Fac should be a number between zero and one. One, when the pipe is fully restrained, i.e. buried for a long distance. Zero when the pipe is subject to no buried axial restraint. The default value for Fac is 0.0. Note that when Fac is 0.001, this indicates to CAESAR II that the pipe is buried but that the soil supports have been modeled. This will cause the hoop stress component, rather than the longitudinal stress, to be added to the operating stresses, conforming to the spirit of the restrained line stress calculation above.