Abstract: A method and apparatus for eliminating the necessity of providing hold-down devices, such as spuds and anchors, for opposing buoyancy in tunnel forms. The method comprises providing a movable counterweight car which preceeds the flow of fluid concretes, as it slopes from the crown of the tunnel forms downward and thus provides negative buoyancy at that area where there is the most fluid concrete and in that area where the most uplift occurs as well as the natural area where there are no forces of the crown helping to prevent flotation. The movable counterweight car is a hollow container curved to match the curvature of the excavated tunnel and clearing the movement of the forms. It has wheels that run on single track rails carried on the inside of the tunnel forms, the container being wholly or partly filled with steel scrap or punchings.