Manhole restraining system for venting out explosive gases in a manhole

1. Field of the Invention A manhole restraining system used for venting out explosive gases in a manhole caused by an explosion. The manhole restraining system comprises a support frame, a two inch thick plate member positioned on top of the support frame, a plurality of restraining assemblies and a manhole cover for covering the manhole. The support frame and the plate member are embedded into a street and positioned above the manhole, where openings are aligned with the manhole. Three retaining assemblies are positioned on opposite sides of the manhole cover. Each retaining assembly includes a rod, a stop plate, a coil spring, a support plate and a nut. The rod extends downwardly through the dirt and the horizontal concrete base ledge, where the stop plate, the coil spring, the support plate and the nut are positioned and secured to the other end of the rod. A PVC pipe is provided with the rod for allowing the rod to move smoothly up and down without any friction. When an explosion occurs in the manhole, the pressure caused by the explosion lifts the plate member from a seated position on the main support frame above the manhole which in turn upwardly moves the rod, the stop plate, the coil spring, the support plate and the nut, where the explosive gases are vented out between the plate member and the main support frame. The stop plate, coil spring, the support plate and the nut absorb most of the energy caused by the explosion. The spring softens the impact and assist in bringing the plate member back down to the main support frame in alignment with the manhole.