Grout Valves provide a way to deliver grout backfill when there is no room in the borehole for an external grout pipe. Durham Geo Grout Valves are one-way valves installed in the bottom of inclinometer casing. After the casing is in place, a grout pipe is lowered through the casing to mate with the valve and deliver the grout.
The gasket-type grout valve is shown at right. You can see the gasket at the base of a smaller diameter pipe. A larger diameter grout pipe slides over the smaller pipe to rest on the gasket. Grout can then be pumped through the valve. When grouting is finished, the remaining grout in the pipe is flushed with water (just enough to displace the grout in the pipe) and then withdrawn from the casing.
Grout valves are easy to use, but require a slightly deeper borehole. Also grout must be mixed carefully so that it does not have lumps that could be caught in the valve mechanism.
The grout pipe is nominal 1.25" pipe. A 1.25" schedule 40 pipe has an ID of 1.35" (35mm). The smaller diameter pipe, which is part of the grout valve, is 3/4" pipe. It has an OD of 1.07" (27 mm).