Biblis nuclear power plant, LAW 2

Within the context of the deconstruction of the nuclear power plant in Biblis, it is necessary to create a waste storage area for the intermediate storage of radioactive waste and residual materials. Stump Spezialtiefbau GmbH was commissioned to manufacture 38 large bored piles DN1000 mm and to carry out measures to improve the condition of the soil.

A supporting wall with large bored piles 14.20 m long had to be set up to the south of the planned structure. The drilling work was done using a combination drilling rig BG28 and the Kelly drilling method. On account of the groundwater conditions, the large bored piles were manufactured under hydrostatic force using the so-called contractor method.

Since the construction plot for the planned waste storage area is built up, the foundation soil had to be improved before construction work could begin. Accordingly, 1,243 concrete pillars DN510 mm were made on a construction plot approx. 4000 m² in size using the full displacement system FDP. The concrete pillars had to embed at least 1 m in the load-bearing foundation soil.

 Proof of meeting the necessary load-bearing horizon was determined for each pile by device recordings made during the drilling process. This allowed optimisation of the pile length. The mean length of the concrete pillars was approx. 7.50 m.

Two drills BG28 and BG36 were used at the same time for manufacturing the full displacement concrete pillars. The concrete was pumped using two mast pumps. The soil improvement measures took a total of five weeks.