Effective embankment reinforcement solutions are supporting the construction of a new £18.4 million carriageway in Bridgwater.
To strengthen bridge abutments and river embankments along a new carriageway in Bridgwater, Somerset – a scheme that will alleviate traffic congestion in the town and open up access to surrounding development land – the project team turned to Maccaferri MacTex W1 and ParaLink to construct effective load transfer platforms.
The Colley Lane Southern Access Road (CLSAR) is an important new construction for the town of Bridgwater, Somerset. The 840-metre carriageway, which will include two new bridges and cycle and pedestrian paths, will provide access to the Colley Lane Industrial Estate from the south, thereby easing congestion in the town, especially during rush hour. It will also open up development sites between the River Parrett and the Taunton and Bridgwater Canal, with the new bridges providing easy access.
The geology of the site is characterised by highly compressible and thick alluvial deposits, associated with the River Parrett floodplain and an infilled clay pit, creating a risk of excessively large and differential settlements, both along the embankments themselves, and in relation to the relatively fixed approach embankments. To tackle this, we proposed bridge abutments constructed from mechanically engineered earth walls (similar to MacWall), supported by ParaLink load transfer platforms (LTPs) over piled foundations.
With this solution, localised differential deformation is prevented at the surface of the embankments by transferring loads onto the pile caps. To support the abutments on either side of the bridge, the ParaLink LTPs will transfer the loads of the reinforced earth walls into the piled foundations beneath. The maximum height of the reinforced earth wall is approximately three metres above the LTP.
ParaLink 400, 500 (for the transverse reinforcement direction) and 800 (for the longitudinal direction) were used across the site. Four different LTPs were designed and installed, including edge piles of 600 millimetres in diameter, and internal piles of 450 millimetres in diameter, with circular pile caps of 900 millimetres in diameter. Since ParaLink increases the capability of the embankment fill to arch, the spacing of the piles was also increased to 2.5 metres, saving the project time and resources. The LTPs were constructed using Class 6I granular fill material.