Renewal of a concrete pipe by pipe-cracking

In many cities around the globe, older existing water and sewage pipes are in need of repair and replacement. Often, utilities also need to increase flow capacity by increasing pipe diameters. During a recent project in Austria, a pipe-cracking system was used to successfully replace deteriorated pipe.

The sequence for the pipe renewal technique is simple: a QuickLock (ladder type) bursting rod is pushed into old pipe by a hydraulically operated bursting rig. The tool head can be equipped with either a cutting blade, which cuts through tough material, or a bursting head, which breaks open brittle pipe material. Almost all old pipe materials can either be cut or burst and new replacement pipe pulled in simultaneously.

The Grundoburst rig is placed in position in the starting pit.

During pipe installation, an expander body provides further bursting of old pipes, as well as displacement of pipe fragments into surrounding soil. Pipe size expansion of up to two nominal pipe dimensions is possible. The bursting technology is used mainly for renewal of pressure pipes (gas and potable water), but has proven successful for instal lation of non-pressure pipes, too. With a maximum pulling force of 125 tons, pipe renewals up to 600 mm in diameter can be carried out.

A new milestone was set for bursting technology in October 2006 in Amstetten in northern Austria with the nation’s first application of the GrundoBurst 1250G from Tracto-Technik by the company Baumeister Karl Fürholzer GmbH, of Arbing.

The initial task in the Linzerstrasse jobsite in Amstetten wasn’t easy. An old rainwater pipe, ND 300 made of steel reinforced concrete, was to be exchanged with a polypropylene pipe with nominal size ND 400. The old pipe was neither statically or hydraulically sound, according to today’s requirements; and the manholes had to be renewed as well.

It was a general written condition not to disrupt traffic flow to the adjacent busy two-lane motorway access road. Further, the pipeline path was extremely difficult to access, as it ran extremely close to a parallel sloping wall. For this reason, a fast solution was required which would both preserve the road surface and entail minimal excavation work.

The GrundoBurst system was chosen, in part, for of its use of patented QuickLock rods that form a tightly connected but flexible rod string. Assembled by clicking the rods together, it provides time savings when compared to systems using screw-together rods.

To commence the pipe bursting method, it’s necessary to excavate starting and target pits. For optimal space and reduction of excavation costs, the old excavated manhole areas were used with the installation lengths between 60 and 80 meters apart.

In total, a pipe length of 200m was renewed in just four working days, including all the manhole replacement work. The authorized site personnel were extremely satisfied and agreed that this trenchless technology should be used even more in the future.