To prevent adherence to the inner wall of a hopper and to facilitate the regulation of a thick film at the outlet of the hopper by providing a delivery conveyer at the delivery port of a hopper, and providing a belt type movable wall for preventing closing action in the inner wall of the hopper, and providing a control device for controlling the speeds of the conveyer and of the belt type movable wall.

A delivery conveyer 3 is provided at the delivery port 2 of a hopper. A belt type movable wall 5 for preventing closing action is provided in the inner wall 4 of the hopper 1. The belt type movable wall 5 varys its attaching position through a thick film regulating mechanism 7 to carry out the regulation of layer thickness on the conveyer 3. A driving motor 3a for the conveyer 3 and a driving motor 5a for the belt type movable wall 5 are connected to a controller 6, which detects the numbers of revolutions of the driving motors 3a, 5a to control the speeds of the conveyer 3 and of the belt type movable wall 5 in a fixed relation. Thus the delivery of soft soil in the hopper and the thickness of a delivery layer can be regulated.