A work crew was tasked with installing a 21-inch diameter, 9-foot long, 200-pound pipe sleeve for a duct bank installation through an underground transformer room (vault). The crew knocked out a hole from the wall of the existing vault leading out to an excavated space. Four crew members, located in the vault, got the pipe sleeve into position, approximately 10-feet off the floor, and were able to push the pipe sleeve into the hole towards the employee inside. The center of gravity of the pipe sleeve shifted and slid into the hole. The employee's left pinky was caught between the pipe sleeve and the concrete wall. The top portion of the pinky required medical amputation.