GRUNDORAM TAURUS puts on a convincing show in Finland

09.01.20 -
The ever increasing railway traffic in the Finnish-Russian border area prompted the Finnish Board of Traffic Infrastructure in Väylävirasto to double the amount of railway tracks from 2 to 4 in Vainikkala in south east Finland. In the wake of this new construction measure for two further railway tracks, they also decided to renew the already existent rainwater pipeline, as the pipe capacity had become insufficient for the drainage of the rainwater. The whole project, assigned by Väylävirasto, was implemented by Sundström Ab Oy Entreprenad, Lepplax. For the crossing of the constantly operated railway tracks, they put their trust in the experts Styrud Boreal Oy from Nurmijärvi, who are specialists for trenchless pipe installations. Based on soil inspections the responsible personnel decided to apply the dynamic ramming method using the GRUNDORAM model Taurus, horizontal ramming machine from Tracto-Technik, which was able to play to its advantages in the underground, consisting of clay, clay silt and layers of gravel.
The village Vainikkala, with around 400 inhabitants is in reality a small, easily comprehensible village, but the location, just about 1 kilometre away from the Russian border turns it into a hotspot for passenger and freight traffic. Trains on their way to Russia, stop here for border and customs checks. A freight terminal turns this small village into a major trading centre for goods between Russia and the EU. Furthermore, the high-speed train Allegro, which travels between Helsinki and St. Petersburg, stops here several times per day.
In 2018 alone, the Finnish Border Security registered 560.000 passengers, who crossed the border at Vainikkala, travelling in both directions. Just one reason why the construction work around the railway tracks was generally a sensitive subject. For this reason, the renewal of a large rainwater pipe through two parallel running new pipes ND 1600 underneath the railway tricks proved to be a very tricky project. 


The renewal of the pipeline involved the installation of two new parallel running pipes ND 1600. In total, both new pipes were installed in three construction stages. The section to cross beneath the operated railway tracks proved to be the most technically challenging section. Initially, this is where the steel protection pipes ND 1800 were installed and where the rainwater pipe, made of a plastic coated steel pipe ND 1600 was later to be inserted. 


As a change of position of the railway tracks was to be avoided, due to ground movements, the experts from Styrud Boreal Oy decided to apply the dynamic ramming method for the crossing. With the bore method they had initially had in mind, there was the danger of too much ground material being excavated during the parallel running bores, which could have caused the railway tracks either to bulge upwards or to subside, due to the cover depth of three metres. Furthermore, test bores in the area of both tracks had indicated, that the underground soil consisted mainly of clay or clay silt and in the apex area of the tracks also layers of gravel. Taking this into consideration, ideal soil conditions for a GRUNDORAM TAURUS. A further plus factor: The application of the horizontal rammer proved to be even more cost-effective than the bore method. Not least because, for example, abutments are not required with the ramming process and therefore allow shorter set-up times.


In order to ram the steel pipes ND 1800 in over a length of 21 m and in a depth of 1.80 m beneath the railway tracks, it was first of all necessary to set-up a construction pit with a length of 26 m, then align the pipes, so they could be connected firmly with the air-driven rammer, enabling the impact energy to be transmitted optimally over the whole length of the steel pipe. The GRUNDORAM TAURUS possesses a thrust force of 20,000 kN and rammed the steel pipe with 180 strokes per minute continuously into the ground. The special soil removal adapter has two openings, allowing parts of the soil to escape inside the steel pipe and relieve pressure. About 50 % of the remaining soil core was excavated from the pipe with water and compressed air after completion of the ramming process. To achieve this, the staff members from Styrud Boreal Oy welded a plate to the open end of the steel pipe in the starting pit area and pressurised the space between the plate and soil core with water and compressed air. This pressure pushed more than half of the soil core into the direction of the target pit area and out of the steel pipe. The remainder of the soil material was removed out of the pipe with a horizontal boring spiral conveyer. Once this work was completed, the media pipe ND 1600 was installed inside the protection pipe. 
After 10 days in total, the installation of both steel protection pipes had been completed to the fullest satisfaction of Sundström Ab Oy Entreprenad: “The ramming process was successfully carried out without any unforeseen incidents. The protection pipes and the media pipe were installed with a good quality and high precision.” The decision to back the dynamic ramming method proved to be an excellent and definitely the right choice. 



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