To insure that lateral force of the cylinders maintains pressure in a hydraulic aluminum shoring system, the rails, and the plywood used with or attached to the rails, must bear on a firm trench face at the cylinder locations. If there is a void, behind the cylinders, between the rail/plywood and the trench face, it must be filled with soil, sand, rocks, timbers or any material that provides firm bearing for the cylinders. I repeat any material will do if it provides firm bearing.
Note: The adequacy of the fill material will be proven when the hydraulic cylinder is pumped up to working pressure. If the cylinder maintains pressure and is firm between the faces of the excavation, the system is working. The pressure points behind each hydraulic cylinder activate the soil arching in the face of the excavation.
It is not necessary for the entire rail, or all of the plywood, to be bearing on the excavation face. Only the area of the system directly behind the hydraulic cylinders must be bearing.
It is necessary to inspect each cylinder each working day to insure that the working pressures are being maintained.
BURSON ENGINEERING
512-794-1086 jimburson@sbcglobal.net September 27, 2005
