Calculating a Cementitious Liner’s Load Response to Produce an Efficient Wall Thickness

The design performance limits of a cementitious liner are either (1) ring compressive strength (i.e., in thrust) or (2) cracking of the lining (i.e., in ring bending). Which of these is in control is a function of the cover depth, radius of curvature of the arc element(s) of the liner, any live load present, and the thickness of the liner. Lining assumes that the existing soil-structure interaction system is in a state of equilibrium at the time of the rehabilitation. Loads coming onto the liner after its installation mean that if there are any live loads that can reach the liner due to the shallowness of the cover, they should be accounted for in the liner's design along with any external hydrostatic pressure that is acting on it at the depth of the host pipe structure. This paper discusses how to determine the load response behavior of the liner by using the arch rise parameter of the critical arc element of the liner and provides the design engineer with how to then calculate the stresses and displacements of the liner without any consideration of the current structural capabilities of the host pipe structure (i.e., standalone). Recognizing the load response behavior provides the design engineer with the confidence to calculate the most efficient shell structure that is more often in compression, which is the greater of the strengths of these cementitious liner systems.