Trenchless Jacking Pipeline with Two Curved Sections

The project “Zielona Góra” included 1149 meters of HOBAS CC-GRP Sewer Pipe Systems of DE 1099 and 1229 and SN 128000 with a rectilinear and two curved sections with a radius of 350 m and 175 m. In case of rectilinear microtunneling the compressive force is distributed evenly on the entire pipe. The challenge oft this curved pipe jacking project was the fact that in the case of angular deflections at pipe connections the compressive force is not applied centrally to the pipe cross-section but acts eccentrically. This fact may result in exceeding the allowable stress, and consequently in pipe damage. According to the analyses, HOBAS CC-GRP Jacking Pipe Systems with a ring stiffness of 128000 N/mm² were selected. The allowable jacking force for such pipes for rectilinear microtunneling was 4660 kN, while for the curved section a jacking force of 3000 kN was allowed. Despite the curve, HOBAS CC-GRP Jacking Pipe Systems with their smooth outside surface could easily be jacked with only 3000 kN. For the curved section 1 m long pipes were selected, while the straight sections were made using 3 m long pipes. The total length of the section was 270 m, of which the final 115.5 m long section was made along a curve with a radius of 350 m.