Secudrain WAS 7 as vertical drainage system
The B 239 Herford bypass was planned and put out for tender in three sections by the Minden branch of the state highway authorities for road constructions in North-Rhine Westphalia, Germany. The contract for the third section was awarded to a joint venture between Bickhardt Bau AG and Bickhardt Bruckenund Ingenieurbau GmbH in Kirchheim, Germany. The job involved building a bridge across the B 239 road to close up the gap between the Lockhauser Street and the exit from the A 2 highway. Prior to commencing construction of the bridge abutments, a bored pile wall was erected. The design also provided for the installation of a drainage layer between the bored pile wall and facing for the bridge abutment and on the wing walls. The requirements made on the tendered vertical drainage layer follow those of WAS 7, a German drainage recommendation. It allows drainage in the vertical for those areas in contact with earth at a rate in the back-filling of structures of > 0.3 l/s*m under the respective earth pressure. After examining all of the tenders submitted, the decision was finally taken to install the geosynthetic drainage system Secudrain WAS 7 produced by NAUE GmbH & Co. KG.
Secudrain WAS 7 is a three-dimensional drainage system consisting of a stable, pressureresistant, corrugated collection layer encased with a filter nonwoven layer on each side. The highly effective level of stability of the corrugated collection layer gives this product which was developed specially for WAS 7 applications the required drainage rate of 0.3 l/s*m even for bridge abutments to a depth of about 12 m. In addition, Secudrain WAS 7 meets all other WAS 7 requirements:
- high weather resistance
- effective AOS in the nonwoven filter ranging from 0.07 mm to 0.2 mm and
- water permeability of the filter nonwoven 100 times higher than that of the soil.
As Secudrain is easy to handle and install, it was possible to install the drainage layer section for section as the level regulating concrete course was put down, Secudrain was rolled out at the bored pile wall and spot-fixed using shot-anchors. The cavities were then filled in with concrete prior to installing the pre-fabricated facing elements. The use of 1,500 m² of Secudrain on the bridge abutments of the B 239 Herford bypass will ensure long-term and controlled drainage of any water occurring. Simple and safe installation, even on complicated construction shapes, provided a cost-efficient solution which would not have been possible using conventional mineral materials.