This technique traps the victims inside a self-repairing dome of earth which is almost instantaneously able to reform, even after Kiba hit it with his Passing Fang. Jirōbō was able to absorb the chakra of anyone trapped inside, something he enjoyed greatly. However, Jirōbō's chakra was not evenly distributed throughout the dome. Near the back, relative to him, his chakra was much weaker, making the dome weaker in that spot.
The name of this technique shows a clever use of language. Dorō (土牢) means "Earth Prison." However, the usual pronunciation of these kanji is "tsuchirō," meaning "dungeon." Likewise, dōmu (堂無) is written with the kanji for "Magnificent Nothingness," but, when written in katakana (ドーム), it means "dome."