Skip to content

Reinforced soil wall for a working platform for 1000 ton crane and TBM machine: Elan Valley Aqueduct, Bleddfa, Wales, UK

The Elan Valley Aqueduct (EVA) rehabilitation project consists of the replacement of some sections of the existing aqueduct built over a 100 years ago, which currently supplies water to Birmingham and surrounding areas, from mid-Wales. This paper refers to one of the replacement sections of the old structure where it was required to construct a new conduit with a tunnel of 1.8km long and 3.0m diameter. For the construction of the bypass conduit, a horizontal working platform of 160m long and maximum 13.3m high was required to support the construction traffic, the 1000 ton crane to assemble the Tunnel Boring Machine (TBM) and the 150 ton TBM. The solution consisted on a Reinforced Soil Wall using Strata geogrids of 120 and 60 kN/m and on-site cohesive material as part of the cut-and-fill balance of the project. The fill material was very susceptible to weather conditions and it was required to follow a strict testing regime during the installation and compaction of each layer to ensure the stability and good performance of the structure. On top of the Reinforced Soil Wall (RSW), a granular platform was constructed using biaxial Tenax geogrids to distribute the heavy loadings. The RSW was constructed between April and June 2016 and the tunnel was successfully completed in November 2016 with the extraction of the Tunnel Boring Machine.