Abstract: A pilot valve system is controlled by the pressure differential between a lower chamber and an upper chamber. A fluid passageway in the lower chamber fluidly connects an inlet to first and second outlets. By varying the pressure differential, the placement of a stem within the fluid passageway is varied so fluid can flow between the inlet and only one of the first and second outlets at a time. Pressure in the lower chamber can be varied by using a second fluid to exert pressure against a bottom end of the stem. Pressure in the upper chamber is varied by using an adjusting screw to urge a spring against the diaphragm.

Abstract: This disclosure relates to pavement systems and methods for paving that are suitable for locations containing a generally weak subgrade with a California Bearing Ratio of four (4) or lower. The pavement system includes a first geogrid layer placed directly on the subgrade; a first granular layer upon the first geogrid layer, the first granular layer having a thickness of from 0.5 times to 20 times the aperture distance of the geogrid layer; a first geocell layer upon the first granular layer comprising a geocell and an infill material; and a capping layer over the geocell layer. A second geocell/geogrid layer can be placed beneath the capping layer, if desired. An optional surface layer may be applied upon the capping layer if desired. The resulting pavement system provides long-term support for pavements applied over the pavement system.