On the radial contact pressure of parallel buried pipes for district heating

For the design and calculation of buried district heating pipe systems the magnitude of radial contact pressures acting on the pipes is of importance, since these pressures affect the friction forces which may be mobilized. For parallel buried pipes, the stress distribution is generally expected to be different from the case of a single pipe. The present investigation compares radial stresses according to current design directives for buried single pipes with numerically calculated stresses for parallel buried pipes. The calculations show a deviation of the radial stress distributions in particular for the springline area. The results are compared with former theoretical investigations, which predicted a reduction of radial contact pressures between the two pipes. This is verified for small-diameter pipes. With larger pipe diameters a stress increase was identified between the pipes. However, with regard to the average radial pressure only slight differences between single pipes and parallel buried pipes were found.