Trenchless pipe renewal with GRUNDOCRACK
The first traces of settlement in the small Austrian community of Elixhausen near Salzburg in Austria stem way back from the uppermost Stone Age. Findings of stilt houses from the third millennium b. c. are followed by settlement and grave finds from the Bronze Age and the younger Iron Age almost without gap. In Roman times, great estates and mansions were allocated to privileged places; archaeological evidence or written records for the Middle Ages are not available, however. Elixhausen was first mentioned by name as around the year 1000. With the beginning of the modern era, the development of the town takes its course with the construction of a proper great church: from formerly 141 habitants (in 1751) to 617 at the census of population in the year 1951, the present municipality of Elixhausen has grown to a population of almost 3,000, due to immigration.
The respectable demographic development has a lot to do with the location of the municipality: bedded in the Lakeland of Salzburg, in the midst of a cultured farming landscape with farmsteads and hamlets in the north-east of Salzburg, only ten kilometres away from the lively provincial capital, life is at its best. The infrastructure offers good preconditions as an attractive business site for trade, services and industries, which is not the least of reasons for making one's home there.
The Mattseer state road (L 101) is the main communication road to Salzburg for Elixhausen and the surrounding villages and municipalities. It is a broad, very heavily frequented road; especially during the commuter traffic, car after car are stringed together here. Where the road branches out to the Perling Road in the district of Ursprung, a pipe culvert beneath the Mattseer state road for discharging rain water was badly in need of renewal. The aspects of damage were obvious: due to improper installation and subsequent broadening of the state road, the rather old heavy load-bearing concrete pipes ND 400 had shifted and formed a set-off by up to 20 percent; their functioning order was massively limited by these occurrences and demanded quick restoration.
The case is determined
The conditions on site immediately forbade any thoughts of applying open trench pipe renewal with conventional excavation of the line from the minds of the experienced planners of the Karl & Peherstorfer ZT GmbH. On the one side, the measure would have caused an absolute traffic chaos with massive holdups and hampered vehicle movement on this extremely busy road; on the other side, the pipe culvert lead through an embankment fill at a depth of 4 m which would clearly have driven the excavation costs to immense heights. After sighting and evaluating all economical, social and ecological facts, specifications and circumstances, the case was determined: only trenchless pipe renewal beneath the Mattseer state road using the pipe bursting method was in the running to replace the old heavy load-bearing concrete pipes ND 400 underground by new pipes in the same bore path. For this project, dynamic pipe bursting was the method of choice; here, the thrust of the bursting machine is supported by the pulling force of a cable winch. In this way, a safe course through the intended path can be guaranteed; therefore this pipe bursting method is particularly useful for the underground renewal of old pipe lines with a distinct offset. The new replacements were four Aqualine PE 100 RC pipes, ND 400 SDR 17 (12 m installation length each), produced by Pipelife Austria. These are "especially recommended for trenchless installation projects, above all if the demands on the pipe system quality are extremely high".
All here, all clear
Also located nearby, the company Erdbau Franz Eder GmbH & Co.KG was commissioned with the execution of the pipe bursting operation. The company looks back on many years of experience in the underground installation technologies, owns a well-equipped vehicle and machinery pool and can therefore guarantee high efficiency and flexibility. Among others, their machinery includes pipe ramming machines manufactured by TRACTO-TECHNIK; quickly and without complications, they can be modified and used as pipe crackers for dynamic pipe bursting. And exactly this equipment was needed for the building measure on hand.
The first working step was to prepare the new pipes for pulling in. Because the stream bed offered sufficient space for laying out the pipes very generously, the team decided to pull in a long pipe. First of all, the four 12 m long PE 100 RC pipes were butt-welded to form a pipe string. When this variant of heating element butt welding is applied, the welding mirror, consisting of a PTFE (polytetrafluoroethylene) coated metal surface in most cases, is placed between the surfaces which shall be welded together. In this way, adhesion between the pipe and the heating element is prevented.
The choice on the most suitable machinery was quickly made: because the old pipes were particularly hard-wearing heavy load-bearing concrete pipes, the people in charge decided to put the GRUNDOCRACK into use, the GRUNDORAM pipe ramming machine type GIGANT converted to a pipe cracker with a bursting head of ND 480 on the front cone. Dynamic pipe bursting uses the dynamic power of the cracker exclusively for the thrust performance and breaking up of the old pipes - in this case the power of the pipe ramming machine. In detail, the compressed air in the machine body accelerates a piston which acts upon the ramming head; the power unleashed in progress allows the greatest possible thrust, due to the optimal load transmission by way of the cones.
At first, a simple cable pulling winch was selected. It didn't take long to realise that this winch was unsuitable for the job; therefore it was replaced by a Bagela gipsy winch RW 10.
Everything under control
After the "launch failure" due to the wrong winch choice, work could finally commence with the replacement: assisted by the gipsy winch and its maximum pulling force of up to 100 kN, the ramming machine was put in front, for one to guarantee the safe, on-target guidance through the old pipe path, secondly to support the perfect induction of the dynamic energy for bursting and expanding the very resilient old heavy load-bearing concrete pipes. At a depth of 4 m, the GRUNDOCRACK worked its way through the banked up loose soil with an impact power of up to 2,860 Nm, effortlessly and without any problems: the old soil was broken up with loud creaking and crashing noises, the shards were pushed into the surrounding soil and the 43 m long PE 100-RC pipe string was pulled in. The net bursting operation took no longer than 2.5 hours.
A plan comes together
To carry out the renewal of the pipe culvert with the GRUNDOCRACK system using the dynamic pipe bursting method was a good and forward-looking decision with convincing advantages, seen from an economical, ecological and social point of view. Almost imperceptible by residents and the car drivers driving along the Mattseer state road as if stringed closely together nose-to-tail, especially during commuter traffic, the 43 m long pipe culvert for the storm water run-off beneath the embankment fill at the branch-off to Perling Road in Elixhausen was renewed all round. On the whole, the company Eder GmbH und Co. KG needed only two days for this project.
It was a great swift team achievement by the planners, builders and naturally the cracker.