TERRA AG recently completed a multiple bore crossing under a busy train line in the Swiss Alps. The train line crossed in this project is used by many tourists every year and features the highest train station in Europe, otherwise known as the ‘Top of Europe’.

Four HDPE pipes, with an outside diameter of 162 mm, had to be laid under the railway track. To avoid disruptions to this service during construction the contractor Peter Roth from Grindelwald decided to use the TERRA-HAMMER T135 F.

The HDPE pipes were required for water pipes, power lines and some control cables to feed into a new snow machine for the ski resort Grindelwald – Kleine Scheidegg.

The T135 F made a pilot bore with a 135 mm first. Then the T135 F, with an expander, increased the bore diameter to 204 mm and pulled in the HDPE pipe simultaneously.

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In total, four parallel bores were necessary with a 1 m distance between each bore.

The complete job site was finished within one day. It was possible to complete the project in such a short time frame because most of the equipment for the job site was flown in with a helicopter.

Machine technology

The T135 F is an underground piercing tool (‘mole’) with a diameter of 135 mm. It allows piercing bores in lengths of up to 25 m. It requires compressed air with a volume of 2.4 m cubed per minute, at seven bars.

The unique combi-head displaces the ground and its demolition steps guarantee ,extremely high accuracy. The machines longitudinal grooves give speed,` and the combi-head can be used in nearly all ground conditions except rock, even in the hard Swiss ground.

The TERRA-HAMMER runs forward and in reverse. It has a remote-controlled reverse that is activated with a small lever at the oiler, even under operation. TERRA invented the remote-controlled reverse in 1987.

The TERRA-HAMMER consists of less than 20 single pieces, whereas other moles consist of more than twice the parts. This simple design ensures reliability and a long life span, said the company.

The head of the TERRA-HAMMER is hollow. Thereby the main piston can be 25 per cent heavier than conventional pistons of piercing tools with the same length giving the TERRA-HAMMER high speed and productivity.

35 years of TERRA

The Swiss manufacturer TERRA AG celebrated its 35th anniversary in 2010 – starting out as a four-person firm, today TERRA products are sold in more than 75 countries worldwide.