Construction of grout-impregnated fabric-reinforced pipes

A method is evaluated for constructing pipes by injecting grout between an inner tube that can be inflated and an outer tube comprising a reinforcing mat in a fabric envelope. The mat is open-textured to allow easy impregnation by the grout and is sufficiently rigid to govern the wall thickness of the hardened pipe. The fabric envelope is permeable to water but impermeable to cement. Excess water is forced through the fabric by inflating the inner tube, carrying with it the grout, which lodges in the mat to harden, after which pressure is removed. Cyclic pressure is applied to simultaneously prestress the fabric and densify the grout. Fabric properties and the impregnation mechanism are described. Pipe ring stiffnesses are measured by the three-edge bearing test as a function of grout composition and pressure processing parameters. Potential applications include trenched and submarine pipes and tunnels, culverts, rock tunnel liners, and underground tanks.