Abstract: Employee #1 was mixing materials for a tunnel grout operation inside a 9-ft.-diameter steel-formed tunnel. He was standing up inside a slant ended muck box, which was being used for sand storage. On the back end of the box was a pallet of approximately 20 bags of cement resting unsecured on the overhang end. Employee #1 was emptying out the sand when the weight of the cement counterweighted the sand, causing the unsecured muck box on its dolly to tip up, pitching him approximately 2 to 3 feet into the tunnel roof. Employee #1 was wearing a hard hat and was dazed. He was released from the emergency room with a sore head and neck.