Spherical jacking pipes – articulated pipe connections with optimal transmission of forces

Construction of underground pipelines increasingly takes place by trenchless construction, using, among other methods, hydraulic pipe jacking as well as microtunneling. The pipe-jacking machines can be controlled, enabling jacking of horizontally curving pipelines (space curves). The prerequisites for this are that the pipes can be angled against each other in the area of pipe connections. Based on the state of technology, pipes – mostly concrete and/or reinforced concrete with plane faces – are used for the jacking sections. The angling reduces the area available for the transmission of forces. To prevent falling below the permissible compressive stresses of the concrete, pressure transmission rings with various designs are commonly used. The objective of this procedure is to once again and at least partially compensate the loss of the force transmission area by means of deformation of the pressure-transmission rings.

The development of spherical jacking pipes with articulated pipe connections takes a different approach. This innovative project aims to improve both the transmission of forces among the pipes as well as to minimize the wall thickness of the jacking pipes by optimizing the geometry of the pipe joints, in connection with the use of an innovative
high-performance concrete. Towards this end, an innovative pipe design with a so-called spherical joint was developed within the scope of a doctoral thesis at the Department of Construction Operations and Construction Economics of TU Kaiserslautern.
The objective of the innovative joint geometry is to maximize the contact area between two jacking pipes, even when angled, to consolidate the distribution of stress at the joints and at the same time prevent the pipe joint from breaking open during jacking in curves.