kiln is smaller than Duff's, at 12.5' long with a 13' chimney. One of the unique features of a train kiln is the stepped floor inside the bourry box, where wood ash lands before being pulled into the ware chamber. Stoking takes place on one side of the bourry box through a sliding soft-brick door. Firings typically last 28-30 hours.