Abstract: A method and apparatus for forming wet concrete employing a slip form having a radially expandable elastic outer shell comprising pouring concrete around the exterior surface of the outer shell and applying a fluid under pressure to the interior surface of the outer shell. The pressure of the fluid is pulsated so that the outer shell expands and contracts to reduce the friction between the outer shell and the concrete. The reduction in friction allows the form to be moved longitudinally along the concrete with reduced tearing of the surface of the concrete.

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.

Abstract: The specification discloses a process for manufacture of welded aluminum grating and the like wherein weldable grade aluminum cross bars having a form similar to a wedge having a rounded apex are abutted against bearing bars and a voltage is applied through the parts to create resistance welds. Special preparation such as cleaning or notching of the area of the aluminum bars that are to be welded are eliminated.