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Grout holes with W80, Ohra dam, Oberhof, Germany

Drilling of grout holes in an inspection tunnel under the Ohra dam in Oberhof, Germany . The inspection tunnel which extends under the dam has a length of 100 meter and an inclination of 25 degrees. The purpose of the grout holes which has a length varying from 50-90 meter was to create a grout curtain against the dam. Stump Spezialtiefbau GmbH was the drilling contractor.

Project Description:

The apartment building complex of Tunahus in Lund, southern Sweden, wanted to reduce their heating costs for its 203 apartments. The answer was an energy storage consisting of 35 holes with a depth of 190 meters which gives a total of 6,650 meters. The first 30-60 meters are cased. Malmberg is the turn key contractor for the complete project which includes drilling (performed by Malmberg Borrning AB) and installation of the heat pump facility. Wassara was chosen due to the difficult formation, which consists of clay, silt, gravel and fractured zones in the bedrock.


The Wassara technology has been very advantageous in the "hard to penetrate" geology around Lund.

Equipment: Hammer Wassara W80
  Bit Wassara 95 mm
  Pump Woma
  Drilling fluid Clean water
  Drill pipe OD 76 mm, length 1500 mm


Diamec 262
  Formation Soft granite